区域气候模式分辨率对夏季降水模拟的影响

Influence of spatial resolution in a regional climate model on summer precipitation simulation

利用最新发布的区域气候模式RegCM4,选取3种水平分辨率,3种垂直分辨率,对2001～2003年6～8月气候状况进行模拟,将模拟降水与GPCP降水资料在季、月、日尺度进行对比分析,研究分辨率对夏季降水模拟的影响,得到主要结论:RegCM4模拟结果能较好地反映模拟区域降水由东南向西北递减的分布趋势,模拟降水量随水平、垂直分辨率的增加而减小,当水平分辨率为30 km,垂直分辨率为14层时,全区域模拟降水偏差最小;不同区域、不同月份区域平均降水对分辨率的敏感性存在明显差异;在高海拔区域,分辨率对降水模拟影响显著,随着水平分辨率的提高,模拟降水更接近观测值;模拟日降水强度分布的峰值随着垂直分辨率的提高,向弱降水方向移动显著;分辨率配置主要影响模拟降水偏差的低频分量及24 d周期分量,通过合理调整分辨率配置可以有效减小模拟系统误差。

This paper utilizes the latest version of Regional Climate Model（RegCM4） with three different horizontal and vertical resolutions to simulate the regional climate in China during June to August,2001-2003.The simulated precipitation is compared to the GPCP（Global Precipitation Climatology Project） precipitation at daily,monthly and seasonal time scales in an effort to study the influence of spatial resolution on summer precipitation simulation.The main conclusions to come out of this study are the following.The new version of RegCM4 is able to better simulate the distribution pattern of precipitation.Simulated precipitation amounts tend to decrease from southeast to northwest,and the amount decreases with the increase of both horizontal and vertical resolutions.Precipitation simulated with horizontal grid spacing of 30 km and 14 vertical levels will have the least bias among the all experiments.The sensitivity of simulated precipitation to the model resolution varies differently over different regions and at different times of the year.The spatial resolution will have more influence on precipitation simulation in higher altitudes.The simulated peak value of daily precipitation decreases with the increase of spatial resolutions.The resolution will have more profound impacts on the low-frequency bias and the 24-day period component in the daily precipitation series.Thus,the system error can be reduced effectively by adjusting the model spatial resolutions.