1. Experiments with the microwave emissivity model concerning the brightness temperature observation error & SSM/I evaluation Henning Wilker, MIUB Matthias Drusch, ECMWF

2. Extended Kalman Filter Analysis x soil moisture vector to forecast x a soil moisture analysis vector x b soil moisture background vector y observations M forecast operator H observation operator B background error covariance matrix R observation error covariance matrix

3. Question Do we need a bias correction for the observed brightness temperatures due to the uniform vertical distribution of modelled soil moisture?

4. Example

5. Approach SGP99 gravimetric soil moisture measurements (0 - 2.5 cm and 2.5 - 5 cm) Layer Difference Statistics Artificial soil moisture profiles Set of brightness temperatures Brightness temperature bias and rms error Microwave emissivity model Classified by „days after rain event“

6. SGP99 site-averaged soil moisture

7. SGP99 soil moisture layer differences

9. Creation of soil moisture profiles Assumptions: 2) 3)  = mean soil moisture layer difference of all SGP99 sites r = Gaussian random number s  = standard deviation of soil moisture layer difference = measured mean soil moisture (0-5cm) 1)

10. Artificial soil moisture profiles one day after rain event at site LW03

11. Brightness temperature distribution at site LW03 one day after rain event

12. Artificial soil moisture profiles six days after rain event at site LW03

13. Brightness temperature distribution at site LW03 six days after rain event

14. Brightness temperature bias due to the soil moisture profile at site LW03

15. Conclusions  Radiative transfer modelling indicates that the lacking knowledge of the soil moisture profile could cause systematic errors of about 5 K in modelled brightness temperatures.  The T B -bias is a function of precipitation and dry-down time and could be taken into account in the assimilation scheme (further studies are needed).  Vertical structures in soil moisture which are not represented by the hydrological model can cause rms-errors of ~6 K. In the assimilation experiments an error of 2 K was assumed.

16. Preparations for ELDAS soil moisture validation with SSM/I brightness temperatures Workpackage 4200 Objective: Validation of ELDAS soil moisture fields with SSM/I brightness temperatures over sparsely vegetated regions

17. SSM/I: Few details SSM/I = Special Sensor Microwave Imager passive microwave radiometer onboard the DMSP satellites Frequencies Footprint (Ghz) Pol. Size (km²) ---------------------------------------- 19.35 h,v 43 x 69 22.235 v 40 x 60 37.0 h,v 30 x 38 85.5 h,v 13 x 15 Start: 1987 Incidence angle: 53.1° Revisit time: ~ twice per day

18. SSM/I: Available data Brightness temperatures aggregated to an Equal-Area Scalable Earth (EASE) grid Horizontal resolution: 25 km (global) Temporal resolution: daily (1988 - 2001) Example of EASE-gridded brightness temperatures (horizontally polarized), 15. September 2000

19. Validation approach Land surface microwave emissivity model ELDAS soil moisture fields Additional soil, vegetation and atmospheric parameters TOA brightness temperatures Comparison of SSM/I and ELDAS-derived TBs

20. Examine time series at selected validation sites (Badajoz, Tomelloso?). Purpose: Investigation of temporal development of ELDAS-derived brightness temperatures (including major rain event and following dry-down). Maybe additional soil, vegetation and/or atmospheric parameters available? Selected case study (central Spain?). Purpose: Examination of spatial distribution of ELDAS-derived brightness temperatures (for example rain events touching only limited areas). Merging of ELDAS grid and EASE grid required. Point validation Area validation

21. Required input data for the microwave model Volumetric water contentMARS archive Soil temperatureMARS archive Sand/Clay percentageMARS? / soil type? Bulk density ? / average value? Surf. roughness (rms height) ???? Atm. Profiles of p, T, RHMARS Parameter Source Vegetation coverMARS Vegetation temperatureSoil surface temperature (MARS) Vegetation water content ? / vegetation type (MARS) Other vegetation parametersVegetation type (MARS)

22. Brightness Temperature (H-Pol.), Badajoz

23. Brightness Temperature (V-Pol.), Badajoz

24. Brightness Temperature Anomaly (H-Pol.), Badajoz

25. Brightness Temperature Anomaly (V-Pol.), Badajoz

26. Polarization Index, Badajoz

27. Anomaly of Polarization Index, Badajoz

28. Daily precipitation amount, Badajoz

29. Daily mean temperature, Badajoz

30. Summary  Preparation of SSM/I-data completed.  First look at validation site Badajoz is promising.  Availability of additional soil and vegetation parameters …?  Open issue yet: merging of ELDAS and SSM/I EASE grid.  Untill ELDAS fields are available, testing of technical procedures with reanalysis data?