Reanalyses and a High-Resolution Model Fail to Capture the “High Tail” of CAPE Distributions
Reanalyses and a High-Resolution Model Fail to Capture the “High Tail” of CAPE Distributions
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DOI：
10.1175/jcli-d-20-0278.1
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发表时间：
2020-12
影响因子：
4.9
通讯作者：
Ziwei Wang;J. Franke;Zhenqi Luo;E. Moyer
中科院分区：
文献类型：
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作者：
Ziwei Wang;J. Franke;Zhenqi Luo;E. Moyer
对流有效位能（CAPE）在气候模拟中有着重要的意义，因为它在恶劣天气和模式构建中都发挥着重要作用。CAPE的极端水平（>2000 J kg−1）与高影响天气事件有关，CAPE被广泛用于对流参数化，以帮助确定对流的强度和时间。然而，到目前为止，很少有研究系统地评估CAPE偏差在气候模式的背景下，没有解决偏置CAPE分布的高尾。这项工作比较了来自四个来源的约20万夏季邻近探测的CAPE分布：观测无线电探空仪网络[综合全球无线电探空仪档案（IGRA）]，0.125°再分析（ERA-Interim和ERA 5），以及由ERA-Interim驱动的4公里对流允许区域WRF模拟。再分析和WRF模型都一致显示CAPE的分布过于狭窄，在基于地表的CAPE中，高尾（>第90百分位数）系统性地偏低了10%，在其他CAPE定义中甚至更多。这一“缺失的尾部”对应于与影响最相关的条件。所有数据集的CAPE偏差都是由表面温度和湿度驱动的：再分析和WRF模型低估了观测到的极端高温和潮湿的情况。这些结果表明，减少陆面和边界层模式的不准确性是准确再现CAPE的关键。
Convective available potential energy (CAPE) is of strong interest in climate modeling because of its role in both severe weather and in model construction. Extreme levels of CAPE (>2000 J kg−1) are associated with high-impact weather events, and CAPE is widely used in convective parameterizations to help determine the strength and timing of convection. However, to date few studies have systematically evaluated CAPE biases in models in a climatological context, and none have addressed bias in the high tail of CAPE distributions. This work compares CAPE distributions in ~200 000 summertime proximity soundings from four sources: the observational radiosonde network [Integrated Global Radiosonde Archive (IGRA)], 0.125° reanalyses (ERA-Interim and ERA5), and a 4-km convection-permitting regional WRF simulation driven by ERA-Interim. Both reanalyses and the WRF Model consistently show too-narrow distributions of CAPE, with the high tail (>90th percentile) systematically biased low by up to 10% in surface-based CAPE and even more in alternate CAPE definitions. This “missing tail” corresponds to the most impacts-relevant conditions. CAPE bias in all datasets is driven by surface temperature and humidity: reanalyses and the WRF Model underpredict observed cases of extreme heat and moisture. These results suggest that reducing inaccuracies in land surface and boundary layer models is critical for accurately reproducing CAPE.