1. 10/05/041 Utilisation of satellite data in the verification of HIRLAM cloud forecasts Christoph Zingerle and Pertti Nurmi

2. 10/05/041 ● verification, the task ● the forecasting system HIRLAM ● observations = satellite data ● making forecast and observation comparable ● an example ● summary ● future Contents

3. 10/05/041 Task ● Verification of the HIRLAM cloud forecast - detection of deficiencies in the cloud forecast scheme - feasibility of different approaches to verification using satellite data - methodology of verifying cloud forecasts and its operational implementation

4. 10/05/041 HIRLAM at FMI - FMI is running the reference HIRLAM (RCR) operationally - resolution 0.2 deg horizontal (438x336 grid points, ~ 22 km) 40 levels vertical (up to 10 hPa) - semi-lagrangian advection - 3D–Var analysis (no satellite data) - lateral boundary conditions from ECMWF - Denmark, Finland, Iceland, Ireland, Netherlands, Norway, Spain and Sweden (France) ● HIgh Resolution Limited Area Model

5. 10/05/041 HIRLAM RCR domain

6. 10/05/041 Satellite Observations ● satellite data at FMI from: - METEOSAT 7/8: high resolution (temporal and spatial) coarse resolution at the edges - like Finland - with limb darkening - NOAA polar orbiting satellites high spatial resolution coarse temporal resolution

7. 10/05/041 Observation – Forecast ● Model to Satellite: ● Satellite to Model: - transferring the parameters forecasted by the model to observations - Radiative Transfer Model uses model data to simulate observed radiances and Tb’s - transferring the observations to parameters forecasted by the model - Cloud classification scheme generally thresholding methods based on typical cloud properties

8. 10/05/041 Model to Satellite ● Radiative Transfer Model (RTM) - RTTOV 7 - a fast RTM for the assimilation of satellite data calculates radiances (and Tb's) as seen by a satellite instrument uses profiles oftemperature humidity cloud fraction cloud liquid water cloud ice water ozone surface properties

9. 10/05/041 Model to Satellite ● 'synthetic' NOAA AVHRR image (10.8µ) - 24 h forecast from HIRLAM - AVHRR because of the high resolution provided even at the poles

10. 10/05/041 Observation Re-sampling ● NOAA AVHRR satellite image - re-sampling needed - preprocessed (AAPP) AVHRR image (calibrated and navigated) pixel center in the grid-box corresponding to the HIRLAM grid pixel assigned to this grid-box - Assumptions: HIRLAM grid value represents average over all the values in box neighbouring pixels don't differ much from each other

11. 10/05/041 full resolution, 30.4.2004 (10.8µ) after re-sampling, 30.4.2004 (10.8µ)

12. 10/05/041 simulated, 30.4.2004 (10.8µ) observed, 30.4.2004 (10.8µ)

13. 10/05/041 Difference: observed - simulated Difference > 40 K: Model error?

14. 10/05/041 observed / simulated Tbrelative frequency of Tb observed simulated Summary distributions

15. 10/05/041 Summary ● RTTOV - a tool to simulate satellite measurements as close as possible - surface parameters and transmission (clouds) dependent ● observations - simple re-sampling of NOAA AVHRR data is sufficient - re-sampling will be more sophisticated for other instruments ● verification of HIRLAM - cloud forecast scheme not yet verified extensively - approach to verification looks promising

16. 10/05/041 Future ● examine approaches to verification - satellite to observation approach (SAFNWC software) - pattern recognition methods ● expand to other satellite data (instruments) - Meteosat data over Europe - polar orbiting satellites over Scandinavia and Nordic Countries ● operational verification - refine methodology to verify cloud forecasts - improve the operational verification package of FMI