Airborne Doppler radar observations of convective plumes and radar ‘fine-lines’ ERAD02-A-00007

Reflectivities and Doppler velocities from an airborne 95 GHz radar are used to describe the detailed (~25 m) vertical structure of plumes and mesoscale convergence lines (‘fine-lines’) in the optically-clear convective boundary-layer (CBL). Multiple radar configurations are used, including a profiling mode, with fixed antennas looking up and down, and a vertical-plane dual-Doppler mode, employing a nadir and slant-forward antenna. Some 70 hours of combined radar and in situ aircraft data were collected over the central Great Plains of North America in late spring of 2002. Echo plumes clearly mark the depth of the quiescent CBL depth contain updraft cores. A preliminary analysis of coincident aircraft data suggest that these plumes are buoyant and that they contain more water vapor. The detectability and detailed tomography of coherent buoyant eddies in the CBL (‘thermals’) is unprecedented. A comprehensive study of their echo, vertical velocity, and thermodynamic structure in 2D sections is under way. The vertical structure of radar ‘fine-lines’ varies. Fronts, drylines, and horizontal roll vortices were sampled, on several occasions just before the outbreak of deep convection along the line. A velocity cross-section through the leading edge of a cold front shows characteristics of a density current head.