학술논문

Adjustment of the Summer Marine Boundary Layer around Point Sur, California.
Document Type
Article
Source
Monthly Weather Review. Sep99, Vol. 127 Issue 9, p1. 17p.
Subject
*WIND measurement
*ATMOSPHERIC temperature
*METEOROLOGY
SUR, Point (Calif.)
Language
ISSN
0027-0644
Abstract
An instrumented C-130 aircraft flew over water around Point Sur, California, on 17 June 1996 under strong northwest wind conditions and a strong marine inversion. Patterns were flown from 30- to 1200-m elevation and up to 120 km offshore. Nearshore, marine air accelerated past Point Sur, reaching a surface maximum of 17 m s 21 in the lee. Winds measured over water in and above the marine layer were alongshore with no significant cross-shore flow. Sea level pressure, 10-m air temperature, and air temperature inversion base generally decreased toward the coast and were an absolute minimum just downcoast of the wind speed maximum. The sea surface temperature also decreased toward the coast, but was an absolute minimum directly off Point Sur. The near-coast, air temperature inversion base height was 400 m north of Point Sur, decreased to a minimum of 50 m in the lee of Point Sur, then increased farther to the south. Wind speeds were at a maximum centered along the air temperature inversion base; the fastest was 27 m s 21 in the lee of Point Sur. Using a Froude number calculation that includes the lower half of the capping layer, the marine layer in the area is determined to have been supercritical. Most of the marine layer had Froude numbers between 1.0 and 2.0 with the extreme range of 0.8-2.8. Temperatures in the air temperature inversion in the lee were substantially greater than elsewhere, modifying the surface pressure gradient. The overall structure was a hydraulic supercritical expansion fan in the lee of Point Sur under the influence of rotation and surface friction. The Naval Research Laboratory nonhydrostatic Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) indicated a broad, supercritical marine boundary layer moving to the south along central California and Point Sur during the aircraft flight. The marine boundary layer thinned and accelerated into the lee of Point Sur, which was the site of the fastest sea level wind speed along... [ABSTRACT FROM AUTHOR]