Assessment of Aircraft Icing Potential and Maximum Icing Altitude from Geostationary Meteorological Satellite Data

Abstract

A satellite product that displays regions of aircraft icing potential, along with corresponding cloud-top heights, has been developed using data from the Geostationary Operational Environmental Satellite (GOES) imager and sounder. The icing product, referred to as the Icing Enhanced Cloud-top Altitude Product (ICECAP), is created hourly for the continental United States and southern Canada, and is color coded to show cloud-top altitudes in 1.9-km (6000 ft) intervals. Experimental ICECAP images became routinely available on the Internet during the spring of 2004. Verification of separate ICECAP components (imager icing potential and sounder cloud-top heights) using aircraft pilot reports (PIREPs) indicates that the product provides useful guidance on the spatial coverage and maximum altitude of current icing conditions, but not icing intensity, stratification, or minimum altitude. The imager icing potential component of ICECAP was compared with the operational 40-km resolution National Weather Service (NWS) current icing potential and NWS Airman’s Meteorological Advisories via the NOAA Real-Time Verification System, while GOES cloud-top heights were compared with altitudes of moderate or greater icing from PIREPs. Benefits and deficiencies of the GOES icing product are discussed.

Observation of a freezing drizzle episode: A case study

“…Reflectance in the latter channel was converted to albedo using the Lambert method, to avoid dependence on solar zenith angle. In the daytime, shortwave infrared (SWIR) data contain contributions from both emitted thermal and reflective solar energy (Ellrod and Bailey, 2007). Thermal emission at 3.9 μm was subtracted to use only the solar reflected component (Nakajima and Nakajima, 1995).…”

“…An approximation of cloud-top temperature and a determination of cloud phase can be obtained using infrared window channels (Ellrod and Bailey, 2007). Liquid water droplets tend to accumulate near the tops of stratiform cloud layers, so they can be identified using satellite data.…”

“…Factors needed to form freezing drizzle are cloud tops of − 15°C or warmer, narrow cloud thickness, weak mesoscale uplift, stably stratified conditions, high relative humidity (RH) at low levels, and low concentrations of both ice crystals and ice nuclei (Cober et al, 1996;Ellrod and Bailey, 2007).…”

Comparison of in‐flight aircraft icing algorithms based on ECMWF forecasts

“…The icing forecasts are verified against the PIREPs using scores widely applied in the evaluations of icing algorithms (Brown et al, 2002;Ellrod and Bailey, 2007). These scores are derived from contingency tables, as illustrated in Table S1.…”

Evaluation of the national airspace system aggregate performance sensitivity

“…Unlike many of the other meteorological phenomena, icing is not directly measured. Instead, icing conditions, or the risk of icing, is evaluated heuristically using up to dozens of ground-based, satellite and airborne measurements [2,3]. The potential for icing occurs when aircraft encounter supercooled liquid water droplets.…”