春季西风急流异常对甘肃极端天气的影响

Influence of Abnormal Westerly Jet on Extreme Weather in Spring in Gansu Province

采用1970—2011年春季甘肃42a的气象观测资料、MICAPS常规资料,按照春季发生的各类别灾害性天气标准,分析研究了干旱、大风、强沙尘暴(黑风)、强寒潮等天气过程与西风急流振荡之间的关系。结果表明:①西风急流轴、核的振荡强度与范围,与甘肃春季极端天气的发生发展有直接的关联性,尤其是西风急流在欧亚范围内稳定,且向高纬度65°N地区发展时,易造成甘肃河西及河东大部分地方持续性的干旱。②西风急流带南下发展到巴尔喀什湖附近,转折为"L"型流场,并向东南方向发展时,其中短波分裂急流轴、核直入甘肃,易造成春季的强寒潮等极端天气事件。③只要有较强的高空急流带引导,近地面强风场中就有急流发展,大风、强沙尘暴、寒潮等极端天气就会袭击甘肃。

Some weather processes such as drought,strong wind,strong sandstorm,cold wave etc.in Gansu during 1970-2011 are analyzed based on the meteorological data and according to the standard of disaster weather occurring in spring.The relationship between disaster weather and westerly jet oscillation is obtained based on the convention MICAPS data.The oscillation strength and spatial scope of the axis and nucleus of westerly jet have direct connection with occurrence and development of disaster weather occurred in Gansu in spring.When westerly jet developed steadily in Eurasian and moved to 65° N latitude,continuous drought occurred in most regions of Hexi and Hedong regions of Gansu province.When westerly jet moved down south to the Balkhash Lake and developed to ＂L＂ flow field,strong cold wave events are easily formed in Gansu resulting from short-wave splited rapids axis and nucleus enter Gansu in spring.Generally,if only high jet exists,jet at near surface must develops,and strong wind,strong sandstorm,cold wave events will take place in Gansu in spring.