Land-ocean shifts in tropical precipitation linked to surface temperature and humidity change
Lambert, FH; Ferraro, AJ; Chadwick, R
Date: 8 March 2017
Journal
Journal of Climate
Publisher
American Meteorological Society
Publisher DOI
Abstract
A compositing scheme that predicts changes in tropical precipitation under
climate change from changes in near-surface relative humidity (RH) and
temperature is presented. As shown by earlier work, regions of high tropical
precipitation in general circulation models (GCMs) are associated with high
near-surface RH and temperature. ...
A compositing scheme that predicts changes in tropical precipitation under
climate change from changes in near-surface relative humidity (RH) and
temperature is presented. As shown by earlier work, regions of high tropical
precipitation in general circulation models (GCMs) are associated with high
near-surface RH and temperature. Under climate change, we find that high
precipitation continues to be associated with the highest surface RH and temperatures
in most CMIP5 GCMs, meaning that it is the “rank” of a given GCM
gridbox with respect to others that determines how much precipitation falls
rather than the absolute value of surface temperature or RH change, consistent
with the weak temperature gradient approximation. Further, we demonstrate
that the majority of CMIP5 GCMs are close to a threshold near which
reductions in land RH produce large reductions in the RH-ranking of some
land regions, causing reductions in precipitation over land, particularly South
America, and compensating increases over ocean. Recent work on predicting
future changes in specific humidity allows us to predict the qualitative sense of
precipitation change in some GCMs when land surface humidity changes are
unknown. However, the magnitudes of predicted changes are too small. Further
study, perhaps into the role of radiative and land-atmosphere feedbacks
that we neglect, is necessary.
Mathematics and Statistics
Faculty of Environment, Science and Economy
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