Climatology of a Summer Coastal Boundary Layer with 1290-MHz Wind Profiler Radar and a WRF Simulation

Abstract

study of the Israeli summer coastal boundary layer (BL) with a 1290-MHz wind profiler located 3.5 km from the coastline has revealed four main features associated with the sea-breeze onset: 1) by midday the boundary layer height drops by an average value of 250 m, 2) a sea-breeze calm zone (SBCZ) develops near the top of the onshore BL, 3) persistent strong downdrafts, with average values of 0.35 m s?1, invigorate from the BL top downward, and 4) a combination of the SBCZ and strong downdrafts may cause an elevated plume released from 250?300-m-tall coastal stacks to reach the ground only 3.5 km downwind. Results from the Weather Research and Forecasting (WRF) numerical weather model confirmed the development of a sea-breeze downdraft zone up to 4 km onshore. Such a zone, which was observed as a cloudless strip in satellite images [Moderate Resolution Imaging Spectroradiometer (MODIS)], may be a result of persistent large BL eddies that develop to horizontal transverse rolls. Because the WRF-simulated downdraft magnitude is weaker by a factor of more than 5 than the profiler measurements, the magnitude of the downdrafts is inconclusive.