On the determination of global ocean wind and wave climate from satellite observations

Abstract

Three extensive global wind speed and wave height datasets (altimeter, radiometer, model reanalysis) are analysed to investigate the global wind speed and wave height climate. Despite the fact that these datasets have all been carefully calibrated, they show systematic differences in wind speed. At high latitudes both altimeter and radiometer winds are biased high compared to buoy measurements. Altimeter winds are more impacted than radiometer winds. Based on the assumptions that altimeter winds respond primarily to the surface wave spectrum mean squared slope and radiometer winds respond primarily to the surface wave spectrum dissipation, it is shown that the observed differences are a result of changes in atmospheric stability. An analysis which accounts for differences in air and water temperatures describes the observed differences with surprising accuracy. Based on this analysis corrections to both altimeter and radiometer winds are proposed which account for the influence of atmospheric stability. It is also shown that satellites preferentially measure at particular local times of day. As winds have a diurnal variation in magnitude, this preferential measurement time can also bias statistical values obtained from such satellite systems.