Dual-Doppler Lidar Measurement of Winds in the JAWS Experiment

Abstract

Two 10.6 ?m coherent Doppler lidars participated in the Joint Airport Weather Studies (JAWS) Project field experiment, conducted in summer 1982 near Denver's Stapleton International Airport. One was operated by NOAA/ERL, Wave Propagation Laboratory (WPL), the other by NASA, Marshall Space Flight Center (MSFC). Periodic coordinated scans were made with the two lidars spared 15 km apart. This permitted the calculation of Cartesian winds. This paper presents 1) a brief comparison of radar and lidar system and performance characteristics, 2) results of the first dual-Doppler analyses to be based upon lidar measurements and 3) a comparison of radial wind estimates between the MSFC lidar and a 5.5 cm Doppler radar operated by the National Center for Atmospheric Research (NCAR). Dual-Doppler analyses were made for the flow behind gust fronts, with the desired flow fields consistent with both surface winds measured by the NCAR Portable Automated Mesonet (PAM) and models derived from previous studies of Great Plains thunderstorm outflows. A comparison of low elevation scans made by the MSFC lidar and the NCAR CP-4 Doppler radar revealed distinct differences which could be explained by a bias in the radar estimates (toward weaker velocities) due to ground clutter contamination. Root-mean-square (rms) difference between radar- and lidar-measured radial velocities was 3.1 m s?1 which could be explained by other causes; however, the mean of the radar data set was 1?2 m s?1 lower than that of the lidar. These findings are consistent with a recent previous study comparing the WPL lidar with the NCAR CP-3 5.5 cm radar.