【作者】 尹瑞雪；

【导师】 潘峰；

【作者基本信息】 兰州大学 ， 应用气象学， 2012， 硕士

【摘要】 随着城市化的不断发展,城市效应对大气的影响逐渐成为数值模拟研究中一个不可忽视的环节。WRY模式提供了若干模拟城市区域的参数化方案,包括Slab模式和单层城市冠层模式(UCM)等。本文使用Slab和UCM这两种方法对2005年1月26日至30日晴空背景下的兰州城区气象特征进行了模拟,并对两种模式的模拟结果进行对比分析。同时,对WRF模式使用的USGS下垫面土地利用类型资料进行了调整,使其更好的描述兰州市城区下垫面特征。(1)模拟结果显示,在冬季夜间城市地表能冷却边界层大气温度。相对Slab模式,单层城市冠层模式能更好的反映这种冷却作用,使用单层城市冠层模式的WRF能更准确的预报夜间地面2m温度。但在白天两种模式预报的差别甚小。从模拟结果与实际观测数据对比来看,UCM模拟冬季地面温度要优于Slab模式。(2)单层城市冠层模式在计算低层风廓线时,考虑了城市街谷对风速的影响,加大了地表的有效粗糙度,其拖拽作用增大了大气向下的动量通量,使得城区的近地面风速减小。(3)使用单层城市冠层模式减少了向下的净短波辐射和净长波辐射。由于使用了单层城市冠层模式更好的预报了夜间地表低温,所以该方案模拟出的地表感热通量减小。作为反馈,地表感热通量的减小使近地面大气温度更低。(4)城市冠层的存在倾向于抑制夜间边界层湍流的发展,这种作用在冷空气过境时表现的尤为显著。更多还原

【Abstract】 In a rapidly urbanizing world, investigating the effect of urban area to the atmosphere becomes an important problem in the area of numerical modeling. WRF Model provided several option in urban simulation, including slab model and a single layer urban canopy model (UCM). These two approaches are used in simulating weather of Lanzhou between Jan26th and30th in2005. The performance of these two methods in simulating urban effect is compared and analyzed. The default USGS land use data are modified in order to give better description of the real situation in Lanzhou. We found that:(1) In winter, urban canopy acts as a thermal sink, in which way the model using UCM gets more accurate prediction of2m temperature;(2) By including the effect of street canyon on wind, model with UCM gives better prediction of near surface wind,(3) Using UCM can reduce the net downward shortwave and long-wave radiation. Surface sensible heat is also reduced, which may be a result from the lower temperature predicted by UCM,(4) It appears urban canopy tends to suppress the development of turbulance in boudary layer at night, and this effect can be apmlified when cold advection exists.更多还原