Summary of Robust Increases in Midlatitude Static Stability in Global Warming Simulations
by Frierson, which appears
in Geophysical Research Letters.
Primary arguments:
-
Increase in static stability in midlatitudes is a consistent response of
global climate models.
-
The increase in midlatitude stability is especially true in the Southern
Hemisphere and in summer (polar amplification in Northern Hemisphere winter
is the primary opposing factor).
Discussion:
Based on intuition originally developed from our simplified moist GCM (Frierson et al 2006) and further studied in a full GCM over simplified boundary conditions (Frierson 2007), we study the midlatitude static stability in fully coupled global warming simulations from the WRCP CMIP3 multi-model database.
Our previous studies have demonstrated the strong importance of the
midlatitude moisture content on the static stability of the
midlatitudes. This is essentially due to the fact that moist
convection occurs frequently in the warm regions of baroclinic eddies.
So, with increased temperatures and moisture content in global
warming simulations, can we detect an increase in static stability?
The answer is a resounding yes, with 158 out of 160
model-season-hemispheres examined in this study experiencing an
increase in midlatitude stability with global warming. Only two
Northern Hemisphere winter model simulations which have large polar
amplification experience a decrease in midlatitude static stability.
An increase in midlatitude static stability is a robust feature
of global warming simulations.
A recent paper of ours (Frierson, Lu and Chen 2007)
has examined the possibility that the well-documented widening of the
Hadley circulation with global warming may in fact be due to the
midlatitude static stability increase shown here. We investigate
this in the Frierson, Lu and Chen paper by considering a wide range of
full and idealized GCM experiments, over simplified boundary
conditions.
The plot above shows the change in potential temperature with global
warming, averaged over 21 different models. In addition to
familiar features such as enhanced warming in the tropical upper
troposphere, stratospheric cooling, and polar amplification in the
Northern Hemisphere winter, there is also an increase in midlatitude
static stability (the potential temperature increases more at 400 hPa
than at the surface, everywhere except for the high latitude Northern
Hemisphere winter).
Full citation:
Frierson, D. M. W.
Robust Increases in Midlatitude Static Stability in Global Warming Simulations.
Geophysical Research Letters, 33, L24816,
doi:10.1029/2006GL027504, 2006.
The official journal link can be found here.
A PDF download of the full paper can be found here.
This download is courtesy of the American Geophysical Union, who owns sole
rights to it.
The download is subject to copyright laws and statutes. For more
information, please visit the AGU website.
|
|