CWRF对青藏高原气温和降水模拟效果的综合评估

Evaluation of CWRF simulation of temperature and precipitation on the Qinghai-Tibet Plateau

利用CWRF(Climate-Weather Research and Forecasting model)对中国区域气候的31 a多物理集合模拟试验,分析了该模式对青藏高原气温和降水的模拟效果及其对水平分辨率和物理过程参数化方案的敏感性。结果表明:1)CWRF降尺度全面改善了全球模式对高原气温和降水的模拟,使气温年循环的均方根误差减小近1℃,月降水量年循环的均方根误差减小10~40 mm,同时显著提高了各月气温和降水与实测资料年际变化的相关系数,最高提升0.6;2)模式分辨率对降水模拟有显著影响,不同分辨率模拟降水差异高达60 mm(54%),模拟偏差随分辨率提高先降低后上升,转折在30 km左右;3)物理过程参数化方案对气温和降水模拟影响显著,不同方案模拟的各月平均气温相差1~4℃,夏季各月降水量相差20~100 mm,其中对气温模拟影响最大的是辐射方案,对降水影响最大的是积云方案。本文为CWRF局地优化对物理参数化及水平分辨率等如何选择提供了依据。

Multi-physics ensemble simulation experiments of regional climate in China by CWRF(Climate-Weather Research and Forecasting model) for the period 1979—2016 were applied to analyze and evaluate the simulation of temperature and precipitation over the Tibetan Plateau and its sensitivity to horizontal resolution and parameterization scheme of physical processes.The results show that: 1) Compared with global models,CWRF downscaling improves the simulation of temperature and precipitation over the plateau,reduces the root mean square error (RMSE) of the annual temperature cycle by nearly 1 ℃,and decreases the RMSE of the annual cycle of precipitation by 10—40 mm.At the same time,it significantly improves the correlation coefficient between simulated and measured interannual variability,with the highest increase of 0. 6;2) Model’s resolution has a significant impact on precipitation simulation.The difference of simulated precipitation by models with the different resolution is as high as 60 mm (54%),and the simulation deviation first decreases and then increases with the increased resolution,and the turning point is about 30 km;3) Physical process parameterization scheme has a significant impact on temperature and precipitation simulation. The difference in monthly average temperature between different schematais 1-4 ℃,and the difference in monthly precipitation in summer is 20—100 mm.Among them,the radiation scheme has the highest impact on temperature simulation,and the cumulus scheme has the utmost impact on precipitation.This paper provides a basis for the selection of physical parameterization and horizontal resolution for CWRF local optimization.