针对北极地区典型月份期间的大气数值模拟分析

本文利用极地中尺度数值模式Polar MM5对2005年7月17日～19日， 2007年12月20日～24日北极地区大气环流进行了中尺度数值模拟， 分析比较了北极夏季典型代表月7月间和冬季典型代表月12月间大气特征。数值分析表明，在500hPa高度上，12月和7月极区的大气环流都主要由2个波动控制；夏季的冰岛低压在冬季表现为一个高压系统，并且伸展到格陵兰岛上空。我们选择了2个北极地区探空站与相应温度场和风场的数值模拟结果进行了对比，表明数值模式能够很好地再现观测到得大气分布特征，表现为小的模式偏差和较高的相关系数。夏季7月份期间, Barrow 站2m处空气温度，感热通量和潜热通量具有明显的日变化特征和极地逆温层结垂直结构特征；冬季12月份期间，Barrow 站2m处空气温度，感热通量和潜热通量呈现出反位相变化的特征，虽然各通量峰值远小于夏季时的情形，但是北极所考虑站点下垫面在冬季12月和夏季7月份都是大气的热源和水汽源。

Atmospheric Numerical Analyses over Arctic Region during the period of typical months

The modeled atmospheric circulations around the Arctic region during the period of 17-19, July, 2005 and 20-24, December, 2007 with the Polar MM5 are presented, respectively. The numerical analyses indicated there were two fluctuation modes existed over the Pole both in summer and winter season. There was an Iceland low additionally in summer simulation instead of a high pressure system existed around the Iceland in winter. And this high pressure system extended to the Greenland. Two upper-air observations from the Arctic are used to verify the simulated atmospheric state for the variables of temperature and wind. The model is found to reproduce the observed atmospheric state with smaller biases and larger correlation coefficients for the variables considered. Moreover, the mesoscale model reflected evident diurnal cycles for the temperature at height of 2m, sensible heat and latent heat fluxes at station Barrow in July; and the inversed temperature at Barrow was also simulated by the model, effectively. In winter, T2m and turbulent fluxes took on the characteristics of anti-phase state. The Arctic landuse was the heat and moisture source of the atmosphere, although the amplitude of fluxes in winter was far less than the state of summer.