THERMODYNAMIC VARIABILITY WITHIN THE CONVECTIVE BOUNDARY-LAYER DUE TOHORIZONTAL CONVECTIVE ROLLS

Data from the Convection and Precipitation/Electrification (CaPE) Expe riment conducted during the summer of 1991 are used to examine and qua ntify the horizontal variability of temperature and moisture within th e convective boundary layer (CBL). Potential temperature variations we re only about 0.5 K, while variations in water vapor mixing ratio valu es of 1.5-2.5 g kg(-1) were observed throughout the CBL. Using radar, aircraft, and sounding data, it is shown that horizontal convective ro lls are the likely cause of these variabilities. The enhanced moisture occurred within the roll updraft regions, thus rolls were transportin g moist air from the surface upward. The observed cloud-base heights, obtained from cloud photogrammetry, were produced from the highest moi sture values within the roll updraft regions. Since the roll ascending branches contained moisture values that were most representative of t he observed cloud-base heights, it is likely that measurements from wi thin the roll updrafts would provide the best estimate of the potentia l for deep, moist convection.