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Special Session 5: Ocean-atmosphere interaction, multi-scale climate variability and their implication for biogeochemical processes |
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Ten-year aerosol trend over the United States associated with ENSO, NAO and anthropogenic activities
SS5-10
Siwei Li* , NOAA center for atmospheric Sciences, Howard University
Presenter Email: siwei.li@howard.edu
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| Attributing the recent decadal trends of aerosol abundance to natural or anthropogenic activities has been inconclusive, but remains important for aiding climate predictions and air quality policy decisions given the influential role of aerosols on climate and air quality. Large-scale meteorological processes could perturb the aerosol distributions through changes in aerosol emissions by altering the precipitation and/or soil moisture, or through aerosol transport via atmospheric circulation feedbacks. This study investigates the relationship of trends of aerosol abundance between 2000 and 2010 with large-scale climatic variations such as El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and anthropogenic activities. It is shown that anthropogenic emission dominated the decrease of aerosol optical depth (AOD) and particulate matter less than 2.5 microns (PM2.5) in United States during the ten-year study period. Regression analysis suggests that ENSO, NAO and anthropogenic activities can explain 77 percent of observed AOD and can explain 88 percent of in situ observed PM2.5 trend (with seasonal variation removed). Separately anthropogenic activities can explain 65 per cent of AOD and 84 percent of PM2.5 while the ENSO and NAO can explain 32 per cent of AOD and only 8 per cent of PM2.5. These findings suggest that anthropogenic activities drove the reduction of AOD and PM2.5 over the United States. The magnitude of influence of large-scale climatic variability on AOD is comparable to that of anthropogenic activities on AOD and cannot be ignored in estimation of AOD. |
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