Identification and examination of damaging crop hailswaths in the U.S. Midwest.

摘要

This study investigates the utility of satellite imagery and National Weather Service (NWS) severe hail reports to detect damaging crop hailswaths during the 2009 U.S. Midwest warm season. Hailswaths were identified based on Normalized Difference Vegetation Index (NDVI) difference imagery from Moderate Resolution Imaging Spectroradiometer (MODIS) data. Results illustrate that all hailswaths occurred from June-August with peak frequency in July. This suggests the importance of crop phenology when using NDVI imagery to identify hailswaths. Despite peak frequencies of severe hail reports in June, July had the most hailswaths due to the susceptibility of crop-hail damage as the growing season progresses. The majority of hailswaths were identified in Nebraska, South Dakota, Iowa, and Kansas with much smaller frequencies observed in states further north and east. States such as Missouri had high numbers of severe hail reports yet no hailswaths, which may indicate the importance of the underlying land cover type when detecting hailswaths. This study also examines the characteristics of thunderstorms that resulted in hailswaths and classifies their dominant storm type based on analysis of radar morphologies over the length of the hailswath. Results reveal that 71% of all hailswaths were caused by supercells, with 13% cluster of cells, 9% isolated cells, and 7% broken squall lines. These results indicate that the majority severe hail hazards related to agriculture damage are caused by organized cellular convection. Identification of hailswaths using satellite imagery and examination of storm morphology associated with these damaging storms ultimately provides additional data on adverse hazards associated with severe hail.