Abstract
High-resolution sea surface observations by spaceborne synthetic aperture radar (SAR) instruments are sorely neglected resources for meteorological applications in polar regions. Such radar observations provide information about wind speed and direction based on wind-induced roughness of the sea surface. The increasing coverage of SAR observations in polar regions calls for the development of SAR-specific applications that make use of the full information content of this valuable resource. Here we provide examples of the potential of SAR observations to provide details of the complex, mesoscale wind structure during polar low events, and examine the performance of two current wind retrieval methods. Furthermore, we suggest a new approach towards accurate wind vector retrieval of complex wind fields from SAR observations that does not require a priori wind direction input that the most common retrieval methods are dependent on. This approach has the potential to be particularly beneficial for numerical forecasting of weather systems with strong wind gradients, such as polar lows.
Highlights
MethodsThe two satellites fly in the same orbital plane with a 180 ◦ phase difference
Our analysis of a polar low event that was misrepresented by the AROME-Arctic model shows that the potential benefits of high-resolution synthetic aperture radar (SAR) observations cannot be reached with current wind retrieval methods that heavily rely on a correct representation of the wind direction by a numerical model
Two common wind retrieval techniques are applied to SAR dual polarisation observations of the sea surface backscatter during a polar low event with complex wind structure
Summary
The two satellites fly in the same orbital plane with a 180 ◦ phase difference This constellation can potentially image most of the European Arctic in all weather conditions, twice daily on a descending (southward) morning pass, and an ascending (northward) evening pass. This potential is not realised due to the alternation between different observation modes over land and sea surfaces, the interferometric wide swath mode (IW) and the extra wide swath mode (EW), respectively. The dual polarisation observation mode results in two data sets for each image, one for the horizontally polarised transmitted and received signal (HH) known as the copol signal, and the other channel for the horizontally polarised transmission and vertically polarised backscatter (HV) referred to as crosspol signal
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