Kevin Grise

(University of Virginia)

Do mid-latitude jet shifts cause cloud feedbacks?

What Meteo Colloquium Homepage GR
When Feb 10, 2016
from 03:30 pm to 04:30 pm
Where 112 Walker
Contact Name Sukyoung Lee
Contact email
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Kevin Grise

In response to increasing atmospheric greenhouse gas concentrations, most global climate models project that the mid-latitude jet streams will shift poleward over the 21st century.  Consequently, the tracks of mid-latitude low-pressure systems and their associated cloud features are also anticipated to shift poleward over this time.  As these cloud features move from a lower to a higher latitude, they will move from a latitude of greater incoming solar radiation to one of less incoming solar radiation.  Thus, it seems logical to assume that such poleward movement in the clouds will lead to a warming feedback, as the clouds will be reflecting less solar radiation when they move to higher latitudes.

In this talk, I will challenge this notion using satellite observations from the NASA CERES mission.  By looking at interannual variability in the jet location and cloud-radiative effects, I will show that a poleward jet shift is not associated with cloud-radiative warming in the Southern Hemisphere and is only associated with cloud-radiative warming in some seasons in the Northern Hemisphere.  Most global climate models are incapable of capturing these patterns, particularly in the Southern Hemisphere, where many models indicate robust cloud-radiative warming effects with a poleward jet shift.  Reasons for these model-observational differences will be diagnosed, and the implications of these model biases for future climate projections will be explored.