The Use of Satellite Imagery to Assess Tornado Damage in the Central Appalachian Region
Case Study: April 28th, 2002 La Plata, MD. Tornado
Ongoing Research
Remote Sensing Imagery Analysis/Discussion
Overview
Data Providers
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Country vs. Regional Tornadoes by Year
US Tornadoes by Year Central Appalachian Tornadoes by Year
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Figure 1: Tornado track layer (NOAA-SPC) overlaid onto a USGS Digital Elevation Layer.
La Plata, Maryland (March 14, 2002) Landsat Band 3
La Plata, Maryland (May 5, 2002) Landsat Band 3
Intensity F-4*
Length 64 Miles
Injuries 122
Fatalities 3
Property Damage > $100 million
• EF-Scale implemented in 2007 (*) • Picture and data compliments of DOC published
Service assessment
Accessibility Frequency Resolution Inventory
Google Earth Public Variable/Limited Variable (High) Variable
Landsat 7^ Public 16 Days 30 Meter 1999 – Present
Landsat 8 Public 16 Days 30 Meter (MS) 2013 – Present
MODIS Public 1 - 2x Daily 250 Meter (R/NIR) 2000 - Present
Aster Public 16 Days/Variable 15 Meter 2000 - Present
NDVI Public Dependent on Source Dependent on Source Dependent on Source
NLCD Public 5 Years 30 Meter 1992, 2001, 2006, 2011
Aerial Photos Variable Variable Variable (High) Variable
Table 3
Figure 5 Figure 6
Figure 8 Figure 7
Objectives
• Determine the advantages and disadvantages of different remote sensing techniques in the detection and refinement of tornado damage paths, with a focus eventually on weaker tornadoes in remote areas.
• Create a matrix to be used at the warning forecast office level, highlighting the
availability of these images, along with their timeliness and ease of accessibility for use in post-tornadic event assessments.
• Damage visibility: imagery type vs. magnitude of event • At what EF rating is each imagery type useful in determining
presence of tornado damage? • 5 cases per magnitude category. How often is damage observed
using each imagery type? • Damage visibility: land cover differences in damage visibility
• Does the land cover type significantly affect how visible damage is between the imagery types?
• Damaged land reclamation • How long after an event does the damage persist? • Does that change depending on event intensity?
• Automated tornado detection based on before and after remotely sensed images
References
An overview of the imagery considered is shown in Table 3 above. The study focused mainly on easily accessible technologies at a warning forecast office site.
Takeaways: • Cloud cover often negatively affects the frequency of available images across all
platforms considered. • In general, as the resolution of the products increased, the frequency, inventory,
and image window decreased. • Greater data storage is required for higher resolution imagery • The availability and use of aerial photographs is highly variable, and situationally
dependent. • Google Earth images have very high resolution with little data storage. However, it
is highly variable and at times, limited. • Seasonal differences can provide a large source of error within each platform,
especially in the spring and fall with foliage gains and losses.
A comprehensive review of the 2002 La Plata, Maryland tornado was completed due to the event’s high intensity, known data availability, past available research conducted, and close proximity to the central Appalachian Mountains Region. Two types of satellite images are presented below, along with a National Weather Service damage path image (originally published in the September 2002 service assessment) (Figure 4). Using both Landsat 7 (Figures 5 + 6) and Google Earth (Figures 7 + 8) before and after images, a definable tornado scar from the event is clearly visible in the same areas outlined by the storm survey in the F2 to F4 damage range. Intermittent damage is also visible in the lower damage classified areas, especially in the lower resolution Landsat imagery. While the Google Earth images were at a higher resolution, the damage wasn’t as noticeable throughout the study area. This was mainly due to the elapsed time between the event and the image date. Landsat 7 images have a recurrence interval of 16 days, while Google Earth images are highly variable both spatially and temporally, especially pre-2008. In this circumstance, the Landsat 7 image (Figure 6) was taken only a week after the event, providing the user with rapid and more useful data. The next available Google Earth image (Figure 8) was taken approximately 3 years after the event, which introduces both natural and industrial land reclamation error to the image. Also, the comparison before image (Figure 7), is incomplete spatially, with portions of the image dating back to the 1980s, which leads to a significant loss in resolution. Thus, while higher resolution Images would be more beneficial for the users in this circumstance, other factors can certainly limit it’s overall utility.
United States of America. Department of Commerce. NOAA - National Weather Service. Service Assessment- La Plata, Maryland, Tornado Outbreak of April 28, 2002. N.p.: n.p., n.d. Print.
*Additional References are available upon request
Table 1
Figure 2
Figure 3
Table 2
Figure 4
^ May 31, 2003- Scan line corrector failure on Landsat 7 imager
