Improving US extreme precipitation simulation: sensitivity to physics parameterizations
Improving US extreme precipitation simulation: sensitivity to physics parameterizations
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DOI：
10.1007/s00382-020-05267-6
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发表时间：
2020-04
期刊：
影响因子：
4.6
通讯作者：
Chao Sun;Xin‐Zhong Liang
中科院分区：
文献类型：
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作者：
Chao Sun;Xin‐Zhong Liang
气候模型往往低估了降雨强度，而产生了更频繁的光事件，导致在极端降水模拟中存在明显的偏差。为了减少这种偏差并更好地了解其根本原因，我们在区域气候-天气研究和预报模式(CWRF)中测试了25个物理配置的集合。所有配置都是由ECMWF-中期再分析推动的，并在1980-2015年间持续整合在网格间距为30公里的毗邻美国上空。它们共同代表了CWRF模拟美国极端降水特征的能力，它们的传播描述了交替物理参数化的结构不确定性。在所有物理构型中，美国极端降水模拟对积云参数化最为敏感。总体上，集合积云参数化(ECP)最能再现日95百分位数降水的季节平均空间型(P95)。其他积云方案严重低估了P95，特别是在对流盛行季节的海湾国家和中西部各州。具有ECP的CWRF的表现优于驱动再分析，尽管其每日大气湿度数据同化，但驱动再分析大大低估了P95。暖季CWRF对ERI的改善比冷季大得多。单独改变ECP闭合假设产生了两组不同的对流加热/干燥效应：一组主要通过改变总降水强度改变P95，另一组主要通过改变雨天频率来改变P95。微物理、辐射、边界层和陆面过程也影响了结果，特别是在天气和对流强迫混合的情况下，他们的一些参数化方案与ECP合作，进一步改进了第95页。
Climate models tend to underestimate rainfall intensity while producing more frequent light events, leading to significant bias in extreme precipitation simulation. To reduce this bias and better understand its underlying causes, we tested an ensemble of 25 physics configurations in the regional Climate-Weather Research and Forecasting model (CWRF). All configurations were driven by the ECMWF-Interim reanalysis and continuously integrated during 1980–2015 over the contiguous United States with 30-km grid spacing. Together they represent CWRF’s ability to simulate characteristics of US extreme precipitation, and their spread depicts the structural uncertainty from alternate physics parameterizations. The US extreme precipitation simulation was most sensitive to cumulus parameterization among all physics configurations. The ensemble cumulus parameterization (ECP) was overall the most skilled at reproducing seasonal mean spatial patterns of daily 95th percentile precipitation (P95). Other cumulus schemes severely underestimated P95, especially over the Gulf States and the Central-Midwest States in convective prevailing seasons. CWRF with ECP outperformed the driving reanalysis, which substantially underestimated P95 despite its daily atmospheric moisture data assimilation. The CWRF improvement over ERI is much larger in warm than cold seasons. Changing alone ECP closure assumptions produced two distinct clusters of convective heating/drying effects: one altered P95 mainly by changing total precipitation intensity and another by changing rainy-day frequency. Microphysics, radiation, boundary layer, and land surface processes also impacted the result, especially under mixed synoptic and convective forcings, and some of their parameterization schemes worked with ECP to further improve P95.