Influence of the Synoptic-Scale Flow on Sea Breezes Observed during CaPE

Abstract

Mean sea-breeze characteristics were determined by analyzing a number of sea-breeze events during offshore, parallel, and onshore flow regimes during the Convection and Precipitation/Electrification Experiment (CaPE). It was observed that offshore flow cases exhibited the widest, and relatively strongest, radar-detected thin lines. The thin-line reflectivity values steadily increased during the day. In contrast, a thin line was detected only during late afternoon on parallel flow days while no easily identifiable thin line was observed during onshore flow days. The gradients of temperature and moisture, as measured by a surface meteorological station during sea-breeze passage, were strongest and weakest during offshore and onshore flow days, respectively. In addition, the moisture and temperature gradients across the leading edge of the sea breeze steadily increased during the day and were strongest during late afternoon. Using dual-Doppler techniques, the detailed kinematic structure of the sea-breeze circulation for offshore and onshore flow regimes is presented. In particular, detailed measurements of the sea-breeze return flow at upper levels are presented for both offshore and onshore flow events for the first time. The observed inland propagation speed for offshore and parallel flow events is consistent with calculated values for density currents. Onshore flow events, however, are observed to move inland at a rate that is slower than what is expected for a density current.