1. Page 1© Crown copyright Simulation of radar reflectivities in the UK Met Office model: comparison with CloudSat Data Alejandro Bodas-Salcedo, M.E. Brooks and M. Webb GERB Science Team Meeting, Abingdon, 3 May 2007

2. Page 2© Crown copyright Outline Introduction The A-Train and CloudSat Our approach Description of the simulator: subcomponents Global forecast model: comparison with observations Conclusions and future work

3. Page 3© Crown copyright Relevance of clouds in the ARB  The vertical distribution and overlap of cloud layers determine the magnitude and vertical profile of radiative heating, which then exerts an influence in the large-scale circulation. ATM Radiation BudgetATM CRFs

4. Page 4© Crown copyright Impact on ocean heat transport  By modulating the distribution of heating between the atmosphere and the surface, clouds influence the circulation of the oceans. (Glecker, GRL, 2005)

5. Page 5© Crown copyright Feedback loop These large-scale impacts are connected to cloud physical properties through a feedback loop. (Stephens et al., BAMS, 2002) This loop involves a wide range of spatio-temporal scales => the Unified Model appears to be an adequate framework to link interactions at different scales

6. Page 6© Crown copyright A new perspective on clouds and the SARB (http://cloudsat.atmos.colostate.edu/mission/formation_flying)

7. Page 7© Crown copyright Synergy between active and passive sensing (ESA SP-1257(1), 2001)

8. Page 8© Crown copyright CloudSat - Launch April 28 th 2006. Operations began on June 2 nd. - Nadir pointing, 94GHz radar. - 500m vertical resolution, oversampled at 240m. - 1.4km x 2.5 km horizontal resolution - Sensitivity ~-28 dBZ - Dynamic range: 80 dBZ - Calibration: 2 dBZ

9. Page 9© Crown copyright Our approach  To facilitate the exploitation of CloudSat and CALIPSO data in numerical models, we are developing a system that allows to simulate the signal that CloudSat/CALIPSO would see in a model- generated world.  CFMIP CloudSat/CALIPSO Simulator (C3S):  LMD/IPSL, LLNL, CSU, UW, Met Office  Flexible tool to simulate active instruments in models (climate, forecast, cloud-resolving)  This 'model-to-satellite' approach has proven successful in recent years, with the development of the ISCCP simulator 1 and the simulation of satellite channel radiances 2. 1: (Klein and Jakob, 1999; Webb et al., 2001) 2: (Ringer et al., 2003)

10. Page 10© Crown copyright Subcomponents C3S MAIN SCOPS SG PRECIP C3S SUB-GRID CLOUDSATCALIPSOSUMMARY STATISTICS

11. Page 11© Crown copyright Case study I: analysis chart 2006/07/07 Transect trough a mature extra-tropical system Analysis chart valid at 18 UTC CloudSat overpass from 15:14:38 to 15:21:01 B A.

12. Page 12© Crown copyright Case study I: MSG composite RGB 321 (1.6 , 0.8 , 0.6  ) 1330 UTC: turquoise clouds contain ice crystals, whilst white clouds are water clouds (inc. fog). Vegetation creates a green signal and sandy areas are pink. Snow covered ground is turquoise. B A

13. Page 13© Crown copyright Case study I: Z e AB 1/120 1/55

14. Page 14© Crown copyright Case study II: analysis chart 2006/12/09 Transect trough a mature extra-tropical system Analysis chart valid at 12 UTC CloudSat overpass from 14:57:10 to 15:03:53 A B

15. Page 15© Crown copyright Case study II: MSG composite A B

16. Page 16© Crown copyright Case study II: Z e AB

17. Page 17© Crown copyright Case study III: analysis chart 2006/12/14 Transect trough a quasi-stationary front Analysis chart valid at 18 UTC CloudSat overpass from 15:12:36 to 15:15:53 A B

18. Page 18© Crown copyright Case study III: MSG composite A B

19. Page 19© Crown copyright Case study III: Z e AB

20. Page 20© Crown copyright Cloud/Precipitation occurrence

21. Page 21© Crown copyright North Atlantic statistics

22. Page 22© Crown copyright Conclusions and future work  Tool to simulate radar reflectivities in the UM  New perspective on clouds and precipitation  Comparisons with global forecast model:  The overall vertical structure of ML systems is well represented  LS precipitation is also generally well captured in the occluded sector  Cloud top height matches very well the obs.  Indications of too much cirrus/cirrostratus  Indications of too much drizzle production  Need to develop more quantitative, statistically-based approaches  Developing a community simulator:  CFMIP CloudSat/CALIPSO Simulator (C3S) (LMD/IPSL, LLNL, CSU)  Flexible tool to simulate active instruments in models (climate, forecast, cloud-resolving)

23. Page 23© Crown copyright