Estimation of Wind Induced Ocean Microwave Emission at C- and X-band Frequencies from the AMSR2 Measurements over the Arctic Waters

Passive microwave ocean response to sea surface wind speed at C- and X-bands is estimated using numerical modeling of the atmosphere — ocean system brightness temperatures (BTs) and the measurements of the Advanced Microwave Scanning Radiometer 2 (AMSR2) over cold waters. A large dataset of the AMSR2 measurements over the Arctic open water seas for a whole year is collected to match up measurements and modeling results. ERA-Interim reanalysis data are explored to calculate the AMSR2 BTs. The sea surface wind speeds (SWS) are retrieved from the AMSR2 6.9 and 10.65 GHz measurements at both vertical and horizontal polarization with an algorithm developed earlier using an old version of the geophysical model function (GMF) for the BT dependency on SWS. Only SWS less than 20 m/s are used to derive the new GMFs to minimize the effect of foam. The new GMFs are compared to old ones and found to be very close for both vertically and horizontally polarized microwave signal at 6.9 GHz and a little bit different for the signal at 10.65 GHz — more for vertically and less for horizontally polarized signal. The new experimental models of the ocean response to SWS may be used for verification and elaboration of theoretical GMFs for cold Arctic waters for low to moderate sea surface winds.