Background
The authors write that "the East Asian summer monsoon (EASM) is a distinctive component of the Asian climate system," which they indicate is "characterized by wind reversal and heavy precipitation during summer over East Asia (Lau and Li, 1984)." And while further noting that "the evolution and variability of the monsoon have a big impact on human society across the region," they suggest that "better prediction of the monsoon's variation may greatly benefit those people inhabiting the region."

What was done
To determine the abilities of atmospheric general circulation models (AGCMs) to capture the major features of the EASM, ten models that participated in the Coupled Model Intercomparison Project/Atmospheric Model Intercomparison Project (CMIP5/AMIP) - which used observational sea surface temperature (SST) and sea ice data to drive the AGCMs during the period 1979-2008 - were evaluated by comparing their output with observations and AMIP II simulations.

What was learned
In regard to model shortcomings in the Meiyu/Changma/Baiyu rainbelt, Feng et al. report that (1) "the intensity of rainfall is underestimated in all the models," that these biases are caused by (2) "a weak western Pacific subtropical high" and (3) "accompanying eastward southwesterly winds in group I models," as well as by (4) "a too strong and west-extended western Pacific subtropical high," plus (5) "westerly winds in group II models." In addition, they report that (6) "considerable systematic errors exist in the simulated seasonal migration of rainfall," and that (7) "notable northward jumps" and (8) "rainfall persistence remain a challenge for all the models."

What it means
In light of these several model deficiencies, it would appear that the world's climate modelers are ever learning, but never quite attaining the knowledge needed to accurately represent the many facets of the various phenomena that converge to establish the ever-shifting nature of different aspects of earth's complex climate system, as represented in this study by the East Asian summer monsoon.

Reference
Lau, K.M. and Li, M. 1984. The monsoon of East Asia and its global associations - A survey. Bulletin of the American Meteorological Society 65: 114-125.