The Impact of Low-Level Moisture Errors on Model Forecasts of an MCS Observed during PECAN
The Impact of Low-Level Moisture Errors on Model Forecasts of an MCS Observed during PECAN
复制标题
低水平湿度误差对 PECAN 期间观测到的 MCS 模型预测的影响
DOI：
10.1175/mwr-d-16-0296.1
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发表时间：
2017
影响因子：
3.2
通讯作者：
Schumacher, Russ S.
中科院分区：
文献类型：
--
作者：
Peters, John M.;Nielsen, Erik R.;Parker, Matthew D.;Hitchcock, Stacey M.;Schumacher, Russ S.
本文研究了2015年6月24日至25日在爱荷华州的平原夜间高架对流（PECAN）现场活动期间，对高架中尺度对流系统（MCS）附近环境的预报误差。该MCS的东侧产生了一个外流边界（OFB），并沿该OFB向东南沿着移动。MCS的西侧在系统的OFB以北约100公里处保持准静止状态，并产生局部洪水。对流有效位能（CAPE）增加，对流抑制（CIN）减弱，对流有效位能（CAPE）增强，对流抑制（CIN）减弱。相比之下，该模型分析和预测大大低估CAPE和高估CIN，由于他们的水分代表性不足。数值模拟分析了MCS在东北方向太远的不同距离处的位置。MCS位移误差与模式对低层湿度的代表性不足以及与之相关的对包裹初始高度与其自由对流水平之间垂直距离的代表性过高密切相关（ 与CIN相关）。被高估的 在模式中，导致空气包需要不切实际地在逐渐的中-α尺度抬升区域中向东北方向移动，然后这些包才开始对流。这些结果表明，错误的MCS预测数值预报模式有时可能会导致分析不良的低层湿度场。
This article investigates errors in forecasts of the environment near an elevated mesoscale convective system (MCS) in Iowa on 24–25 June 2015 during the Plains Elevated Convection at Night (PECAN) field campaign. The eastern flank of this MCS produced an outflow boundary (OFB) and moved southeastward along this OFB as a squall line. The western flank of the MCS remained quasi stationary approximately 100 km north of the system’s OFB and produced localized flooding. A total of 16 radiosondes were launched near the MCS’s eastern flank and 4 were launched near the MCS’s western flank.Convective available potential energy (CAPE) increased and convective inhibition (CIN) decreased substantially in observations during the 4 h prior to the arrival of the squall line. In contrast, the model analyses and forecasts substantially underpredicted CAPE and overpredicted CIN owing to their underrepresentation of moisture. Numerical simulations that placed the MCS at varying distances too far to the northeast were analyzed. MCS displacement error was strongly correlated with models’ underrepresentation of low-level moisture and their associated overrepresentation of the vertical distance between a parcel’s initial height and its level of free convection ( , which is correlated with CIN). The overpredicted in models resulted in air parcels requiring unrealistically far northeastward travel in a region of gradual meso-α-scale lift before these parcels initiated convection. These results suggest that erroneous MCS predictions by NWP models may sometimes result from poorly analyzed low-level moisture fields.
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影响因子：
3.1
作者：
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通讯作者：
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DOI：
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发表时间：
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DOI：
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发表时间：
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期刊：
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作者：
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