Spatiotemporal Distribution Characteristics of Ammonia during the Asian Summer Monsoon

The spatial distribution characteristics of atmospheric ammonia (NH₃) in East Asia from June to September 2008–2011 were investigated using data from the Michelson interferometer for passive atmospheric sounding on the ENVISAT satellite, the AIRS detector on the Aqua satellite, and the global atmospheric chemistry–climate model EMAC. The results show that the highest concentration of NH₃ near the surface appears in northern India, and deep convection exists in the Bay of Bengal near northern India in summer. This deep convection can transport short-lived NH₃ to the upper troposphere and lower stratosphere (UTLS) because of the high altitude of the Qinghai-Tibet Plateau. Therefore, an upward transport column of NH₃ over the Qinghai-Tibet Plateau exits and is the main channel for the upward transportation of NH₃. During the Asian summer monsoon, the location of the Asian summer monsoon anticyclone dominates the spatial distribution of NH₃ in the UTLS area. The high-concentration center of NH₃ continues to exist during the anticyclone, and its position corresponds well with the position of the anticyclone center. During the anticyclone, one or two NH₃ high-concentration centers exist in the anticyclone center, implying that a change in the circulation pattern of the anticyclone has important effects on the NH₃ distribution.