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Global inter-comparison of 12 land surface heat flux estimates

A global inter-comparison of 12 monthly mean land surface heat flux products for the period 1993-1995 is presented. The inter-comparison includes some of the first emerging global satellite-based products (developed at Paris Observatory, MPI for Biogeochemistry, University of California Berkeley, University of Maryland, and Princeton University) and examples of fluxes produced by reanalyses (ERA-Interim, MERRA, NCEP-DOE) and off-line land surface models (GSWP-2, GLDAS CLM/Mosaic/Noah). An inter-comparison of the global latent heat flux (Qle) annual means shows a spread of order 20 W m−2 (all-product global average of order 45 W m−2 ). A similar spread is observed for the sensible (Qh) and net radiative (Rn) fluxes. In general, the products correlate well with each other, helped by the large seasonal variability and common forcing data for some of the products. Expected spatial distributions related to the major climatic regimes and geographical features are reproduced by all products. Nevertheless, large Qle and Qh absolute differences are also observed. The fluxes were spatially averaged for 10 vegetation classes. The larger Qle differences were observed for the rain forest, but when normalized by mean fluxes the differences were comparable to other classes. In general, the correlations between Qle and Rn were higher for the satellite based products compared with the reanalyses and off-line models. The fluxes were also averaged for 10 selected basins. The seasonality was generally well captured by all products, but large differences in the flux partitioning were observed for some products and basins.

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Plain English Discussion

The surface fluxes of heat and water over land drive both weather and climate. They are much harder to calculate over land than the surface fluxes over the ocean, and different models give different results. The reason for these differences is that the energy reaching the ground (which drives evaporation) depends on the amount of cloud (clouds reflect sunlight and trap heat radiation from the earth); and evaporation at the surface depends on the amount of water in the soil and on wet leaves, and how all the different types of vegetation across the surface of the Earth are modeled. This paper compares the surface fluxes calculated from 12 different models. Five models calculate the surface fluxes using satellite data, three are global forecast models that analyze both atmospheric and satellite measurements, and four are models for the vegetation at the land-surface. By showing the differences between the flux estimates, we hope to improve the models.

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Full Citation

Jiménez, C., C. Prigent, B. Mueller, S. I. Seneviratne, M. F. McCabe, E.F. Wood, W. B. Rossow, G. Balsamo, A. K. Betts, P. A. Dirmeyer, J. B. Fisher, M. Jung, M. Kanamitsu, R. H. Reichle, M. Reichstein, M. Rodell, J. Sheffield, K. Tu and K. Wang (2011), Global inter-comparison of 12 land surface heat flux estimates. J. Geophys. Res., 116, D02102, doi:10.1029/2010JD014545.