World ocean mean monthly waves, swell, and surface winds for July through October 1978 from SEASAT radar altimeter data

Abstract

Data acquired by the SEASAT radar altimeter during the satellite's three‐month lifetime are used to obtain mean monthly maps of significant wave height, minimum swell, and surface wind speed for the world oceans. The SEASAT lifetime 26 June to 10 October 1978, corresponds to the Arctic summer and Antarctic winter. Thus, the highest sea states as derived from the radar altimeter data occur in the high latitudes of the Southern Ocean, reaching the mean monthly extreme magnitudes of 6‐m significant wave height, 5‐m minimum swell amplitude, and 12 m/s surface wind speed. Several features of the wave and wind fields agree with conventional descriptions. For example, the principal zonal wind regimes of the westerlies and trade winds and the doldrums and monsoon region are clearly evident in the monthly averages. Significant wave height and swell, whose mean fields always appear to be smoother than the mean wind speed fields, exhibit minima near the doldrums and steady increases southward and northward to the westerlies. However, superimposed on these general patterns is significant variability with spatial scales as small as 1000 km. For both the northern and southern hemispheres for each of the three months analyzed, the western sides of the oceans have consistently lower significant wave height and swell then do the eastern sides. In the Southern Ocean, the maps document a clockwise migration of the region of absolute maximum waves and winds from the Atlantic eastward to the Indian Ocean and finally into the Pacific Ocean from July to September–October 1978.