In order to examine the impact of ocean roughness and bogus typhoons on the east Asian summer monsoon circulation, three runs with a regional climate model (RegCM2) for 1994 summertime simulation were conducted: a control run (CTRL), a run with RegCM2 coupled to an ocean-wave model (WAVE), and a run with RegCM2 coupled to a wave model and a bogus typhoon scheme (WBGS). The National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalyses were used for initial and lateral boundary conditions. The regional climate model with a fixed value of roughness length over the ocean (CTRL) did not adequately simulate the extreme anomalous summer monsoon of 1994. However, the simulation of the atmosphere-wave coupled model (WAVE) produced better anomalous features than CTRL, closer to the 1994 extreme summer climate. In WAVE the roughness length over the ocean was increased to over twice the fixed value. The maximum values of roughness length were found in the active monsoon regions. Increased ocean roughness length resulted in more changes over land rather than over the ocean due to more moisture supplies from the ocean, such that the maximum changes of surface climate occurred over China. In particular, the differences between CTRL and WAVE were relatively large over areas of warmer ground temperature, such as central China. In WBGS the roughness length over the ocean was increased by about 20% relative to that of WAVE under the high wind conditions induced by bogus typhoons. It was also found that the seasonal march of the east Asian summer monsoon was better reproduced in WBGS than in the other two simulations. The bogus typhoons in east Asia played an important role in simulating the variations of surface climate and lower troposphere circulations associated with storms, including typhoons, by the transport of heat and moisture toward the midlatitude land areas. However, the precipitation in WBGS was degraded comparing to that of CTRL. This study suggests that proper simulation of east Asian summer monsoon circulations, especially during an active typhoon season, requires the proper representation of ocean roughness length and typhoons.