利用RAMS模式对山谷城市兰州冬季湖泊效应的数值模拟

利用美国科罗拉多州立大学和MRC/ASTER发展的RAMS中尺度气象模式， 以NECP再分析资料为初、 边值条件， 在兰州城区东面设计了有湖和无湖两个试验， 做了72 h三重嵌套模拟试验， 分别模拟了两种情况下冬季兰州山谷地区的湖泊效应和大气边界层特征。模拟结果表明： （1）白天兰州山谷地区谷风在14：00强度达到最大。加入湖泊后， 14：00湖风强度增大， 湖风对谷风没有明显影响， 只对湖区及岸边附近的风场有影响。兰州山谷地区20：00以后山风开始出现， 到05：00左右北山山风的风速大于南山山风。05：00以后南山山风风速增大， 山谷以偏西风为主。加入湖泊后， 陆风也在夜间02：00左右表现的最为明显， 陆风和山风相互叠加， 导致兰州山谷东部地区西风风速增大； （2）加入湖泊后， 对周围地区气温的影响表现为夜间有增温作用， 增温作用随着离湖泊的距离渐远而减弱。在靠近湖区处夜间的近地面逆温强度减弱； （3）加入湖泊后， 对靠近湖面处空气相对湿度的影响表现为减小， 对靠近湖西岸陆地上近地面空气相对湿度的影响表现为先减小后增加， 这一点在夜间表现的最明显， 对靠近湖面处空气绝对湿度的影响表现为增加； （4）加入湖泊后， 湖区的净辐射和感热通量都减小， 湖的东西两岸的净辐射和感热通量都增大。在22：00到凌晨05：00之间， 靠近湖西岸的陆地上净辐射和感热通量也有所增大。

Numerical Simulation of Winter Lake Effect in Valley City of Lanzhou Using RAMS Model

An artificial lake is made to the east low-lying region of Lanzhou city area for the purpose of exploring new air pollution control in Lanzhou City. In this investigation, two set of triple nested experiments which include without and with the lake experiments were conducted using the mesoscale numerical model RAMS developed by Colorado State University and the MRC / ASTER, and the characteristics of atmospheric boundary layer and lake effect in valley city were simulated. The results are as follows: (1) During the day, the intensity of valley breeze is maximum at 14:00. After making a artificial lake, lake breeze strength increases at 14:00, and the lake breeze has no significant effect on the valley breeze except for the surface of lake and the shore near the lake. During the night, the mountain breeze is emergence after 20:00 at night, around 05:00 the mountain breeze speed of north mountain is greater than south mountain. After 05:00, the mountain breeze speed of south mountain increases. The valley is main the west wind. After making a artificial lake, the lake breeze is obvious around 02:00, and land breeze and mountain breeze overlapping with each other, leading to the eastern part of Lanzhou valley westerly wind speed increased. (2) The temperature around the lake is increased in the winter, and the intensity of increase is weakened with the distance from the lake further away. The intensity of inversion temperature near the lake is lower at night. (3) After making an artificial lake, the air relative humidity is reduced on the nearr surface of the lake. Near the west shore of the lake, the air relative humidity for the first reduced then increases. It is obvious in the evening. the air absolute humidity is increase on the near surface of the lake. (4) The net radiation and sensible heat flux are obviously reduced in the lake area. Near the east and west shore of the lake, the net radiation and sensible heat flux are increased more. In the evening between 22:00 to 05:00, the net radiation and sensible heat also increases at the inland where the distance from the lake is a little far away.