GOES-East Cloud Top Signatures of Weakly Forced Snow Events (237)
Patrick Ayd, NOAA/NWS, Bismarck, ND
Phil Schumacher, NOAA/NWS
Dan Baumgardt, NOAA/NWS
During the first full winter of GOES-East operations, the lack of an ice crystal signature at cloud top was consistently noted across the Northern Plains and Upper Mississippi Valley for weakly forced snow events, especially in sub-freezing air masses. Many times, supercooled liquid was detected at cloud top on Advanced Baseline Imager (ABI) Band 5 (1.61 µm near infrared &ldquoSnow/Ice Band&rdquo), as well as multiple red-green-blue composites that exploit cloud top phase identification. These signatures were shared with satellite scientists at UW-Madison CIMMS, resulting in a collaborative Research-to-Operations-to-Research (R2O2R) loop. The result was a re-framing of the operational application of conceptual models relating to satellite interrogation of stratified cloud phases as outlined in Schupe et al. (2008).
Multiple GOES-East operational cases of cloud top signatures in snow events will be presented in light of the findings of Schupe et al. (2008). In weakly forced events, it was found that the presence of liquid droplets at cloud top is not indicative as to whether ice crystals exist within the cloud, and are not necessarily predictive as to whether the surface precipitation type will be freezing rain or snow. Further, the use of cloud-top brightness temperature via ABI Band 13 (10.35 µm) is not sufficient to determine the presence of ice crystals at cloud top. Instead, the authors recommend the use of the 1.61 µm reflectance in daytime to determine the presence of ice or liquid at cloud top.