SONIA I. SENEVIRATNE, DANIEL LTHI, ET AL. COREY GODINE,
ATMOSPHERIC SCIENCES PROGRAM Land-atmosphere coupling and climate
change in Europe
Slide 2
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
Slide 3
What is coupling? Increased atmospheric greenhouse gases change
coupling dynamics Projected large fluxes in climatic extremes
Humans cant cope with large variability
Slide 4
Extreme Summers in Europe HOT 2003 heatwave and drought COLD
2002 and 2005 torrential flooding
Slide 5
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!
Slide 6
Models and Equations Four 30-year-long experiments (RCM) Two
recent (CTL, CTL uncoupled ), 1960-1989 Two future (SCEN, SCEN
uncoupled ), 2070-2099 Uncoupled models remove surface influences
Equations:
Slide 7
Models and Equations Future regional model greenhouse gas
scenario based on IPCC specifications 3 numerical global models
Global scenarios from present and future taken from 12 different
IPCC global models
Slide 8
Analysis How does land-atmosphere coupling affect the future
temperature/precipitation variability in Europe in the future?
Slide 9
Data from each individual model Differences between each model
External forcings only (ie, atmospheric circulations) External
forcings + Land-atmosphere coupling
Slide 10
Why such a large change in T? Large difference between GLACE (a
present-climate model) and the model runs on previous page CTL
SCEN
Slide 11
Why such a large change in T? The percentage of variation in
summer temperature due to land-atmosphere coupling
Slide 12
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)
Slide 13
Evapotranspiration and Temperature Negative correlation =
strong soil control over evapotranspiration (ie, coupling) Positive
correlation = strong atmospheric control over evapotranspiration
(ie, uncoupled)
Slide 14
What about precipitation? Models are less certain about the
relationship between land-atmosphere coupling and precipitation
variability
Slide 15
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
Slide 16
Opinions Temperature correlations convincing Run CTL and SCEN
against more coupling models to confirm results Would like more
information about relationship between evapotranspiration and
coupling Needs more development in precipitation correlation
Teleconnection problems! Many other process could contribute to
projected shift in surface temperatures Would have liked more
accurate/effective global models to supplement regional models