[22-Feb-2022] The PO.DAAC is pleased to announce the availability of the PI-produced Multi-Mission Optimally Interpolated Sea Surface Salinity (OISSS) Monthly Level-4 V1.0 dataset based on the AQUARIUS/SAC-D, SMAP and SMOS level-2 mission data gridded on a 0.25 degree spatial grid with a monthly time scale. The optimal interpolation is applied to each mission data set to create a gap free gridded product. The dataset is the monthly averaged product from the OISSS 7-day dataset which provides the monthly mean SSS, monthly climatological mean SSS based on the 10-year data record, and monthly anomaly SSS values. It was produced by the International Pacific Research Center (IPRC), University of Hawaii at Manoa in collaboration with Remote Sensing Systems (RSS), Santa Rosa, California. It covers the period from September 2011 through September 2021, and will be updated regularly every 6 months as new data permit. The dataset is CF/ACDD metadata conventions compliant, and includes an estimated SSS uncertainty field. The multi-mission OISSS Level 4 V1.0 dataset is described, discoverable, and accessible both on-premise and in the cloud via the PO.DAAC data portal, as are the associated technical documentation and the addendum technical document. General information regarding the Aquarius, SMAP and SMOS missions are available from the respective mission websites. Users are encouraged to visit PO.DAAC Cloud Data Page for detailed information about cloud data access. We recommend users to download the data using the data-subscriber tool. Currently, the cloud OPeNDAP service is available, but it only works with the DAP4 data model which is invoked by adding the suffix ".dap.nc4" to the query request. 10.5067/SMP10-4UMCS Oleg Melnichenko, Peter Hacker, James Potemra, Thomas Meissner, and Frank Wentz (2021). Aquarius/SMAP sea surface salinity optimum interpolation analysis, IPRC Technical Note No. 7, May 7, 2021. Melnichenko, O., P. Hacker, N. Maximenko, G. Lagerloef, and J. Potemra, 2014: Spatial Optimal Interpolation of Aquarius Sea Surface Salinity: Algorithms and Implementation in the North Atlantic, J. Atmos. Oceanic Technol., 31, 1583-1600. Melnichenko, O., P. Hacker, N. Maximenko, G. Lagerloef, and J. Potemra, 2016: Optimum interpolation analysis of Aquarius sea surface salinity, J. Geophys. Res. Oceans, 121, 602-616, doi:10.1002/2015JC011343. Related PO.DAAC Animation Comments/Questions? Please contact podaac@podaac.jpl.nasa.gov or visit the PO.DAAC Forums.