Increase in resolution is key in improving GCMs over South Asia

Accurate simulation of the South Asian summer monsoon is still an unresolved challenge. There has not been a benchmark effort to decipher the origin of undesired yet virtually invariable unsuccessfulness of Global Climate Models (GCMs) over this region. Here we combine comprehensive analyses of GCMs in the 5th phase of Coupled Model Intercomparison Project and a set of low- and high-resolution climate model experiments to unravel statistically significant association between the modeling errors in summer precipitation and in overlying monsoon dynamics. Fourfold increase in the horizontal grid spacing in our climate model experiment eliminates most of the dynamical errors that substantially corrects the simulation of monsoon onset phase and seasonal precipitation distribution through improvements in the representation of precipitation moisture sources and monsoon depressions trajectories. These results highlight the substantial increase in resolution as a key step towards improving the representation of South Asian summer monsoon in the next generation of GCMs.