1. Are the results of PILPS or GSWP affected by the lack of land surface- atmosphere feedback? Is the use of offline land surface models in LDAS making optimal use of the assimilated data? We need experiments designed to quantify land – atmosphere feedback in land surface modelling and data assimilation. This will take the next step in the complexity chain from offline land surface models to fully coupled GCM’s. Focus on land – atmosphere coupling by means of turbulent exchange, but discarding the processes related to radiation and precipitation. Report of the GLASS workshop on land – atmosphere interaction Bart van den Hurk, Paul Houser and Jan Polcher 19-20 April, 2002 TOA Radiation Horizontal Flux Divergence s Single Column Model Land Surface Model (www.arm.gov) A Single Column Model

2. The main scientific questions: When and where does land – atmosphere interaction play a significant role in the evolution of land-atmosphere fluxes and state variables? Does the absence of this coupling in PILPS-like calibration/evaluation experiments put a strong constraint on the general applicability of the results of these experiments? Is the solution of a land data assimilation experiment using an offline land surface model configuration different from a system that includes land – atmosphere feedback?

3. PHASE 1: GOAL: Inventory conditions (climate, land cover and –heterogeneity, synoptic situation) where modelled fluxes and state variables are sensitive to the land-atmosphere coupling. ACTION: For a number of locations and time periods, the behaviour of land surface models in an offline and a coupled mode (using a SAM – Simplified Atmospheric Model) will be compared. The SAM should be able to calculate the vertical exchange processes due to turbulence, thermodynamics and radiation, but does not necessarily supply the precipitation and radiation forcing to the land surface. PHASE 2: GOAL: Identify the nature of the land – atmosphere coupling by varying the combinations land model – boundary layer model in a systematic way. ACTION: Use a common land – atmosphere coupler (which is being established within the ALMA action of GLASS), and start with providing a single boundary layer model, to which a range of land surface models can be connected. PHASE 3: GOAL: The relation between data assimilation and land – atmosphere feedback will be addressed. ACTION: In this phase, a combination of an offline model and SCM should be allowed to assimilate additional data that are not present in the forcings already provided. These additional data could consist of surface state variables (soil moisture, snow), atmospheric quantities (screen level parameters, surface heating rates), surface fluxes or combinations of these obtained from co-located field experiments or remote sensing.

4. Known Actions ELDAS: Coupling TESSEL, the surface scheme in the DWD Lokal Modell, and the ISBA models to a common SCM and assimilation procedure. Individual Efforts –Hoshin and Luis? –Christa and Paul: NASA-AIST coupling of LIS 1km global LSM to PBL model –Others?

5. The First International Local-Coupled Action Field Experiment (FILCAFE) GOAL: Collect a specifically targeted dataset to meet the objectives of the GLASS local-coupled action. –A well-defined mesoscale hydrologic catchment (for surface water balance observations) –Observations from groundwater table through PBL –Include heterogeneity in elevation, vegetation, soils, climate (inc. snow), etc. –Observation platforms: In-situ: weather, fluxes, snow, soil moisture, groundwater, vegetation Aircraft: fluxes, temperature, moisture, microwave, etc. Soundings: tethered Satellite: various Questions: What should the spatial scale and heterogeneity be? When, where, and how long? Is this experiment of interest? Parameters Soil Properties Vegetation Properties Elevation & Topography Subgrid Variation Catchment Delineation River Connectivity Forcing Precipitation Wind profiles Humidity profiles Radiation Air Temperature profiles Fluxes Evapotranspiration Sensible Heat Flux PBL fluxes Radiation Runoff Drainage Isotopes/carbon States Soil Moisture Groundwater Surface Water Temperature (soil, veg, air) Humidity Wind Pressure Snow Carbon Nitrogen Biomass

6. How do we get action on the GLASS local-coupled action? Bart van den Hurk, Hoshin Gupta, Luis Bastidas, Jan Polcher, Christa Peters-Lidard, Paul Houser Develop a Phase 1 experimental plan Put in place tools (SCM) and datasets Engage the community