Updates of Aquarius’ CAP Ocean Surface Salinity and Wind Retrieval Algorithm
[14-Nov-2013] Yueh, S., Tang, W., Fore, A., and Hayashi, A.
Presented at the 2013 Aquarius/SAC-D Science Team Meeting
This paper describes Aquarius' version-3.0 Combined Active-Passive (CAP) retrieval algorithm for simultaneous retrieval of surface salinity and wind. The major updates to the CAP V3.0 algorithm include the galactic reflection correction, Faraday rotation (FR) and Antenna Pattern Correction (APC) as well as the geophysical model functions (GMF) of wind, wave and rain impacts. We use a series expansion with Gaussian basis functions to approximate the scattering coefficients of ocean surfaces. This results in more accurate modeling of the reflection of galactic radiation and consequently significantly reduces the ascend-descending bias in the salinity retrievals. This improvement along with the FR and APC corrections greatly reduces the errors of Aquarius CAP salinity retrievals. We assess the accuracy of CAP's salinity by comparison with ARGO's monthly gridded salinity obtained from the Asia-Pacific Data-Research Center (APDRC). The RMS differences between CAP and APDRC-ARGO salinities on 1x1 degree latitude and longitude grid are less than 0.2 psu for a significant part of the global oceans, except the regions in the Inter-tropical Convergence Zone (ITCZ), near the outflow of major rivers and high latitudes, where the differences could be a result of surface stratification lack of ARGO observations.