Satellite remote sensing of turbulent heat fluxes

This paper reviews recent progress and remaining problems in the derivation of turbulent heat fluxes from satellite data. Satellite derived flux fields are important for the evaluation of coupled ocean-atmosphere circulation models, they can provide forcing for ocean models, and have the potential to better understand the spatial and temporal variability of the exchange of heat and momentum between ocean and atmosphere. Here the focus is on summarising which data sets already exist and what techniques were used to derive them. Estimates of surface wind speeds from scatterometers and passive microwave radiometers made large progress over the last decade. Somewhat troublesome are still the methods for deriving air humidity and air temperature. Comparisons of existing global satellite derived data sets among each other revealed large regional differences. However, the agreement among the satellite data sets is much better than that with well established in situ and reanalysis data sets. Therefore it is necessary to foster assessments of the quality of all three kinds of data. The SEAFLUX initiative provides at least a very good database and builds a suitable framework to assess the quality of existing data sets as well as retrievals on the pixel scale.