河南省2012年3月23日致灾大风形成及维持原因

The Formation Reasons of Disaster-causing Gale in Henan on March 23, 2012

2012年3月23日河南省发生了一次致灾大风天气过程.此次天气过程强度大、时间短,影响范围广,灾害比较大.为了找出此次大风发生的成因,利用常规观测资料以及NCEP分析资料对这次过程进行诊断分析.结果表明:①此次致灾大风过程是在中高层低槽强烈斜压发展,槽后强的冷平流不断南下,较强的高空风动量下传,高低空存在强的下沉运动,地面大的气压梯度和变压梯度等共同作用下产生的;②此次大风天气过程中,温度槽始终落后于高度槽,强烈的斜压作用使高空槽发展.在槽后强冷平流作用下,高空槽加深发展并东移南下,引导冷空气东移南下,冷空气向南移动的过程中,冷平流不断加强,河南上空冷暖平流共同作用,使得锋区进一步加强,风力加大;③中高层的强冷平流是此次大风过程的主要热力因子,低层冷平流较弱;④此次大风天气中高空风动量下传起到了重要作用,强风速从河南西北部自上而下,自西向东传播;⑤强的气压梯度力是此次大风天气形成的主要原因之一.预报河南大风时要关注西安、北京和郑州之间的气压差,在西北路冷空气影响时,如果西安加压,北京减压,风速就有增大的趋势,反之,如果西安和北京都加压,虽然西安和郑州的气压梯度较大,风力也不会很大.

There has been occurred a disaster-causing gale on March 23,2012 in Henan Province. This process has four characteristics-strong intensity,short time,wide range of influence and serious disaster. The diagnostic analysis has been made utilizing the conventional observations and NCEP reanalysis data to find the probable causes of this process. The results show that this process is occurred by the combined action of some conditions. They are the trough of the mid-high level developing strongly baroclinic,the stronger cold advection after the trough continuous down south,the downward propagating of the stronger upper wind momentum,the strong sinking motion between upper and low air,the big pressure gradient and allobaric gradient on the ground,and so on. Between this heavy wind weather,the strong baroclinic effect makes the upper trough developed due to the temperature trough always lagged behind the height trough. Under the action of the strong cold advection which behind the trough,the upper trough deepened development and down southeast,consequently guide the cold air moved southeastward. The cold advection has been continuously strengthened during the course of the southward movement of the cold air,the front area has been further strengthened and the wind power has been increased as a result of the coefficient results between the cold and warm air over Henan. The stronger cold advection of the high-level is the main heating factor of the gale process,the cold advection of the lower-level is weaker. The downward propagat ing of the upper wind momentum plays an important role in this strong wind. The strong wind speed, which comes from the northwest of Henan,spreads from top to down and from west to east. The leading cause of this heavy wind weather is the strong pressure gradient force. The pressure differences between Xi’an,Beijing and Zhengzhou needs more attention when forecasts the heavy wind weather in Henan. In the northwest cold air,if the pressure of Xi’an increase and the pressure of Beijing decrease,the wind speed has increased trend. Conversely, if the pressure of Xi’an and Beijing both increase,the wind speed will not be very strong although the pressure gradient between Xi’an and Zhengzhou is larger.