Publication Date:
2020-05-07
Description:
Recent research has found that diurnal pulses are ubiquitous features of tropical cyclones. To gain further insight into the characteristics of these pulses, a case study of an electrically active (ACT) cooling pulse and an off-the-clock ACT cooling pulse that occurred in Hurricane Harvey (2017) was conducted. Using GridSat-B1 IR brightness temperatures, World Wide Lightning Location Network (WWLLN) lightning data, the 85–91-GHz channels on microwave satellite imagers, and Level-II Doppler radar reflectivity data from WSR-88D stations (i.e., NEXRAD), these pulses were found to share many similar characteristics: both propagated outward on the right-of-shear side of Harvey and were associated with elevated cloud ice content and high reflectivity. Additionally, using HRRR model output, both pulses were found to be associated with 1) column-deep total condensate, 2) a surface cold pool, 3) an overturning circulation, and 4) an enhanced low-level jet. These characteristics are similar to those found in tropical squall lines, supporting the tropical squall-line interpretation of diurnal pulses put forth in recent studies. A hypothesis for ACT pulse initiation was then introduced, tested, and confirmed: inner rainbands that propagated outward into a more favorable environment for deep convection reinvigorated into ACT pulses that had tropical squall-line characteristics.
Print ISSN:
0027-0644
Electronic ISSN:
1520-0493
Topics:
Geography
,
Geosciences
,
Physics
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