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- Title
Seamless Detection of Cutoff Lows and Preexisting Troughs.
- Authors
Kasuga, Satoru; Honda, Meiji; Ukita, Jinro; Yamane, Shozo; Kawase, Hiroaki; Yamazaki, Akira
- Abstract
We propose a new scheme based on geopotential height fields to detect cutoff lows starting in the preexisting trough stage. The intensity and scale derived from the proposed scheme will allow for a better understanding of the cutoff low life cycle. These cutoff lows often accompany mesoscale disturbances, causing adverse weather-related events, such as intense torrential rainfall and/or tornadoes. The proposed scheme quantifies the geometric features of a depression from its horizontal height profile. The height slope of a line intersecting the depression bottom and the nearest tangential point (optimal slope) locally indicates the intensity and scale of an isolated depression. The strength of the proposed scheme is that, by removing a local background height slope from a geopotential height field, the cutoff low and its preexisting trough are seamlessly detected as an identical depression. The distribution maps for the detected cutoff lows and preexisting troughs are illustrated along with their intensities, sizes, and local background flows estimated from snapshot height fields. We conducted climatological comparisons of cutoff lows to determine the utility of the proposed scheme. Significance Statement: We propose a new automated numerical scheme for upper-tropospheric cyclones (cutoff lows) and their earlier developmental stage as troughs (preexisting troughs). Cutoff lows are frequently associated with much smaller-scale hazardous phenomena at the surface, such as tornadoes. The proposed scheme can extract locations with transitions that are as smooth as possible and estimate their intensities, sizes, and even the local background flows behind them using nonpreprocessed (snapshot) basic weather data consisting of geopotential height fields.
- Subjects
TORNADOES; GEOPOTENTIAL height; SURFACE phenomenon; CYCLONES; ATMOSPHERIC circulation
- Publication
Monthly Weather Review, 2021, Vol 149, Issue 9, p3119
- ISSN
0027-0644
- Publication type
Article
- DOI
10.1175/MWR-D-20-0255.1