Rémy Roca Laurence Picon Laboratoire de Météorologie Dynamique, Paris, France and

1. Free Tropospheric Humidity from GEO - a long time series perspective- Rémy Roca Laurence Picon Laboratoire de Météorologie Dynamique, Paris, France and Hélène Brogniez LATMOS, Guyancourt, France

2. Climate and humidity in the troposphere Scales of interest to the relative humidity ? Relative Humidity (%) Mixing of extra-tropical / tropical air is taking place at short time scale (synoptic to intraseasonal) And explain the variability of the FTH distribution Humidity is influenced by thermodynamics AND dynamics The high frequency variation is key to our better understanding of moisture and its links to climate

3. What do we get from the « water vapor » channel on board the METEOSAT spacecraft ? Free tropospheric humidity The FCDR from LMD: Homogeneous Clear Sky Radiance record The TCDR from LMD: FTH Climatology and variability Current work and perspectives for space/time extension Outline of the presentation

4. What do we get from the METEOSAT WV channel ? Interpretation of the clear sky scene of the 6.3 microns channel in terms of layer averaged relative humidity (Soden and Bretherton, 1993; Stephens et al., 1996) Assumption is valid in the Tropics ! Much complicated in the mid latitudes How bad is it to use ECMWF to compute p0 ? What should the <> operator should be ?

5. What do we get from the METEOSAT WV channel ? Picon et al., JGR, 2003

6. What do we get from the METEOSAT WV channel ? Dry case Moist case mean curve [Soden and Bretherton, 1996] weighting function f() [Stephens et al, 1996] local Jacobian [Brogniez et al, 2004] No/Weak contribution from the lower levels Which operator for the vertical average ?

7. What do we get from the METEOSAT WV channel ?

8. What do we get from the METEOSAT WV channel ? Improved sampling by keeping the scenes with low levels clouds (following the UTH product approach of EUMETSAT) Daily average built from 8xdaily imagery provides a better spatial characterization and estimates From Brogniez et al., 2006

9. What do we get from the METEOSAT WV channel ? A broad layer of the troposphere over the intertropical belt -belongs to GEWEX not to SPARC High time resolution -good sampling -access to shorter time scales (which are relevant) A long term record ?

10. The FCDR from LMD: 1983-2005 MET2 MET3 4 3 MET4 Original MET5 Upgrade of calibration technique (Schmetz, 1989) Upgrade of calibration technique (van de Berg, et al., 95) ISCCP DX Normalized Instead of nominal • Two upgrades corrected according to the work of Picon et al., JGR, 2003 but with ERA40 instead of ERA15. • The DX data change of implementation corrected thanks to interaction with ISCCP people (V. Golea)

11. The FCDR from LMD: 1983-2005 MET2 MET3 4 3 MET4 Original MET5 Homogenized

12. The FCDR from LMD: 1983-2005 MET2 MET3 4 3 MET4 Original MET5 Homogenized Brogniez et al., JCLIM, 2009

13. The TCDR from LMD: FTH 1983-2005 Brogniez et al., JCLIM, 2009 0.625° 3 hourly Brogniez et al., JCLIM, 2009

14. AMIP2: Comparing summer 1984-1995 And the GCMs ? Brogniez et al., 2005, GRL

15. Current work and perspectives Extension in SPACE and TIME of both the FCDR and the TCDR Work on METEOSAT nominal to extend it into the MSG era in cooperation with CMSAF Example #1: Two METEOSAT spacecrafts 1998-nowadays

16. Clear Sky Radiance using a modified version of the SAFNWC cloud classification The Megha-Tropiques Mission Example #2: Towards the GEO ring FTH product GOES-E 1500GMT 3 channels GOES-W 2100GMT 3 channels Example of SAF NWC cloud mask run onto various platforms (Courtesy of G Sèze, LMD) MTSAT 0300GMT 4 channels • Inter calibration of the WV channels accross platforms from the GEO from GSICS

17. Thank you !

18. What do we get from the METEOSAT WV channel ? NOAA based Upper Tropospheric Humidity July 1980-1998 Data from Bates et al., 2001 The driest zone in the world is located over the Eastern Mediterranean sea Is in the METEOSAT area !