Taiwan Local Circulation with Mountain Effect during Cold Surge Period

As located to the south-east of Wu-Yi Mountain (WYM), the weather of Taiwan is affected by the land-sea distribution and complex terrain. When the cold-air leading edge moves out from the Mainland during the cold surge period, the system is subject to the influence of WYM. The results of numerical simuation point out that the main impact of WYM on the cold surge system is to make the pressure increase windward and decrease leeward, and the temperature increase leeward. The wind field is guided by WYM with changing directions and increasing the speed around Taiwan. The presence of strong northeasterly winds in winter over the Taiwan Strait and the northern part of Taiwan is mainly induced by WYM. Under the Impact of such strong winds, the cold-air leading edge accelerates southward over Taiwan Strait. Without the presence of WYM, the temperature gradient would increase and the surface temperature would be lower over the Taiwan area during the cold surge. Also the coverage and intensity of the leading edge of cold air would increase with a thicker layer of cold air aloft.