Extended Abstract (348K)P1.6
Combining lightning with satellite data for analysis and prediction
Roderick A. Scofield, NOAA/NESDIS/ORA, Camp Springs, MD; and R. J. Kuligowski and S. Qiu
Lightning data represent a very useful complement to satellite imagery for analyzing and predicting the evolution of Mesoscale Convective Systems (MCSs). As Meso-Gamma Towers develop within an MCS, graupel (or rimed ice crystals) begins to form in the upper portions of the cloud and then falls through a layer of supercooled water droplets and ice crystals. The resulting collisions induce a charge separation that is resolved in the form of lightning strokes. The relationships between cloud properties and lightning will be explored using a combination of Lightning Detection and Ranging (LDAR) data (detects cloud to ground stokes only) and Geostationary Operational Environmental Satellite (GOES) Imager visible, 3.9-µm, and 10.7-µm data to depict the life cycle of a MCS. Initially, lightning data were combined with the GOES 10.7-µm. As expected, the lightning frequency was a function of the life cycle stage of the MCS: initiation, maturity, and dissipation. There appears to be some relationship between the colder cloud top temperatures (CTT), especially in the upwind (tighter gradient) portion, and the most intense lighting. A critical threshold for cloud to ground lightning to occur seems to be CTTs colder than – 30 oC . Other useful re-occurring features include increases in lightning intensity as CTTs became colder. Also, the nowcasting of MCS propagation and mergers is more readily accomplished through a combination of LDAR and GOES. In fact, mergers are sometimes followed by increasing lightning intensity. Therefore, it appears that LDAR and GOES 10.7-µm data have similar relationships to rainfall, where the lightning is much better at pinpointing the heavy rainfall cores. In addition, the possibility of using proximity soundings to predict severe lightning events will be evaluated. Former National Weather Service forecaster Doyle Cook hypothesized that severe lightning events are signaled by a stability reversal in the mid-levels. A stability reversal occurs when the temperature lapse rate changes from potentially unstable in the lower portion of the MCS-producing air mass to potentially stable in the middle and upper troposphere. This reversal should occur between the 0ºC and -10ºC isotherms, allowing graupel to impinge on supercooled water droplets and thus to produce lightning prior to the initial downdrafts of the individual cumulonimbus (CB). This would indicate that frequent lightning flashes would occur before the mature stage is reached and would continue until the CB enters the dissipating stage. Prediction of severe lightning events has many potential applications. In a dry environment, wildfire risk from lightning strokes could be predicted. In a moist environment, flash flood risk from heavy rain associated with severe lightning events could be more accurately evaluated. Consequently, forecasters and response personnel could benefit significantly from an expansion of the understanding of the relationship of lightning to the convective life cycle. Additional possible applications include precipitation estimation and nowcasting. In the future, if the lightning detectors are placed on GOES, total flash counts (cloud to ground and in-cloud) can be measured that would lead to improved severe weather nowcasting and prediction.
Poster Session 1, Poster Session 1
Monday, 10 January 2005, 2:30 PM-4:00 PM
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