5A.5 The Impact of Satellite Resolution in Identification of Hail Swaths

Tuesday, 24 January 2017: 11:30 AM
Conference Center: Tahoma 3 (Washington State Convention Center )
Philip N. Schumacher, NWS, Sioux Falls, SD; and K. Gallo, J. M. Boustead, and A. Ferguson

Hail can cause significant damage to crops and structures across the United States. In the central United States, millions of dollars in crop losses have been documented from wind-driven hail. Hail damage that covers a large area can be identified on satellite using the Normalized Difference Vegetation Index (NDVI). NDVI is used to determine the health of crops and other vegetation. Hail damage to plants can result in large decreases in NDVI and has been observed on VIIRS (Visible Infrared Imaging Radiometer Suite), MODIS (Moderate Resolution Imaging Spectroradiometer), and LANDSAT images. With the launch of GOES-R, NDVI will become available multiple times per day, albeit with lower resolution than the polar-orbiting satellites mentioned. How lower resolution imagery will affect the detection of hail swaths and the degree of damage associated with hail swaths is unknown.

To answer how detection of hail swaths is impacted by satellite resolution, detailed damage surveys were done across eastern South Dakota and eastern Nebraska during June and July of 2014 for three hail events. In all three events, wind-driven hail over several miles caused significant damage to crops and structures. Crop damage was photographed within the hail swath, and the swaths were rated by the degree of damage to the crop. The rating scale ranged from 1, indicating no damage, to 4, indicating near 100% loss of crops.  After assigning damage ratings, the NDVI change at the location of each photograph was determined from VIIRS (~450-m resolution), MODIS (1-km resolution), and simulated GOES-R (2.2-km resolution) imagery. The maximum estimated size of hail (MESH) from the Multi-Radar Multi-Sensor System dataset was also assigned to each photograph. We determined that larger changes in NDVI were associated with higher rated damage when examining VIIRS and MODIS imagery.  However, the decreased resolution of GOES-R imagery resulted in no relationship between NDVI change and the degree of damage to crops for 2 of the 3 cases.

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