Comparison of Biases in Warm-Season WRF Forecasts in North and South America
Comparison of Biases in Warm-Season WRF Forecasts in North and South America
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DOI：
10.1175/waf-d-20-0062.1
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发表时间：
2021-05
影响因子：
2.9
通讯作者：
Jeremiah O. Piersante;R. Schumacher;K. Rasmussen
中科院分区：
文献类型：
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作者：
Jeremiah O. Piersante;R. Schumacher;K. Rasmussen
使用WRF模式在20公里网格间距上进行不同参数化的集合预报，用于调查和比较北美和南美的降水和大气剖面预报偏差。通过对NCEP第4阶段降水分析的验证，表明2016-2017年期间，除降水量和降水季节外，积云参数化（CP）对北美地区降水预测技能的影响最大。根据北美和南美的业务无线电探空仪对集合子集的验证发现，在温暖季节，两大洲的预报都具有相当大的中层干偏，特别是在700 hPa。具体分析表明，大的中层误差与高地形以东的中尺度对流系统（mcs）和来自北美和南美落基山脉和安第斯山脉的西风沉降流有关。然而，南美的错误率始终高于北美。这可能是由于安第斯山脉复杂的地形和相对于落基山脉较高的平均海拔，这允许更深的低空喷射和持久的mcs，这两者都是20公里模拟难以解决的。在RELAMPAGO野外活动的数据可用性之后，作者希望这项工作能够激发对北美和南美大型降水系统的进一步比较，因为它们对两个大陆都有很大的影响。
Ensemble forecasts using the WRF Model at 20-km grid spacing with varying parameterizations are used to investigate and compare precipitation and atmospheric profile forecast biases in North and South America. By verifying a 19-member ensemble against NCEP Stage IV precipitation analyses, it is shown that the cumulus parameterization (CP), in addition to precipitation amount and season, had the largest influence on precipitation forecast skill in North America during 2016-2017. Verification of an ensemble subset against operational radiosondes in North and South America finds that forecasts in both continents feature a substantial mid-level dry bias, particularly at 700 hPa, during the warm season. Case-by-case analysis suggests that large mid-level error is associated with mesoscale convective systems (MCSs) east of the high terrain and westerly subsident flow from the Rocky and Andes Mountains in North and South America. However, error in South America is consistently greater than North America. This is likely attributed to the complex terrain and higher average altitude of the Andes relative to the Rockies, which allow for a deeper low-level jet and long-lasting MCSs, both of which 20-km simulations struggle to resolve. In the wake of data availability from the RELAMPAGO field campaign, the authors hope that this work motivates further comparison of large precipitating systems in North and South America, given their high impact in both continents.