The Dryline on 22 May 2002 during IHOP_2002: Convective-Scale Measurements at the Profiling Site

Abstract

A unique set of measurements of wind, water vapor mixing ratio and boundary layer height variability was observed during the first MOP dryline mission of 22 May 2002. Water vapor mixing ratio fiom the Scanning Raman Lidar (SRL), high-resolution profiles of aerosol backscatter fiom the HARLIE and wind profiles fiom the GLOW are combined with the vertical velocity derived fiom the NCAR/ISS/MAPR and the high-resolution FMCW radar to reveal the convective variability of the cumulus cloud-topped boundaxy layer. A combined analysis of the in-situ and remote sensing data fiom aircraft, radiosonde, lidars, and radars reveals moisture variability within boundary layer updraft and downdraft regions as well as characterizes the boundary layer height variability in the dry and moist sides of the dryline.The profiler site measurements will be tied to aircraft data to reveal the relative intensity and location of these updrafts to the dry line. This study provides unprecedented high temporal and spatial resolution measurements of wind, moisture and backscatter within a dryline and the associated convective boundary layer. IXXODUCTIONThe dryline occurs in the mid-west of the US and is sometimes called a "dew point ftont" or "dry fi~nt." It is a boundary between warm, moist air that originated fiom the Gulf of Mexico and hot, dry air from the Mexican Plateau and southwest desert. It is sometimes a hvored zone for initiation of severe weather (Rhea, 1966). Dryline moisture differences and sharpness (Fujita 1958 In this paper, we focus on the quantification of the small-scale variability of boundary layer parameters, key to understanding convective initiation. The variability in the convective boundary layer moisture, wind and temperature fields and their importance in the initiation of storms have been discussed in the literature (Weckwerth et al., 1996; Crook, 1986 andWeckwerth, 2000 and Convective Boundary Layer (CBL) structure with many measurements f?om aircraft, radar, profiler, and profiles of infrared moisture and temperature and other data to study thermodynamic variability in and around clear air updrafts during a dryline event. Variations of the moisture plumes as the dryline moved back and forth over the ground site are observed and the site specific profile observations are related to the larger picture using aircraft and radar based measurements.A brief description of the synoptic setting using satellite, sonde and radar data is presented in section 2. Many of the profiler instruments at Homestead are relatively new and information on their performance may not be easily accessible. Thus, in section 3, a brief discussion of the Homestead-based instruments and their measurements on 22 May 2002 are presented. 5Analysis and synthesis of the data and supporting evidence fiom aircraft observations on the day are presented in section 4. A summary and some conclusions are presented in section 5. SYNOPTIC SETTING Satellite dataSatellite and surface analysis indicated that starting about 1600 (all times UTC) there wa...

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