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
Abstract:
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.