|
GEOPHYSICAL
RESEARCH LETTERS, VOL. 35, L02807, doi:10.1029/2007GL032333, 2008
Decadal growth of black carbon emissions in India
S.
K. Sahu et al.
Abstract
A
Geographical Information System (GIS) based methodology has been used to
construct the black carbon (BC) emission inventory for the Indian geographical
region. The distribution of emissions from a broader level to a spatial
resolution of 1° × 1° grid has been carried out by considering micro level
details and activity data of fossil fuels and bio-fuels. Our calculated total BC
emissions were 1343.78 Gg and 835.50 Gg for the base years 2001 and 1991
respectively with a decadal growth of around 61%, which is highly significant.
The district level analysis shows a diverse spatial distribution with the top
10% emitting districts contributing nearly 50% of total BC emission. Coal
contributes more than 50% of total BC emission. All the metropolitan cities show
high BC emissions due to high population density giving rise to high vehicular
emissions and more demand of energy.
Keywords:
emissions; black carbon; fossil fuel; bio-fuel; inventory.
Index
Terms:
0345
Atmospheric Composition and Structure: Pollution: urban and regional (0305,
0478, 4251); 0305 Atmospheric Composition and Structure: Aerosols and particles
(0345, 4801, 4906); 1605 Global Change: Abrupt/rapid climate change (4901,
8408); 1610 Global Change: Atmosphere (0315, 0325); 1630 Global Change: Impacts
of global change (1225).
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L05810, doi:10.1029/2007GL032680, 2008
Ice core record of rising lead pollution in the North Pacific atmosphere
E.
Osterberg et al.
Abstract
A
high-resolution, 8000 year-long ice core record from the Mt. Logan summit
plateau (5300 m asl) reveals the initiation of trans-Pacific lead (Pb) pollution
by ca. 1730, and a >10-fold increase in Pb concentration (1981–1998 mean
= 68.9 ng/l) above natural background (5.6 ng/l) attributed to rising
anthropogenic Pb emissions from Asia. The largest rise in North Pacific Pb
pollution from 1970–1998 (end of record) is contemporaneous with a decrease in
Eurasian and North American Pb pollution as documented in ice core records from
Greenland, Devon Island, and the European Alps. The distinct Pb pollution
history in the North Pacific is interpreted to result from the later
industrialization and less stringent abatement measures in Asia compared to
North America and Eurasia. The Mt. Logan record shows evidence for both a rising
Pb emissions signal from Asia and a trans-Pacific transport efficiency signal
related to the strength of the Aleutian Low.
Keywords:
lead; pollution; Asia.
Index Terms:
0345
Atmospheric Composition and Structure: Pollution: urban and regional (0305,
0478, 4251); 0365 Atmospheric Composition and Structure: Troposphere:
composition and chemistry; 0724 Cryosphere: Ice cores (4932); 0330 Atmospheric
Composition and Structure: Geochemical cycles (1030); 0489 Biogeosciences: Trace
element cycling (4875).
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L05606, doi:10.1029/2007GL032874, 2008
Spectral description of oceanic near-surface variability
Shane Elipot et al.
Abstract
This
paper provides a spectral description of near-surface oceanic velocity
variability on a global scale. Rotary spectra of drifter velocities are
estimated in zonal bands of the Indian, Pacific and Atlantic Oceans. The
partition of energy between cyclonic and anticyclonic frequencies clearly
identifies inertial oscillations at all latitudes. The meridional distribution
of near-inertial energy is described in detail. The polarization of
super-inertial energy is consistent with internal waves dynamics. Thus, the
distribution of super-inertial energy may be a manifestation of freely
propagating near-inertial waves on the β-plane.
Keywords:
drifters; polarization; inertial.
Index Terms:
4512
Oceanography: Physical: Currents; 4544 Oceanography: Physical: Internal and
inertial waves; 4572 Oceanography: Physical: Upper ocean and mixed layer
processes; 4294 Oceanography: General: Instruments and techniques.
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L05804, doi:10.1029/2007GL032901, 2008
Modeling the influence of North Atlantic multidecadal warmth on the Indian
summer rainfall
Shuanglin Li et al.
Abstract
Ensemble experiments with an atmospheric general circulation model reveal that a
positive (warm) ocean phase of the Atlantic Multidecadal Oscillation (AMO)
increases Indian summer rainfall. The intensification is driven by extratropical
North Atlantic warmth, with some cancellation associated with monsoon weakening
in response to tropical North Atlantic warmth. Mechanistically, warm
extratropical North Atlantic SSTs increase local rainfall, inducing an arching
extratropical wavetrain response. The latter leads to intensified northern
subsidence of monsoon mean meridional streamflow as well as widespread low
surface pressure over North Africa, the Middle East and the western Indian Ocean
contributing to a strengthened Indian monsoon trough and increased monsoon
rainfall. Warm tropical North Atlantic SSTs primarily increase local tropical
Atlantic rainfall that induces a tropically-confined response consisting of low
level easterly wind anomalies over the Indian Ocean and dynamically induced
subsident drying over India.
Keywords:
Atlantic Multidecadal Oscillation; Indian summer rainfall; monsoon.
Index Terms:
0429
Biogeosciences: Climate dynamics (1620); 1616 Global Change: Climate variability
(1635, 3305, 3309, 4215, 4513); 3339 Atmospheric Processes: Ocean/atmosphere
interactions (0312, 4504); 3354 Atmospheric Processes: Precipitation (1854);
3337 Atmospheric Processes: Global climate models (1626, 4928).
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L05701, doi:10.1029/2007GL032017, 2008
State-dependent atmospheric noise associated with ENSO
Jong-Seong Kug et al.
Abstract
A
strong relationship between ENSO (El Nino/Southern Oscillation) and atmospheric
short-term variability in the near-surface zonal wind is reported in the present
study. On one hand, anomalies in the variance of the short-term atmospheric
variability over the western Pacific tend to lead El Nino development. On the
other hand, the activity of the fast atmospheric variability over the central
Pacific is simultaneously correlated to the NINO3.4 SST. The significant
correlation exists over the broad range of atmospheric variability from the
synoptic time scale to the inter-seasonal time scale. This finding supports the
notion that the ENSO–state dependence of the atmospheric variability serves as a
source of stochastic forcing for ENSO. Furthermore, it is demonstrated that
there is a significant interdecadal change in this dependence. The
state-dependent noise becomes much stronger in the recent period, which possibly
explains the recent increase of the ENSO activities, consistent with the recent
theory of noise-induced destabilization effect for ENSO.
Keywords:
ENSO;
WWB/MJO; ENSO-noise interaction.
Index Terms:
4522
Oceanography: Physical: ENSO (4922); 3265 Mathematical Geophysics: Stochastic
processes (3235, 4468, 4475, 7857); 3339 Atmospheric Processes: Ocean/atmosphere
interactions (0312, 4504); 4504 Oceanography: Physical: Air/sea interactions
(0312, 3339); 3305 Atmospheric Processes: Climate change and variability (1616,
1635, 3309, 4215, 4513).
ENERGY & ENVIRONMENT, VOLUME 18 No. 7+8 2007
GLOBAL WARMING: FORECASTS BY SCIENTISTS VERSUS SCIENTIFIC FORECASTS
Kesten C. Green et al.
ABSTRACT
In
2007, the Intergovernmental Panel on Climate Change’s Working Group One, a panel
of experts established by the World Meteorological Organization and the United
Nations Environment Programme, issued its Fourth Assessment Report. The Report
included predictions of dramatic increases in average world temperatures over
the next 92 years and serious harm resulting from the predicted temperature
increases. Using forecasting principles as our guide we asked: Are these
forecasts a good basis for developing public policy? Our answer is “no”. To
provide forecasts of climate change that are useful for policy-making, one would
need to forecast (1) global temperature, (2) the effects of any temperature
changes, and (3) the effects of feasible alternative policies. Proper forecasts
of all three are necessary for rational policy making. The IPCC WG1 Report was
regarded as providing the most credible long-term forecasts of global average
temperatures by 31 of the 51 scientists and others involved in forecasting
climate change who responded to our survey. We found no references in the
1056-page Report to the primary sources of information on forecasting methods
despite the fact these are conveniently available in books, articles, and
websites. We audited the forecasting processes described in Chapter 8 of the
IPCC’s WG1 Report to assess the extent to which they complied with forecasting
principles. We found enough information to make judgments on 89 out of a total
of 140 forecasting principles. The forecasting procedures that were described
violated 72 principles. Many of the violations were, by themselves, critical.
The forecasts in the Report were not the outcome of scientific procedures. In
effect, they were the opinions of scientists transformed by mathematics and
obscured by complex writing. Research on forecasting has shown that experts’
predictions are not useful in situations involving uncertainly and complexity.
We have been unable to identify any scientific forecasts of global warming.
Claims that the Earth will get warmer have no more credence than saying that it
will get colder.
Keywords:
accuracy, audit, climate change, evaluation, expert judgment, mathematical
models, public policy.
JOURNAL OF GEOPHYSICAL
RESEARCH, VOL. 111, D11301, doi:10.1029/2005JD006763, 2006
Validation of
Polar Ozone and Aerosol Measurement (POAM) III version 4 stratospheric water
vapor
J. Lumpe
et.al.
Abstract
The Polar Ozone
and Aerosol Measurement (POAM) III solar occultation instrument has been
measuring water vapor at high latitudes since April 1998. Retrievals extend from
5 to 50 km, with 5–7% precision throughout the stratosphere and a vertical
resolution of 1 (3) km in the lower (upper) stratosphere. Estimated systematic
errors in the stratosphere are 10–15%. In this paper, we validate the POAM III
version 4 stratospheric water vapor using correlative measurements from
satellite, airborne, and balloon-borne platforms. The resulting comparisons show
that POAM water vapor is high compared to correlative measurements in the middle
to lower stratosphere. The satellite (Halogen Occultation Experiment (HALOE) and
Stratospheric Aerosol and Gas Experiment (SAGE) II) comparisons also indicate a
sunrise/sunset bias in the POAM data, with sunset (Southern Hemisphere)
retrievals larger than sunrise (Northern Hemisphere) retrievals by 5–10%. In the
Northern Hemisphere, POAM is approximately 5–10% high compared to all validation
data sets between 12 and 35 km. At higher altitudes this difference decreases,
such that POAM agrees with HALOE at 40 km and is lower by 10% at 50 km. In the
Southern Hemisphere, POAM is 15–25% higher than HALOE below 35 km, with
differences decreasing to 10% by 50 km. Similar differences are seen with SAGE
II. Despite these systematic differences the POAM water vapor data are
self-consistent and show no long-term trends in accuracy or precision.
Statistical comparisons of the water vapor variability measured by POAM, HALOE,
and SAGE II show very good agreement. The POAM data are therefore valid for
scientific studies, and the science community is encouraged to use this unique
data set.
Keywords:
water vapor; polar stratosphere; validation.
Index Terms:
0340 Atmospheric Composition and Structure: Middle atmosphere: composition and
chemistry; 0394 Atmospheric Composition and Structure: Instruments and
techniques; 3360 Atmospheric Processes: Remote sensing.
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D10308, doi:10.1029/2005JD006454, 2006
Long-term
evolution of upper stratospheric ozone at selected stations of the Network for
the Detection of Stratospheric Change (NDSC)
W.
Steinbrecht et.al.
Abstract
The long-term
evolution of upper stratospheric ozone has been recorded by lidars and microwave
radiometers within the ground-based Network for the Detection of Stratospheric
Change (NDSC), and by the space-borne Solar Backscatter Ultra-Violet instruments
(SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation
Experiment (HALOE). Climatological mean differences between these instruments
are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series
from all instruments, averaged from 35 to 45 km altitude, track each other very
well and typically agree within 3 to 5%. SBUV seems to have a slight positive
drift against the other instruments. The corresponding 1979 to 1999 period from
a transient simulation by the fully coupled MAECHAM4-CHEM chemistry climate
model reproduces many features of the observed anomalies. However, in the upper
stratosphere the model shows too low ozone values and too negative ozone trends,
probably due to an underestimation of methane and a consequent overestimation of
ClO. The combination of all observational data sets provides a very
consistent picture, with a long-term stability of 2% or better. Upper
stratospheric ozone shows three main features: (1) a decline by 10 to 15% since
1980, due to chemical destruction by chlorine; (2) two to three year
fluctuations by 5 to 10%, due to the Quasi-Biennial Oscillation (QBO); (3) an
11-year oscillation by about 5%, due to the 11-year solar cycle. The 1979 to
1997 ozone trends are larger at the southern mid-latitude station Lauder (45°S),
reaching −8%/decade, compared to only about −6%/decade at Table Mountain (35°N),
Haute Provence/Bordeaux (≈45°N), and Hohenpeissenberg/Bern(≈47°N). At Lauder,
Hawaii (20°N), Table Mountain, and Haute Provence, ozone residuals after
subtraction of QBO- and solar cycle effects have levelled off in recent years,
or are even increasing. Assuming a turning point in January 1997, the change of
trend is largest at southern mid-latitude Lauder, +11%/decade, compared to
+7%/decade at northern mid-latitudes. This points to a beginning recovery of
upper stratospheric ozone. However, chlorine levels are still very high and
ozone will remain vulnerable. At this point the most northerly mid-latitude
station, Hohenpeissenberg/Bern differs from the other stations, and shows much
less clear evidence for a beginning recovery, with a change of trend in 1997 by
only +3%/decade. In fact, record low upper stratospheric ozone values were
observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and
Haute Provence, in the winters 2003/2004 and 2004/2005.
keywords:
ozone; stratosphere; global change.
Index Terms:
0340 Atmospheric Composition and Structure: Middle atmosphere: composition and
chemistry; 1610 Global Change: Atmosphere (0315, 0325); 0394 Atmospheric
Composition and Structure: Instruments and techniques; 1626 Global Change:
Global climate models (3337, 4928); 1650 Global Change: Solar variability
(7537).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D10307, doi:10.1029/2005JD006058, 2006
Estimation of
atmospheric methane emissions between 1996 and 2001 using a three-dimensional
global chemical transport model
Yu-Han Chen.
et.al
Abstract
Using an
atmospheric inversion approach, we estimate methane surface emissions for
different methane regional sources between 1996 and 2001. Data from 13
high-frequency and 79 low-frequency CH4
observing sites have been averaged into monthly mean values with associated
errors arising from instrumental precision, mismatch error, and sampling
frequency. Simulated methane mole fractions are generated using the 3-D global
chemical transport model (MATCH), driven by NCEP analyzed observed meteorology
(T62 resolution), which accounts for the impact of synoptic and interannually
varying transport on methane observations. We adapted the Kalman filter to
optimally estimate methane flux magnitudes and uncertainties from seven
seasonally varying (monthly varying flux) and two aseasonal sources (constant
flux). We further tested the sensitivity of the inversion to different observing
sites, filtered versus unfiltered observations, different model sampling
strategies, and alternative emitting regions. Over the 1996–2001 period the
inversion reduces energy emissions and increases rice and biomass burning
emissions relative to the a priori emissions. The global seasonal emission peak
is shifted from August to July because of increased rice and wetland emissions
from southeast Asia. The inversion also attributes the large 1998 increase in
atmospheric CH4
to global wetland emissions. The current CH4
observational network can significantly constrain northern emitting regions but
not tropical emitting regions. Better estimates of global OH fluctuations are
also necessary to fully describe interannual methane observations. This is
evident in the inability of the optimized emissions to fully reproduce the
observations at Samoa.
Index Terms:
0365 Atmospheric Composition and Structure: Troposphere: composition and
chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent
transport and chemistry.
PM2.5
chemical composition and spatiotemporal variability during the California
Regional PM10/PM2.5
Air Quality Study (CRPAQS)
Judith C.
Chow et.al.
Abstract
The
14-month-long (December 1999 to February 2001) Central California Regional PM10/PM2.5
Air Quality Study (CRPAQS) consisted of acquiring speciated PM2.5
measurements at 38 sites representing urban, rural, and boundary environments in
the San Joaquin Valley air basin. The study's goal was to understand the
development of widespread pollution episodes by examining the spatial
variability of PM2.5,
ammonium nitrate (NH4NO3),
and carbonaceous material on annual, seasonal, and episodic timescales. It was
found that PM2.5
and NH4NO3
concentrations decrease rapidly as altitude increases, confirming that
topography influences the ventilation and transport of pollutants. High PM2.5
levels from November 2000 to January 2001 contributed to 50–75% of annual
average concentrations. Contributions from organic matter differed substantially
between urban and rural areas. Winter meteorology and intensive residential wood
combustion are likely key factors for the winter-nonwinter and urban-rural
contrasts that were observed. Short-duration measurements during the intensive
operating periods confirm the role of upper air currents on valley-wide
transport of NH4NO3.
Zones of representation for PM2.5
varied from 5 to 10 km for the urban Fresno and Bakersfield sites, and increased
to 15–20 km for the boundary and rural sites. Secondary NH4NO3
occurred region-wide during winter, spreading over a much wider geographical
zone than carbonaceous aerosol.
Keywords:
Fresno Supersite; PM2.5; ammonium nitrate; organic matter; spatial distribution.
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D10304, doi:10.1029/2005JD006522, 2006
Observations
of Asian air pollution in the free troposphere at Mount Bachelor Observatory
during the spring of 2004
Peter Weiss-Penzias
et.al.
Abstract
This paper
describes the chemical, aerosol, and meteorological measurements taken at Mount
Bachelor Observatory (MBO), a new mountaintop site in central Oregon, USA
(44.0°N, 121.7°W, 2763 m above mean sea level). During the initial campaign (28
March to 19 May 2004) we evaluated the utility of this location as a site to
observe the global atmosphere, especially the free troposphere (FT). We observed
some boundary layer (BL)/upslope flow during the daytime, which produced a
37–62% higher average water vapor mixing ratio (WV) compared to radiosonde data
taken from similar altitudes in western Oregon. However, recently subsided air
masses with low WV contained significantly elevated concentrations of carbon
monoxide (CO), total gaseous mercury (TGM), and ozone (O3),
(25 ppbv, 0.16 ng/m3,
and 13.9 ppbv, respectively), compared to periods with high-WV measurements.
These enhancements represent a significant influence from Asian long-range
transport (ALRT). One specific time period (“event”) on 25 April produced some
of the largest CO, TGM, O3,
and particulate scattering (σsp)
measurements ever seen along the West Coast due to ALRT. Enhancement ratios
between these species are consistent with the major source being Asian
industrial emissions. In particular, the ΔTGM/ΔCO enhancement ratio was
0.0045–0.0048 ng/m3/ppbv
for all ALRT events, similar to the value previously obtained from pollution
plumes directly downwind of east Asia. A smaller pollution event of North
American origin produced a ΔTGM/ΔCO value of only 0.0013 ng/m3/ppbv,
suggesting that the ΔTGM/ΔCO value is an effective tracer of ALRT. Finally,
thousands of kinematic back trajectories were calculated for each event to
evaluate sources and transport processes.
Keywords:
Asian air pollution; free troposphere; long-range transport.
Index Terms:
0368 Atmospheric Composition and Structure: Troposphere: constituent transport
and chemistry; 0341 Atmospheric Composition and Structure: Middle atmosphere:
constituent transport and chemistry (3334); 0345 Atmospheric Composition and
Structure: Pollution: urban and regional (0305, 0478, 4251); 0305 Atmospheric
Composition and Structure: Aerosols and particles (0345, 4801, 4906).
Time-dependent
inversion estimates of global biomass-burning CO emissions using Measurement of
Pollution in the Troposphere (MOPITT) measurements
Avelino F.
Arellano Jr. et.al.
Abstract
We present an
inverse-modeling analysis of CO emissions using column CO retrievals from the
Measurement of Pollution in the Troposphere (MOPITT) instrument and a global
chemical transport model (GEOS-CHEM). We first focus on the information content
of MOPITT CO column retrievals in terms of constraining CO emissions associated
with biomass burning and fossil fuel/biofuel use. Our analysis shows that
seasonal variation of biomass-burning CO emissions in Africa, South America, and
Southeast Asia can be characterized using monthly mean MOPITT CO columns. For
the fossil fuel/biofuel source category the derived monthly mean emission
estimates are noisy even when the error statistics are accurately known,
precluding a characterization of seasonal variations of regional CO emissions
for this source category. The derived estimate of CO emissions from biomass
burning in southern Africa during the June–July 2000 period is significantly
higher than the prior estimate (prior, 34 Tg; posterior, 13 Tg). We also
estimate that emissions are higher relative to the prior estimate in northern
Africa during December 2000 to January 2001 and lower relative to the prior
estimate in Central America and Oceania/Indonesia during April–May and
September–October 2000, respectively. While these adjustments provide better
agreement of the model with MOPITT CO column fields and with independent
measurements of surface CO from National Oceanic and Atmospheric Administration
Climate Monitoring and Diagnostics Laboratory at background sites in the
Northern Hemisphere, some systematic differences between modeled and measured CO
fields persist, including model overestimation of background surface CO in the
Southern Hemisphere. Characterizing and accounting for underlying biases in the
measurement model system are needed to improve the robustness of the top-down
estimates.
Keywords:
carbon monoxide; MOPITT; biomass burning; inverse modeling.
Index Terms:
0322 Atmospheric Composition and Structure: Constituent sources and sinks; 3260
Mathematical Geophysics: Inverse theory; 3360 Atmospheric Processes: Remote
sensing; 0490 Biogeosciences: Trace gases; 0368 Atmospheric Composition and
Structure: Troposphere: constituent transport and chemistry.
Chemical ozone
loss and related processes in the Antarctic winter 2003 based on Improved Limb
Atmospheric Spectrometer (ILAS)–II observations
Simone Tilmes
et.al.
Abstract
In this study,
ILAS-II (Improved Limb Atmospheric Spectrometer) measurements were used to
analyze chemical ozone loss during the entire Antarctic winter 2003, using the
tracer-tracer correlation technique. The temporal evolution of both the
accumulated local chemical ozone loss and the loss in column ozone in the lower
stratosphere is in step with increasing solar illumination. Half of the entire
loss in column ozone of 157 DU occurred during September 2003. By the end of
September 2003, almost the total amount of ozone was destroyed between 380 and
470 K. Further, ozone loss rates increased strongly during September for the
entire lower stratosphere. The values of accumulated ozone loss and ozone loss
rates are strongly dependent on altitude. Once ozone loss is saturated during
September, especially at latitudes between 380 and 420 K, ozone loss rates
decrease, and accumulated ozone loss can no longer increase. Moreover, at
altitudes above 470 K, accumulated ozone loss depends on the amount of PSCs
occurring during winter and spring. During September, ozone mixing ratios show a
large day to day variation. Box model simulations by the Chemical Lagrangian
Model of the Stratosphere (CLaMS) show that this is a result of the different
histories of the observed air masses. Further, the box model supports the
general evolution of ozone loss values during September as a result of the
strong increase of halogen catalyzed ozone destruction.
Keywords:
polar ozone loss; Antarctic winter 2003; ILAS-II observations.
Index Terms:
0340 Atmospheric Composition and Structure: Middle atmosphere: composition and
chemistry; 0341 Atmospheric Composition and Structure: Middle atmosphere:
constituent transport and chemistry (3334); 0325 Atmospheric Composition and
Structure: Evolution of the atmosphere (1610, 8125).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D09301, doi:10.1029/2005JD006407, 2006
Global impact
of road traffic on atmospheric chemical composition and on ozone climate forcing
Ulrike
Niemeier et.al.
Abstract
Automobile
emissions are known to contribute to local air pollution and to photochemical
smog in urban areas. The impact of road traffic on the chemical composition of
the troposphere at the global scale and on climate forcing is less well
quantified. Calculations performed with the chemical transport MOZART-2 model
show that the concentrations of ozone and its precursors (NOx, CO, and
hydrocarbons) are considerably enhanced in most regions of the Northern
Hemisphere in response to current surface traffic. During summertime in the
Northern Hemisphere, road traffic has increased the zonally averaged ozone
concentration by more than 10% in the boundary layer and in the extratropics by
approximately 6% at 500 hPa and 2.5% at 300 hPa. The summertime surface ozone
concentrations have increased by typically 1–5 ppbv in the remote regions and by
5–20 ppbv in industrialized regions of the Northern Hemisphere. The
corresponding ozone-related radiative forcing is 0.05 Wm−2.
In order to assess the sensitivity of potential changes in road traffic
intensity, two additional model cases were considered, in which traffic-related
emissions in all regions of the world were assumed to be on a per capita basis
the same as in Europe and in the United States, respectively. In the second and
most dramatic case, the surface ozone concentration increases by 30–50 ppbv
(50–100%) in south Asia as compared to the present situation. Under this
assumption, the global radiative forcing due to traffic-generated ozone reaches
0.27 Wm−2.
Keywords:
road traffic; atmospheric chemistry; climate forcing.
Index Terms:
0365 Atmospheric Composition and Structure: Troposphere: composition and
chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent
transport and chemistry; 0322 Atmospheric Composition and Structure: Constituent
sources and sinks; 0325 Atmospheric Composition and Structure: Evolution of the
atmosphere (1610, 8125).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D08104, doi:10.1029/2005JD006670, 2006
Relaxing the
well-mixed greenhouse gas approximation in climate simulations: Consequences for
stratospheric climate
C. L. Curry
et.al.
Abstract
The climatic
consequences of relaxing the uniform greenhouse gas (GHG) assumption in the
Canadian Centre for Climate Modelling and Analysis atmospheric general
circulation model are examined. A simple chemical loss parameterization for
nitrous oxide, methane, CFC-11, and CFC-12 is employed that includes
stratospheric water vapor production from methane oxidation. Multidecadal mean
distributions of these species are obtained that compare reasonably well with
UARS satellite observations of the stratosphere. The radiative impact of these
changes is a widespread cooling of the stratosphere (with a spatially averaged,
annual mean value of 0.6 K), compared to the model with specified uniform GHG
distributions. This cooling results from an approximate doubling of the amount
of middle to upper stratospheric moisture (as a result of methane oxidation) and
exceeds the radiatively induced warming due to decreases in the other GHGs.
Annual mean temperature changes of up to +8 K in the upper winter polar
stratosphere, by contrast, are dynamically induced because of increases in the
residual mean circulation and associated heating.
Keywords:
greenhouse gases; middle atmosphere; water vapor.
Index Terms:
0340 Atmospheric Composition and Structure: Middle atmosphere: composition and
chemistry; 3334 Atmospheric Processes: Middle atmosphere dynamics (0341, 0342);
3359 Atmospheric Processes: Radiative processes.
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D08303, doi:10.1029/2005JD006527, 2006
On the origin
of surface ozone and reactive nitrogen observed at a remote mountain site in the
northeastern Qinghai-Tibetan Plateau, western China
T. Wang et.al.
Abstract
Measurements of
surface ozone (O3),
carbon monoxide (CO), nitric oxide (NO), and total reactive nitrogen (NOy)
were made, in conjunction with other trace gases and fine aerosols, at Mount
Waliguan (WLG, 36.28°N, 100.90°E, 3816 m above sea level) in the late spring and
summer of 2003 in order to better understand the source(s) of ozone and other
chemically active gases over the remote highlands of western China. The average
mixing ratio (plus or minus standard deviation) was 58 (±9) ppbv for O3,
155 (±41) ppbv for CO, and 3.83 (±1.46) ppbv for NOy
in the spring phase, compared to a summer average value of 54 (±11) ppbv for O3,
125 (±36) ppbv for CO, and 3.60 (±1.13) ppbv for NOy.
The daytime (0800–1759 local time) average NO mixing ratios were 72 (±79) pptv
and 47 (±32) pptv in the spring and summer, respectively. The ozone mixing
ratios exhibited a minimum in late morning, while CO (and NOy
in spring) showed enhanced concentrations at night. The latter is in contrast to
the diurnal behaviors observed in many remote mountain sites. Analysis of 10-day
back trajectories using output from Fifth-Generation National Center for
Atmospheric Research/Penn State University Mesoscale Model (MM5) simulations
shows that air masses from the remote western regions contained the lowest level
of CO (121–129 ppbv) but had the highest O3
(60 ppbv), compared to the other three air mass groups that were impacted by
anthropogenic emissions in eastern/southern China and in the Indian
subcontinent. Ozone correlated negatively with CO (and water vapor content),
particularly during summer in air originating in the west, suggesting that the
high-ozone events were mostly derived from the downward transport of the upper
tropospheric air and not from anthropogenic pollution. An examination of in situ
chemical measurements (CO-NOy
correlation, ethyne/propane, and benzene/propane) as well as Measurements of
Pollution in the Troposphere (MOPITT) and Moderate-Resolution Imaging
Spectroradiometer (MODIS) remote-sensing data revealed some impacts from forest
fires in central Asia in the late spring of 2003 on the background
concentrations of trace gases over western China. While the O3
and CO levels at WLG are comparable to those at remote continental sites in
Europe and North America, the NOy
concentrations were substantially higher at WLG. The possible reasons for the
abnormally high NOy
levels are discussed. While more studies are needed to pin down these
sources/causes, including a possible contribution from long-range transport, we
believe that microbial processes in soils and animal wastes associated with
animal grazing were an important cause of the elevated NOy.
The observed daytime NO concentrations imply a net photochemical production of O3
at WLG, suggesting a positive contribution of photochemistry to the ozone
budget.
Keywords:
tropospheric ozone; reactive nitrogen; trajectory analysis; soil emission;
biomass burning; Tibetan Plateau.
Index Terms:
0365 Atmospheric Composition and Structure: Troposphere: composition and
chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent
transport and chemistry; 0478 Biogeosciences: Pollution: urban, regional and
global (0345, 4251).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D08302, doi:10.1029/2005JD006348, 2006
Role of
tropospheric ozone increases in 20th-century climate change
Drew Shindell
et.al.
Abstract
Human activities
have increased tropospheric ozone, contributing to 20th-century warming. Using
the spatial and temporal distribution of precursor emissions, we simulated
tropospheric ozone from 1890 to 1990 using the NASA Goddard Institute for Space
Studies (GISS) chemistry model. Archived three-dimensional ozone fields were
then used in transient GISS climate model simulations. This enables more
realistic evaluation of the impact of tropospheric ozone increases than prior
simulations using an interpolation between preindustrial and present-day ozone.
We find that tropospheric ozone contributed to the greater 20th-century warming
in the Northern Hemisphere extratropics compared with the tropics and in the
tropics compared with the Southern Hemisphere extratropics. Additionally, ozone
increased more rapidly during the latter half of the century than the former,
causing more rapid warming during that time. This is especially apparent in the
tropics and is consistent with observations, which do not show similar behavior
in the extratropics. Other climate forcings do not substantially accelerate
warming rates in the tropics relative to other regions. This suggests that
accelerated tropospheric ozone increases related to industrialization in the
developing world have contributed to the accelerated tropical warming. During
boreal summer, tropospheric ozone causes enhanced warming (>0.5°C) over polluted
northern continental regions. Finally, the Arctic climate response to
tropospheric ozone increases is large during fall, winter, and spring when
ozone's lifetime is comparatively long and pollution transported from
midlatitudes is abundant. The model indicates that tropospheric ozone could have
contributed about 0.3°C annual average and about 0.4°C–0.5°C during winter and
spring to the 20th-century Arctic warming. Pollution controls could thus
substantially reduce the rapid rate of Arctic warming.
Keywords:
tropospheric ozone; climate; Arctic.
Index Terms:
1610 Global Change: Atmosphere (0315, 0325); 1622 Global Change: Earth system
modeling (1225); 0365 Atmospheric Composition and Structure: Troposphere:
composition and chemistry; 0345 Atmospheric Composition and Structure:
Pollution: urban and regional (0305, 0478, 4251); 9315 Geographic Location:
Arctic region (0718, 4207).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D08206, doi:10.1029/2005JD006620, 2006
Dynamics of
the sulphate aerosol size distribution on a global scale
Xiaoyan Ma
et.al.
Abstract
Parameterizations for size-dependent aerosols have been implemented in the
Canadian Centre for Climate Modelling and Analysis (CCCma) atmospheric general
circulation model (AGCM). This new model version considers comprehensive
physical and chemical processes that are associated with the sulphate aerosol
size distribution, including nucleation, condensation, hygroscopic growth,
aqueous-phase chemistry, and dry and wet deposition. Results from in situ
surface and airborne observations and remote sensing were used to validate the
model. The comparisons give evidence for realistic sulphate size distributions
over the regions where sulphate is the dominant aerosol type. In agreement with
earlier published studies, it is found in sensitivity tests that the global
sulphate burden is predominantly affected by wet deposition. However, the mass
size distribution is mainly affected by coagulation, condensation, and
below-cloud scavenging on the global scale. There is only weak sensitivity of
the simulated mass size distribution to changes in in-cloud oxidation and the
efficiency of nucleation. It is shown that the low sensitivities are caused by a
compensating effect of coagulation in the former and low sensitivity of the mass
size distribution to changes in nucleation rate and condensation efficiency for
the latter case.
Keywords:
sulphate aerosol; size distribution; nucleation and condensation; coagulation;
dry deposition; wet deposition.
Index Terms:
0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801,
4906); 0321 Atmospheric Composition and Structure: Cloud/radiation interaction;
4801 Oceanography: Biological and Chemical: Aerosols (0305, 4906).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D08301, doi:10.1029/2005JD006338, 2006
Multimodel
ensemble simulations of present-day and near-future tropospheric ozone
D. S.
Stevenson et.al.
Abstract
Global
tropospheric ozone distributions, budgets, and radiative forcings from an
ensemble of 26 state-of-the-art atmospheric chemistry models have been
intercompared and synthesized as part of a wider study into both the air quality
and climate roles of ozone. Results from three 2030 emissions scenarios, broadly
representing “optimistic,” “likely,” and “pessimistic” options, are compared to
a base year 2000 simulation. This base case realistically represents the current
global distribution of tropospheric ozone. A further set of simulations
considers the influence of climate change over the same time period by forcing
the central emissions scenario with a surface warming of around 0.7K. The use of
a large multimodel ensemble allows us to identify key areas of uncertainty and
improves the robustness of the results. Ensemble mean changes in tropospheric
ozone burden between 2000 and 2030 for the 3 scenarios range from a 5% decrease,
through a 6% increase, to a 15% increase. The intermodel uncertainty (±1
standard deviation) associated with these values is about ±25%. Model outliers
have no significant influence on the ensemble mean results. Combining ozone and
methane changes, the three scenarios produce radiative forcings of −50, 180, and
300 mW m−2,
compared to a CO2
forcing over the same time period of 800–1100 mW m−2.
These values indicate the importance of air pollution emissions in short- to
medium-term climate forcing and the potential for stringent/lax control measures
to improve/worsen future climate forcing. The model sensitivity of ozone to
imposed climate change varies between models but modulates zonal mean mixing
ratios by ±5 ppbv via a variety of feedback mechanisms, in particular those
involving water vapor and stratosphere-troposphere exchange. This level of
climate change also reduces the methane lifetime by around 4%. The ensemble mean
year 2000 tropospheric ozone budget indicates chemical production, chemical
destruction, dry deposition and stratospheric input fluxes of 5100, 4650, 1000,
and 550 Tg(O3)
yr−1,
respectively. These values are significantly different to the mean budget
documented by the Intergovernmental Panel on Climate Change (IPCC) Third
Assessment Report (TAR). The mean ozone burden (340 Tg(O3))
is 10% larger than the IPCC TAR estimate, while the mean ozone lifetime (22
days) is 10% shorter. Results from individual models show a correlation between
ozone burden and lifetime, and each model's ozone burden and lifetime respond in
similar ways across the emissions scenarios. The response to climate change is
much less consistent. Models show more variability in the tropics compared to
midlatitudes. Some of the most uncertain areas of the models include treatments
of deep tropical convection, including lightning NO
x
production; isoprene emissions from vegetation and isoprene's
degradation chemistry; stratosphere-troposphere exchange; biomass burning; and
water vapor concentrations.
Keywords:
intercomparison; modeling; tropospheric ozone.
Index Terms:
0365 Atmospheric Composition and Structure: Troposphere: composition and
chemistry; 0368 Atmospheric Composition and Structure: Troposphere: constituent
transport and chemistry; 0345 Atmospheric Composition and Structure: Pollution:
urban and regional (0305, 0478, 4251); 0322 Atmospheric Composition and
Structure: Constituent sources and sinks.
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D07106, doi:10.1029/2005JD005850, 2006
Observations
of extremely low tropopause temperature over the Indian tropical region during
monsoon and postmonsoon months: Possible implications
A. R. Jain
et.al.
Abstract
The present
study examines the possible role of the “freeze and dry effect,” which is
generally believed to occur when the tropopause temperature is lower than 191 K.
So far, there is observational evidence to support the role of the “freeze-dry
mechanism” over the western Pacific region, in particular, over Indonesia. The
paper presents observations from four intensive radiosonde/GPS sonde campaigns
during summer monsoon and postmonsoon seasons from a number of stations in the
tropical Indian region. Observations provide clear evidence of the existence of
tropopause temperature lower than 191 K. Analysis suggests that cold tropopause
occurs over a wide area of 5° × 5° in latitude and longitude and more often
around local midnight hours. Cold tropopause temperature appears to occur more
often over the ocean as compared to the coastal stations. The observations at
the coastal stations show that on the days of low temperature, the tropopause is
cooler by ∼8 K than the climatological temperature for the Indian equatorial
region and ∼3.5 K from the mean of all observations. It is noted that on the
days of observed cold tropopause, the lapse rate just below the tropopause is
closer to the dry adiabatic lapse rate. This indicates a rapid cooling in a
narrow height range. The present observations thus provide evidence that the
freeze-dry mechanism could be operating over a wide area, which includes the
Indian tropical region. The possible role of atmospheric convection and also of
atmospheric waves in producing low tropopause temperatures is examined and
discussed.
Keywords:
tropical tropopause; critical temperature; atmospheric convection; thin clouds
in upper troposphere; stratospheric dehydration; stratosphere-troposphere
exchange.
Index Terms:
3362 Atmospheric Processes: Stratosphere/troposphere interactions; 3374
Atmospheric Processes: Tropical meteorology; 0368 Atmospheric Composition and
Structure: Troposphere: constituent transport and chemistry.
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D06205, doi:10.1029/2004JD005759, 2006
Influence of
relative humidity upon pollution and dust during ACE-Asia: Size distributions
and implications for optical properties
S. G. Howell
et.al.
Abstract
An extensive set
of aerosol physical and optical measurements was taken over the waters east of
Asia during the Aerosol Characterization Experiment-Asia (ACE-Asia) project in
the spring of 2001. Dust storms upwind of the study area combined with intense
pollution plumes from coastal cities yielded an opportunity to examine both
types of aerosol, in isolation and as they interacted. Scattering calculated
from aerosol size distributions measured with an optical particle counter agreed
well with simultaneous nephelometer measurements. We periodically heated sample
air to evaporate sulfates and organic material. The change in volume upon
heating agreed well with simultaneous measurements of aerosol composition. This
volatile material was distributed on dust in rough proportion to surface area.
Here we use the particle size and composition data to improve estimates of
scattering at ambient humidity and to examine the effects of mixing on the
optical properties of both pollution and dust aerosols. The presence of dust
results in uptake of soluble and condensible species onto its surface and
thereby reduces the mass scattering efficiency of the pollution aerosol by 50%
and suppresses the change in scattering due to relative humidity (f(RH))
by up to 35%.
Keywords:
ACE-Asia; aerosols; humidity.
Index Terms:
0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801,
4906); 0345 Atmospheric Composition and Structure: Pollution: urban and regional
(0305, 0478, 4251); 0360 Atmospheric Composition and Structure: Radiation:
transmission and scattering; 0365 Atmospheric Composition and Structure:
Troposphere: composition and chemistry
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D06304, doi:10.1029/2005JD006237, 2006
Estimates of
global biomass burning emissions for reactive greenhouse gases (CO, NMHCs, and
NOx)
and CO2
Atul K. Jain
Abstract
Open fire
biomass burning and domestic biofuel burning (e.g., cooking, heating, and
charcoal making) algorithms have been incorporated into a terrestrial ecosystem
model to estimate CO2
and key reactive GHGs (CO, NO
x
, and NMHCs) emissions for the year 2000. The emissions are
calculated over the globe at a 0.5° × 0.5° spatial resolution using tree density
imagery, and two separate sets of data each for global area burned and land
clearing for croplands, along with biofuel consumption rate data. The estimated
global and annual total dry matter (DM) burned due to open fire biomass burning
ranges between 5221 and 7346 Tg DM/yr, whereas the resultant emissions ranges
are 6564–9093 Tg CO2/yr,
438–568 Tg CO/yr, 11–16 Tg NO
x
/yr (as NO), and 29–40 Tg NMHCs/yr. The results indicate that
land use changes for cropland is one of the major sources of biomass burning,
which amounts to 25–27% (CO2),
25 –28% (CO), 20–23% (NO), and 28–30% (NMHCs) of the total open fire biomass
burning emissions of these gases. Estimated DM burned associated with domestic
biofuel burning is 3,114 Tg DM/yr, and resultant emissions are 4825 Tg CO2/yr,
243 Tg CO/yr, 3 Tg NO
x
/yr, and 23 Tg NMHCs/yr. Total emissions from biomass burning are
highest in tropical regions (Asia, America, and Africa), where we identify
important contributions from primary forest cutting for croplands and domestic
biofuel burning.
Keywords:
biomass; biofuel; emission.
Index Terms:
0365 Atmospheric Composition and Structure: Troposphere: composition and
chemistry; 1615 Global Change: Biogeochemical cycles, processes, and modeling
(0412, 0414, 0793, 4805, 4912); 1631 Global Change: Land/atmosphere interactions
(1218, 1843, 3322).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D06301, doi:10.1029/2005JD006455, 2006
Carbon
emissions from a temperate peat fire and its relevance to interannual
variability of trace atmospheric greenhouse gases
Benjamin
Poulter et.al.
Abstract
The contribution
of wildfire in peatlands outside of boreal and tropical regions to interannual
variability of global carbon emissions has been relatively little studied. There
are 0.19 to 0.88 million km2
of localized peat deposits in the temperate zone (30–50° latitude) where
drainage and climate change may affect the status of this potentially large
carbon pool. For example, in the coastal plain of North Carolina, USA, where
wildfire is common, over 325 teragrams of carbon (Tg C) are stored in peat
deposits up to 5 m deep. We estimated carbon emissions for a temperate peatland
fire in North Carolina using remote sensing to reconstruct burn severity and
topographic lidar to constrain peat burn depths. Total carbon emissions for the
fire ranged from 1 to 3.8 Tg, with spatially heterogeneous patterns of carbon
fluxes (0.2 to 11 kg C m−2)
responding to variation in vegetation type, peat burn depth, soil substrate
(mineral or organic), and fire severity. To maintain a carbon sink in this
region at the current rates of carbon sequestration (0.109 to 0.127 kg C m−2
yr−1)
we estimated a fire return interval of greater than 20–80 years. Continued
drainage and future drought could decrease the fire return interval to less than
20 years or increase peat burn depths thereby converting these peatlands into a
net carbon source. On a global scale, this study suggests that temperate
peatland fires may emit up to 0.32 petagrams of carbon during drought years, a
significant contribution to interannual greenhouse gas variability.
Keywords:
carbon; fire; peat.
Index Terms:
0426 Biogeosciences: Biosphere/atmosphere interactions (0315); 0428
Biogeosciences: Carbon cycling (4806); 0439 Biogeosciences: Ecosystems,
structure and dynamics (4815); 0497 Biogeosciences: Wetlands (1890); 1640 Global
Change: Remote sensing (1855).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D05109, doi:10.1029/2005JD006290, 2006
Global
observed changes in daily climate extremes of temperature and precipitation
L. V.
Alexander et.al
Abstract
A suite of
climate change indices derived from daily temperature and precipitation data,
with a primary focus on extreme events, were computed and analyzed. By setting
an exact formula for each index and using specially designed software, analyses
done in different countries have been combined seamlessly. This has enabled the
presentation of the most up-to-date and comprehensive global picture of trends
in extreme temperature and precipitation indices using results from a number of
workshops held in data-sparse regions and high-quality station data supplied by
numerous scientists world wide. Seasonal and annual indices for the period
1951–2003 were gridded. Trends in the gridded fields were computed and tested
for statistical significance. Results showed widespread significant changes in
temperature extremes associated with warming, especially for those indices
derived from daily minimum temperature. Over 70% of the global land area sampled
showed a significant decrease in the annual occurrence of cold nights and a
significant increase in the annual occurrence of warm nights. Some regions
experienced a more than doubling of these indices. This implies a positive shift
in the distribution of daily minimum temperature throughout the globe. Daily
maximum temperature indices showed similar changes but with smaller magnitudes.
Precipitation changes showed a widespread and significant increase, but the
changes are much less spatially coherent compared with temperature change.
Probability distributions of indices derived from approximately 200 temperature
and 600 precipitation stations, with near-complete data for 1901–2003 and
covering a very large region of the Northern Hemisphere midlatitudes (and parts
of Australia for precipitation) were analyzed for the periods 1901–1950,
1951–1978 and 1979–2003. Results indicate a significant warming throughout the
20th century. Differences in temperature indices distributions are particularly
pronounced between the most recent two periods and for those indices related to
minimum temperature. An analysis of those indices for which seasonal time series
are available shows that these changes occur for all seasons although they are
generally least pronounced for September to November. Precipitation indices show
a tendency toward wetter conditions throughout the 20th century.
Keywords:
climate extremes; observations; temperature; precipitation; trends.
Index Terms:
1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513); 3305
Atmospheric Processes: Climate change and variability (1616, 1635, 3309, 4215,
4513); 3354 Atmospheric Processes: Precipitation (1854).
JOURNAL OF
GEOPHYSICAL RESEARCH, VOL. 111, D05305, doi:10.1029/2005JD006512, 2006
Ozone, water
vapor, and temperature in the upper tropical troposphere: Variations over a
decade of MOZAIC measurements
Sarah E.
Bortz et.al.
Earth System
Science Department, University of California, Irvine, Irvine, California, USA
Abstract
The MOZAIC
(Measurement of Ozone and Water Vapor by Airbus In-service Aircraft) program (Marenco
et al., 1998) has archived in situ measurements of temperature, water vapor, and
ozone from August 1994 to December 2003. We analyze the trends, seasonality, and
interannual variability of these quantities at aircraft cruise levels (7.7–11.3
km) within the tropics (20°S–20°N). Mean lapse rates for temperature and
log(water vapor) are nearly identical in both tropics. The root-mean-square
variance in temperature over cruise levels, seasons, and years is small, ≤1°C.
The seasonal range in water vapor, a factor of 2.5, is much larger than expected
from the seasonal range in temperature (1.7°C) if the two scale with the lapse
rate relation or the Clausius-Clapeyron equation. The mean ozone abundance in
the region sampled is 45 ppb in the north tropics and 50 ppb in the south
tropics. This 112-month period shows a clearly linear increase in ozone over the
north tropics with a trend fit of 1.12 ± 0.05 ppb/yr. In the south tropics,
which has a large seasonal range of over 25 ppb, the trend is less obvious but
still robust, 1.03 ± 0.08 ppb/yr. These trends in the upper troposphere are
twice as large as reported for surface ozone over the tropical Atlantic (Lelieveld
et al., 2004), but this pattern of ozone increases is consistent with projected
increases driven by industrial emissions.
Keywords:
upper tropical troposphere; tropospheric ozone trends; MOZAIC.
Index
Terms:
0365
Atmospheric Composition and Structure: Troposphere: composition and chemistry;
0368 Atmospheric Composition and Structure: Troposphere: constituent transport
and chemistry; 1610 Global Change: Atmosphere (0315, 0325); 3399 Atmospheric
Processes: General or miscellaneous.
Modeling of episodic particulate matter events using a 3-D air quality model
with fine grid: Applications to a pair of cities in the US/Mexico border
Yu-Jin Choi, Peter Hyde b and H.J.S.
Fernando a
aEnvironmental Fluid Dynamics Program, Department of Mechanical and
Aerospace Engineering, Arizona State University, Tempe, AZ 85285, USA
bArizona Department of Environmental Quality, Phoenix, AZ 85102,
USA
Received 15 November 2005; revised 3 March 2006; accepted 7 April 2006.
Available online 23 June 2006.
Abstract
High (episodic)
particulate matter (PM) events over the sister cities of Douglas (AZ) and Agua
Prieta (Sonora), located in the US–Mexico border, were simulated using the 3D
Eulerian air quality model, MODELS-3/CMAQ. The best available input
information was used for the simulations, with pollution inventory specified
on a fine grid. In spite of inherent uncertainties associated with the
emission inventory as well as the chemistry and meteorology of the air quality
simulation tool, model evaluations showed acceptable PM predictions, while
demonstrating the need for including the interaction between meteorology and
emissions in an interactive mode in the model, a capability currently
unavailable in MODELS-3/CMAQ when dealing with PM. Sensitivity studies on
boundary influence indicate an insignificant regional (advection) contribution
of PM to the study area. The contribution of secondary particles to the
occurrence of high PM events was trivial. High PM episodes in the study area,
therefore, are purely local events that largely depend on local meteorological
conditions. The major PM emission sources were identified as vehicular
activities on unpaved/paved roads and wind-blown dust. The results will be of
immediate utility in devising PM mitigation strategies for the study area,
which is one of the US EPA-designated non-attainment areas with respect to PM.
Keywords:
Particulate matter; 3D air quality
model; Dust; High winds; US/Mexico border; Semi-arid area
A
high-resolution NOx emission factor model for North American
motor vehicles
Rakesh B. Singh1, a, and James J.
Sloan a,
aWaterloo Centre for Atmospheric Sciences, University of Waterloo,
Waterloo, Ont., Canada N2L 3G1
Received 26 October 2005; accepted 9 April 2006. Available online 21 June
2006.
Abstract
Criteria air contaminant
inventories in Canada show that approximately 60% of NOx is
produced from the transportation sector alone. NO2, which is
present at higher levels in the winter than in the summer, has been identified
as the main pollutant responsible for non-traumatic deaths and hospitalization
in Canadian cities. Therefore, accurate emission estimates of
vehicle-generated NOx are needed, especially at the
micro-scale level. The MOBILE
emission model, which is widely used in Canada, provides only aggregated
emission factors at very low resolution. Many studies have shown that
MOBILE
emission data are unreliable for many applications—particularly for
air-quality modelling. In contrast to the aggregated nature of the
MOBILE
data, the new disaggregated model, MicroFacNOx, uses
time-dependent site-specific vehicle fleet information to calculate emission
factors at high spatial and temporal resolution. MicroFacNOx
evaluation in a range of traffic fleet and meteorological conditions shows
very encouraging results. Sensitivity analyses of the model reveal that its
results depend on traffic fleet composition, speed and ambient temperature.
MicroFacNOx results are suitable for use in human exposure
assessment and by city planners in decision making for growth management. The
effect of vehicle-related NOx on ozone in the vicinity of a
large urban area is a good example of an unsolved problem that would benefit
from the MicroFacNOx modelling approach.
Keywords:
Micro-scale; Emission model; Mobile
sources; Air-quality model; Human exposure
Comparison of oil and fuel particle chemical signatures
with particle emissions from heavy and light duty vehicles
Matthew T. Spencer, Laura G. Shields, David A.
Sodeman a, Stephen M. Toner a and Kimberly A. Prather
a,
aDepartment of Chemistry and Biochemistry, University of
California, San Diego, La Jolla, CA 92093-0314, USA
Received 13 October 2005; revised 28 February 2006; accepted 9 April 2006.
Available online 30 June 2006.
Abstract
In order to establish
effective vehicle emission control strategies, efforts are underway to perform
studies which provide insight into the origin of the source of vehicle
particle emissions. In this study, the mass spectral signatures of individual
particles produced from atomized auto and diesel oil and fuel samples were
obtained using aerosol time-of-flight mass spectrometry (ATOFMS). The major
particle types produced by these samples show distinct chemistry, falling into
several major categories for each sample. Lubricating oils contain calcium and
phosphate based additives and although the additives are present in low
abundance (1–2% by mass), calcium and phosphate ions dominate the mass spectra
for all new and used oil samples. Mass spectra from used oil contain more
elemental carbon (EC) and organic carbon (OC) marker ions when compared to new
oils and exhibit a very high degree of similarity to heavy duty diesel vehicle
(HDDV) exhaust particles sampled by an ATOFMS. Fewer similarities exist
between the used oil particles and light duty vehicle (LDV) emissions. Diesel
and unleaded fuel mass spectra contain polycyclic aromatic hydrocarbon (PAH)
molecular ions, as well as intense PAH fragment ions 25(C2H)−,
49(C4H)−, and inorganic ions 23Na+,
39K+, 95(PO4)−.
Unleaded fuel produced spectra which contained Na+ and K+;
likewise, LDV particle emission spectra also contained Na+ and K+.
Comparing oil and fuel particle signatures with HDDV and LDV emissions
enhances our ability to differentiate between these sources and understand the
origin of specific marker ions from these major ambient particle sources.
Keywords:
Aerosol; ATOFMS; Diesel; Oil; Climate
Bottom-up estimate of biomass burning in mainland China
Xiaoyuan Yan a, b, , Toshimasa Ohara
b, c and Hajime Akimoto a
aInstitute of Soil Science, Chinese Academy of Sciences, Nanjing
210008, PR China
bFrontier Research Center for Global Change, Japan Agency for
Marine-Earth, Science and Technology, Shaowa-machi, 3173-25 Yokohama, Japan
cNational Institute of Environmental Sciences, Onogawa 16-2,
Tsukuba, Japan
Received 14 March 2006; accepted 11 April 2006. Available online 16 June
2006.
Abstract
To assess the
contribution of biomass burning to the emissions of atmospheric trace species
in China, we estimated various biomass-burning activities using statistical
data, survey data, expert estimates and a satellite data set. Fuel wood and
crop residue burned as fuel and in the field are the major sources of biomass
burning in China, accounting for nearly 90% of the total biomass burning on
dry weight base. Field burning of crop residue estimated from satellite burned
area is less than 1% of that estimated from ground survey data; because of
this and because biofuel is burned indoor, the majority of biomass burning in
China is not seeable from satellite. Statistical data showed that the
occurrence of forest fire in China has decreased dramatically since the 1980s;
however, the forest fire area detected by satellites in 2000 was 13 times that
shown by statistics. Grassland fires are a minor source of biomass burning in
China. We estimated carbon monoxide (CO) emission from open biomass burning
(field burning of crop residue and forest and grassland fires) to be 16.5 Tg
in 2000, with a 90% uncertainty range of 3.4–34 Tg. Uncertainties in CO
emission factors, especially for field burning of crop residue, contributed
much more to the variance than those in the activity data. This suggests the
importance of narrowing the uncertainty range of emission factors.
Keywords:
Biofuel; Forest fires; Fate of crop
residue; Field burning; Emissions
Comparison of spatial and temporal variations of aerosol optical thickness and
particulate matter over Europe
R.B.A. Koelemeijer, a, , C.D. Homan1,
a and J. Matthijsen a
aNetherlands Environmental Assessment Agency (MNP), P.O. Box 303,
3720 AH Bilthoven, The Netherlands
Received 8 December 2005; revised 13 April 2006; accepted 20 April 2006.
Available online 21 June 2006.
Abstract
To mitigate the harmful
effect of particulates on human health, EU wide limit values for
concentrations have been set. However, particulate matter (PM) measurements
suffer from substantial uncertainty because PM is difficult to measure on a
routine basis, which is necessary for monitoring compliance. Moreover,
different measurement and calibration methods are used in the many air-quality
networks in Europe. Consequently, the understanding of PM levels over Europe
as a whole is rather limited. We aim to improve this situation by making use
of additional information from satellite observations. As a first step, we
present here a comparison for Europe of spatio-temporal variations of PM with
those of aerosol optical thickness (AOT) measured by the MODIS satellite
instrument, for 2003. The MODIS measurements clearly show the major aerosol
source regions in Northern Italy, Southern Poland, and the
Belgium/Netherlands/Ruhr area, as well as individual large cities and
industrialised valleys (Rhone, Danube). The spatial correlation between yearly
average PM10 and AOT is 0.6 for rural background stations.
The seasonal variation
of AOT and PM is distinctly different, however. Throughout most of Europe, the
AOT as measured by MODIS has a clear minimum in the winter months. The
seasonal variation in PM differs across Europe, and at many locations the
seasonal variation is less marked than that of the AOT. Consequently, the
correlation between one-year time-series of AOT with PM10/PM2.5 is low (0.3).
The correlation between PM and AOT is improved when the AOT is divided by the
boundary layer height and, to a lesser extent, when it is corrected for growth
of aerosols with relative humidity. In that case, the average correlation is
0.5 (PM10) and 0.6 (PM2.5), averaged over rural and (sub) urban background
stations. These results indicate that AOT measurements can be useful to
improve the monitoring of PM distributions over Europe.
Keywords:
Particulate matter; AIRBASE; Aerosol
optical thickness; MODIS; Europe
Inventory of black carbon and organic carbon emissions from China
Guoliang Cao a, b,, Xiaoye Zhang
a and Fangcheng Zheng b
aKey Laboratory of Atmospheric Chemistry, Centre for Atmosphere
Watch & Services, CMA; Chinese Academy of Meteorological Sciences, Beijing
100081, PR China
bSchool of environmental and municipal engineering, Xi’an
University of Architecture & Technology, Xi’an, 710055, PR China
Received 28 October 2005; revised 15 May 2006; accepted 25 May 2006.
Available online 24 July 2006.
Abstract
We present detailed
high-resolution emission inventories of black carbon (BC) and organic carbon (OC)
from China in the year 2000. The latest fuel consumption data, including
fossil and biomass fuels and socio-economic statistics were obtained from
government agencies, mostly at the county level. Some new emission factors (EFs)
from local measurements also were used. National and regional summaries of
emissions are presented, and girded emissions at 0.2°×0.2° resolution are
shown. Our calculated emissions were 1500 Gg for BC and 4100 Gg for OC, mainly
due to the burning of coal and biofuels. The carbonaceous aerosol emissions
estimated here are higher than those in previous studies, mainly because coal
burning by rural industries and residences were previously underestimated.
More carbonaceous aerosols are emitted from eastern China than western China.
A strong seasonal dependence is observed for emissions, with peaks in May and
October and low emissions in April and July; this seasonality is mainly due to
patterns in residential heating and agriculture waste open burning.
Keywords:
Carbonaceous aerosol; China; Emission
inventory; Seasonality
Satellite remote sensing of particulate matter and air quality assessment over
global cities
Pawan Gupta a, Sundar A. Christopher
a,, Jun Wang b, Robert Gehrig c, Yc Lee
d and Naresh Kumar e, f
aDepartment of Atmospheric Sciences, The University of Alabama in
Huntsville, Huntsville, AL, USA
bNOAA/UCAR Postdoctoral Fellow, Department of Earth and Planetary
Science, Harvard University, MA, USA
cEMPA, Laboratory for Air Pollution, Dubendorf, Switzerland
dGreen Council, New World Tower 1, Hong Kong
eUniversity of Iowa, Iowa City, IA, USA
fBrown University, Providence, RI, USA
Received 31 October 2005; revised 8 March
2006; accepted 10 March 2006. Available online 20 July 2006.
Abstract
Using 1 year of aerosol
optical thickness (AOT) retrievals from the MODerate resolution Imaging
Spectro-radiometer (MODIS) on board NASA's Terra and Aqua satellite along with
ground measurements of PM2.5 mass concentration, we assess
particulate matter air quality over different locations across the global
urban areas spread over 26 locations in Sydney, Delhi, Hong Kong, New York
City and Switzerland. An empirical relationship between AOT and PM2.5
mass is obtained and results show that there is an excellent correlation
between the bin-averaged daily mean satellite and ground-based values with a
linear correlation coefficient of 0.96. Using meteorological and other
ancillary datasets, we assess the effects of wind speed, cloud cover, and
mixing height (MH) on particulate matter (PM) air quality and conclude that
these data are necessary to further apply satellite data for air quality
research. Our study clearly demonstrates that satellite-derived AOT is a good
surrogate for monitoring PM air quality over the earth. However, our analysis
shows that the PM2.5–AOT relationship strongly depends on aerosol
concentrations, ambient relative humidity (RH), fractional cloud cover and
height of the mixing layer. Highest correlation between MODIS AOT and PM2.5
mass is found under clear sky conditions with less than 40–50% RH and when
atmospheric MH ranges from 100 to 200 m. Future remote sensing sensors such as
Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)
that have the capability to provide vertical distribution of aerosols will
further enhance our ability to monitor and forecast air pollution. This study
is among the first to examine the relationship between satellite and ground
measurements over several global locations.
Keywords:
Aerosols; Satellite remote sensing; Air quality;
Mega cities
A
preliminary assessment of major air pollutants in the city of Suzhou, China
Francesca Costabile a, , Giuliano
Bertoni a, Franco Desantis a, Fenjuan Wang a,
Hong Weimin b, Liu Fenglei b and Ivo Allegrini a
aC.N.R.—IIA, Via Salaria, Km 29,3; 00016, Monterotondo Scalo, Roma,
Italy
bEnvironmental Monitoring Centre, Suzhou, PR China
Received 6 September 2005; revised 9 May 2006; accepted 16 May 2006.
Available online 18 July 2006.
Abstract
Nitrogen oxides (NO2
and NOx), sulphur dioxide (SO2), and benzene,
toluene, xylene (BTX) in ambient air were preliminarily assessed, by diffusive
sampling technique, in 2003 through three measurement campaigns at 100
locations in the Chinese city of Suzhou. Statistical analysis of space series
so-generated was performed to infer source contributions and frequency
distributions (FD). It was found that nitrogen oxides, benzene and xylene were
mostly emitted from motor vehicles; in contrast, industrial sources were a
major contributor to sulfur and toluene pollution. Normal FD (NFD) described
significantly SO2 in summer and NO2 and NOx
in autumn (95% confidence interval); on the contrary, BTX presented a most
peculiar FD rather different to the NFD. Lognormal distribution was often
unacceptable. Predominant factors influencing FDs and its normality were found
to be associated to those elements conditioning air pollutant diffusion:
meteorology (wind speed and direction), relevant emission sources (especially
for toluene), emission seasonality (mainly for SO2 and NOx),
and photochemistry (mainly for NO2 and xylene).
Keywords:
Urban air pollution; Frequency
distribution; Normality test; BTX; China
Aromatic hydrocarbons emissions in diesel and biodiesel
exhaust
Sérgio Machado Corrêa a,
and Graciela Arbilla b
aUniversidade do Estado do Rio de Janeiro, Faculdade de Tecnologia,
27523-000, Resende, Brazil
bUniversidade Federal do Rio de Janeiro, Instituto de Química,
21949-900, Rio de Janeiro, Brazil
Received 9 March 2006; revised 27 May 2006; accepted 28 May 2006.
Available online 18 July 2006.
Abstract
Regulated emissions of
biodiesel blends are reasonably well documented in several works,
non-regulated emissions, on the contrary, lack research. In this work, mono-
and polycyclic aromatic hydrocarbons (MAHs and PAHs, respectively) emission
tests were performed with a heavy-duty diesel engine, fueled with pure diesel
(D) and biodiesel blends (v/v) of 2% (B2), 5% (B5) and 20% (B20%). The main
objective of this study is to investigate the effect of the biodiesel addition
on the emission profile of MAHs and PAHs. The tests were conducted using a six
cylinder heavy-duty engine, typical of the Brazilian fleet of urban buses, in
a steady-state condition under 1500 rpm. The PAHs were sampled with Teflon
filters and XAD-2 cartridges and were identified by gaseous chromatograph
coupled to a mass spectrometer (GC/MS) and quantified by flame ionization
detection (GC/FID). The MAHs were sampled with active charcoal cartridges and
analyzed by GC/FID. Both MAHs and PAHs filters and cartridges were extracted
with dichloromethane in an ultrasonic bath. Ten PAHs and eight MAHs were
identified and the average reduction of MAHs was 4.2% (B5), 8.2% (B5), and
21.1% (B20). The average reduction for PAHs was 2.7% (B2), 6.3% (B5), and
17.2% (B20). However, some PAHs and MAHs emissions increased because of/due to
the biodiesel blends like phenanthrene, ethyl benzene, and trimethyl benzenes.
Keywords:
Polycyclic aromatic hydrocarbons;
Mono-aromatic hydrocarbons; Vehicular emissions; Biodiesel; Diesel
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