摘要
利用WRF及其耦合单层城市冠层模式(UCM,Urban Canopy Model),对2012年12月4日夜间西安地区温度异常演变的天气过程进行模拟分析。结果表明,耦合了城市冠层模式的WRF系统能够较好地模拟出西安夜间温度异常升高的局地性特征,考虑了精细化下垫面分类模拟的逐时温度演变更接近实况,平均绝对误差小。天气系统与地处秦岭北麓关中平原的特殊地形是引起西安地区夜间出现温度不降反增的主要原因。首先表现在西北路冷空气推动锋前暖空气从高海拔地区到达关中平原引起的下沉增温效应;其次受秦岭地形阻挡的影响,西安地区近地层锋前的暖空气被急剧压缩出现短暂升温。城区地表温度存在显著的热岛效应,由于城区不透水下垫面的扩大,使得城区地表的水汽通量显著减小,感热通量增大,潜热通量减小,西安城区夜间气温异常升高幅度较其它区县明显偏大。
Based on new land use data in urban of Xi' an, a temperature anomaly evolution event at night on 4 December 2012 in Xi' an region was simulated by WRF model coupling single - layer Urban Canopy Model ( UCM ). The results show that the WRF/UCM model with new land use could be well to simulate the increasing anomaly of air temperature at night on 4 December 2012 in Xi' an. The evolution of simulated hourly temperature with new land use was better close to the observation, and the mean absolute error was small. The weather system and special terrain acted together to cause the process of increasing temperature anomaly at night in xi' an. On the one hand, the warm air ahead of cold front was driven by the cold air with northwest path from high altitude to Guanzhong Plain, and the sinking of air caused air temperature to increase. On the other hand, the warm air on surface layer was sharply compressed war- ming because of the blocking of Qinling Mountain. Compared with surrounding districts, the urban heat island effect was more obvious in urban area of Xi' an. The surface upward moisture flux was significantly reduced, sensible heat flux increased and latent heat flux decreased owe to the increase of waterproof underlying in urban, and then the scope of temperature increase of urban at night was obvi- ously bigger than surrounding areas. Thus, the temperature difference caused by the urban heat island is an important factor to elabo- rate temperature forecast.
出处
《干旱气象》
2015年第2期270-277,共8页
Journal of Arid Meteorology
基金
陕西省博士基金项目(2014B-1)
陕西省气象局"火车头计划"数值预报应用研究创新团队项目
陕西省社会发展攻关项目(2013K13-04-04)共同资助