A STUDY OF COMPOSITE CITRUS MORPHOLOGY USING DATA FROM A 94-GHZ RADARAND CORRELATIONS WITH TEMPERATURE AND LARGE-SCALE VERTICAL MOTION

In order to improve the representation of clouds in climate models, we require a better understanding of the relationship among cloud proper ties and the synoptic-scale state of the atmosphere. In order to inves tigate this issue as it pertains to a specific class of citrus clouds, we have combined a 2 month data set of radar reflectivities observed at State College, Pennsylvania, using a W-band radar with output from a mesoscale model that uses 3-hourly data assimilation. Products of th e analysis include statistical distributions of fundamental citrus clo ud properties, such as frequency of occurrence, base, top and midcloud height, and layer thickness. We also consider the relationships betwe en cirrus reflectivity and the large-scale meteorological state define d by area-averaged temperature and vertical velocity. Overall, citrus clouds are observed 32% of the time, and 51% of those events occur in conjunction with lower-level clouds. Most of the citrus occur in thin layers (<1.5 lan thickness). Cirrus occurrence appears to be related t o largescale meteorological factors but the relationships are complex. The majority of the cirrus we observed occurred at temperatures lower than -35 degrees C and there is little correlation between radar refl ectivity and temperature. We also used this data set to examine the us efulness of a satellite-borne W-band radar.