32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Tuesday, 12 August 2003: 9:15 AM
The structure, evolution and cloud processes of a Colorado upslope storm as shown by profiling radiometer, radar and tower data
Paul H. Herzegh, NCAR, Boulder, CO; and S. Landolt and T. Schneider
Poster PDF (856.2 kB)
The general structure of upslope cloud and precipitation systems on the eastern flank of the Colorado Rocky Mountains includes a shallow, stable, moist east or northeast flow at very low levels capped by a sharp temperature inversion, strong shear in the horizontal winds, and an overlying zone of much deeper, strong westerlies. The well-bounded vertical structure of this familiar winter cloud system yields an interesting and relatively well-behaved opportunity to examine and inter-relate the information on thermodynamic and microphysical structure provided by radar, profiling radiometer, ceilometer, rawinsonde and surface observations.

Objectives of this work include an assessment of the thermodynamic structure and liquid water content derived from continuous measurements from a microwave profiling radiometer. This passive instrument obtains brightness temperature data at five frequencies in the K-band water vapor absorption band and seven frequencies in the V-band oxygen absorption band. Inversion techniques yield profiles of temperature, humidity and liquid water content. The latter, especially, is dependent upon assumptions made on cloud depth, which for the upslope cases examined is well known.

A March 2003 upslope case provides a particularly useful opportunity to examine the evolution of upslope structure associated with a widespread freezing drizzle event. The drizzle persisted for several hours before the upslope cloud deepened and produced light to moderate snow. This case is coordinated with the analysis to be presented by Ikeda and Rasmussen in a companion paper. We discuss the system structure as observed by radar, radiometer, rawinsonde and ceilometer data, assess the representativeness of the radiometer-derived information, consider means for optimal use of companion data to improve radiometer profiles, and discuss the cloud processes responsible for the observed evolution.

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