Two types of summertime heating over Asian large-scale orography and excitation of potential-vorticity forcing II.Sensible heating over Tibetan-Iranian Plateau

摘要

Based on analysis and simulation,the interaction of thermal forcing between the Tibetan Plateau(TP) and Iranian Plateau(IP) in summer is investigated.Associated influences on water vapor transport in the Asian subtropical monsoon region and the formation of a cold center in the lower stratosphere over Eurasia are also investigated.Results show that surface sensible heating(SH) over the two plateaus not only have mutual influences but also feedback to each other.SH over the IP can reduce the SH and increase the LH over the TP,whereas the SH over the TP can increase surface heating over the IP,thereby reaching quasi-equilibrium among the SH and LH over the TP,IP SH and atmosphere vertical motion.Therefore,the so-called Tibetan-Iranian Plateau coupling system(TIPS) is constructed,which influences atmosphere circulation.In the TIPS system,interaction between surface SH and LH over the TP plays a leading role.SH of the IP and TP influences on other regions not only have superimposed effects but also mutually offset.Accounting for contributions to the convergence of water vapor transport in the Asian subtropical monsoon region,TP SH contributes more than twice that of the IP.The combined influence of SH over TP and IP represents the major contribution to the convergence of water vapor transport in that region.In addition,the heating effect of TIPS increases the upper tropospheric temperature maximum and lifts the tropopause,cooling the lower stratosphere.Combined with large-scale thermal forcing of the Eurasian continent,the TIPS produces a strong anticyclonic circulation and the South Asian High that warms the upper troposphere and cools the lower stratosphere,thereby affecting regional and global weather and climate.