精细城市边界层模式的建立及应用研究

Development and applications of a fine urban boundary layer model

本文建立了一个精细城市边界层模式,它是针对小型城市模拟应用特点,并在原有较粗网格区域边界层模式及模拟应用的基础上建立的.与原有模式相比,新建模式(1)加入水汽过程,(2)引入了热力粗糙度,(3)考虑了城市人为热源对城市地表能量平衡的贡献及其对城市热岛的影响,(4)考虑了城狭ψ饔市冠层建筑物的动力拖.运用建立的模式分别以北京东南部12 km×18 km范围的一块市区和一个卫星城镇(即亦庄,范围10.5 km×6.7 km)进行了实际模拟试验.通过模拟所获的城市地区地面气温、风速和比湿结果与当地自动气象站观测资料进行比对,结果表明:模式能较好地表征气象条件的日变化规律,模拟结果与实测数据间的相对平均偏差(FB):地面气温为0.02,风速为0.13,空气比湿为0.09.模拟研究了小型城市气象环境的诊断与分析.还分析研究了城乡地区之间气象环境和地面能量平衡的不同特性.取得了良好效果.

A fine urban boundary layer model has been developed in the paper, which is based on the characteristics of town and the original coarse resolution regional boundary layer model as well. It is a three-dimensional nonhydrostatic diagnostic numerical model in the terrain-following coordinate system. The E--e closure scheme was used in the model. Compared with the former model, the new model shows differences in the following aspects： 1） the moisture process, 2） heat roughness length, 3） the contribution of urban anthropogenic heat to urban surface energy balance and its impact on urban heat island, 4） the dynamical drag effect of the urban buildings. Two cases were simulated by this new developed model. One is for the southeast region of Beijing city whose area is 12 km× 18 km and the other one is for a satellite town which is only 10.5 km× 6.7 km in size. The simulated results of near surface temperature, wind speed and specific humidity are in reasonable agreement with the observational results of automatic weather stations, and they actually reflect the diurnal variation of the meteorological environment. The fraction mean bias of near surface temperature is only 0.02, 0.13 and 0.09 for wind speed and specific humidity respectively. In this study the diurnal variation of the meteorological environment is diagnosed and analyzed. The different properties of meteorological environment and surface energy balance between the urban and the rural area are also analyzed.