On The Changes in Convection-Allowing WRF Forecasts of MCS Evolution Due to Decreases in Model Horizontal and Vertical Grid Spacing. Part I: Changes in Cold Pool Evolution
On The Changes in Convection-Allowing WRF Forecasts of MCS Evolution Due to Decreases in Model Horizontal and Vertical Grid Spacing. Part I: Changes in Cold Pool Evolution
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DOI：
10.1175/waf-d-22-0041.1
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发表时间：
2022-08
影响因子：
2.9
通讯作者：
B. Squitieri;W. Gallus
中科院分区：
文献类型：
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作者：
B. Squitieri;W. Gallus
水平网格间距小于3公里的数值预报对流表现的改善程度仍有争议。虽然一些研究表明，需要亚公里水平网格间距来解决对流结构的细节，但其他研究表明，将网格间距从3-4公里减少到1-2公里，对深对流的预测几乎没有额外的价值。此外，很少有研究表明垂直网格间距的变化如何影响雷暴预报，特别是当水平网格间距同时减小时。本研究调查如何暖季美国中部模拟MCS冷池11个观察到的情况下，减少水平网格间距从3到1公里，而增加垂直水平从50到100 WRF运行的影响。与所有其他网格间距相比，3公里100级运行产生了最深和最负浮力的冷池，因为上升气流的分辨率更差，导致向后平流冻结水凝物的通量更高，其融化过程被更精细的垂直网格间距增强，从而更好地解决了融化层。然而，在所有11个案例中，更主要的信号是在1公里的运行更广阔的冷池，更强和更丰富的上升气流集中沿着MCS领导线支持了更大的体积集中向后水凝平流和由此产生的潜热冷却在较低的水平。
The degree of improvement in convective representation in NWP with horizontal grid spacings finer than 3 km remains debatable. While some research suggests sub-km horizontal grid spacing is needed to resolve details of convective structures, other studies have shown that decreasing grid spacing from 3-4 km to 1-2 km offers little additional value for forecasts of deep convection. In addition, few studies exist to show how changes in vertical grid spacing impact thunderstorm forecasts, especially when horizontal grid spacing is simultaneously decreased. The present research investigates how warm-season central U.S. simulated MCS cold pools for eleven observed cases are impacted by decreasing horizontal grid spacing from 3 to 1 km while increasing the vertical levels from 50 to 100 in WRF runs. 3 km runs with 100 levels produced the deepest and most negatively buoyant cold pools compared to all other grid spacings since updrafts were more poorly resolved, resulting in a higher flux of rearward-advected frozen hydrometeors, whose melting processes were augmented by the finer vertical grid spacing, which better resolved the melting layer. However, the more predominant signal among all eleven cases was for more expansive cold pools in 1 km runs, where the stronger and more abundant updrafts focused along the MCS leading line supported a larger volume of concentrated rearward hydrometeor advection and resultant latent cooling at lower levels.