Transcript WP2 Overview

A consistent poleward shift of storm tracks?
Yin 2005
• Storm track (SD of daily MSLP):
A1B-20C (DJF)
• Response is if anything a southward
shift in the North Atlantic.
• Spread > mean in NH.
Zonal mean temperature changes
Stratosphere cools,
Tropopause lifts
Increased Teq - Tpole
Decreased Teq - Tpole
SRESA1B IPCC AR4
Regional forcing
Sea-ice retreat
MOC weakening
Land-sea contrast
Tropical SSTs ->
stationary waves
Zonally symmetric sensitivity
experiments have been done
before.
In WP2 we will use HadGAM1 with
full orography.
WP2.1 Global forcing:
• Globally uniform SST rise
• Increase CO2 only
• Both
WP2.2 Regional forcing:
• North Atlantic SST
• Decreased sea-ice
• Land-sea temperature contrast
Some runs to test linearity
Lorenz and DeWeaver 2007
What effect will increased moisture have?
More latent heating => stronger storm growth => more intense storm track
OR
More latent heating => more efficient heat transport => weaker storm track
Other things to think about:
• Hard to separate moisture increase and upper level temperature gradient
• Test sensitivity to basic state – eg using model and observed background SSTs
NAM
The climate change signal
is baroclinic, so the choice
of level matters.
May apply to storms as
well – eg HernandezDeckers…?
Climate change
How do we include things like this?
Selten et al (2004)
Hypothesis: MOC
weakening is very
important
IPCC AR4
EOF1 of temperature response across
models explains ~1/2 of the spread in wind
response over Europe.
Regression on the MOC response in the
models gives very similar patterns.
Linear regression suggests that the weakening of the MOC
is the dominant contributor to the ensembel mean storm
track response.