Observations of Asian Dust and Agricultural Fire Smoke Episodes: Transport and Impacts on Regional Air Quality in Southeast China

Abstract

This chapter presents an integrated observations of Asian dust and agricultural fire smoke episodes in spring and summer 2011 in Nanjing, China, using multiple satellites, ground-based sensors, and transport model. The source, long-range transport, time-height distribution, optical characteristics, and impacts on the air quality and visibility are demonstrated. The dust episode on May 1 shows two dust layers loading in the planetary-boundary-layer (PBL) and free troposphere originating from the Gobi deserts and Taklimakan deserts, respectively. The dust aerosols show the depolarization ratio of 0.1–0.2, optical depth (AOD) of 1.6 at 500-nm, and Angstrom exponents of 0.2. The hourly PM10 and PM2.5 concentrations show the maximum value of 767 μg/m3 and 222 μg/m3 thus indicating a heavy air pollution. The models are capable of simulating the right timing of dust transport event and primary loading in the PBL. For the episode of agricultural fires on June 3–4, the smoke aerosols are mainly located in the PBL with small depolarization ratio, and the AODs increase up to 3.0 with Angstrom exponent of 1.5–1.6. The PM10 and PM2.5 mass indicate a dramatic increase with the peak value reaching 800 μg/m3 and 485 μg/m3, respectively. The MODIS fire product shows the sources of agriculture fires located in the mid-east China (e.g., Jiangshu, Anhui, and Henan provinces). Regional transports are further illustrated by MODIS, OMI, and CALIPSO. Finally, the evaluations of MODIS-AOD and their correlation with the ground PM10 are illustrated in Nanjing urban area.