Effects of the ground surface temperature anomalies over the Tibetan Plateau on the rainfall over northwestern China and western Mongolia in July

摘要

A significantly negative interannual relationship is identified between the ground surface temperature (GTS) over the Tibetan Plateau (TP) and the rainfall over northwestern China and western Mongolia (NWC-WM) through analyzing the Chinese weather station data, GPCP precipitation, and ERA-Interim reanalysis in July during 1980-2012. This relationship is verified by the model sensitivity experiments carried out by using RegCM4.1 during 1982-2011. The positiveegative GTS forcing of three different magnitudes is added in two key regions over the TP in RegCM4.1. One of the key regions covers the central and eastern TP (denoted as TPC). The other covers the northern and north slope of the TP (denoted as TPN). The model results suggest that when the GTS anomalies in either of the two key regions are negative (positive), the rainfall anomalies over NWC-WM are positive (negative), which is consistent with observations. Furthermore, rainfall anomalies over NWC-WM are more sensitive to the GTS anomalies over the TPN region than those over the southern TP. The model results also reveal that the negative (positive) GTS anomalies over region TPN mainly cause the decrease (increase) of the latent heat release related to rainfall (surface sensible heat) and descent (ascent) over the TPN region but ascent (descent) to the north of the TP between 40 degrees and 50 degrees N. In addition, the specific humidity between 40 degrees and 50 degrees N is increased (decreased). Therefore, the increase (decrease) in specific humidity and the ascent (descent) between 40 degrees and 50 degrees N cause the increase (decrease) in the rainfall over NWC-WM.