BUOY OBSERVATIONS OF THE ATMOSPHERE ALONG THE WEST-COAST OF THE UNITED-STATES, 1981-1990

The distribution of statistical properties of the meteorological and sea surface temperature fields along the west coast of the United States is described based on 10-yearlong observations from buoys deployed by the National Data Buoy Center. The observations suggest that properties vary differently in each of three different regions along the coast: the Southern California Eight which remains sheltered from strong wind forcing throughout the year; the central and northern California coast up to Cape Mendocino, the site of persistent equatorward winds; and the Oregon-Washington coast, where traveling cyclones and anticyclones produce vigorous and variable forcing. Over most of the region the variance in the wind speed is roughly equally divided between the annual cycle and the synoptic forcing, corresponding to periods between 5 and 50 cycles per year. Two seasons, summer and winter, are sufficient to describe the annual cycle. During the summer, two distinct wind speed maxima occur along the coast, one near Point Conception and the other off northern California, between Point Reyes and Point Arena. In the winter a single maximum occurs, located near Point Conception. The atmospheric pressure generally increases with latitude along the coast, but the annual cycle of atmospheric pressure has a different phase, depending on location; off the coast of California, highest pressures are found during the winter, while off Oregon and Washington, the highest pressures occur during the summer. Fluctuations in air and sea temperature are highly correlated, and the sea temperature is usually higher than the air temperature, in the winter. Examination of vertical soundings of the atmosphere at Oakland, Vandenberg Air Force Base and San Diego during the same period of time reveals that a well-defined inversion separates the marine boundary layer (MBL) from the free atmosphere above nearly 90% of the time during the summer and half the time during the winter. Station soundings consistently overestimate the MBL thickness, but the results do suggest that the MBL is supercritical part of the time in the vicinity of the three sites. An attempt is made to examine the interannual variability and compare it to the Southern Oscillation index, although the results are limited because the record length is short compared with interannual timescales. Spatially averaged temperature anomalies increase during winter 1982-1983, coincident with the large El Nino event.