Tropical influences on southwest Asia precipitation in a global atmospheric model.

摘要

The midlatitude dynamic and thermodynamic response to enhanced middle troposphere tropical diabatic heating over the eastern Indian Ocean during the northern hemisphere cold season (December--March) is investigated using the National Center for Atmospheric Research Community Atmosphere Model version 3.1 full global climate model. The dynamic response is similar to the idealized analytic Gill (1980) solution to steady diabatic heating and the thermodynamic response is consistent with theoretical works by Rodwell and Hoskins (1996, 2001) and observational analysis of Barlow et al. (2005). The thermodynamic response indicates that precipitation is suppressed by descending air over Iran, Afghanistan, and Pakistan due to cold temperature advection at middle and upper tropospheric levels. The sensitivity of the midlatitude response to diabatic heating is explored: the long-term steady state response, the short-term monthly response, and the response to variable magnitudes of diabatic heating.