The unique rotating fan-beam feature of SCAT onboard CFOSAT leads to varying geometries across the swath and furthermore leads to varying wind retrieval performance across the swath. The Wind Vector Cells (WVCs) across the swath are classified into outer, sweet and nadir. The sweet WVCs contain the most diverse geometries, which lead to the best wind retrieval performance. In the outer WVCs the azimuth and incidence angle diversity is very limited and the number of views is smallest, which makes the wind retrieval the most ambiguous and difficult to improve. Secondly, in order to improve the wind retrieval, two kinds of NWP Ocean Calibration (NOC) are applied. One is a NOC as a function of incidence angle (NOCinc). The other one is a newly developed NOC as a function of incidence angle and antenna azimuth angle (NOCant), which takes the rotation angle into account. The NOCant correction results in better fits of the Geophysical Model Function than the NOCinc correction does, except for the outer WVCs, where the limited diversity of views determines retrieval quality. The results show that NOCant correction improves the wind speed Probability Distribution Function per WVC and reduces the average wind direction bias and the relative wind direction (relative to the satellite motion direction) biases, as compared to NOCinc correction. In conclusion, the rotating fan-beam feature of SCAT leads to unique and various data characteristics across the swath. Overall the performance of the proposed NOCant correction is better than NOCinc and improves the wind statistics.

Vortex streets formed in the stratocumulus-capped wake of mountainous islands are the atmospheric analogues of the classic Kármán vortex street observed in laboratory flows past bluff bodies. The quantitative analysis of these mesoscale unsteady atmospheric flows has been hampered by the lack of satellite wind retrievals of sufficiently high spatial and temporal resolution. Taking advantage of the cutting-edge Advanced Baseline Imager, we derived km-scale cloud-motion winds at 5-minute frequency for a vortex street in the lee of Guadalupe Island imaged by Geostationary Operational Environmental Satellite-16. Combined with Moderate Resolution Imaging Spectroradiometer data, the geostationary imagery also provided accurate stereo cloud-top heights. The time series of geostationary winds, supplemented with snapshots of ocean surface winds from the Advanced Scatterometer, allowed us to capture the wake oscillations and measure vortex shedding dynamics. The retrievals revealed a markedly asymmetric vortex decay, with cyclonic eddies having larger peak vorticities than anticyclonic eddies at the same downstream location. Drawing on the vast knowledge accumulated about laboratory bluff body flows, we argue that the asymmetric island wake arises due to the combined effects of Earth’s rotation and Guadalupe’s non-axisymmetric shape resembling an inclined flat plate at low angle of attack. The asymmetric vortex decay implies a three-dimensional wake structure, where centrifugal or elliptical instabilities selectively destabilize anticyclonic eddies by introducing edge-mode or core-mode vertical perturbations to the clockwise-rotating vortex tubes.