Clear-air boundary layer observations from radar and water vapor dial

The NCAR S-Pol radar was operating near Milan, Italy during the Mesoscale Alpine Programme (MAP) during September - November 1999. Although this instrument was used primarily to sample rainfall events in the Alps, it was also useful for examining clear-air features prior to convective development. The French LEANDRE II airborne water vapor DIAL was flown in the ARAT aircraft which was based in Innsbruck, Austria during MAP. Its most frequent missions were to map out the moisture inflow from the Mediterranean Sea toward the Alps. It was also capable of sampling moisture profiles over land. The French Merlin aircraft obtained boundary layer flux measurements. The combination of S-Pol's clear-air data, LEANDRE II's water vapor profiles and the Merlin fluxes will be examined to study convective boundary layer (CBL) features.

On 27 October 1999 there were clear skies and low-level southwesterlies near S-Pol. The strong clear-air signature obtained by insects suggested that the CBL depth was approximately 800 m. The LEANDRE II aerosol backscatter signal suggested that the CBL depth varied between 400 and 800 m. The structure of the CBL motions, as suggested by the reflectivity field, will be compared with the fluxes observed by the Merlin and the water vapor profiles observed by LEANDRE II.