Spatial extents of tropical droughts during El Niño in current and
future climate in observations, reanalysis, and CMIP5 models
Abstract
Drought conditions significantly impact human and natural systems in the
Tropics. Here, multiple observational and reanalysis products and
ensembles of simulations from the Coupled Model Intercomparison Project
Phase 5 (CMIP5) are analyzed with respect to drought areal extent over
tropical land regions and its past and future relationships to the El
Niño/Southern Oscillation (ENSO). CMIP5 models forced with prescribed
sea surface temperatures compare well to observations in capturing the
present day time evolution of the fraction of tropical land area
experiencing drought conditions and the scaling of drought area and
ENSO, i.e., increasing tropical drought area with increasing ENSO warm
phase (El Niño) strength. The ensemble of RCP8.5 simulations suggests
lower end-of-the-century El Niño strength-tropical drought area
sensitivity. At least some of this lower sensitivity is attributable to
atmosphere-ocean coupling, as historic coupled model simulations also
exhibit lower sensitivity compared to the observations.