Ocean Surface Winds and Fluxes

The ocean atmosphere interactions are one of the crucial elements in climate variability. The MERRA system does not have a coupled ocean model and data assimilation, but future reanalyses will likely go in this direction. In MERRA, seas surface temperatures are prescribed and ocean surface wind observations (from buoys and satellites) are analyzed. Downward components of the radiation would be related to the parameterized clouds and radiation calculations, as well as the input observations (radiances, temperature and moisture). The following figures prepared for validation compare some winds and fluxes with GEOS5 experiments and other reanalyses.

This following figure shows the daily time-series for Jan 2004 and 2006 U10M and V10M winds at the TAO mooring location of 165E on the equator. GEOS-5 shows good agreement with TAO and matches the minimum and maximum values everywhere. In Jan 2004 and 2006, GEOS-5 is more highly correlated with QSCAT than NCEP CDAS or JRA-25. The NCEP-CDAS analysis shows several periods of larger bias against the observations.

The next figure shows maps of monthly latent heat flux for GEOS5, JRA-25 and NCEP CDAS. GEOS-5 has much less evaporation out of the ocean than JRA-25 and NCEP CDAS, especially in the western boundary currents: Gulf Stream and Kuroshio. Mean and RMS differences between GEOS-5 and JRA-25 and GEOS-5 and NCEP CDAS are much larger than that of NCEP CDAS and JRA-25 in the above region. Similar patterns are seen in January 2004.

In three validation periods investigated so far (Jan/Jul2004 and Jan 2006), GEOS-5 net radiation is more highly correlated with TAO in the Eastern Pacific that other reanalyses.
NCEP-CDAS generally is biased low in most time-periods and TAO locations. GEOS5 also correlates well with the TAO incoming shortwave radiation observations.


The three reanalyses are fairly different in their net heat fluxes. GEOS-5 has less heat loss than both NCEP and JRA in the Kuroshio and Gulfstream areas, and more heat gain off Western Australia. In the 45S-45N band, GEOS5 and JRA have substantial differences.