Origin and structure of a numerically simulated polar low over Hudson Bay
Origin and structure of a numerically simulated polar low over Hudson Bay
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哈德逊湾数值模拟极地低气压的起源和结构
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
David W. Ovens
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文献类型：
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作者：
M. D. Albright;R. J. Reed;David W. Ovens
PSU-NCAR 中尺度模型 (MM4) 用于模拟 1988 年 12 月在哈德逊湾上空形成的极地低压。记录了模拟低压的结构和特征，并提供了敏感性实验结果，旨在阐明气旋发生中涉及的物理机制。随着一个放大的上层冷槽进入该地区，低压在东部海湾的无冰区域上空形成。该模型将极地低气压描述为嵌入较大冷低气压内的一个相对较浅的小型系统。它在结构上类似于微型飓风，但缺乏飓风级的风力。其中心附近的失效率为湿中性，达 550 mb（4 公里）；反气旋外流发生在该水位或紧邻该水位以下。敏感性实验表明，开放水域区域的热量和湿气通量以及深层组织对流中相关的冷凝加热对于发展至关重要。仅显热加热就产生了相对较弱的低压，而在完全被冰覆盖的海湾的实验中却没有形成低压。表面通量和风速之间的反馈增强了这种强度，特别是在海面温度升高8°C的实验中。在后一个实验中，当包括反馈效应时，获得了最小飓风强度的风，但当反馈效应被禁止时，则不然。发现冰缘结构具有相当大的影响。结论是，哈德逊湾极地低气压的形成是深层有组织对流中潜热释放的结果，当上层冷低气压移动到相对温暖的开放水域时，其中发生了大量的热量和湿气，就形成了这种潜热释放。斜压强迫似乎在低发展中几乎没有直接作用。相反，上游冰边界的构造提供了重要的启动和组织机制。 DOI：10.1034/j.1600-0870.1995.00123.x
The PSU-NCAR mesoscale model (MM4) is used to simulate a polar low that developed over Hudson Bay in December 1988. The structure and characteristics of the simulated low are documented, and results are presented of sensitivity experiments aimed at elucidating the physical mechanisms involved in the cyclogenesis. The low formed over an ice-free region in the eastern bay as an amplifying upper-level cold trough advanced into the region. The model depicted the polar low as a small, relatively shallow system embedded within the larger cold low. It resembled a miniature hurricane in structure but lacked hurricane-force winds. The lapse rate near its center was moist neutral to 550 mb (4 km); anticyclonic outlow occurred at and immediately below that level. The sensitivity experiments revealed that fluxes of heat and moisture from the region of open water and the associated condensation heating in deep organized convection were essential to the development. Sensible heating alone produced a relatively weak low and no low formed in an experiment with a completely ice-covered bay. The feedback between the surface fluxes and wind speed enhanced the intensification, especially in an experiment with the sea surface temperature raised by 8 °C. Winds of minimal hurricane intensity were attained in the latter experiment when the feedback effect was included but not when it was disallowed. A sizable impact of the ice-edge configuration was found. It is concluded that the Hudson Bay polar low formed as a consequence of latent heat release in deep organized convection that formed when an upper-level cold low moved over a relatively warm body of open water from which large fluxes of heat and moisture took place. Baroclinic forcing appeared to play little direct role in the low development. Instead, the configuration of the upstream ice boundary provided an important initiating and organizing mechanism. DOI: 10.1034/j.1600-0870.1995.00123.x