INVESTIGATING ALOFT AEROSOLS OVER CENTRAL-EASTERN CHINA USING CALIPSO MEASUREMENTS

Abstract. The rapid development of China in the last decade has brought about serious environmental problems, among which the air quality has attracted much attention. Especially in the winter, haze events with PM_2.5 as the primary pollutant frequently occur, which has a huge strike on people's health. Such cumulative anthropogenic aerosols at surface over haze pollution regions could be lifted upwards by vertical turbulent mixing forming elevated haze layers that subsequent transport to distant regions. This paper attempts to analyze layer top altitude, ratio of anthropogenic source and optical properties by counting events occurring in aloft aerosols layer. CALIPSO satellite instruments are used for statistical analysis by screening layer data over central-eastern China from 2007 to 2016. In the most economically active and polluted areas of China, the North China Plain (NCP) and the Yangtze River Delta (YRD) are compared to analyze trend variations over ten years. Results shows that the frequency of occurrence of aloft layer in South China are higher than in North China, indicating that heat has a strong lifting effect on the planetary boundary layer (PBL). Further, the NCP has a unique high frequency value at 2.5 km, while the YRD has two peaks, 3.5 km and 2 km respectively. Moreover, in the past five years in the NCP (2011–2016) and YRD (2012–2016) regions, the anthropogenic source of pollutants dominated by smoke showed a downward trend year by year. In addition, monthly proportion of smoke and polluted dust are analyzed in NCP and YRD winter. Finally, the volume depolarization ratio is almost distributed within 0.2, indicating that the shape of the particles is irregular. The particulate color ratio has a sharp peak near 0.4–0.7 suggesting that smaller particles dominate the size distribution during the winter months.