The LandFlux Initiative
of the
GEWEX Radiation Panel
Rationale: One of the major goals of the World Climate Research Program’s Global Energy and Water Experiment (GEWEX) is to obtain a quantitative description of the weather-scale variations of the global energy and water cycle over a period of at least 20 years to allow for diagnostic studies of the causes of these variations and to develop predictive capability. Towards that end the GEWEX Radiation Panel (GRP) conducts several global data analysis activities to complete the description of the energy and water cycle: all components are now being worked on either by GRP or other projects (clouds, aerosols, radiative fluxes, precipitation, ocean surface turbulent fluxes, water vapor, temperature, ozone) except the determination of the turbulent sensible and latent heat fluxes over land (and snow-ice) surfaces. In addition, some of the leading sources of uncertainty in the surface radiative flux products now being produced come from uncertainties of land surface and near-surface atmospheric properties. Although there is a lot of work on remote sensing of land properties and numerous studies of land processes, there is no systematic data analysis activity underway to produce complete, physically consistent, global, multi-decadal land property and energy-water flux data products. Two recent efforts took some steps towards fulfilling this need. The International Satellite Land Surface Climatology Project (ISLSCP) produced a decade-long (1986-1995), global compilation of land-surface-process-relevant data products; however, some of the key quantities were actually model outputs. The Global Soil Wetness Project (GSWP) not only produced soil wetness distributions but also produced consistent land surface temperature and turbulent fluxes using land surface process models forced by surface radiation, precipitation and other meteorological data, much of which came from the ISLSCP collection.
Objectives: The GEWEX Radiation Panel (GRP) is launching an activity, called LandFlux, to
develop the needed capabilities and to produce a global, multi-decadal surface turbulent flux data product. There are (at least) three pathways to determining these fluxes: (1) using satellite and other measurements to infer the physical properties of the atmosphere and surface needed to calculate turbulent fluxes using a “bulk formula” approach, (2) forcing/constraining a land surface model using observations as was done for GSWP, or (3) employing a full assimilation approach with a land process model (or even a coupled land-atmosphere model) and observations.
Workshops
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