Episodes of cross-polar transport in the Arctic troposphere during July 2008 as seen from models, satellite, and aircraft observations

Abstract. During the POLARCAT summer campaign in 2008, two episodes (2–5 July and 7–10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes from Siberian forest fires and anthropogenic sources in East Asia embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART and the Eulerian chemical transport model TOMCAT with retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite. The main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the model simulations. However, finer-scale structures are too quickly diffused in the Eulerian model. Applying the IASI averaging kernels to the model data is essential for a meaningful comparison. Using aircraft data as a reference suggests that the satellite data are biased high, while TOMCAT is biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual pollution state of the Arctic atmosphere.

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Episodes of cross-polar transport in the Arctic troposphere during July 2008 as seen from models, satellite, and aircraft observations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-26361-2010 ◽

2010 ◽

Vol 10 (11) ◽

pp. 26361-26410 ◽

Cited By ~ 4

Author(s):

H. Sodemann ◽

M. Pommier ◽

S. R. Arnold ◽

S. A. Monks ◽

K. Stebel ◽

...

Keyword(s):

Transport Model ◽

Chemical Transport ◽

The Arctic ◽

Actual State ◽

Chemical Transport Model ◽

Horizontal Structure ◽

Model Simulations ◽

Aircraft Observations ◽

Total Column ◽

Aircraft Data

Abstract. During the POLARCAT summer campaign in 2008, two episodes (2–5 July and 7–10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART, the Eulerian chemical transport model TOMCAT, and for numerical aspects the limited-area chemical transport model WRF-Chem. Retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite are used as a total column CO reference for the two simulations. Main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the model simulations. However, finer-scale structures are too quickly diffused in the Eulerian models. Aircraft data suggest that the satellite data are biased high, while TOMCAT and WRF-Chem are biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual state of the atmosphere.

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Chemical ozone loss and ozone mini-hole event during the Arctic winter 2010/2011 as observed by SCIAMACHY and GOME-2

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-3247-2014 ◽

2014 ◽

Vol 14 (7) ◽

pp. 3247-3276 ◽

Cited By ~ 16

Author(s):

R. Hommel ◽

K.-U. Eichmann ◽

J. Aschmann ◽

K. Bramstedt ◽

M. Weber ◽

...

Keyword(s):

Transport Model ◽

Polar Vortex ◽

The Arctic ◽

Optical Absorption Spectroscopy ◽

Late Winter ◽

Total Column Ozone ◽

Bromine Oxide ◽

Ozone Loss ◽

Catalytic Cycles ◽

Total Column

Abstract. Record breaking loss of ozone (O3) in the Arctic stratosphere has been reported in winter–spring 2010/2011. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and polar stratospheric clouds (PSC) retrieved from measurements made by SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric CHartography) on-board Envisat (Environmental Satellite), as well as total column ozone amount, retrieved from the measurements of GOME-2 (Global Ozone Monitoring Experiment) on MetOp-A (Meteorological Experimental Satellite). Similarly we use the retrieved data from DOAS (Differential Optical Absorption Spectroscopy) measurements made in Ny-Ålesund (78.55° N, 11.55° E). A chemical transport model (CTM) has been used to relate and compare Arctic winter–spring conditions in 2011 with those in the previous year. In late winter–spring 2010/2011 the chemical ozone loss in the polar vortex derived from SCIAMACHY observations confirms findings reported elsewhere. More than 70% of O3 was depleted by halogen catalytic cycles between the 425 and 525 K isentropic surfaces, i.e. in the altitude range ~16–20 km. In contrast, during the same period in the previous winter 2009/2010, a typical warm Arctic winter, only slightly more than 20% depletion occurred below 20 km, while 40% of O3 was removed above the 575 K isentrope (~23 km). This loss above 575 K is explained by the catalytic destruction by NOx descending from the mesosphere. In both Arctic winters 2009/2010 and 2010/2011, calculated O3 losses from the CTM are in good agreement to our observations and other model studies. The mid-winter 2011 conditions, prior to the catalytic cycles being fully effective, are also investigated. Surprisingly, a significant loss of O3 around 60%, previously not discussed in detail, is observed in mid-January 2011 below 500 K (~19 km) and sustained for approximately 1 week. The low O3 region had an exceptionally large spatial extent. The situation was caused by two independently evolving tropopause elevations over the Asian continent. Induced adiabatic cooling of the stratosphere favoured the formation of PSC, increased the amount of active chlorine for a short time, and potentially contributed to higher polar ozone loss later in spring.

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Record-breaking ozone loss in the Arctic winter 2010/2011: comparison with 1996/1997

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-7073-2012 ◽

2012 ◽

Vol 12 (15) ◽

pp. 7073-7085 ◽

Cited By ~ 34

Author(s):

J. Kuttippurath ◽

S. Godin-Beekmann ◽

F. Lefèvre ◽

G. Nikulin ◽

M. L. Santee ◽

...

Keyword(s):

Transport Model ◽

Chemical Transport ◽

The Arctic ◽

Altitude Range ◽

Chemical Transport Model ◽

Model Simulations ◽

Ozone Loss ◽

Elevated Ozone ◽

Record Value ◽

First Time

Abstract. We present a detailed discussion of the chemical and dynamical processes in the Arctic winters 1996/1997 and 2010/2011 with high resolution chemical transport model (CTM) simulations and space-based observations. In the Arctic winter 2010/2011, the lower stratospheric minimum temperatures were below 195 K for a record period of time, from December to mid-April, and a strong and stable vortex was present during that period. Simulations with the Mimosa-Chim CTM show that the chemical ozone loss started in early January and progressed slowly to 1 ppmv (parts per million by volume) by late February. The loss intensified by early March and reached a record maximum of ~2.4 ppmv in the late March–early April period over a broad altitude range of 450–550 K. This coincides with elevated ozone loss rates of 2–4 ppbv sh−1 (parts per billion by volume/sunlit hour) and a contribution of about 30–55% and 30–35% from the ClO-ClO and ClO-BrO cycles, respectively, in late February and March. In addition, a contribution of 30–50% from the HOx cycle is also estimated in April. We also estimate a loss of about 0.7–1.2 ppmv contributed (75%) by the NOx cycle at 550–700 K. The ozone loss estimated in the partial column range of 350–550 K exhibits a record value of ~148 DU (Dobson Unit). This is the largest ozone loss ever estimated in the Arctic and is consistent with the remarkable chlorine activation and strong denitrification (40–50%) during the winter, as the modeled ClO shows ~1.8 ppbv in early January and ~1 ppbv in March at 450–550 K. These model results are in excellent agreement with those found from the Aura Microwave Limb Sounder observations. Our analyses also show that the ozone loss in 2010/2011 is close to that found in some Antarctic winters, for the first time in the observed history. Though the winter 1996/1997 was also very cold in March–April, the temperatures were higher in December–February, and, therefore, chlorine activation was moderate and ozone loss was average with about 1.2 ppmv at 475–550 K or 42 DU at 350–550 K, as diagnosed from the model simulations and measurements.

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Sources of Springtime Surface Black Carbon in the Arctic: An Adjoint Analysis

10.5194/acp-2016-1112 ◽

2017 ◽

Cited By ~ 1

Author(s):

Ling Qi ◽

Qinbin Li ◽

Daven K. Henze ◽

Hsien-Liang Tseng ◽

Cenlin He

Keyword(s):

Natural Gas ◽

Black Carbon ◽

Biomass Burning ◽

Transport Model ◽

Lower Troposphere ◽

Anthropogenic Sources ◽

The Arctic ◽

Anthropogenic Source ◽

Gas Flaring ◽

Arctic Front

Abstract. We quantify source contributions to springtime (April 2008) surface black carbon (BC) in the Arctic by interpreting surface observations of BC at five receptor sites (Denali, Barrow, Alert, Zeppelin, and Summit) using a global chemical transport model (GEOS-Chem) and its adjoint. Contributions to BC at Barrow, Alert, and Zeppelin are dominated by Asian anthropogenic sources (40–43 %) before April 18 and by Siberian open biomass burning emissions (29–41 %) afterward. In contrast, Summit, a mostly free tropospheric site, has predominantly an Asian anthropogenic source contribution (24–68 %, with an average of 45 %). We compute the adjoint sensitivity of BC concentrations at the five sites during a pollution episode (April 20–25) to global emissions from March 1 to April 25. The associated contributions are the combined results of these sensitivities and BC emissions. Local and regional anthropogenic sources in Alaska are the largest anthropogenic sources of BC at Denali (63 %), and natural gas flaring emissions in the Western Extreme North of Russia (WENR) are the largest anthropogenic sources of BC at Zeppelin (26 %) and Alert (13 %). We find that long-range transport of emissions from Beijing-Tianjin-Hebei (also known as Jing-Jin-Ji), the biggest urbanized region in Northern China, contribute significantly (~ 10 %) to surface BC across the Arctic. On average it takes ~ 12 days for Asian anthropogenic emissions and Siberian biomass burning emissions to reach Arctic lower troposphere, supporting earlier studies. Natural gas flaring emissions from the WENR reach Zeppelin in about a week. We find that episodic, direct transport events dominate BC at Denali (87 %), a site outside the Arctic front, a strong transport barrier. The relative contribution of direct transport to surface BC within the Arctic front is much smaller (~ 50 % at Barrow and Zeppelin and ~ 10 % at Alert). The large contributions from Asian anthropogenic sources are predominately in the form of ‘chronic’ pollution (~ 40 % at Barrow and 65 % at Alert and 57 % at Zeppelin) on 1–2 month timescales. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic. Both finer temporal resolution of biomass burning emissions and accounting for the Wegener-Bergeron-Findeisen (WBF) process in wet scavenging improve the source attribution estimates.

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Long-term MAX-DOAS network observations of NO<sub>2</sub> in Russia and Asia (MADRAS) during the period 2007–2012: instrumentation, elucidation of climatology, and comparisons with OMI satellite observations and global model simulations

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-7909-2014 ◽

2014 ◽

Vol 14 (15) ◽

pp. 7909-7927 ◽

Cited By ~ 52

Author(s):

Y. Kanaya ◽

H. Irie ◽

H. Takashima ◽

H. Iwabuchi ◽

H. Akimoto ◽

...

Keyword(s):

Satellite Data ◽

Transport Model ◽

Satellite Observations ◽

Global Model ◽

Optical Absorption Spectroscopy ◽

Ozone Monitoring Instrument ◽

Vertical Column ◽

Data Set ◽

Model Simulations

Abstract. We conducted long-term network observations using standardized Multi-Axis Differential optical absorption spectroscopy (MAX-DOAS) instruments in Russia and ASia (MADRAS) from 2007 onwards and made the first synthetic data analysis. At seven locations (Cape Hedo, Fukue and Yokosuka in Japan, Hefei in China, Gwangju in Korea, and Tomsk and Zvenigorod in Russia) with different levels of pollution, we obtained 80 927 retrievals of tropospheric NO2 vertical column density (TropoNO2VCD) and aerosol optical depth (AOD). In the technique, the optimal estimation of the TropoNO2VCD and its profile was performed using aerosol information derived from O4 absorbances simultaneously observed at 460–490 nm. This large data set was used to analyze NO2 climatology systematically, including temporal variations from the seasonal to the diurnal scale. The results were compared with Ozone Monitoring Instrument (OMI) satellite observations and global model simulations. Two NO2 retrievals of OMI satellite data (NASA ver. 2.1 and Dutch OMI NO2 (DOMINO) ver. 2.0) generally showed close correlations with those derived from MAX-DOAS observations, but had low biases of up to ~50%. The bias was distinct when NO2 was abundantly present near the surface and when the AOD was high, suggesting a possibility of incomplete accounting of NO2 near the surface under relatively high aerosol conditions for the satellite observations. Except for constant biases, the satellite observations showed nearly perfect seasonal agreement with MAX-DOAS observations, suggesting that the analysis of seasonal features of the satellite data were robust. Weekend reduction in the TropoNO2VCD found at Yokosuka and Gwangju was absent at Hefei, implying that the major sources had different weekly variation patterns. While the TropoNO2VCD generally decreased during the midday hours, it increased exceptionally at urban/suburban locations (Yokosuka, Gwangju, and Hefei) during winter. A global chemical transport model, MIROC-ESM-CHEM (Model for Interdisciplinary Research on Climate–Earth System Model–Chemistry), was validated for the first time with respect to background NO2 column densities during summer at Cape Hedo and Fukue in the clean marine atmosphere.

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Boundary layer and free-tropospheric dimethyl sulfide in the Arctic spring and summer

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-8757-2017 ◽

2017 ◽

Vol 17 (14) ◽

pp. 8757-8770 ◽

Cited By ~ 3

Author(s):

Roghayeh Ghahremaninezhad ◽

Ann-Lise Norman ◽

Betty Croft ◽

Randall V. Martin ◽

Jeffrey R. Pierce ◽

...

Keyword(s):

Dimethyl Sulfide ◽

Transport Model ◽

Dispersion Model ◽

Open Water ◽

Particle Dispersion ◽

The Arctic ◽

Chemical Transport Model ◽

Model Simulations ◽

Baffin Bay ◽

Mixing Ratios

Abstract. Vertical distributions of atmospheric dimethyl sulfide (DMS(g)) were sampled aboard the research aircraft Polar 6 near Lancaster Sound, Nunavut, Canada, in July 2014 and on pan-Arctic flights in April 2015 that started from Longyearbyen, Spitzbergen, and passed through Alert and Eureka, Nunavut, and Inuvik, Northwest Territories. Larger mean DMS(g) mixing ratios were present during April 2015 (campaign mean of 116 ± 8 pptv) compared to July 2014 (campaign mean of 20 ± 6 pptv). During July 2014, the largest mixing ratios were found near the surface over the ice edge and open water. DMS(g) mixing ratios decreased with altitude up to about 3 km. During April 2015, profiles of DMS(g) were more uniform with height and some profiles showed an increase with altitude. DMS reached as high as 100 pptv near 2500 m. Relative to the observation averages, GEOS-Chem (www.geos-chem.org) chemical transport model simulations were higher during July and lower during April. Based on the simulations, more than 90 % of the July DMS(g) below 2 km and more than 90 % of the April DMS(g) originated from Arctic seawater (north of 66° N). During April, 60 % of the DMS(g), between 500 and 3000 m originated from Arctic seawater. During July 2014, FLEXPART (FLEXible PARTicle dispersion model) simulations locate the sampled air mass over Baffin Bay and the Canadian Arctic Archipelago 4 days back from the observations. During April 2015, the locations of the air masses 4 days back from sampling were varied: Baffin Bay/Canadian Archipelago, the Arctic Ocean, Greenland and the Pacific Ocean. Our results highlight the role of open water below the flight as the source of DMS(g) during July 2014 and the influence of long-range transport (LRT) of DMS(g) from further afield in the Arctic above 2500 m during April 2015.

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Statistical diagnostic and correction of a chemistry-transport model for the prediction of total column ozone

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-525-2006 ◽

2006 ◽

Vol 6 (2) ◽

pp. 525-537 ◽

Cited By ~ 10

Author(s):

S. Guillas ◽

G. C. Tiao ◽

D. J. Wuebbles ◽

A. Zubrow

Keyword(s):

Transport Model ◽

Chemical Transport ◽

Satellite System ◽

Chemical Transport Model ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Total Column Ozone ◽

Noise Component ◽

Column Ozone ◽

Total Column

Abstract. In this paper, we introduce a statistical method for examining and adjusting chemical-transport models. We illustrate the findings with total column ozone predictions, based on the University of Illinois at Urbana-Champaign 2-D (UIUC 2-D) chemical-transport model of the global atmosphere. We propose a general diagnostic procedure for the model outputs in total ozone over the latitudes ranging from 60° South to 60° North to see if the model captures some typical patterns in the data. The method proceeds in two steps to avoid possible collinearity issues. First, we regress the measurements given by a cohesive data set from the SBUV(/2) satellite system on the model outputs with an autoregressive noise component. Second, we regress the residuals of this first regression on the solar flux, the annual cycle, the Antarctic or Arctic Oscillation, and the Quasi Biennial Oscillation. If the coefficients from this second regression are statistically significant, then they mean that the model did not simulate properly the pattern associated with these factors. Systematic anomalies of the model are identified using data from 1979 to 1995, and statistically corrected afterwards. The 1996–2003 validation sample confirms that the combined approach yields better predictions than the direct UIUC 2-D outputs.

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Surface ozone and its precursors at Summit, Greenland: comparison between observations and model simulations

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-14661-2017 ◽

2017 ◽

Vol 17 (23) ◽

pp. 14661-14674 ◽

Cited By ~ 5

Author(s):

Yaoxian Huang ◽

Shiliang Wu ◽

Louisa J. Kramer ◽

Detlev Helmig ◽

Richard E. Honrath

Keyword(s):

Transport Model ◽

Surface Ozone ◽

The Arctic ◽

Chemical Transport Model ◽

Atmospheric Models ◽

Contributing Factors ◽

Model Simulations ◽

Mixing Ratios ◽

The Us ◽

Coarse Model

Abstract. Recent studies have shown significant challenges for atmospheric models to simulate tropospheric ozone (O3) and its precursors in the Arctic. In this study, ground-based data were combined with a global 3-D chemical transport model (GEOS-Chem) to examine the abundance and seasonal variations of O3 and its precursors at Summit, Greenland (72.34° N, 38.29° W; 3212 m a.s.l.). Model simulations for atmospheric nitrogen oxides (NOx), peroxyacetyl nitrate (PAN), ethane (C2H6), propane (C3H8), carbon monoxide (CO), and O3 for the period July 2008–June 2010 were compared with observations. The model performed well in simulating certain species (such as CO and C3H8), but some significant discrepancies were identified for other species and further investigated. The model generally underestimated NOx and PAN (by ∼  50 and 30 %, respectively) for March–June. Likely contributing factors to the low bias include missing NOx and PAN emissions from snowpack chemistry in the model. At the same time, the model overestimated NOx mixing ratios by more than a factor of 2 in wintertime, with episodic NOx mixing ratios up to 15 times higher than the typical NOx levels at Summit. Further investigation showed that these simulated episodic NOx spikes were always associated with transport events from Europe, but the exact cause remained unclear. The model systematically overestimated C2H6 mixing ratios by approximately 20 % relative to observations. This discrepancy can be resolved by decreasing anthropogenic C2H6 emissions over Asia and the US by ∼ 20 %, from 5.4 to 4.4 Tg year−1. GEOS-Chem was able to reproduce the seasonal variability of O3 and its spring maximum. However, compared with observations, it underestimated surface O3 by approximately 13 % (6.5 ppbv) from April to July. This low bias appeared to be driven by several factors including missing snowpack emissions of NOx and nitrous acid in the model, the weak simulated stratosphere-to-troposphere exchange flux of O3 over the summit, and the coarse model resolution.

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Arctic black carbon during PAMARCMiP 2018 and previous aircraft experiments in spring

10.5194/acp-2021-349 ◽

2021 ◽

Author(s):

Sho Ohata ◽

Makoto Koike ◽

Atsushi Yoshida ◽

Nobuhiro Moteki ◽

Kouji Adachi ◽

...

Keyword(s):

Numerical Model ◽

Black Carbon ◽

Biomass Burning ◽

Base Station ◽

Anthropogenic Sources ◽

The Arctic ◽

Core Diameter ◽

Model Simulations ◽

Anthropogenic Contributions ◽

Mass Concentrations

Abstract. Vertical profiles of the mass concentration of black carbon (BC) were measured at altitudes up to 5 km during the PAMARCMiP aircraft-based field experiment conducted around the Northern Greenland Sea (Fram Strait) during March and April 2018, with operation base Station Nord (81.6° N, 16.7° W). Median BC mass concentrations in individual altitude ranges were 7–18 ng m–3 at standard temperature and pressure at altitudes below 4.5 km. These concentrations were systematically lower than previous observations in the Arctic in spring conducted by ARCTAS-A in 2008 and NETCARE in 2015 and similar to those observed during HIPPO3 in 2010. Column amounts of BC for altitudes below 5 km in the Arctic (> 66.5° N, COLBC), observed during the ARCTAS-A and NETCARE experiments were higher by factors of 4.2 and 2.7, respectively, than those of the PAMARCMiP experiment. These differences could not be explained solely by the different locations of the experiments. The year-to-year variation of COLBC values generally corresponded to that of biomass burning activities in northern high latitudes over western and eastern Eurasia. Furthermore, numerical model simulations estimated the year-to-year variation of contributions from anthropogenic sources to be smaller than 30–40 %. These results suggest that the year-to-year variation of biomass burning activities likely affected BC amounts in the Arctic troposphere in spring, at least in the years examined in this study. The year-to-year variations in BC mass concentrations were also observed at the surface at high Arctic sites Ny-Ålesund and Barrow, although their magnitudes were slightly lower than those in COLBC. Numerical model simulations in general successfully reproduced the observed COLBC values for PAMARCMiP and HIPPO3 (within a factor of 2), whereas they markedly underestimated the values for ARCTAS-A and NETCARE by factors of 3.7–5.8 and 3.3–5.0, respectively. Because anthropogenic contributions account for nearly all of the COLBC (82–98 %) in PAMARCMiP and HIPPO3, the good agreements between the observations and calculations for these two experiments suggest that anthropogenic contributions were generally well reproduced. However, the significant underestimations of COLBC for ARCTAS-A and NETCARE suggest that biomass burning contributions were underestimated. In this study, we also investigated plumes with enhanced BC mass concentrations, which were affected by biomass burning emissions, observed at 5 km altitude. Interestingly, the mass-averaged diameter of BC (core) and the shell-to-core diameter ratio of BC-containing particles in the plumes were generally not very different from those in other air sampled, which were considered to be mostly aged anthropogenic BC. These observations provide useful bases to evaluate numerical model simulations of the BC radiative effect in the Arctic region in spring.

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Evolution of aerosol optical thickness over Europe during the August 2003 heat wave as seen from CHIMERE model simulations and POLDER data

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-1853-2006 ◽

2006 ◽

Vol 6 (7) ◽

pp. 1853-1864 ◽

Cited By ~ 55

Author(s):

A. Hodzic ◽

R. Vautard ◽

H. Chepfer ◽

P. Goloub ◽

L. Menut ◽

...

Keyword(s):

Optical Thickness ◽

Forest Fires ◽

Atmospheric Aerosol ◽

Large Scale ◽

Transport Model ◽

Anthropogenic Sources ◽

Chemistry Transport Model ◽

Model Simulations ◽

High Particle ◽

Sun Photometer

Abstract. This study describes the atmospheric aerosol load encountered during the large-scale pollution episode that occurred in August 2003, by means of the aerosol optical thicknesses (AOTs) measured at 865 nm by the Polarization and Directionality of the Earth's Reflectances (POLDER) sensor and the simulation by the CHIMERE chemistry-transport model. During this period many processes (stagnation, photochemistry, forest fires) led to unusually high particle concentrations and optical thicknesses. The observed/simulated AOT comparison helps understanding the ability of the model to reproduce most of the gross AOT features observed in satellite data, with a general agreement within a factor 2 and correlations in the 0.4–0.6 range. However some important aerosol features are missed when using regular anthropogenic sources. Additional simulations including emissions and high-altitude transport of smoke from wildfires that occurred in Portugal indicate that these processes could dominate the AOT signal in some areas. Our results also highlight the difficulties of comparing simulated and POLDER-derived AOTs due to large uncertainties in both cases. Observed AOT values are significantly lower than the simulated ones (30–50%). Their comparison with the ground-based Sun photometer Aerosol Robotic Network (AERONET) measurements suggests, for the European sites considered here, an underestimation of POLDER-derived aerosol levels with a factor between 1 and 2. AERONET AOTs compare better with simulations (no particular bias) than POLDER AOTs.

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