Florida Convective Updraft Structure Using Dual Wavelength Airborne Radar Measurements

NASA conducted the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) during July 2002 for improved understanding of tropical cirrus. One of the goals was to improve the understanding of cirrus generation by convective updrafts. The reasons why some convective storms produce extensive cirrus anvils is only partially related to convective instability and the vertical transport ice mass by updrafts. Convective microphysics must also have an important role on cirrus generation, for example, there are hypotheses that homogeneous nucleation in convective updrafts is a major source of anvil ice particles.

During CRYSTAL-FACE, up to 5 aircraft flying from low- to high-altitudes, were coordinated for the study of thunderstorm-generated cirrus. The NASA high-altitude (20 km) ER-2 aircraft with remote sensing objectives flew above the convection, and other aircraft such as the WB-57 performing in situ measurements flew below the ER-2. The ER-2 remote sensing instruments included two nadir viewing airborne radars. The CRS 94 GHz radar (Li et al 2004) and the EDOP 9.6 GHz radar (Heymsfield et al. 1996) were flown together for the first time during CRYSTAL-FACE and they provided a unique opportunity to examine the structure of 16 July case from a dual-wavelength perspective.

In this paper, we report analyses on the structure of intense convective cores during July 2002 for several cases. In particular, we have utilized the single and dual wavelength Doppler measurements to provide information on the characteristics updraft cores such as vertical motion and reflectivity magnitude, heights of peak updrafts, etc. We will discuss the implications of the dual-wavelength measurements on the microphysical structure in relation to graupel presence and the ice fallspeed estimates assumed in the vertical velocity calculation. Finally, we will compare the updraft characteristics obtained from the downlooking ER-2 radars with those from the NCAR ELDORA radar that sampled some of the same convective storms.