Aerosol Optical Depth Over India

David, Liji M.; Ravishankara, A. R.; Kodros, John K.; Venkataraman, Chandra; Sadavarte, Pankaj; Pierce, Jeffrey R.; Chaliyakunnel, S.; Millet, Dylan B.

doi:10.1002/2017jd027719

Cited by 86 publications

(74 citation statements)

References 63 publications

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“…Figure 13 shows the relative contributions of the local emissions and meteorological factors to the changes in regional AOD for the period 1980-2014, as well as for 1980-1997 and 1998-2014, using Table S3). The above results also confirm that particulate sulfate is the main contributor to fine-mode AOD in anthropogenic-aerosol-dominant regions (Itahashi et al, 2012;David et al, 2018 AMZ and CF,contributing 11.7 %,35.5 % and 28.5 %, respectively. Furthermore, over the dust-dominant regions, wind speed was the strongest meteorological driving factor, explaining 30.3 % and 29.8 % of the variance in AOD over NWC and the SD, respectively.…”

Section: Relative Contributions Of Local Emissions and Meteorologicalsupporting

confidence: 76%

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2019

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when compared with emission factors (0 %-56 %). Further analysis also showed that SO 2 was the dominant emission factor, explaining 12.7 %-32.6 % of the variation in AOD over anthropogenic-aerosol-dominant regions, while black carbon or organic carbon was the leading factor over Published by Copernicus Publications on behalf of the European Geosciences Union. 10498 H. Che et al.: Large contribution of meteorological factors to inter-decadal changesthe biomass-burning-dominant (BBD) regions, contributing 24.0 %-27.7 % of the variation. Additionally, wind speed was found to be the leading meteorological parameter, explaining 11.8 %-30.3 % of the variance over the mineraldust-dominant regions, while ambient humidity (including soil moisture and relative humidity) was the top meteorological parameter over the BBD regions, accounting for 11.7 %-35.5 % of the variation. The results of this study indicate that the variation in meteorological parameters is a key factor in determining the inter-decadal change in regional AOD.

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Section: Relative Contributions Of Local Emissions and Meteorologicalsupporting

confidence: 76%

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2019

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“…The larger MODIS AOD compared to MISR over India has been reported in many previous studies (e.g. Misra et al [10], Ramachandran and Kedia [41], David et al [42]). We show that AOD climatologies from MISR are also more stable than those from MODIS over these two regions.…”

Section: Discussionsupporting

confidence: 49%

How Long should the MISR Record Be when Evaluating Aerosol Optical Depth Climatology in Climate Models?

et al. 2018

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This study used the nearly continuous 17-year observation record from the Multi- angle Imaging SpectroRadiometer (MISR) instrument on the National Aeronautics and Space Administration (NASA) Terra Earth Observing System satellite to determine which temporal subsets are long enough to define statistically stable speciated aerosol optical depth (AOD) climatologies (i.e., AOD by particle types) for purposes of climate model evaluation. A random subsampling of seasonally averaged total and speciated AOD retrievals was performed to quantitatively assess the statistical stability in the climatology, represented by the minimum record length required for the standard deviation of the subsampled mean AODs to be less than a certain threshold. Our results indicate that the multi-year mean speciated AOD from MISR is stable on a global scale; however, there is substantial regional variability in the assessed stability. This implies that in some regions, even 17 years may not provide a long enough sample to define regional mean total and speciated AOD climatologies. We further investigated the agreement between the statistical stability of total AOD retrievals from MISR and the Moderate Resolution Imaging Spectroradiometer (MODIS), also on the NASA Terra satellite. The difference in the minimum record lengths between MISR and MODIS climatologies of total AOD is less than three years for most of the globe, with the exception of certain regions. Finally, we compared the seasonal cycles in the MISR total and speciated AODs with those simulated by three global chemistry transport models in the regions of climatologically stable speciated AODs. We found that only one model reproduced the observed seasonal cycles of the total and non-absorbing AODs over East China, but the seasonal cycles in total and dust AODs in all models are similar to those from MISR in Western Africa. This work provides a new method for considering the statistical stability of satellite-derived climatologies and illustrates the value of MISR’s speciated AOD data record for evaluating aerosols in global models.

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“…Nevertheless, the AOD in autumn in South America, SEA, SC and CF is clearly high, which is mainly attributable to the emission of large amounts of fine aerosol particles (i.e., BC and OC) from frequent biomass burning in these regions (Thornhill et al, 2018;Ikemori et al, 2018;Chen et al, 2017). Notably, fine particulate matter composed of sulfate-nitrateammonium aerosols, which is produced by high-intensity anthropogenic activities in autumn and winter, is still the main contributor to high AOD in eastern China and India (Gao et al, 2018;David et al, 2018).…”

Section: Global Aod Distribution and Interannual Evolution Of Regionamentioning

confidence: 99%

Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

et al. 2019

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Abstract. Aerosol optical depth (AOD) has become a crucial metric for assessing global climate change. Although global and regional AOD trends have been studied extensively, it remains unclear what factors are driving the inter-decadal variations in regional AOD and how to quantify the relative contribution of each dominant factor. This study used a long-term (1980–2016) aerosol dataset from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis, along with two satellite-based AOD datasets (MODIS/Terra and MISR) from 2001 to 2016, to investigate the long-term trends in global and regional aerosol loading. Statistical models based on emission factors and meteorological parameters were developed to identify the main factors driving the inter-decadal changes of regional AOD and to quantify their contribution. Evaluation of the MERRA-2 AOD with the ground-based measurements of AERONET indicated significant spatial agreement on the global scale (r= 0.85, root-mean-square error = 0.12, mean fractional error = 38.7 %, fractional gross error = 9.86 % and index of agreement = 0.94). However, when AOD observations from the China Aerosol Remote Sensing Network (CARSNET) were employed for independent verification, the results showed that MERRA-2 AODs generally underestimated CARSNET AODs in China (relative mean bias = 0.72 and fractional gross error =-34.3 %). In general, MERRA-2 was able to quantitatively reproduce the annual and seasonal AOD trends on both regional and global scales, as observed by MODIS/Terra, although some differences were found when compared to MISR. Over the 37-year period in this study, significant decreasing trends were observed over Europe and the eastern United States. In contrast, eastern China and southern Asia showed AOD increases, but the increasing trend of the former reversed sharply in the most recent decade. The statistical analyses suggested that the meteorological parameters explained a larger proportion of the AOD variability (20.4 %–72.8 %) over almost all regions of interest (ROIs) during 1980–2014 when compared with emission factors (0 %–56 %). Further analysis also showed that SO2 was the dominant emission factor, explaining 12.7 %–32.6 % of the variation in AOD over anthropogenic-aerosol-dominant regions, while black carbon or organic carbon was the leading factor over the biomass-burning-dominant (BBD) regions, contributing 24.0 %–27.7 % of the variation. Additionally, wind speed was found to be the leading meteorological parameter, explaining 11.8 %–30.3 % of the variance over the mineral-dust-dominant regions, while ambient humidity (including soil moisture and relative humidity) was the top meteorological parameter over the BBD regions, accounting for 11.7 %–35.5 % of the variation. The results of this study indicate that the variation in meteorological parameters is a key factor in determining the inter-decadal change in regional AOD.

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Aerosol Optical Depth Over India

Cited by 86 publications

References 63 publications

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How Long should the MISR Record Be when Evaluating Aerosol Optical Depth Climatology in Climate Models?

Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

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