The South Asian Monsoon: How Difficult It Has Been to Model
Bollasina, M.A. and Ming, Y. 2013. The general circulation model precipitation bias over the southwestern equatorial Indian Ocean and its implications for simulating the South Asian monsoon. Climate Dynamics 40: 823-838.
In the words of the two researchers, "the oceanic bias, which develops in spring and reduces during the monsoon season, is associated [with] a consistent precipitation and circulation anomalous pattern over the whole Indian region," where "in the vertical, the areas are linked by an anomalous Hadley-type meridional circulation, whose northern branch subsides over northeastern India significantly affecting the monsoon evolution (e.g., delaying its onset)." And they indicate that "the ability of local anomalies over the SWEIO to force a large-scale remote response to the north is further supported by numerical experiments with the GFDL spectral dry dynamical core model."
Given such findings, Bollasina and Ming say their study "makes the case that the precipitation bias over the SWEIO is forced by the model excess response to the local meridional sea surface temperature gradient through enhanced near-surface meridional wind convergence," and they thus conclude that "a detailed investigation into the model physics to identify possible parameters which may alleviate the model bias would be the natural extension of this work."