摘要
利用NCEP/NCAR逐日每6 h再分析资料,对2002-2004年发生在祁连山区附近的20次降水过程进行了合成分析。发现在40°N200 hPa高空存在一支东西走向的高空西风急流;降水一般发生在高空西风急流轴的南侧,在高空西风急流轴的北侧有冷空气下沉,南侧有上升的暖湿气流,在高空急流轴的下方形成了次级环流;在高空急流轴出口区的右侧,存在强烈的辐散上升运动,而对应的低层存在强烈的辐合上升区,这种高低层辐散辐合的配置非常有利于强对流天气形成;这支高空西风急流轴的存在对祁连山区的降水有深远影响,而急流轴位置的变化势必影响到降水落区。因此,利用高空西风急流轴预报祁连山区降水及河西走廊地区降水具有很好的指导意义。
The analysis and summary are made of the 20 rainfall events occurred around the Qilian Mountain from 2002 to 2004 by use of the re.analyzed day-to-day 6h NCEP/NCAR data. The results show that there was a upper-level westerly jet from east to the west at 40 N, 200 hPa; precipitation generally took place in the south side of the jet axis, and there was cold downdrafts on the north side of the jet axis, warm and humid up-current on the south side, and the sub-circulations beneath; there was strong divergent ascending motion on the right side of the entrance area of the jet axis, and accordingly there existed strong convergence ascending area at the lower levels. The collocation of divergence and convergence at the upper and lower levels is beneficial to the formation of strong convection weather. The existence of the westerly jet axis at high altitudes is of profound influence to the precipitation over the Qilian mountain areas, and the position variation of the jet axis affects the location of the precipitation.
出处
《气象科技》
2007年第4期489-494,共6页
Meteorological Science and Technology
基金
国家科技攻关重大项目"西部开发科技行动"之"祁连山空中云水资源开发利用研究"(2004BA901A16)资助
关键词
高空急流
次级环流
祁连山区
降水
upper-level westerly Jet, secondary circulation, Qilian Mountain, precipitation
