Mechanisms of Global Warming Impacts on Robustness of Tropical Precipitation Asymmetry

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Title:	Mechanisms of Global Warming Impacts on Robustness of Tropical Precipitation Asymmetry
Authors:	Tan, Pei-Hua Chou, Chia Tu, Jien-Yi
Contributors:	大氣系
Keywords:	TRANSIENT CLIMATE-CHANGE ASIAN SUMMER MONSOON TEMPERATURE-VARIATIONS HYDROLOGICAL CYCLE PHYSICAL PROCESSES SYSTEM MODEL EL-NINO TRENDS 20TH-CENTURY VARIABILITY
Date:	2008
Issue Date:	2009-11-04 11:04:46 (UTC+8)
Abstract:	Hemispherically and temporally asymmetric tropical precipitation responses to global warming are evaluated in 13 different coupled atmosphere-ocean climate model stimulations. In the late boreal summer, hemispherical averages of the tropical precipitation anomalies from the multimodel ensemble show a strong positive trend in the Northern Hmeisphere and a weak negative trend in the Southern Hemisphere. In the late austral summer, on the other hand, the trends are reversed. This implies that the summer hemisphere becomes wetter and the winter hemisphere becomes a little drier in the tropics. Thus, the seasonal range of tropical precipitation, differences between wet and dry seasons, is increased. Zonal averages of the precipitation anomalies from the multimodel ensemble also reveal a meridional movement, which basically follows the seasonal migration of the main convection zone. Similar asymmetric features can be found in all 13 climate model simulations used in this study. Based on the moisture budget analysis, the vertical moisture advection associated with mean circulation is the main contribution for the robustness of the asymmetric distribution of the tropical precipitation anomalies. Under global warming, tropospheric water vapor increases as the temperature rises and most enhanced water vapor is in the lower troposphere. The acending motion of the Hadley circulation then transports more water vapor upward, that is, anomalous moisture convergence, and enhances precipitation over the main convection zones. On the other hand, the thermodynamic effect associated with the descending motion of the HAdley circulation, that is, anomalous moisture divergence, reduces the precipitation over the descending regions.
Relation:	JOURNAL OF CLIMATE Volume: 21 Issue: 21 Pages: 5585-5602
Appears in Collections:	[Department of Atmospheric Sciences & Graduate Institute of Earth Science / Atmospheric Science ] journal articles

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