High sensitivity of tropical precipitation to local sea-surface temperature
Good, P; Chadwick, R; Holloway, CE; et al.Kennedy, J; Lowe, JA; Roehrig, R; Rushley, SS
Date: 26 October 2020
Journal
Nature
Publisher
Nature Research
Publisher DOI
Abstract
Precipitation and atmospheric circulation are the coupled processes through which tropical
ocean surface temperatures drive global weather and climate. Influences of local ocean
temperatures on precipitation are hard to disentangle from remote effects of conditions
elsewhere; and the full influence of the recently-discovered shallow ...
Precipitation and atmospheric circulation are the coupled processes through which tropical
ocean surface temperatures drive global weather and climate. Influences of local ocean
temperatures on precipitation are hard to disentangle from remote effects of conditions
elsewhere; and the full influence of the recently-discovered shallow circulations
is unclear.
Uncertainty in precipitation observations, and limited observations of circulation , further
obstruct understanding. Despite decades of research, persistent biases remain in many
numerical model simulations, including excessively-wide tropical rainbands, the
‘double-intertropical convergence zone (ITCZ) problem’ and too-weak responses to the
El Niño Southern Oscillation (ENSO). These demonstrate stubborn gaps in our
understanding, and reduce confidence in forecasts and projections. Here we show that the
real world has a high sensitivity of seasonal tropical precipitation to local sea-surface
temperatures (higher than in all but 4 of the 47 models studied), associated with strong
shallow circulations. Our results apply to both temporal and spatial variation, over regions
where climatological precipitation is around 1 mm/day or greater. Novel analysis of multiple
independent observations, combined with physical constraints and model data, underpin these
findings. A large spread in model behaviour is further linked to differences in shallow
convection, providing a focus for accelerated research, to improve seasonal forecasts through
multidecadal climate projections.
Mathematics and Statistics
Faculty of Environment, Science and Economy
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