Elevated Mixed Layers during Great Lake Lake-Effect Events: An Investigation and Case Study from OWLeS
Elevated Mixed Layers during Great Lake Lake-Effect Events: An Investigation and Case Study from OWLeS
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大湖效应事件期间的混合层升高：OWLeS 的调查和案例研究
DOI：
10.1175/mwr-d-22-0344.1
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发表时间：
2024
影响因子：
3.2
通讯作者：
Jurewicz, Michael L.
中科院分区：
文献类型：
--
作者：
Greybush, Steven J.;Sikora, Todd D.;Young, George S.;Mulhern, Quinlan;Clark, Richard D.;Jurewicz, Michael L.
在安大略冬季湖泊效应系统（OWLeS）现场项目的密集观测期（IOP）期间发射的rawinsondes数据显示，在OWLeS湖泊效应事件期间，安大略湖附近对流层下部的高架混合层（EML）相对常见。保守地说，在290次OWLeS IOP探测中，有193次存在EML。从OWLeS IOP探测得到的EML基准压力分布揭示了两类EML，一类具有相对低海拔的基准（900-750 hPa），另一类具有相对高海拔的基准（750-500 hPa）。据推测，EML的前类，这是本研究的重点，是，有时，个别五大湖相关的中尺度过程的结果。WRF再分析领域的案例研究在OWLeS领域的项目提供了两种手段的证据，低海拔基地EML可以起源于湖泊效应边界层对流和相关的中尺度环流。首先，这种电磁层可以在中尺度螺线管环流的上层出流分支中形成。疏散的大湖修正对流边界层空气高空然后躺在上面的环境空气的更大的静态稳定性，形成EML。第二，这样的EML可以形成在没有中尺度螺线管环流时，大湖修改对流边界层溢出环境空气的密度较大。再分析场表明，与大湖修正对流边界层相关的EML和静稳定性降低层可以从其形成区域顺风延伸数百公里。业务的影响和未来的研究途径进行了讨论。
Data from rawinsondes launched during intensive observation periods (IOPs) of the Ontario Winter Lake-Effect Systems (OWLeS) field project reveal that elevated mixed layers (EMLs) in the lower troposphere were relatively common near Lake Ontario during OWLeS lake-effect events. Conservatively, EMLs exist in 193 of the 290 OWLeS IOP soundings. The distribution of EML base pressure derived from the OWLeS IOP soundings reveals two classes of EML, one that has a relatively low-elevation base (900–750 hPa) and one that has a relatively high-elevation base (750–500 hPa). It is hypothesized that the former class of EML, which is the focus of this research, is, at times, the result of mesoscale processes related to individual Great Lakes. WRF reanalysis fields from a case study during the OWLeS field project provide evidence of two means by which low-elevation base EMLs can originate from the lake-effect boundary layer convection and associated mesoscale circulations. First, such EMLs can form within the upper-level outflow branches of mesoscale solenoidal circulations. Evacuated Great Lakes–modified convective boundary layer air aloft then lies above ambient air of a greater static stability, forming EMLs. Second, such EMLs can form in the absence of a mesoscale solenoidal circulation when Great Lake–modified convective boundary layers overrun ambient air of a greater density. The reanalysis fields show that EMLs and layers of reduced static stability tied to Great Lakes–modified convective boundary layers can extend downwind for hundreds of kilometers from their areas of formation. Operational implications and avenues for future research are discussed.