An update on the GOES-R ABI overshooting top and enhanced-V anvil thermal couplet detection algorithms

An overshooting convective cloud top is defined by the American Meteorological Society as “a domelike protrusion above a cumulonimbus anvil, representing the intrusion of an updraft through its equilibrium level”. A single overshooting top (OT) exists for less than 30 minutes and has a maximum diameter of ~15 km. Despite the relatively small size and short duration of an OT, storms with OTs often produce hazardous weather conditions such as aviation turbulence, frequent lightning, large hail, damaging wind, tornadoes, and heavy rainfall. OTs found in combination with a U or V shaped region of cold infrared window brightness temperatures (BTs) are often indicative of an especially severe thunderstorm. The method used for OT detection is called IRW-texture because it utilizes BT spatial gradients (i.e. texture) to identify clusters of pixels that are significantly colder than the surrounding anvil cloud and have a size consistent with commonly observed OTs. Once an OT has been identified by the IRW-texture technique, the focus can be directed toward the objective detection of the enhanced-V signature. While the enhanced-V is often highly variable in infrared imagery, the one aspect of the enhanced-V that remains fairly constant are the “arms” of the V signature enclosing a warm region downwind of the OT to form an “anvil thermal couplet”. The anvil thermal couplet is the focus of the enhanced-V detection algorithm.

The IRW-texture OT and enhanced-V anvil thermal couplet detection algorithms are currently being developed for future operations with the Geostationary Operational Environmental Satellite Advanced Baseline Imager (GOES-R ABI) within the GOES-R Aviation Algorithm Working Group. As GOES-R ABI will offer 2 km spatial resolution in the infrared channels, we can use current satellite instruments to emulate the imagery that will be available in the future with GOES-R ABI. An update on the development of the OT and enhanced-V anvil thermal couplet detection algorithms will be provided. In addition, some examples of algorithm output and validation using MODIS, AVHRR, MSG SEVIRI, CloudSat, and CALIPSO data will be included.