2. 1 03/0045a © Crown copyright Evaluating water vapour in HadAM3 with 20 years of satellite data Richard P. Allan Mark A. Ringer Met Office, Hadley Centre for Climate Prediction and Research Thanks to Tony Slingo (ESSC) and John Edwards

3. 2 03/0045 © Crown copyright Water vapour feedback RH distribution and variability crucial to water vapour and cloud feedback (e.g. Soden et al; Wielicki et al. (2002) Science) Importance of water vapour feedback –strong positive feedback –robust physical basis –links to cloud feedback Simulations of satellite UTH radiances to evaluate HadAM3

4. 3 03/0045 © Crown copyright Satellite clear-sky sampling Model simulations: ERA-40 and CERES daily data (Jan 98)

5. 4 03/0045 © Crown copyright Sensitivity to clear-sky sampling Jan 1998 T_6.7 bias (K) OLRc bias (Wm-2)

6. 5 03/0045 © Crown copyright Experiment Ensemble of AMIP-type HadAM3 runs –Standard resolution, 19 levels, 1978-1999 –HadISST SST/sea-ice forcing –Radiance code active each rad-time-step –(see Ringer et al. (2003) QJ, in press) –Additional forcings

7. 6 03/0045 © Crown copyright Observations Satellite observations –column water vapour, CWV »SMMR 1979-84, SSM/I 1987-99 –clear-sky OLR »ERBS (1985-89), ScaRaB (1994/5), CERES (1998) –UTH channel brightness temperature, T 6.7 »HIRS 1979-1998 rms bias ~2.5 kg m -2 ~5 W m -2 ~1.5 K

8. 7 03/0045 © Crown copyright Mean and difference to observations 60 o S-60 o N oceans

9. 8 03/0045 © Crown copyright T 6.7 (K) (mb/day) OLRc (W m -2 ) CWV (kg m -2 )

10. 9 03/0045 © Crown copyright Column Water Vapour difference (kg m -2 HadAM3-OBS) DJF JJA

11. 10 03/0045 © Crown copyright Effects of clear-sky sampling Type II HadAM3-OBS (JJA) Type I T 6.7 c OLRc

12. 11 03/0045 © Crown copyright EOF analysis of HadAM3 and HIRS channel 12 T_6.7 radiances

13. 12 03/0045 © Crown copyright Interannual monthly anomalies over the tropical oceans Reduce effects of local changes in atmospheric circulation Maximise reliability of satellite data Also additional forcings considered

14. 13 03/0045 © Crown copyright

15. 14 03/0045 © Crown copyright

16. 15 03/0045 © Crown copyright Clear-sky sampling: interannual variability Light blue: Type I (weighted by clear-sky fraction) Dark Blue: Type II (standard diagnostic)

17. 16 03/0045 © Crown copyright Summary Simulations of satellite brightness temperatures sensitive to RH Consistent decadal variability suggests small DRH realistic Clear-sky sampling is important for infrared channel climatologies but not interannual variability Overactive circulation in HadAM3 Limitations of data

18. 17 03/0045a © Crown copyright Visit the Met Office at booth 145