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Examination of Global Midlatitude Atmospheric River Lifecycles Using an Object‐Oriented Methodology
Journal of Geophysical Research: Atmospheres ( IF 3.8 ) Pub Date : 2020-11-03 , DOI: 10.1029/2020jd033425
Eric J. Shearer 1 , Phu Nguyen 1 , Scott L. Sellars 2 , Bita Analui 1 , Brian Kawzenuk 3 , Kuo‐lin Hsu 1 , Soroosh Sorooshian 1, 4
Affiliation  

Tracking atmospheric rivers (ARs) across their lifecycles is a field of recent interest with a multitude of emerging methodologies. The CONNected‐objECT (CONNECT) algorithm is adapted for the tracking of global midlatitude AR lifecycles and associated precipitation by implementing a seeded region growing segmentation algorithm, creating the AR‐CONNECT algorithm. To facilitate the permissiveness of the methodology, AR‐CONNECT is without hard‐coded geometric criteria yet is still shown to extract synoptic‐scale elongated objects >99.99% of the time. One of the consequences of the methodology is the ability to occasionally track atmospheric water vapor anomalies before evolving into AR geometries, effectively tracking AR genesis further back than other studies. With the aid of subdaily satellite‐derived rain data, we investigate the climatology, trends, and patterns of AR lifecycles from 1983–2016 and compare with other AR tracking studies. We find that AR frequency, genesis, and terminus locations are in generally good agreement with other AR tracking methodologies, though with key differences, and that AR frequencies in each hemisphere are determined by the number of AR hotspots. Furthermore, we uncover evidence that certain AR characteristics, such as frequency, areal extent, and duration, show evidence of increasing trends. Midlatitude precipitation uncovered by AR‐CONNECT shows contributions up to 50% over land and 65% over the ocean. Trend analysis of AR precipitation shows an increase in precipitation associated with ARs propagated by the Southern Jet Stream and ARs that traverse over the Sahara Desert, among others, but is determined not to be a driver of changes in global precipitation.

中文翻译:

使用面向对象的方法研究全球中纬度大气河流生命周期

跟踪整个生命周期中的大气河流(AR)是最近引起人们关注的一个领域,其中涉及许多新兴方法。通过实现播种区域增长分割算法,创建AR-CONNECT算法,CONNected-objECT(CONNECT)算法适用于跟踪全球中纬度AR生命周期和相关的降水。为简化方法的使用,AR‐CONNECT没有硬编码的几何准则,但仍显示提取比例大于99.99%的天气尺度拉长物体。该方法的结果之一是能够在演变成AR几何形状之前偶尔跟踪大气中的水汽异常,从而比其他研究更有效地追溯AR的起源。借助次日卫星衍生的降雨数据,我们调查了气候,1983-2016年AR生命周期的趋势和模式,并与其他AR追踪研究进行比较。我们发现,AR频率,起源和终点位置与其他AR跟踪方法通常具有很好的一致性,尽管有关键的区别,并且每个半球的AR频率由AR热点的数量决定。此外,我们发现证据表明某些AR特征(例如频率,区域范围和持续时间)显示出趋势呈上升趋势。AR-CONNECT发现的中纬度降水显示陆地上的贡献高达50%,海洋上的贡献高达65%。对AR降水的趋势分析表明,与南方急流和穿越撒哈拉沙漠的AR传播的AR相关的降水增加,
更新日期:2020-11-18
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