Extended Abstract (232K)13.3
Integration of satellite-derived cloud phase, cloud top height, and liquid water path into an operational aircraft icing nowcasting system
Julie A. Haggerty, NCAR, Boulder, CO; and F. McDonough, J. Black, S. Landolt, C. Wolff, S. Mueller, P. Minnis, and W. L. Smith
Operational products used by the U.S. Federal Aviation Administration to alert pilots of hazardous icing provide nowcast and short-term forecast estimates of the potential for the presence of supercooled liquid water and supercooled large droplets. The Current Icing Product (CIP) system employs basic satellite-derived information, including a cloud mask and cloud top temperature estimates, together with multiple other data sources to produce a gridded, three-dimensional, hourly depiction of icing probability and severity. Advanced satellite-derived cloud products developed at the NASA Langley Research Center (LaRC) provide a more detailed description of cloud properties (primarily at cloud top) compared to the basic satellite-derived information used currently in CIP.
Cloud hydrometeor phase, liquid water path, cloud effective temperature, and cloud top height as estimated by the LaRC algorithms have been evaluated for accuracy in supercooled liquid cloud scenarios. Comparisons of these products with in situ measurements established their quality in the identification of meteorological conditions associated with in-flight icing. Introduction of these products into the fuzzy logic scheme that CIP uses to combine various data sources requires development of membership functions for each field. The membership functions map the data sets onto a 0 to 1 scale reflecting their relation to the expected presence of clouds and/or supercooled liquid water that would result in icing. A confidence value, based on the quality of the data sets is also determined. Specific products used in the initial integration phase are the LaRC cloud mask, the cloud hydrometeor phase product, and the cloud top height and effective temperature. The cloud mask and phase products are expected to refine the horizontal location of supercooled liquid near cloud top and improve the detection of anomalously cold icing clouds. The LaRC cloud top height and effective temperature fields will improve the CIP estimate of cloud top height, which is often over-estimated, by incorporating these satellite products with model-derived vertical profiles of relative humidity, equivalent potential temperature, and total condensate. Minimizing the cloud top height overestimate significantly reduces the volume of airspace identified as containing icing conditions, and thereby increases the efficiency of the algorithm significantly while maintaining a high probability of detection. A second phase of this work will apply the LaRC liquid water path field to enhance the CIP icing severity product. Examples of CIP products before and after the integration of the LaRC satellite-derived products will be presented at the conference.
Session 13, Inflight Icing
Thursday, 24 January 2008, 3:30 PM-5:00 PM, 226-227
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