EOS Validation Program

Institution: University of Arizona
Phone: (520) 621-6836
FAX: (520) 621-6833
E-mail: krider@air.atmo.arizona.edu

William J. Koshak, NASA Marshall Space Flight Center

December 2001
Final Report, September 2003

A Lightning Imaging Sensor (LIS) on the TRMM satellite is currently sampling the location, time-of-occurrence, and optical energy of lightning sources at regular intervals throughout the tropics. The NASA Kennedy Space Center (KSC) and USAF Eastern Range (ER) are operating a Lightning Detection and Ranging (LDAR) system and a large network of electric field mills (the LPLWS system) to detect lightning and electrified clouds over the east coast of Florida. Under NASA Grant NAG5-6461 (NRA-97 MTPE-03), the above Investigators will:

1) Validate the LIS response on both intracloud and cloud-to-ground flashes using the LDAR and LPLWS data sets.

2) Develop new methods for analyzing field mill data that extend the detection range and improve the accuracy of the LPLWS system. For example, we will try using LDAR data to constrain the geometrical parameters of lightning sources while inverting the field mill data. If this approach is successful, then we should be able to analyze complex flashes of large spatial extent, and we will more than double the useable range of the LPLWS system at the KSC-ER.

3) Investigate whether there is a relationship between the total light signal detected by LIS and the charge transfer in the associated lightning flash. We believe that, to first order, the integrated light signal is a function of the length of the discharge channels and their locations within the cloud. The length of channels, in turn, is controlled by the volume and amount of charge that is transported by the flash. Therefore, we will investigate whether and how the location and spatial extent of channels (the LDAR system) are related to lightning charges (the LPLWS system), and we will see how both of the above relate to the optical signals that are detected by LIS.

4) Verify the accuracy of radiative transfer computations that predict the fraction of lightning photons that escape various cloud surfaces. Radiometric measurements from the ground will be compared to LIS measurements under conditions where the source locations inside the cloud have been determined from the LDAR and LPLWS data sets.

5) Apply the results of all of the above to obtain improved estimates of the locations and magnitudes of the current sources in thunderstorms and the associated relationships between lightning and precipitation.