关键词: 沙尘暴, 中低压, 垂直环流圈

Abstract: This paper analyses the strong sand and dust storm weather occurred in the Northwest China on the April 5, 1994. It probes into several aspects such as synoptic facts, synoptic causes and dynamic diagnostics etc. Thus, it reveals the physical mechanism of the formation of east-gale sand and dust storm weather. Under the favourable high-level circulation situation, there were three dominant synoptic systems which induced sand and dust storm weather in the low-level, including 1)the development and replace of Nanjiang thermal low; 2)the production and development of middle scale low; 3)Mongolia high pressure and its cold front went down south, which formed a strong pressure gradient, allobaric gradient and temperature gradient between Hexi middle scale low. It wasthe important mechanism for gale sand and dust storm to transform the potential energy into kinetic energy.

Key words: Sand and dusts torm, Middle lower pressure, Vertical circulation circle