中尺度模式对冬季兰州市低空风场和温度场的数值模拟

Mesoscale Simulations of Winter Low－Level Wind and Temperature Fields in Lanzhou City

利用美国ＮＣＡＲ新一代中尺度模式ＭＭ５Ｖ３， 对山谷城市兰州冬季风场和温度场进行了数值模拟研究， 模拟结果与现有理论及观测事实基本一致， 表明ＭＭ５Ｖ３中尺度模式可用于研究山谷城市的大气边界层情况， 模式能够较好地模拟山谷城市冬季边界层的风场和温度场特征。模拟结果分析表明， 位于河谷盆地内的兰州， 冬季近地面风场是山谷风环流和城市热岛环流共同作用的结果， 冬季夜间地面流场辐合明显， 低空盛行东风， 夜间距地３００ ｍ左右， 风向转变为偏西风， 白天风向转变高度高于夜间， 大约在５００ ｍ以上； 冬季温度场逆温特征明显。

The new mesoscale numerical model MM5V3 has been used to simulate the winter wind and temperature fields in lanzhou and the simulated results are consistent with theory and observational facts. The model has been proved to have good quality in simulating the characters of winter valley wind and temperature inversion, thus it can be used to study the atmospheric boundary layer structure of Lanzhou valley city. The main results are as follows: The winter wind fields of near surface in Lanzhou are resulted from the interactions of valley wind with the urban heat island. The prevailing low－level winds are from the east and they turn into the west at hight of about 300 m above the surface at night, but about 500 m at daytime. The temperature inversion character is obvious in the morning and at night.