A CONNECTION BETWEEN MEAN WAVE HEIGHT AND ATMOSPHERIC-PRESSURE GRADIENT IN THE NORTH-ATLANTIC

Comparison of long-term trends in mean wave height in the North Atlantic with values of annual mean atmospheric pressure gradient in the North Atlantic measured between the Iceland Low and the Azores High suggests, for the period of overlap between the data set of Bacon and Carter and of Sahsamanoglou (early 1950s to 1980), a correlation between these two measures. This paper, using monthly mean values of significant wave height (H(S)) derived from measurements at two sites, one oceanic (Ocean Weather Station Lima) and one coastal (Seven Stones Light Vessel), covering the period 1962-1988, investigates correlation between (firstly) annual mean values and (secondly) monthly mean values of H(S) and of pressure gradient. The annual mean values of pressure gradient are shown to be linked to the long-term changes in wave climate described by Bacon and Carter. The large annual cycles in the monthly mean values of both variates are found to be in phase; furthermore, correlation between the two variates independent of the annual cycle is found. Finally, the correlation between the annual means is used to generate a hindcast mean wave climate for Seven Stones Light Vessel (and also, tentatively, for the whole north-east Atlantic) from 1873 to the present, which suggests that present conditions are as high as have been observed since 1873.