ASAR and ASCAT in Polar Low Situations

Abstract

orecasting and monitoring polar lows are, to a large degree, based on satellite observations from passive radiometers and from scatterometer winds in addition to synoptic observations and numerical models. Synthetic aperture radar (SAR) brings higher resolution compared to other remotely sensed sources of ocean wind, such as scatterometer data and passive microwave wind products. The added information in polar low situations from SAR and the increased-resolution scatterometer wind fields are investigated. Statistically, higher variability in the MetOp Advanced Scatterometer (ASCAT) wind is clearly found during polar low situations compared to all situations. Slightly more variability is also seen in the ASCAT 12.5-km wind product compared to the operational European Centre for Medium-Range Weather Forecasts (ECMWF) model surface winds. In two analyzed polar low cases, Environmental Satellite (Envisat) Advanced SAR (ASAR) images reveal numerous interesting features, such as the sharp fronts and the location and strength of the strongest wind field in the polar low. It is likely that if SAR images are available to operational weather forecasting, that it can in some cases lead to earlier detection of polar lows. However, a reliable wind field from SAR is still needed.