Thursday, 26 January 2012: 8:45 AM
Regional Comparison of GOES Cloud-Top Properties, Radar Characteristics, and Lightning Initiation
Room 256 (New Orleans Convention Center )
Lightning forecast is particularly important for human safety and aviation industry. Radar reflectivity is usually used for lightning initiation nowcasting with a typical lead time of ~20 min. Previous study showed that satellite observations can potentially contribute to LI forecast with a longer lead time (~35min). This work makes comparison on the regional difference to investigate further the predictability of LI via satellite data. In this study, 10 previously identified Geostationary Operational Environmental Satellite (GOES-12) Infrared (IR) Interest Fields (IFs) in the hour before LI are studied together with the NEXRAD composite radar reflectivity. A total of ~70 lightning-producing storms occurred in 2009 summer season are manually tracked. The behavior of ~40 storms from the Kennedy Space Center in Florida and ~30 from Oklahoma are compared in terms of radar characteristics and GOES IR IFs. This study put together the satellite and radar features and tendencies within 1 hour before LI to show how the radar and satellite characteristics evolve in Florida and Oklahoma.
Results indicate that rainfall develops much sooner in the Florida storms, due to the presence of higher moisture and hence a warm rain process within developing cumulus clouds, and later in Oklahoma lightning-producing storms. CFAD analysis reveals that this rainfall-lightning lead-time is on the order of 30-50 minutes over Florida, whereas it may be only 10-15 min in Oklahoma. Although rainfall develops earlier in Florida, the GOES infrared observations suggest the presence of weaker updrafts compared to Oklahoma events, despite there being higher CAPE values in Florida. With a lack of moisture in Oklahoma, rainfall develops nearer the time of LI, and sounding analysis suggests higher cloud bases supportive of wider updrafts. CFAD analyses also suggest that to defined processes of graupel/ice microphysics development in the two regions, one being the lofting of larger water particles generated by warm rain processes in Florida, while the other being formation of ice aloft within updraft cores in Oklahoma. Ongoing work is toward further understanding how 11 GOES infrared and reflectance fields behave in concert with environmental factors and radar CFADs.