Mesoscale spatial and temporal variability of meteorological observations from an array of buoys in JASIN-1978

Abstract

Observations of wind speed and direction, air and sea temperatures and solar radiation were obtained from an array of buoys in JASIN-1978 conducted in the area northwest of Scotland in the summer of 1978. The observations were analyzed to show spatial and temporal variability in the mesoscale fields. Spectra of wind speed and air and sea temperatures were computed to illustrate the distribution of variance over periods ranging from 3.5 min to 40 days. When plotted on log-log graphs, the spectral estimates generally decreased with slopes between −3/2 and −2 with increasing frequency. Spectra of air and sea temperatures had a peak at the diurnal period but not the wind speed spectrum. When plotted in variance-preserving form, the spectrum of wind speed was consistent with a spectral gap and was qualitatively similar to other observations of low-frequency spectra. On the basis of auto- and cross-correlation analyses, it appeared that mesoscale eddies propagated through the array of buoys with the mean wind speed except during times of frontal passages. The cross-correlation between wind speed and air temperature showed evidence of horizontal roll vortices or some other forms of organized convection.