13th Conference on Applied Climatology and the 10th Conference on Aviation, Range, and Aerospace Meteorology

Monday, 13 May 2002
The impacts of microphysical schemes and parameter choices on icing diagnoses using the UAF integrated in-flight icing diagnostic algorithm for Alaska
Jeffrey S. Tilley, Univ. of Alaska, Fairbanks, AK; and X. Meng and G. Kramm
Poster PDF (149.2 kB)
In a companion poster we describe the development and components of an Alaskan In-Flight Icing diagnostic algorithm derived from a similar algorithm developed at NCAR/RAP for the continental United States. One of the components of this algorithm is model output from the Penn State/NCAR Mesoscale Model MM5.

Within the MM5 model there are a variety of choices for the treatment of cloud microphysical processes, the majority of which are based upon well-known formulations developed by various researchers over the past decade. Previous modeling investigations for high latitude in-flight icing events have suggested that there is some sensitivity of the simulated cloud and precipitation structure to the choice of cloud microphysical parameterization. However, these investigations, as well as the somewhat unique parameter space comprising the high latitude cloud environment, also imply that no current formulation is entirely adequate.

In another companion poster, we examine the sensitivity simulated high latitude cloud and precipitation structures, during a 3-day period of June 1998, to various microphysical treatments in the MM5 modeling system. Included in these experiments are not only runs which utilize the standard model options but other runs which modify baseline ice nuclei concentrations, temperature thresholds and supersaturation thresholds used within the schemes.

All of these possibilities could translate into different simulated three-dimensional temperature, water vapor and hydrometeor species distributions within the cloud and in the near-cloud environment. As such, these different microphysical treatments could have impacts on the resulting diagnosis of in-flight icing with the UAF algorithm. In this poster we will examine this issue by ingesting the various MM5 output fields used in the companion study and intercomparing the resulting icing diagnoses. In this fashion we expect to obtain a preliminary assessment as to the sensitivity of the algorithm output to the model microphysics.

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