GEWEX MOTIVATIONS FOR LANDFLUX ACTIVITY

1. GEWEX MOTIVATIONS FOR LANDFLUX ACTIVITY SUMMARY DISCUSSION -- DRAFT May 2007

2. (Chronological Order) 1) Cloud—Climate Feedback Problem Led to ISCCP, SRB and GPCP 2) Important (leading) Sources of Uncertainty for SRB are Land Surface (Sea Ice) Properties = Temperature, Emissivity, Spectral Albedo 3) Completion of Global (Atmospheric) E&W Cycle Requires Land (Ice) Surface Turbulent Fluxes 4) Connection of Climate Change to Human Interests Requires Land Hydrology Predictions = Water Storage (Lakes, Soil Moisture, Snow/Ice, Acquifer) and Runoff (Discharge, Floods)

3. ISSUES 1. Formulation of Land Surface Fluxes in terms of measurable quantities (FPAR -> Spectral Albedo, SH aero temp -> skin temp & aero drag, NDVI -> ???) 2. Vegetation Structure & Function not available in needed detail – how critical is using biosphere constraints on energy & water fluxes? (EO-1 analysis possibility), ACTION? (highlight importance of continuing work) ***3. Content (and organization/access) of Flux Tower data (how useful are these data without radiation and/or soil moisture/hydrology – ie, what is the best “verification”??, also issue of location) – Recommendation from GEWEX to ILEAPS and CEOP (Endorse “FluxNet” goals and recommend more urgent attention on organizing data access/distribution – follow BSRN model) ---- PLAN is to partner with GRP for Comparison WS in 2008 4. Canopy Structure Surveys (radar, lidar) -- in work in future 5. SCALE = Spatial Heterogeneity is in Ts & land properties (not forcing so much – precip?) ACTION? () 6. What do we use for validation? Other sources possible? 7. What Measurements are desired, finished, mature but needing systematic processing, algorithms need work? 8. Study topographic, roughness and vegetation effects on various signals ACTION? 9. Recommend to GLASS (maybe with GRP) to figure out how to improve large-scale hydrological parameters used in models – maybe other GEWEX group ***10. More Development of Flux-Parameter Relationships from In Situ Experiments – ACTION = ILEAPS/FLUXNET but also GEWEX research (CEOP??) – Revision of Tower Data Strategy

4. Methodology Ideas (Wood): Different “formulae” approaches driven by radiation (incoming) and precip, wind, Ta & Qa (Lin): ET estimate from microwave index plus radiation (Betts): Given Surface Radiation, RH and Precip, estimate Evaporative Fraction (Houser/Rodell): Assimilation Approaches (eventually fully coupled – get Houser slide) (force off-line land surface model = GSWP approach) (Beljaars) – Re-analysis derived results (Entekabi): Straight ET estimate from bulk equations using remote sensing inputs – formulation is separated into different contributions (not veg-type dependent explicitly) – essence: radiation = sensible heat flux reduced by EF-based factor (Basic): Bulk formulae for SH and ET with remote sensing inputs ---- VALIDATION OF RESULTING PRODUCTS

5. Observation Constrained Hybrid PBL/Land Model LandFlux Algorithm Proposal Relaxed to reanalysis • Way forward: • Year 1: Proof-of-concept • Year 2-3: 20 year product • Eval/Calibration plan 1-D Boundary Layer Turbulence Model Global land ½ degree 20+ years 3 hr estimates • Observational Constraints: • (Consistent 1983-current) • Surface Radiation (i.e. ISCCP) • Precipitation (i.e. GPCP) • Surface Skin Temperature • Near-Surface T &RH • Innundation • Albedo • Vegetation Phenology & LAI • Snow Cover & SWE • Soil Moisture (if available) • LandFlux Products: • Surface Radiation Balance • Latent Heat Flux • Sensible Heat Flux • CO2 Flux • Momentum Flux Land Model

6. Parameters of Interest Partitioning of Solar Radiation Spectral Reflectance (Albedo, FPAR, surface inhomogeneity) Skin – Air Temperatures, Windspeed for Sensible Heat Flux (Inhomogeneity, emissivity, canopy profiles) Evaporative Fraction Partitioning of Precipitation ET Soil Moisture (different layers) Standing Water Amounts (Inundation, Snow – Freeze/Thaw) Runoff Land Holding Capacity? Deep Storage

7. Potential and Status DEM and Runoff models Y Y Albedo (spectral) Y Y Skin Temperature (diurnal) Y R (emissivity) Y R Vegetation Properties Y R (hi-res description) Y R Surface Meteorology Y Yr Precipitation Y Y Snow Water Amount Y Yr Flooding (standing water) Y R Water Levels (& discharge) P R Soil Moisture P R Water Storage P R Surface Radiation Y Y

8. TO-DO LIST 1. Fix the AVHRR – Albedo (FPAR), NDVI record (merge to MODIS/MERIS/SEVERI record) (similarly, fix microwave calibration record to merge SMMR, SSM/I, AMSR, SSMIS) 2. Finish Comparison/Revision of Albedo Products based on MODIS, MISR, POLDER and connect to AVHRR record (endorse CEOS planned workshop) 3. Finish Prototype Products of Ts (infrared – ATSR, microwave – low frequency) and Compare and Revise (weather satellites, MODIS, LANDSAT thermal, ASTER) -- fund 4. Workshop <Joint with ILEAPS – teamwork <pick sites – identify products – identify common diagnostics – verification strategy -- common inputs> before meeting> for Global Turbulent Flux Products in 18 months (pick common time period 2003-2005 <CEOP, TERRA/AQUA, SEVERI> – website for description of tasks, common resources & datasets, results)

9. Recommendations • We need an international coordination of “landflux” sites (like BSRN model)? – should augment BSRN sites or bring flux-tower sites up to BSRN standards – energy/water/carbon (with hydrology) – NEED EXPERIENCES FROM PILPS AND GSWP -- (TO ILEAPS?) • We need to make recommendations for Albedo workshop (TO WHOM – CEOS, TOPC/GCOS) • (EXPAND TO STRATEGY) We need to stimulate progress on multi-satellite analyses <simultaneous multi-variate retrieval> and data-model analyses of land surface fluxes and hydrology (TO WHOM – GRP/GLASS/GEWEX) – SET UP FOR DEVELOPING PREDICTION CAPABILITY

10. Actions • (Organize & Conduct Albedo Workshop) • Organize & Conduct Flux Product Comparison Workshop

11. PLAN Revise Meeting Report – Distribute for Comment GEWEX NEWS report of meeting Start Organization of Next Workshop for late 2008 Report to GRP, then to GEWEX