[1] Partitioning of solar energy at the Earth surface has significant implications in climate dynamics, hydrology, and ecology. Consequently, spatial mapping of energy partitioning from satellite remote sensing data has been an active research area for over two decades. We developed an algorithm for estimating evaporation fraction (EF), expressed as a ratio of actual evapotranspiration (ET) to the available energy (sum of ET and sensible heat flux), from satellite data. The algorithm is a simple two-source model of ET. We characterize a landscape as a mixture of bare soil and vegetation and thus we estimate EF as a mixture of EF of bare soil and EF of vegetation. In the estimation of EF of vegetation, we use the complementary relationship of the actual and the potential ET for the formulation of EF. In that, we use the canopy conductance model for describing vegetation physiology. On the other hand, we use ''VI-T s '' (vegetation index-surface temperature) diagram for estimation of EF of bare soil. As operational production of EF globally is our goal, the algorithm is primarily driven by remote sensing data but flexible enough to ingest ancillary data when available. We validated EF from this prototype algorithm using NOAA/AVHRR data with actual observations of EF at AmeriFlux stations (standard error ffi 0.17 and R 2 ffi 0.71). Global distribution of EF every 8 days will be operationally produced by this algorithm using the data of MODIS on EOS-PM (Aqua) satellite.

Climate data show significant increases in precipitation and humidity over the U.S. since 1900, yet the role of these hydro‐climatic changes on the reported U.S. carbon sink is incompletely understood. Using a prognostic terrestrial ecosystem model, we simulated 1900–1993 continental U.S. carbon fluxes and found that increased growth by natural vegetation was associated with increased precipitation and humidity, especially during the 1950–1993 period. CO2 trends and warmer temperatures had a lesser effect. Two thirds of the increase in observed forest growth rates could be accounted for by observed climatic changes, including the confluence of earlier springs and wetter autumns leading to a lengthening of the vegetation carbon uptake period. However, regional differences in precipitation trends produced differing regional carbon sink responses. The strong coupling between carbon and hydrologic cycles implies that global carbon budget studies, currently dominated by temperature analyses, should consider changes in the hydrologic cycle.

[1] We propose the use of Degree Confluence Project (hereby DCP) information as a new method for validating land cover maps. The DCP is a volunteer-based project that aims to collect onsite information from all the degree confluences (intersections of integer level latitude and longitude gridlines) in the world. We assessed the reliability and effectiveness of DCP-derived data in validating land cover maps. As a result, we obtained land cover validation information superior to the validation information obtained by visual interpretation of Landsat images. By using DCPderived validation information (at 749 confluences), we evaluated existing land cover maps for Eurasia (GLC2000, MOD12, UMD, and GLCC). The agreements between the DCP-derived validation information and the land cover maps were 55% for GLC2000, 58% for MOD12, 54% for UMD, and 50% for GLCC. Although MOD12 and GLC2000 had somewhat better agreements than the other maps, there is no significant difference between the two.

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The surface energy flux balance and total evapotranspiration were estimated using the eddy correlation, and bandpass covariance technique over a tropical monsoon environment within the framework of GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment (GAME). The aim of this present study is to obtain information on the seasonal variation of heat and water vapor exchanges between the atmosphere and terrestrial land cover (complex area) in tropical monsoon environment.The result indicated the daily integrated values of net radiation, sensible heat, latent heat and ground heat flux during the observation period from July 1998 to February 1999 were 10.76 MJ m À2 , 2.32 MJ m À2 , 5.18 MJ m À2 and 0.03 MJ m À2 , respectively. Sensible and latent heat fluxes were the dominant energy partitioning components throughout the year. The seasonal difference in surface fluxes between wet and dry seasons was seen, and the latent heat flux was dominant in the monsoon, corresponding with the increase of specific humidity after frequent precipitation. Whereas the sensible heat flux increased as the surface temperature increased in the absence of rainfall during the dry season. However, the closure of energy balance remained unresolved as with the foregoing experimental studies. The estimated amount to evapotranspiration was 526 mm versus 641 mm of actual precipitation, and accounted for about 80% of the precipitation during this period.