Hydroclimate of the Western United States Based on Observations and Regional Climate Simulation of 1981–2000. Part I: Seasonal Statistics
Hydroclimate of the Western United States Based on Observations and Regional Climate Simulation of 1981–2000. Part I: Seasonal Statistics
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基于 1981-2000 年观测和区域气候模拟的美国西部水文气候 第一部分：季节统计。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
X. Bian
中科院分区：
文献类型：
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作者：
L. Leung;Y. Qian;X. Bian
美国西部区域气候表现出大气环流与地形相互作用的明显痕迹。这种多样化气候状态的独特特征对气候建模提出了挑战。本文提供了详细的观测分析和区域气候模拟，以提高我们对该地区气候的认识和模式。本研究使用的主要数据是基于站点观测和NCEP - NCAR全球再分析的1/88格点温度和降水数据。这些数据用于评估由NCEP - NCAR再分析的大尺度条件驱动的第五代宾夕法尼亚州立大学-国家大气研究中心（Penn State - NCAR）中尺度模式（MM5）进行的20年区域气候模拟。研究的区域气候特征包括季节平均和极端降水；降水率分布；降水强度、频率和季节性。此外，还分析了降水与地表温度之间的关系，作为评估区域气候模拟在地表水文模拟中的效果的一种手段；分析了降水与海拔之间的关系，作为地表地形和空间分辨率影响的诊断。后者是在横跨美国西部各种地形特征的五个东西样带上进行的。这些分析表明，区域模拟真实地反映了许多区域气候特征。模拟的季节平均和极端降水与观测值相当。区域模拟产生与观测值相当的大范围降水速率的降水。冷季降水偏大，西部盆地和山间降水偏大，暖季西南部降水偏小。夏季西北和西南地区降水频率呈减少趋势，而降水强度呈减少趋势，导致该地区夏季平均降水不足。由于模拟中普遍存在暖偏，也有一种趋势，即更多的降水事件与较暖的温度有关，这可能影响积雪和径流的模拟。
The regional climate of the western United States shows clear footprints of interaction between atmospheric circulation and orography. The unique features of this diverse climate regime challenges climate modeling. This paper provides detailed analyses of observations and regional climate simulations to improve our understanding and modeling of the climate of this region. The primary data used in this study are the 1/88 gridded temperature and precipitation based on station observations and the NCEP‐NCAR global reanalyses. These data were used to evaluate a 20-yr regional climate simulation performed using the fifth-generation Pennsylvania State University‐National Center for Atmospheric Research (Penn State‐NCAR) Mesoscale Model (MM5) driven by large-scale conditions of the NCEP‐NCAR reanalyses. Regional climate features examined include seasonal mean and extreme precipitation; distribution of precipitation rates; and precipitation intensity, frequency, and seasonality. The relationships between precipitation and surface temperature are also analyzed as a means to evaluate how well regional climate simulations can be used to simulate surface hydrology, and relationships between precipitation and elevation are analyzed as diagnostics of the impacts of surface topography and spatial resolution. The latter was performed at five east‐west transects that cut across various topographic features in the western United States. These analyses suggest that the regional simulation realistically captures many regional climate features. The simulated seasonal mean and extreme precipitation are comparable to observations. The regional simulation produces precipitation over a wide range of precipitation rates comparable to observations. Obvious biases in the simulation include the oversimulation of precipitation in the basins and intermountain West during the cold season, and the undersimulation in the Southwest in the warm season. There is a tendency of reduced precipitation frequency rather than intensity in the simulation during the summer in the Northwest and Southwest, which leads to the insufficient summer mean precipitation in those areas. Because of the general warm biases in the simulation, there is also a tendency for more precipitation events to be associated with warmer temperatures, which can affect the simulation of snowpack and runoff.