Orographic Effects on Landfalling Lake-Effect Systems
Orographic Effects on Landfalling Lake-Effect Systems
复制标题
地形对登陆湖泊效应系统的影响
DOI：
10.1175/mwr-d-21-0314.1
复制
发表时间：
2022
影响因子：
3.2
通讯作者：
Minder, J. R.
中科院分区：
文献类型：
--
作者：
Gowan, T. M.;Steenburgh, W. J.;Minder, J. R.
登陆的湖泊和海洋效应（以下简称湖泊效应）系统经常与地形相互作用，改变降水的分布和强度，降水经常以雪的形式降落。在这项研究中，我们研究了地形对两种湖泊效应系统模式的影响：长湖轴平行（LLAP）带和广泛覆盖的开孔对流。具体来说，我们对椭圆形湖泊产生的 LLAP 带和开放湖泊（即没有侧翼海岸线）产生的广泛覆盖、开孔对流生成理想化的大涡模拟，该湖泊具有下游沿海平原、500 米的峰值和 2000 米的山脊。在没有地形的情况下，LLAP带与沿海斜压区相交，在该区上升和水凝物质量增长最大化，而运输和沉降产生内陆降水最大值。 500 米峰值不会显着改变这种结构，但由于地形上升、水凝物质量增加和亚云升华减少而略微增强降水。相比之下，2000 米的山脊会阻挡海岸线两侧的大陆流，从而破坏该带。这与湖泊和陆地之间的表面加热差异相结合，导致低层水流逆转，使沿海斜压区和近海降水量最大值移动。相比之下，在开放湖泊、开放单元模拟中，水流在地形上移动。在 500 米峰值以上，尽管较强的上升气流减弱，但较弱 (<1 m s−1) 上升气流和弱降水增强的频率增加。然而，越过 2000 米海脊，浮力和对流强度急剧增加，导致降水量增加八倍。总体而言，这些结果凸显了地形对两种常见湖泊效应模式影响的差异。意义陈述登陆的湖泊和海洋效应暴风雪经常与丘陵、山脉和高地地区相互作用，改变降雪的分布和强度。使用具有简化的湖泊形状和地形特征的高分辨率数值模型，我们说明了地形特征如何影响两种常见类型的湖泊效应风暴，以及为什么长湖轴平行（LLAP）带可以具有较高的降水率，但与广泛覆盖的开孔对流相比，地形增强作用较弱。
Landfalling lake- and sea-effect (hereafter lake-effect) systems often interact with orography, altering the distribution and intensity of precipitation, which frequently falls as snow. In this study, we examine the influence of orography on two modes of lake-effect systems: long-lake-axis-parallel (LLAP) bands and broad-coverage, open-cell convection. Specifically, we generate idealized large-eddy simulations of a LLAP band produced by an oval lake and broad-coverage, open-cell convection produced by an open lake (i.e., without flanking shorelines) with a downstream coastal plain, 500-m peak, and 2000-m ridge. Without terrain, the LLAP band intersects a coastal baroclinic zone over which ascent and hydrometeor mass growth are maximized, with transport and fallout producing an inland precipitation maximum. The 500-m peak does not significantly alter this structure, but slightly enhances precipitation due to orographic ascent, increased hydrometeor mass growth, and reduced subcloud sublimation. In contrast, a 2000-m ridge disrupts the band by blocking the continental flow that flanks the coastlines. This, combined with differential surface heating between the lake and land, leads to low-level flow reversal, shifting the coastal baroclinic zone and precipitation maximum offshore. In contrast, the flow moves over the terrain in open lake, open-cell simulations. Over the 500-m peak, this yields an increase in the frequency of weaker (<1 m s−1) updrafts and weak precipitation enhancement, although stronger updrafts decline. Over the 2000-m ridge, however, buoyancy and convective vigor increase dramatically, contributing to an eightfold increase in precipitation. Overall, these results highlight differences in the influence of orography on two common lake-effect modes.Significance StatementLandfalling lake- and sea-effect snowstorms frequently interact with hills, mountains, and upland regions, altering the distribution and intensity of snowfall. Using high-resolution numerical modeling with simplified lake shapes and terrain features, we illustrate how terrain features affect two common types of lake-effect storms and why long-lake-axis-parallel (LLAP) bands can feature high precipitation rates but weaker orographic enhancement than broad-coverage, open-cell convection.