Evolution of the Monterey Bay Sea-Breeze Layer As Observed by Pulsed Doppler Lidar

Abstract

As part of the Land/Sea Breeze Experiment (LASBEX) to study the sea breeze at Monterey Bay, the pulsed Doppler lidar of the NOAA/ERL Wave Propagation Laboratory performed vertical and nearly horizontal scans of the developing sea breeze on 12 days. Analyses of Doppler velocity data from these scans revealed details on the growth of the sea-breeze layer and on the horizontal variability of the sea breeze resulting from inland topography. Two days were selected for study when the ambient flow was offshore, because the onshore flow of the sea breeze was easy to discern from the background flow. Sequences of vertical cross sections taken perpendicular to the coast showed the beginnings of the sea breeze beneath the land breeze at the coast and the subsequent growth of the sea-breeze layer horizontally and vertically. On one of the days a transient precursor?a ?minor sea breeze??appeared and disappeared before the main sea breeze began in midmorning. Other issues that the lidar was well suited to study were the compensating return flow, the Coriolis effect, the effects of topography, and the growth of the dimensions of the sea-breeze layer. No return flow above the sea breeze and no Coriolis turning of the sea-breeze flow were found even through the late afternoon hours. Terrain effects included an asymmetry in the development of the sea breeze over water as opposed to over land and the persistence into the late morning hours of southeasterly flow from the Salinas River valley toward the vicinity of the lidar. Vertical and horizontal dimensions of the sea-breeze layer were determined from lidar vertical cross sections. From these, length-to-width aspect ratios were calculated, which were then compared with aspect ratios derived from recent analytical models. The theoretical values compared poorly with the observed values, most likely because the complicating effects of topography and stability were not accounted for in the theoretical models.