The cross-calibrated, multi-platform (CCMP) ocean surface wind product: Current status and plans

A new cross-calibrated, multi-platform (CCMP) ocean surface wind product with wide-ranging research applications in meteorology and oceanography became available at the Physical Oceanography Distributed Active Archive Center in May 2009. The principal data set, denoted as Level 3.0, has global ocean coverage (except for the Arctic Ocean) with 25-kilometer resolution every 6 hours for more than 20 years, beginning in July 1987. Applying an enhanced variational analysis method (VAM) to multiple input data sources creates the Level 3.0 data set. The VAM performs quality control and optimally combines wind observations from several individual satellite microwave radiometer and scatterometer sensors along with available conventional ship and buoy wind observations and (ECMWF) analyses. The two other levels of data processing are denoted as levels 2.5 and 3.5. The Level 2.5 data sets, one for each passive microwave sensor, are obtained by assigning directions from the VAM analyses (i.e., the Level 3.0 data) to the input wind speed observations. The Level 3.5 data sets are obtained by averaging the Level 3.0 data set over 5-day and monthly periods. Differences between the VAM analyses and wind observations used are very small. Comparisons of the VAM analyses with withheld WindSat observations are also very good.Compared to conventional analysis and reanalysis products from numerical weather prediction centers, the CCMP winds are significantly different in some synoptic cases, result in different storm statistics, and provide enhanced high-spatial resolution time averages of ocean surface wind. In individual synoptic cases, for example, the CCMP winds sometimes depict storms in different locations or reveal entirely new closed wind circulations. With respect to storm statistics, the net impact of assimilating satellite surface winds in the VAM is generally to increase the maximum vorticity and wind speed. As an example of the use of CCMP time averaged data sets, tropical streamline analyses of the monthly averaged VAM analyses reveal the evolution of the El Niño - Southern Oscillation in high spatial definition. In addition, patterns in the wind speed difference between the CCMP winds and ECMWF backgrounds often reveal strong ocean currents.Currently, the CCMP data sets extend from July 1987 through June 2008. Future plans include extending the data. As ocean wind vector data from additional satellite missions become available from RSS, these data will be added to the VAM inputs, and the affected periods will be reprocessed.