Influence Of Winter Monsoon On Aerosol Transport And Distribution In East Asia

With the rapid economic development in East Asia, atmospheric aerosol becomes one of the key air pollutants, whose spatial and temporal distribution was affected by the East Asian monsoon climate. In this study, MODIS/AOD and TOMS/UVAI aerosol products, as well as NCEP reanalysis monthly meteorological field data were used to statistically analyze variation characteristics of East Asia winter monsoon from 1979 to 2011 and distribution of aerosol in East Asia. In this study, with the use of observation data and model simulation, analysis on the effect of East Asia winter monsoon on the distribution of aerosol were carried out.Firstly, analysis of MODIS/AOD indicated that average AOD is about 0.55 in spring, which is 0.49 in summer. AOD is higher in spring and summer than it’s in autumn and winter. Average AOD is 0.38 in autumn and winter. Sichuan Basin and the areas including the middle and lower reaches of the Yangtze River, North China display high value of AOD. AOD shows an apparent seasonal variability with the vast high-value area near 32.5°N in spring. AOD over East Asia increased more significantly in winter than in summer in recent ten years. Study shows that AOD in winter displays an obvious increasing trend and the highest value is 0.44 while the lowest value is 0.36. The highest value occurred in February with largest area covered Sichuan Basin and the areas including the middle and lower reaches of the Yangtze River, North China. And the second highest value happened in December while AOD in January was lowest.Secondly, two different monsoon indexes and observation data were used to analyze the effect of East Asia winter monsoon on the distribution of aerosol. Investigations showed that the East Asian winter monsoon has strong inter-annual and inter-decadal variations, while inter-annual variation was more significant. In 1979-2014, East Asian winter monsoon exhibits a gradually decreasing trend. Two different winter monsoon index were used to choose strong winter monsoon years and weak winter monsoon years. In strong years, differential pressure between mainland and sea increases,500hPa trough in East Asia deepened, northerly winds anomalies occurred in East Asia. Wind field enhancement will lead more cold air southeast toward, which bring much cool weather over East Asia. While, atmospheric circulation shows opposite pattern in weak winter monsoon years. Aerosol variance analysis between strong and weak East Asian winter monsoon (EAWM) proved that anomalies of EAWM have a remarkable impact on spatial distribution of aerosol. The areas including the middle and lower reaches of the Yangtze River, North China display high value of AOD both in strong and weak monsoon years, which indicates the reason of high value aerosol is the local anthropogenic emissions. In strong EAWM years, aerosol is transported southward by northerly winds enhancement and AOD anomalies in the north and south are negative and positive, whereas the opposite is observed during weak monsoon years.Finally, a scheme of a strong monsoon year (2010) and a weak monsoon year (2005) were simulated by RegCCMS. Results show that the column burden of aerosol difference rang between strong EAWM and weak EAWM is-80mg·m-2～25mg·m-2. The more close to the ground, the more obvious difference between strong and weak years. The concentration of aerosol difference rang between strong EAWM and weak EAWM is-14-30μg·m-3 on the surface while it is-10-23μg·m-3 in the 850hPa.