Extended validation of Aeolus winds with wind-profiling radars in Antarctica and Arctic Sweden

Abstract. Winds from two wind profiling radars, ESRAD in Arctic Sweden and MARA on the coast of Antarctica, are compared with collocated winds measured by the Doppler lidar onboard the Aeolus satellite for the time period July 2019–May 2021. Data is considered as a whole, and subdivided into summer/winter and ascending (afternoon) /descending (morning) passes. Mean differences (bias) and random differences are categorised (standard deviation and scaled median absolute deviation) and the effects of different quality criteria applied to the data are assessed, including the introduction of the ‘modified Z-score’ to eliminate gross errors. This last criterion has a substantial effect on the standard deviation, particularly for Mie winds. Significant bias is found in two cases, for Rayleigh/descending winds at MARA (-1.4 (+0.7) m/s) and for all Mie winds at ESRAD (+1.0 (+0.3) m/s). For the Rayleigh wind bias at MARA, there is no obvious explanation for the bias in the data distribution. For the Mie wind at ESRAD there is a clear problem with a distribution of wind differences which is skewed to positive values (Aeolus HLOS wind > ESRAD wind). Random differences (scaled median absolute deviation) for all data together are 5.9 / 5.3 m/s for Rayleigh winds at MARA/ESRAD respectively , and 4.9 / 3.9 m/s for Mie winds. These represent an upper bound for Aeolus wind random errors since they are due to a combination of spatial differences, and random errors in both radar winds and Aeolus winds.