A STUDY ON REGIONAL CHANGE OF NATURAL ENVIRONMENT OF CHINA INFLUENCED BY SOUTHWEST MONSOON

As an important part of Asian monsoon,southwest monsoon has much influence on natural environment of China.Since southwest monsoon developed,the height of Qinghai-Tibet Plateau was too low to prevent it.Moreover,the thickness of southwest monsoon keeps becoming thicker and stronger along with the mountain area,especially the rise of Hengduan Mountain.Meanwhile,The cyclone feature of south branch of the westerly play a leading role in the development of southwest monsoon.Southwest monsoon is more active and wider than southeast monsoon;it can influence the most areas in the west of Mt.Taihang.During Middle-Pleistocene,the height of Qinghai-Xizang Plateau uplift to 3 000 m high.At the same time,Quaternary maximum glaciations and hypsithermal appeared.The effect of dynamic and thermodynamic of plateau strengthened further and the southwest monsoon became thicker.Southwest monsoon plays an important role in natural environment of China.Since Late Pleistocene,the average altitude of Qinghai-Xizang Plateau has rise to 4 500～5 000 m nowadays and uplift of Himalaya Mountain is able to prevent southwest monsoon from advancing into Qinghai-Xizang Plateau and continental district.The area controlled by southwest monsoon has shrunk to the southwest of Yangtze River upper reach and southeast of Qinghai-Xizang Plateau.