SONIA I . SENEVIRATNE, DANIEL LÜTHI , ET AL .

COREY GODINE, ATMOSPHERIC SCIENCES PROGRAM

Land-atmosphere coupling and climate change in Europe

What is “coupling?”

Studies use two different hypotheses: Surface processes & future changes in radiation

budget Future summertime atmospheric circulation

modification

Models do not take into account increasing greenhouse gases likely in the future

Coupling = Atmospheric circulations (temperature or precipitation) + Soil moisture

What is “coupling?”

Increased atmospheric greenhouse gases change coupling dynamics

Projected large fluxes in climatic extremes

Humans can’t cope with large variability

Extreme Summers in Europe

HOT2003 heatwave and

drought

COLD2002 and 2005

torrential flooding

The Big Ideas

Goal: Discover role of land-atmosphere coupling in yearly summer temperature & precipitation extremes in Europe

Researchers used several different models

Not a lot of math Great Scot!

Models and Equations

Four 30-year-long experiments (RCM) Two recent (CTL, CTLuncoupled), 1960-1989 Two future (SCEN, SCENuncoupled), 2070-2099 Uncoupled models remove surface influences

Equations:

Models and Equations

Future regional model greenhouse gas scenario based on IPCC specifications 3 numerical global models

Global scenarios from present and futuretaken from 12 different IPCC global models

Analysis

How does land-atmosphere coupling affect the future temperature/precipitation variability in Europe in the future?

Data from each individual model

Differences between each modelExternal forcings only (ie, atmospheric circulations)External forcings + Land-atmosphere coupling

Why such a large change in T?

Large difference between GLACE (a present-climate model) and the model runs on previous page

CTL SCEN

Why such a large change in T?

The percentage of variation in summer temperature due to land-atmosphere coupling

Why such a large change in T?

Models show land-atmosphere coupling is correlated with a higher temperature change

SCEN predicts that land-atmosphere coupling will shift to east and north

Consistent with other recent model runs (IPCC, PRUDENCE)

Evapotranspiration and Temperature

Negative correlation = strong soil control over evapotranspiration (ie, coupling)

Positive correlation = strong atmospheric control over evapotranspiration (ie, uncoupled)

What about precipitation?

Models are less certain about the relationship between land-atmosphere coupling and precipitation variability

Conclusion

Land-atmosphere coupling is strongly affected by an increase in greenhouse gases

Northward shift of European climate zones

Strong positive correlation between land-atmosphere coupling and temperature variability Strong negative correlation between coupling and

evapotranspiration

Weak correlation between land-atmosphere coupling and precipitation variability

Opinions

Temperature correlations convincing Run CTL and SCEN against more coupling models to

confirm results Would like more information about relationship between

evapotranspiration and couplingNeeds more development in precipitation

correlationTeleconnection problems!

Many other process could contribute to projected shift in surface temperatures

Would have liked more accurate/effective global models to supplement regional models

Questions?

Thank you!