A Comparison of Air-Sea Heat Fluxes Obtained from Satellite and Reanalysis Based Products
Keith, Haines; Valdivieso, Maria
University of Reading, UNITED KINGDOM
The primary purpose of the present work is to assess the degree of consistency between global air-sea flux data sets, both those based on satellite products and those based on atmosphere and ocean reanalysis. So far we have analyzed the homogeneity and closure of the reanalysis-based flux products, and compared them with model independent products including the Objectively Analyzed Ocean-Atmosphere Fluxes (OAFlux, Yu et al., 2008) combined with net shortwave and longwave data from the International Satellite Cloud Climatology Project (ISCCP, Zhang et al., 2004) over the satellite era from 1993 through 2009. Most reanalyses show a positive imbalance in global surface heating with an ensemble-mean of 5 Wm-2 over the 17 year period, decreasing steadily after 2003-2004 when more ocean observations are available. This is far smaller than the 25 Wm-2 global heat flux imbalance in OAFlux+ISCCP product, which has been attributed to too strong amplitude of shortwave radiation. A comparison of the spatial flux maps reveals that the main discrepancies between available products are located across the tropical Pacific, the WBCs and in the Southern Ocean. The resulting implied northward heat transports show a large range of estimates among products which are due to a combination of flux bias and oceanic heat storage, although bias and storage effects cannot be separated so far.
Local ground truth comparisons using in situ buoy data are now underway and reveal that mean values from ocean/coupled reanalysis-based fluxes are systematically low compared to ISCCP+OAFlux data, although variability on seasonal to interannual timescales is generally in good agreement. Ongoing work is now looking at additional satellite based products and at individual flux components representing radiative and turbulent transfers.