1. Responses of the Mediterranean climate to tropical forcing Laurent Li (li@lmd.jussieu.fr) Laboratoire de Météorologie Dynamique (LMD) Institut Pierre-Simon Laplace (IPSL) CNRS/UPMC, Paris, France Mediterranean Z500 ACC predictability Mediterranean T2m and precip time evolution predictability A holographic effect of atmospheric nudging (also from SST forcing)

2. Simulations performed with LMDZ 8 series + control 38 years 1971 to 2008 May to September Ensemble of 10 members

3. Forcing zone in green: Africa, Asia and Tropics Target zone in red: Mediterranean Sea AfNFIVCl: ERA(Af) SST(clim): Atmospheric forcing from ERA in Africa, SST climatology AfNFIVIV: ERA(Af) SST(Obs): Atmospheric forcing from ERA in Africa, SST as observed AfNFIVCl: ERA(As) SST(clim): Atmospheric forcing from ERA in Asia, SST climatology AfNFIVIV: ERA(As) SST(Obs): Atmospheric forcing from ERA in Asia, SST as observed TrNFIVCl: ERA(Tr) SST(clim): Atmospheric forcing from ERA in Tropics, SST climatology TrNFIVIV: ERA(Tr) SST(Obs): Atmospheric forcing from ERA in Tropics, SST as observed NonudgIV: No atmospheric forcing from ERA, SST as observed NonudgTr: No atmospheric forcing from ERA, SST as observed in Tropics, but climatology elsewhere NonudgCl: No atmospheric forcing from ERA, SST climatology LMDZ-global: 2° in latitude and 3° in longitude Period: 1971/2008 May, June, July, August Ensemble: 10 members

4. Can we predict the Mediterranean climate ? in terms of ACC (Anomalous Correlation Coefficient) for 500-hPa geopotential height

5. No Tr No IV Tr Cl Tr IV As Cl As IV Af Cl Af IV ERA SST 0.04 -0.03 0.40.470.320.290.470.45 ACC Anomalious Correlation Coefficient of 500-hPa geopotential height over the Med Region

6. Can we predict the Mediterranean climate ? in terms of temporal evolution for surface air temperature and precipitation

7. SST climSST observée No nudging0.00.78 (0.74) Nudging Af0.55 (0.53)0.73 (0.72) Nudging As0.57 (0.54)0.86 (0.85) Nudging Tr0.59 (0.63)0.76 (0.74) Temporal correlation coefficient between LMDZ and CRU (ERA) 2-m air temperature for the Mediterranean basin

8. SST climSST observée No nudging0.00.24 (0.02) Nudging Af0.81 (0.57)0.74 (0.54) Nudging As0.71 (0.50)0.56 (0.34) Nudging Tr0.82 (0.61)0.74 (0.52) Temporal correlation coefficient between LMDZ and CRU (ERA) Rainfall rate for the Mediterranean dasin

9. Mediterranean area summer rainfall rate (mm/day) over land, with only SST forcing: - global: 0.24 correlation CRU - tropical: 0.37 correlation CRU Mediterranean area summer rainfall rate (mm/day) over land, with tropical atmospheric forcing: - global SST: 0.74 correlation CRU - no SST: 0.82 correlation CRU Extra-tropical SST (including the Med Sea) can have negative contribution to the rainfall prediction in the Med area ! ?

10. Is there a holographic effect of atmospheric nudging ?

11. Surface air temperature °C (over land) Precipitation rate mm/d (over land)

12. Surface air temperature °C Precipitation rate mm/d Iberia South-France

13. Surface air temperature °C Precipitation rate mm/d Italy Greece-Turkey

14. Surface air temperature °C Precipitation rate mm/d North-Africa-West North-Africa-East

15. Surface air temperature °C Precipitation rate mm/d Middle-East

16. Conclusions Atmospheric nudging is an interesting technique, complementary to the traditional approach of SST forcing. Mediterranean climate predictability of Z500 ACC: poor from SST, significant from tropical atmospheric forcing. Mediterranean climate predictability of temporal evolution: a certain holographic effect is observed for both surface air temperature and precipitation; SST from extra-tropics seems have negative contribution for precipitation.