A Doppler radar study of convective draft lengths over Darwin, Australia

Abstract

AbstractData from an upward-pointing wind profiler radar pair at Darwin in tropical Australia are used to determine the characteristics of individual convective up- and downdrafts observed at the site. Drafts are identified as vertically contiguous regions of instantaneous upward or downward motion exceeding 0.2 ms−1. Most updrafts and downdrafts found are less than 2 km in vertical extent, and updrafts exceeding 5 km vertical length carry no more than 33% of the total upward mass flux. Updraft length correlates positively with rain rates, and on very high rain rates (greater than 20 mm/hr), average updraft lengths are ~5 km. Typical peak updraft velocities increase from ~2.5 ms−1 for the smallest to ~ 4 ms−1 for the largest drafts, while those for downdrafts remain ~ 2 ms−1 regardless of size. These results are broadly consistent with other numerical modeling studies, but contrast with the common view of deep convection as being dominated by continuous, deep drafts.