The Identification and Verification of Hazardous Convective Cells Over Oceans Using Visible and Infrared Satellite Observations

Three algorithms based on geostationary visible and infrared (IR) observations, are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The algorithms were developed at the Naval Research Laboratory (NRL), National Center for Atmospheric Research (NCAR), and Aviation Weather Center (AWC). The performance of the algorithms in detecting potentially hazardous cells is determined through verification based upon data from National Aeronautical and Space Administration (NASA) Tropical Rainfall Measuring Mission (TRMM) satellite observations of lightning and radar reflectivity, which provide internal information about the convective cells. The probability of detection of hazardous cells using the satellite algorithms can exceed 90% when lightning is used as a criterion for hazard, but the false alarm ratio with all three algorithms is consistently large (~40%), thereby exaggerating the presence of hazardous conditions. This shortcoming results in part from limitations resulting from the algorithms' dependence upon visible and IR observations, and can be traced to the widespread prevalence of deep cumulonimbi with weak updrafts but without lightning, whose origin is attributed to pronounced departures from non-dilute ascent.