COWVR BRIGHTNESS TEMPERATURE CALIBRATION AND TWO-LOOK WIND DIRECTION PERFORMANCE

K. Nelson¹, F. Wentz¹, T. Meissner¹, R. Lindsley¹

¹Remote Sensing Systems

The COWVR instrument is a technological demonstration of a compact, low-cost polarimetric microwave radiometer for measuring wind speed and direction over the ocean surface. COWVR’s internal calibration system allows Earth observations over the entire scan, which enables two-look retrievals. In the first half of the presentation, we will discuss the additional calibration required to tie COWVR brightness temperatures (TBs) to GMI’s absolutely calibrated TBs. We will show the post-calibration daily timeseries of TB biases between COWVR and GMI over the ocean and Amazon, and additionally present the TB biases as a function of scan angle. In the second half of the presentation, we will compare COWVR’s two-look wind directions with retrievals that use only one of COWVR’s looks against model winds from NCEP and ERA5, CCMP, ASCAT-C, and moored buoys. In this analysis, we will discuss how certain relative wind directions are prone to error in the COWVR one-look retrievals. These include (1) relative wind directions that correspond to the minima and maxima of the wind direction emissivity model where there are clusters in the frequency of data, and (2) downwind observations which have lower skill rates and higher root-mean-square errors. Due to the diversity of relative wind directions when both looks are available, the two-look capability significantly improves the wind direction retrieval.