Diurnal Effects of Regional Soil Moisture Anomalies on the Great Plains Low-Level Jet
Diurnal Effects of Regional Soil Moisture Anomalies on the Great Plains Low-Level Jet
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DOI：
10.1175/mwr-d-19-0135.1
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发表时间：
2019-12
影响因子：
3.2
通讯作者：
Matthew A. Campbell;Craig R. Ferguson;D. Burrows;M. Beauharnois;G. Xia;L. Bosart
中科院分区：
文献类型：
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作者：
Matthew A. Campbell;Craig R. Ferguson;D. Burrows;M. Beauharnois;G. Xia;L. Bosart
大平原低空急流(GPLLJ)对大平原暖季水资源(降水)、风资源和恶劣天气爆发有贡献。过去的研究表明，需要天气和局地中尺度物理机制(Holton和Blackadar机制)来解释GPLLJ的可变性。虽然土壤水分-PBL相互作用是局部力学理论的核心，但区域土壤水分异常对GPLLJ速度、北向渗透和恶劣天气倾向的日效应还不是很清楚。在这项研究中，两个31人的WRF-ARW随机动能后向散射方案集合模拟了一个典型的暖季GPLLJ个例，在CONUS范围内土壤干湿两种情况下。在GP(24°-48°N，103°-90°W)，2100UTC(下午)感热和层高的集合平均差分别为25-150Wm−2和100-700m，最终导致GPLLJ850-hPA风速差1-4m S−1 12小时(0900UTC；清晨)。白天旱地边界层较大的热量积累影响了GP(天气条件和Holton机制)的东西位势高度梯度，导致GP北部较深的热低，从而导致地转风的增加。干燥土壤上白天增强的湍流混合影响了PBL结构(Blackadar机制)，导致非地转风增加。夜间地转风和非地转风建设性地相互作用，导致干燥土壤上夜间GPLLJ较快。CIN(~50-150J kg−1)和CAPE(~500-1000J kg−1)的集合差异对恶劣天气预报具有重要意义。
The Great Plains (GP) low-level jet (GPLLJ) contributes to GP warm season water resources (precipitation), wind resources, and severe weather outbreaks. Past research has shown that synoptic and local mesoscale physical mechanisms (Holton and Blackadar mechanisms) are required to explain GPLLJ variability. Although soil moisture–PBL interactions are central to local mechanistic theories, the diurnal effect of regional soil moisture anomalies on GPLLJ speed, northward penetration, and propensity for severe weather is not well known. In this study, two 31-member WRF-ARW stochastic kinetic energy backscatter scheme ensembles simulate a typical warm season GPLLJ case under CONUS-wide wet and dry soil moisture scenarios. In the GP (24°–48°N, 103°–90°W), ensemble mean differences in sensible heating and PBL height of 25–150 W m−2 and 100–700 m, respectively, at 2100 UTC (afternoon) culminate in GPLLJ 850-hPa wind speed differences of 1–4 m s−1 12 hours later (0900 UTC; early morning). Greater heat accumulation in the daytime PBL over dry soil impacts the east–west geopotential height gradient in the GP (synoptic conditions and Holton mechanism) resulting in a deeper thermal low in the northern GP, causing increases in the geostrophic wind. Enhanced daytime turbulent mixing over dry soil impacts the PBL structure (Blackadar mechanism), leading to increased ageostrophic wind. Overnight geostrophic and ageostrophic winds constructively interact, leading to a faster nocturnal GPLLJ over dry soil. Ensemble differences in CIN (~50–150 J kg−1) and CAPE (~500–1000 J kg−1) have implications for severe weather predictability.