1 / 63

Land-atmosphere coupling, climate-change and extreme events +

Land-atmosphere coupling, climate-change and extreme events + Activities with regard to land flux estimations at ETH Zurich Sonia I. Seneviratne Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland LandFlux Meeting, Toulouse, France May 29, 2007. Outline.

nibal
Télécharger la présentation

Land-atmosphere coupling, climate-change and extreme events +

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Land-atmosphere coupling, climate-change and extreme events + Activities with regard to land flux estimations at ETH Zurich Sonia I. Seneviratne Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland LandFlux Meeting, Toulouse, France May 29, 2007

  2. Outline • Land-atmosphere coupling, climate change, and extreme events (Seneviratne et al. 2006) • Land-atmosphere coupling: hot spot in Europe? • Dynamics with climate change • Links with extreme events • Activities with regard to land flux estimations at ETH Zurich • Atmospheric-terrestrial water balance estimates • Some results on models’ estimates (land surface models, GCMs) • SwissFluxnet activities and Rietholzbach catchment site

  3. L-A coupling in Europe Seneviratne et al. 2006, Nature, 443, 205-209

  4. L-A coupling in Europe Koster et al., 2004, Science

  5. L-A coupling in Europe No strong coupling in Europe? How about Mediterranean region? NB: Results based on only one year SST conditions (1994) Koster et al., 2004, Science

  6. T (Koster et al. 2006, JHM) L-A coupling in Europe No strong coupling in Europe? How about Mediterranean region? NB: Results based on only one year SST conditions (1994) Koster et al., 2004, Science

  7. DT Ds/s DT D [ºC] [%] Projected changes in To variability PRUDENCE, CHRM, JJA (2070-2100)-(1960-1990) Schär et al. 2004, Nature IPCC AR4 GCMs, JJA (2080-2100)-(1970-1990) Seneviratne et al. 2006, Nature, suppl. inf.

  8. DT Ds/s DT D [ºC] [%] Projected changes in To variability PRUDENCE, CHRM, JJA (2070-2100)-(1960-1990) Schär et al. 2004, Nature IPCC AR4 GCMs, JJA (2080-2100)-(1970-1990) Seneviratne et al. 2006, Nature, suppl. inf.

  9. DT Ds/s DT D [ºC] [%] Projected changes in To variability PRUDENCE, CHRM, JJA (2070-2100)-(1960-1990) Large changes in To variability What are the responsible mechanisms: Large-scale circulation patterns? Land surface processes? Schär et al. 2004, Nature IPCC AR4 GCMs, JJA (2080-2100)-(1970-1990) Seneviratne et al. 2006, Nature, suppl. inf.

  10. Land-atmosphere coupling experiment Aim: Investigate the role of land-atmosphere coupling for the predicted enhancement of summer temperature variability in Europe Approach: Perform regional climate simulations within the same set-up with and without land-atmosphere couplingfor present and future climate conditions

  11. Summer temperature variability Standard deviation of the summer (JJA) 2-m temperature CTL SCEN CTLUNCOUPLED SCENUNCOUPLED (Seneviratne et al. 2006, Nature)

  12. Summer temperature variability Standard deviation of the summer (JJA) 2-m temperature CTL SCEN Most of the enhancement of summer temperature variability in SCEN disappears in the SCENUNCOUPLED simulation CTLUNCOUPLED SCENUNCOUPLED (Seneviratne et al. 2006, Nature)

  13. Climate change signal vs. LA coupling CLIMATE-CHANGE SIGNAL: SCEN-CTL LA COUPLING STRENGTH IN SCEN: SCEN-SCENUNCOUPLED CONTR. OF EXT. FACTORS TO CC SIGNAL SCENUNCOUPLED-CTLUNCOUPLED CONTR. OF LA COUPLING TO CC SIGNAL (SCEN-SCENUNCOUPLED)-(CTL-CTLUNCOUPLED) Strength of land-atmosphere coupling in future climate is as large as 2/3 of the climate-change signal ! (Seneviratne et al. 2006, Nature)

  14. Climate change signal vs. LA coupling CLIMATE-CHANGE SIGNAL: SCEN-CTL LA COUPLING STRENGTH IN SCEN: SCEN-SCENUNCOUPLED CONTR. OF EXT. FACTORS TO CC SIGNAL SCENUNCOUPLED-CTLUNCOUPLED CONTR. OF LA COUPLING TO CC SIGNAL (SCEN-SCENUNCOUPLED)-(CTL-CTLUNCOUPLED) Contribution of land-atmosphere coupling to climate change signal: dominant factor in Central and Eastern Europe! (Seneviratne et al. 2006, Nature)

  15. P (Koster et al. 2004, Science) T (Koster et al. 2006, JHM) GLACE results for present climate GLACE experiment (Koster et al. 2004; 2006):no high land-atmosphere coupling in Europe neither for temperature nor for precipitation How is the strength of land-atmosphere coupling for present vs. future climate in our simulations?

  16. percentage of To variance explained by coupling [%] Present vs. future climate land-atmosphere coupling strength parameter analogous to GLACE • Locally strong soil moisture-To coupling in present climate (Mediterranean; ≠GLACE) • Shift of region of strong soil moisture-To coupling from the Mediterranean to most of Central and Eastern Europe in future climate (Seneviratne et al. 2006, Nature)

  17. Comparison with IPCC AR4 GCMs Indirect measure of coupling between soil moisture & To: Correlation between summer evapotranspiration and temperature (ET,T2M) Negative correlation: strong soil moisture-temperature coupling (high temperature as result of low/no evapotranspiration) Positive correlation: low soil moisture-temperature coupling(high temperature leads to high evapotranspiration)

  18. RCM 3 “best” GCMs All GCMs Comparison IPCC AR4 GCMs: (ET,T2M) CTL time period SCEN time period Climate-change signal (Seneviratne et al. 2006, Nature)

  19. L-A coupling, Europe: present / future • Strong soil moisture-temperature coupling for the Mediterranean region in the CTL time period (≠GLACE) • Shift of region of strong soil moisture-temperature coupling to Central and Eastern Europe in future climate (transitional climate zone) • Qualitative agreement between RCM experiments and analysis of IPCC AR4 GCMs

  20. Mechanism for To variability increase no limitation wet climate Seasonal Cycle of Soil Moisture Soil moisture [mm] transitional climate CTL (1961-1990) SCEN (2071-2100) below threshold (“plant wilting point”) dry climate Month

  21. Summary • The projected enhancement of To variability in Central and Eastern Europe is mostly due to changes in land-atmosphere coupling • Climate change creates a new hot spot of soil moisture - To coupling in Central and Eastern Europe in the future climate (shift of climate regimes): Dynamic feature of the climate system! • LandFlux: Consider transient modifications with climate forcing (greenhouse gases, aerosols)

  22. Outline • Land-atmosphere coupling, climate changes, and extreme events (Seneviratne et al. 2006a) • Land-atmosphere coupling: hot spot in Europe? • Dynamics with climate change • Links with extreme events • Activities with regard to land flux estimations at ETH Zurich • Atmospheric-terrestrial water balance estimates • Some results on models’ estimates (GSWP/GLDAS-type; GCMs) • SwissFluxnet activities and Rietholzbach catchment site

  23. Atmospheric-Terrestrial Water Balance

  24. Atmospheric-Terrestrial Water Balance • Terrestrial water balance:

  25. Atmospheric-Terrestrial Water Balance • Terrestrial water balance: • Atmospheric water balance:

  26. reanalysis data (ERA-40) Atmospheric-Terrestrial Water Balance • Terrestrial water balance: • Atmospheric water balance: measured streamflow (Rs+Rg) • Combined water balance:

  27. reanalysis data (ERA-40) Atmospheric-Terrestrial Water Balance The water-balance estimates depend only on observed or assimilated variables (≠ P,E) • Terrestrial water balance: Main limitation: valid only for domains > 105- 106 km2 (Rasmusson 1968, Yeh et al. 1998) • Atmospheric water balance: measured streamflow (Rs+Rg) • Combined water balance:

  28. Case Study: Mississippi & Illinois Water-balance Estimates Seneviratne et al. 2004, J. Climate, 17 (11), 2039-2057 corr=0.8, r2=0.71 Observations (soil moisture+ groundwater+snow)

  29. Volga River basin (1972-85) corr=0.8 r2=0.64 Dataset for Mid-latitude River Basins Hirschi et al. 2006, J. Hydrometeorology, 7(1), 39-60 “BSWB” http://iacweb.ethz.ch/data/water_balance/ • divQ & dW/dt: whole ERA-40 period (1958-2002) • runoff data: Global Runoff Data Center (GRDC) Comparisons with soil moisture observations from the Global Soil Moisture Data Bank

  30. Atmospheric-Terrestrial Water Balance • Terrestrial water balance: • Atmospheric water balance: • Combined water balance:

  31. Estimation of large-scale ET Atmospheric water balance: Mackenzie GEWEX Study (MAGS) Peace Louie et al. 2002

  32. Estimation of large-scale ET http://iacweb.ethz.ch/data/water_balance/ Retrospective dataset! (1958-2001, ERA-40; 2001-2007, ECMWF operational forecast analysis; e.g. Hirschi et al. 2006, GRL) The water-balance estimates depend only on observed P and assimilated variables Main limitations: - valid only for domains > 105-106 km2 (Rasmusson 1968, Yeh et al. 1998; Seneviratne et al. 2004, J. Climate, Hirschi et al, 2006, JHM) - Imbalances, drifts of reanalysis data

  33. Outline • Land-atmosphere coupling, climate change, and extreme events (Seneviratne et al. 2006) • Land-atmosphere coupling: hot spot in Europe? • Dynamics with climate change • Links with extreme events • Activities with regard to land flux estimations at ETH Zurich • Atmospheric-terrestrial water balance estimates • Some results on models’ estimates (GSWP/GLDAS-type; GCMs) • SwissFluxnet activities and Rietholzbach catchment site

  34. Precipitation Forcing for LSMs ( Koster et al, 2004: GPCP product, 1979-93) Oki et al 1999: a minimum of about 30 precipitation gauges per 106 km2 or about 2 gauges per 2.5o x 2.5o GPCP grid cell are required for accurate streamflow simulations Fekete et al. 2004: Range between 4 state-of-the-art precipitation datasets (CRU, GPCC, GPCP, and Willmott-Matsuura) (Fekete et al. 2004)

  35. Illinois Volga Don Ob Lena Dnepr Neva Amur Yenisei Effects on Catchment LSM Output r2 vs. ground data, yrs within 1979-93 (anomalies) Soil moisture + snow Precipitation LSM results strongly dependent on quality of forcing...

  36. LAND Modelling: GCMs Water-holding capacity (Seneviratne et al. 2006, JHM)

  37. Modelling: GCMs Soil moisture memory (Seneviratne et al. 2006, JHM)

  38. Modelling: GCMs Soil moisture memory (Seneviratne et al. 2006, JHM)

  39. LAND Modelling: GCMs Water-holding capacity (Seneviratne et al. 2006, JHM)

  40. P Modelling: GCMs Land-atmosphere coupling Significant range in model behaviour… (Koster et al. 2004, Science)

  41. Outline • Land-atmosphere coupling, climate change, and extreme events (Seneviratne et al. 2006) • Land-atmosphere coupling: hot spot in Europe? • Dynamics with climate change • Links with extreme events • Activities with regard to land flux estimations at ETH Zurich • Atmospheric-terrestrial water balance estimates • Some results on models’ estimates (GSWP/GLDAS-type; GCMs) • SwissFluxnet activities and Rietholzbach catchment site

  42. Observations: FLUXNET • Worldwide CO2, water and energy flux measurements (integrating several projects such as AMERIFLUX, CARBOEUROPE, …) • At present, about 200 tower sites • however, still some serious limitations in temporal availability (in Europe, most measurements available after 1995 only) • only few sites with soil moisture measurements http://www-eosdis.ornl.gov/FLUXNET/

  43. Observations: SwissFluxnet X Rietholzbach catchment site (Lysimeter, isotope measurements) Will also focus on soil moisture measurements (ETH Zurich)

  44. Outline • Land-atmosphere coupling, climate changes, and extreme events (Seneviratne et al. 2006a) • Land-atmosphere coupling: hot spot in Europe? • Dynamics with climate change • Links with extreme events • Activities with regard to land flux estimations at ETH Zurich • Atmospheric-terrestrial water balance estimates • Some results on models’ estimates (GSWP/GLDAS-type; GCMs) • SwissFluxnet activities and Rietholzbach catchment site • Conclusions and outlook

  45. Conclusions and outlook • Land processes important in transitional climate zones (e.g. Koster et al. 2004): seasonal forecasting, extreme events NB: possible changes in hot spots’ location with greenhouse warming • Several methods to estimate water storage or ET, atmospheric-terrestrial water estimates are promising (retrospective datasets) • No perfect dataset: but synergies are available

  46. Comparison: Land datasets

  47. A new GEWEX study area for Europe? (hot spot of coupling) Outlook

  48. Temporal Integration (3) Observations (Illinois) Integrated estimates Integration over longer time ranges is not straightforward due to the presence of small systematic imbalances in the monthly estimates Comparison with imbalances from other water-balance studies G97: Gutowski et al. 1997 Y98: Yeh et al. 1998 BR99: Berbery and Rasmuson 1999

  49. Long-term Imbalances and Drifts (1) Rasmusson (1968) threshold for radiosonde data (2.106 km2) Illinois (1987-96) ? Imbalances (mm/d) Illinois (2 .105 km2) Europe Western Russia Asia North America Domain size (km2) Hirschi et al. 2004

More Related