An Inferred Climatology of Icing Conditions Aloft, Including Supercooled Large Drops. Part I: Canada and the Continental United States

Abstract

Because of a lack of regular, direct measurements, little information is available about the frequency and spatial and temporal distribution of icing conditions aloft, including supercooled large drops (SLD). Research aircraft provide in situ observations of these conditions, but the sample set is small and can be biased. Other techniques must be used to create a more unbiased climatology. The presence and absence of icing and SLD aloft can be inferred using surface weather observations in conjunction with vertical profiles of temperature and moisture. In this study, such a climatology was created using 14 yr of coincident, 12-hourly Canadian and continental U.S. surface weather reports and balloonborne soundings. The conditions were found to be most common along the Pacific Coast from Alaska to Oregon, and in a large swath from the Canadian Maritimes to the Midwest. Prime locations migrated seasonally. Most SLD events appeared to occur below 4 km, were less than 1 km deep, and were formed via the collision-coalescence process.

Determining the Flight Icing Threat to Aircraft with Single-Layer Cloud Parameters Derived from Operational Satellite Data

“…Although aircraft icing conditions can form anywhere, they are most commonly found in two geographical regions over North America (Bernstein et al 2007). The first includes the Pacific Northwest, western British Columbia in Canada, and Alaska.…”

“…This location is well situated for observing icing conditions because it lies in the heart of a climatological icing bull's-eye (Bernstein et al 2007). The NIRSS was developed to demonstrate a ground-based remote sensing system concept that could provide accurate detection and warning of inflight icing conditions in the near-airport environment.…”

“…Thompson et al (1997) used satellite data to improve icing diagnoses on the basis of numerical weather analyses by eliminating areas with warm cloud tops. Bernstein et al (2005) describe methods to identify and forecast areas with potential aircraft icing conditions by blending relevant data from multiple sources such as satellite, surface, radar, lightning, and routine PIREPs with model forecasts of temperature, relative humidity, SLW, and vertical velocity. The current and forecast icing products (CIP and FIP, respectively) resulting from this comprehensive approach are proving useful to the aviation community and are available over the contiguous United States (CONUS) and southern Canada in near-real time as supplementary information at the National Oceanic and Atmospheric Administration (NOAA) Aviation Weather Center.…”

“…Minnis et al (2004) exploited these relationships and developed a satellitebased icing algorithm that is based on satellite-derived cloud parameters. Bernstein et al (2006) found that it was particularly useful for directing a research aircraft into icing conditions. That algorithm was selected as the prototype candidate algorithm for the NOAA GOES-R program.…”

Modelling atmospheric icing: A comparison between icing calculated with measured meteorological data and NWP data

“…Atmospheric icing is a complex phenomenon that can occur almost anywhere in the troposphere (Bernstein et al, 2007). In addition to being a parameter that is difficult to describe, icing has not been measured regularly at many sites or for long time periods.…”