Asian summer monsoon anomalies induced by aerosol direct forcing : the role of the Tibetan Plateau

• Published in: Climate dynamics Vol. 26; no. 7-8; pp. 855 - 864
• Main Authors: LAU, K. M, KIM, M. K, KIM, K. M
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-06-2006; Berlin Springer Nature B.V
• Subjects: Aerosols; Air pollution; Black carbon; Climatology. Bioclimatology. Climate change; Dust; Earth, ocean, space; Emissions; Exact sciences and technology; External geophysics; Heat exchangers; Heating; Marine; Meteorology; Monsoons; Slopes; Solar radiation; Summer; Troposphere; Water in the atmosphere (humidity, clouds, evaporation, precipitation); Wind; Middle East; China, People's Rep., Xizang, Tibetan Plateau; Afghanistan; ISW, India; ISW, Pakistan; China, People's Rep; rainfall; atmospheric precipitation; aerosols; Soot; anomalies; Summer monsoon; Rainfall rate; intensity; deserts; Onset time; Geographic distribution; Asia; Pollutant effect; Forcing; dust
• ISSN: 0930-7575; 1432-0894
• DOI: 10.1007/s00382-006-0114-z

In this paper we present results of a numerical study using the NASA finite-volume GCM to elucidate a plausible mechanism for aerosol impact on the Asian summer monsoon involving interaction with physical processes over the Tibetan Plateau (TP). During the pre-monsoon season of March-April, dusts from the deserts of western China, Afghanistan/Pakistan, and the Middle East are transported into and stacked up against the northern and southern slopes of the TP. The absorption of solar radiation by dust heats up the elevated surface air over the slopes. On the southern slopes, the atmospheric heating is reinforced by black carbon from local emission. The heated air rises via dry convection, creating a positive temperature anomaly in the mid-to-upper troposphere over the TP relative to the region to the south. In May through early June in a manner akin to an "elevated heat pump", the rising hot air forced by the increasing heating in the upper troposphere, draws in warm and moist air over the Indian subcontinent, setting the stage for the onset of the South Asia summer monsoon. Our results suggest that increased dust loading coupled with black carbon emission from local sources in northern India during late spring may lead to an advance of the rainy periods and subsequently an intensification of the Indian summer monsoon. The enhanced rainfall over India is associated with the development of an aerosol-induced large-scale sea level pressure anomaly pattern, which causes the East Asia (Mei-yu) rain belt to shift northwestward, suppressing rainfall over East Asia and the adjacent oceanic regions.[PUBLICATION ABSTRACT]