Observations of water vapor and cloud liquid from an airborne dual-frequency radiometer during VORTEX ´95

The fine-scale horizontal variations of water vapor and cloud liquid water are of importance to climate, meteorology, and satellite validation/calibration. The Environmental Technology Laboratory of NOAA has developed a dual-frequency upward- (and downward-) looking radiometer at 23.87 and 31.65 GHz to measure the integrated amounts of water vapor and cloud liquid above an aircraft. Two experiments involving the NOAA WP-3D (tail number N43RF) were conducted in the Oklahoma-Texas region during April 1 to June 15, 1995. The first, the Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX), focused on obtaining detailed observations of mesocyclones and their potential for developing into tornadoes. The second, sponsored by the Department of Energy´s Atmospheric Radiation Program, was to obtain detailed aircraft observations of cloud liquid and water vapor to correlate with short- and long-wave radiation measurements. The almost mutually exclusive goals of the two experiments allowed shared use of NOAA WP-3D aircraft throughout the entire April-June period. During VORTEX, the radiometer was operated on all WP-3D flights; of particular interest were several flights flown in zig zag flight patterns through mesoscale moisture fronts known as “dry lines”. Through the sharp boundaries of dry lines, strong horizontal gradients in moisture can occur. Several of the dry line cases were observed, and examples are shown