The sea breeze circulation during the Land Sea Breeze Experiment (LASBEX) in central California.

Abstract

The sea breeze circulation was investigated using a combination of acoustic Doppler sodar, Doppler lidar and conventional observations in central California on the coast of Monterey Bay in September 1987. The study was called LASBEX (Land Sea Breeze EXperiment) and used the combined effort and resources of the Naval Postgraduate School (NPS), NOAA Wave Propagation Lab (WPL) and Naval Environmental Prediction Research Facility (NEPRF). A monostatic three-axis phased-array Doppler sodar was able to detect the various features of the sea breeze front, which has many of the characteristics of a gravity head current produced in laboratory experiments, such as the longitudinal vortex, lobe and cleft structure, and strong regions of turbulence and convergence. Profiles of the wind field and its component variances were generated every five minutes. Vertical velocities up to 1.0 m/s were detected in the updraft region at the front. Vertical velocity fields were used to derive the horizontal divergence associated with the sea breeze and values of convergence in the range of 4 X 10ˉᶟsˉᶦ and greater were calculated. These are believed to be more accurate values than any found in previous sea breeze studies. Doppler lidar radial velocity information was useful in mapping the various layers and wind structure of the sea breeze. The wind field of the sea breeze seen by the lidar was compared with the sodar. The results of this comparison showed that the sodar was well suited to investigate features under 600 meters in height, such as the updraft region behind the front and the variance of the wind, whereas the lidar was better at describing the larger scale flow, such as the return flow of the sea breeze, the convergence zone along the sea breeze front and prevailing synoptic winds. Together, these instruments gave a comprehensive and complete description of the sea breeze frontal structure, evolution and movement.