A global climatology of favourable conditions for polar lows
A global climatology of favourable conditions for polar lows
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极地低压有利条件的全球气候学
DOI：
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发表时间：
2011
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通讯作者：
Erik W. Kolstad
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作者：
Erik W. Kolstad
极地低压（英语：Polar low，PL）是在两个半球的高纬度地区形成的小规模和强烈的低压系统。由于其有限的空间尺度和短暂的生命周期，天气和气候模式往往无法解决这些系统。克服这个问题的一种方法是为PL定义一个合适的代理，即使在粗分辨率数据集中也可以评估PL形成的可能性。本研究借鉴了以前的研究和63个PL的经验数据库，以量化低层静稳定性和高层强迫对PL形成的各自影响，因为这两个因素都有利于PL的发展。在定义了这两个参数的阈值后，计算了北大西洋、西北太平洋和南半球对热带气旋有利条件的气候特征。在海洋冷空气爆发期间强烈修改的低层静稳定度对PL的形成提出了重要的限制，而高层强迫决定了它们是否会形成。由于拉布拉多海地区的气候对流层顶较低，那里比北欧海更经常发生PL的有利条件，北欧海长期以来一直被认为是北方半球（NH）的主要PL区域。在南半球，PL的有利条件发生的频率大大低于北半球。本文定义的PL指数适用于其它气候学研究和PL预测。皇家气象学会
Polar lows (PLs) are small‐scale and intense low‐pressure systems that form at high latitudes in both hemispheres. Due to their limited spatial scale and brief lifetimes, weather and climate models are often unable to resolve these systems. One way to overcome this problem is to define a suitable proxy for PLs, with which the likelihood of PL formation can be assessed even in coarse‐resolution datasets. This study draws on previous studies and an empirical database of 63 PLs to quantify the respective influences of low‐level static stability and upper‐level forcing on PL formation, as both of these factors are known to favour PL development. Little redundancy between the two parameters is found. After defining threshold values for the two parameters, climatological properties of favourable conditions for PLs are computed for the North Atlantic, the North‐West Pacific and the Southern Hemisphere. The low‐level static stability, which is strongly modified during marine cold‐air outbreaks, puts important constraints on where PLs can form, while the upper‐level forcing determines whether or not they will form. As a result of the climatologically lower tropopause in the Labrador Sea region, favourable conditions for PLs occur more often there than in the Nordic Seas, which has long been believed to be the main PL region in the Northern Hemisphere (NH). In the Southern Hemisphere, favourable conditions for PLs occur substantially less often than in the NH. The PL index defined here is suitable for other climatological studies and PL forecasting. Copyright © 2011 Royal Meteorological Society