NOAA In Situ - Satellite Blended Analysis of Surface Salinity (BASS): Prototype Algorithm and Applications
[03-Dec-2012] Xie, P., Boyer, T., Bayler, E. J., Xue, Y., Byrne, D.A., Reagan, J.R., Locarnini, R.A., and Kumar, A.
Presented at the 2012 AGU Fall Meeting
A prototype analysis of monthly sea surface salinity (SSS) has been constructed on a 1olat/lon grid over the global ocean by blending information from in situ measurements and satellite retrievals. Three data sets are included as inputs to the blended analysis, i.e., in situ SSS measurements aggregated and quality controlled by NOAA/NODC, and the passive microwave (PMW) retrievals from the Aquarius/SAC-D and SMOS satellites, received and post-processed at NOAA/STAR. The in situ SSS measurements used here are mainly from the Argo program, but also include those from the tropical moored buoy array (TAO/TRITON, PIRATA, RAMA) data and CTDs and glider data.
The blended analysis is defined in two sequential steps. First, the bias in the satellite retrievals is removed through PDF matching against the co-located in situ measurements. The final blended analysis is then defined through the optimal interpolation (OI), where the analysis for the previous time step is used as the first guess while the in situ measurements and the bias-corrected satellite retrievals are employed as the observations to update the first guess.
Cross-validations tests are conducted by comparing the blended analysis against the withdrawn SSS measurements from the PIRATA arrays. Results showed improved quantitative accuracy of the blended analysis compared to the satellite estimates and the in situ data alone analysis in the tropical Atlantic. The blended analysis, constructed from January 2010 to the present, is used to examine the co-variability among the SSS, E-P, SST, SSH, and surface wind stress in the annual cycle over the tropical Atlantic and to estimate the SSS bias in the NCEP's Climate Forecast System Reanalysis (CFSR) and Global Ocean Data Assimilation System (GODAS) . Results will be reported at the meeting.