青藏高原非均匀下垫面热力输送系数的估算

Estimation of the Heat Transfer Coefficient over Inhomogeneous Underlying Surface on the Qinghai-Tibetan Plateau

利用欧洲中心的再分析资料(2000—2014年)风速和温度再分析资料,结合增强植被指数、植被类型、地面高程等多种卫星遥感资料以及陆面过程观测资料,在廓线-通量法的基础上,对以往动力和热力粗糙度方案加以改进,建立了更准确的空气动力学粗糙度和热传输附加阻尼的估算方案,进而求得适用于青藏高原非均匀下垫面的热力输送系数。并利用2008年JICA项目试验的涡动相关观测资料与GAM E-Tibet试验的梯度观测资料进行了对比与检验。结果表明:改进的估算方案能够体现高原地形和植被的非均匀特征;青藏高原的粗糙度等相关参数的时空分布特征与植被高度和密度、下垫面的热力条件密切相关;热力输送系数具有南部大于北部,东部大于西部,夏季大于冬季的特征;高植被和地-气温差偏大的区域热力输送系数偏大。

Combined with wind speed and temperature reanalysis data from ERA-Interim by ECMWF,the land surface observations data and a variety of satellite remote sensing data during 2000—2014,based on the profileflux method,this paper aims to get the heat transfer coefficient（CH） that is applicable to Qinghai-Tibetan Plateau,by improving the accuracy of aerodynamic roughness and additional damping of heat transfer（kB-1）. Enhanced Vegetation Index and vegetation height was added to the original profile formula to estimate roughness,which could reflect the effects of vegetation coverage and types on the change of roughness. The differences between ground and air temperature was used to revise the estimation method of kB-1 and get results closer to the actual value. Finally,based on the optimization of above parameters,the heat transfer coefficient over the QinghaiTibetan Plateau in neutral atmospheric stratification is calculated,and its time-space distribution characteristics are analyzed. Eddy correlation data from JICA experiment and gradient observation data from GAME-Tibet experiment in 2008 were used to test the estimates. The results show that the improved computational scheme can reflect the inhomogeneous features of topography and vegetation over Qinghai-Tibetan Plateau; Time-space distribution characteristics of roughness and other related parameters are closely related with vegetation height and density and thermal conditions of underlying surface; Heat transfer coefficient is higher in the south than in the north,it is higher in the east than in the west,and it in summer maximum and winter minimum; The values in different eco-geographical regions have significant difference,it is higher in regions with high vegetation and large differences between ground and air temperature.