Microphysical Enhancement Processes within Stratiform Precipitation on the Barrier and Sub-Barrier Scale of the Olympic Mountains
Microphysical Enhancement Processes within Stratiform Precipitation on the Barrier and Sub-Barrier Scale of the Olympic Mountains
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DOI：
10.1175/mwr-d-20-0164.1
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发表时间：
2020-12
影响因子：
3.2
通讯作者：
Joseph P. Zagrodnik;L. McMurdie;Robert Conrick
中科院分区：
文献类型：
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作者：
Joseph P. Zagrodnik;L. McMurdie;Robert Conrick
2015/16 年奥林匹克山实验 (OLYMPEX) 期间的六种不同情况的高分辨率数值模型模拟用于检查全屏障尺度和较小的次屏障尺度山脊和山谷的动态和微物理降水过程。人们发现，奥林匹克山脉沿海地区中纬度气旋内层状降水的改变程度很大程度上取决于气旋前额区和暖区的天气环境。在前额叶区域，稳定分层流上的屏障规模上升导致海岸高空和较高地形上游的冰产量增加。在低空，横向于次屏障尺度迎风脊的稳定流产生了小规模的山浪，无法产生足够的云水来明显增强迎风脊尺度的降水。在湿中性暖区，屏障的上游侧表现出沿着迎风山脊定向的广泛上升，相邻向下运动的区域较少。沿海山麓产生了大量的云水，在较低的迎风斜坡上产生了更多的云水。融化层上方的冰生成直接发生在屏障上方，冰粒在跨屏障风的作用下进一步向下游平流并溢出到背风处。人们发现，沿海山麓对于主要地形屏障上游云水的产生和维持至关重要，这使得水凝物有更多的时间通过自动转换和收集而达到降水规模，然后再落在较低的迎风斜坡上。
High-resolution numerical model simulations of six different cases during the 2015/16 Olympic Mountains Experiment (OLYMPEX) are used to examine dynamic and microphysical precipitation processes on both the full barrier-scale and smaller sub-barrier-scale ridges and valleys. The degree to which stratiform precipitation within midlatitude cyclones is modified over the coastal Olympic Mountains range was found to be strongly dependent on the synoptic environment within a cyclone’s prefrontal and warm sectors. In prefrontal sectors, barrier-scale ascent over stably stratified flow resulted in enhanced ice production aloft at the coast and generally upstream of higher terrain. At low levels, stable flow orientated transverse to sub-barrier-scale windward ridges generated small-scale mountain waves, which failed to produce enough cloud water to appreciably enhance precipitation on the scale of the windward ridges. In moist-neutral warm sectors, the upstream side of the barrier exhibited broad ascent oriented along the windward ridges with lesser regions of adjacent downward motion. Significant quantities of cloud water were produced over coastal foothills with further production of cloud water on the lower-windward slopes. Ice production above the melting layer occurred directly over the barrier where the ice particles were further advected downstream by cross-barrier winds and spilled over into the lee. The coastal foothills were found to be essential for the production and maintenance of cloud water upstream of the primary topographic barrier, allowing additional time for hydrometeors to grow to precipitation size by autoconversion and collection before falling out on the lower-windward slopes.