Evolution of Meteorological Conditions during a Heavy Air Pollution Event under the Influence of Shallow Foehn in Urumqi,China

The air pollution in Urumqi which is located on the northern slope of the Tianshan Mountains in northwestern China,is very serious in winter. Of particular importance is the influence of terrain-induced shallow foehn, known locally as elevated southeasterly gale(ESEG). It usually modulates atmospheric boundary layer structure and wind field patterns and produces favorable meteorological conditions conducive to hazardous air pollution. During 2013–17, Urumqi had an average of 50 d yr^–1...