Experimental Intraseasonal Forecasting of Asian Summer Monsoon

In boreal summer, the Madden-Julian Oscillation (MJO) has strong interaction with the circulation and variability of Asian summer monsoon. In addition to the eastward propagation along the equator, the MJO in this season also propagates northeastward as Boreal-Summer Intraseasonal-Seasonal Oscillation (BSISO) to influence the wet and dry spells of monsoon over the South and East Asian subcontinent. The active phase of the MJO/BSISO also clusters the occurrences of monsoon lows and tropical cyclones in northern Indian Ocean and Northwest Pacific Ocean.

An atmosphere-ocean coupled system has been developed at University of Hawaii (hereafter UH model). Initialized with NCEP FNL analysis, the UH model has been used to carry out experimental intraseasonal forecasting of monsoon in 2008 boreal summer (a target year of YOTC and AMY). In this study, we inter-compared monsoon forecasts of UH model with the forecasts from CFSv1/v2, and ECMWF. It is found that the intraseasonal forecasting skill in the CFSv2 is much higher than that in the CFSv1, largely due to improved initial conditions. Overall, ECMWF, CFSv2, and UH model have similar predictability with useful skills of the 850-hPa zonal winds and rainfall, respectively, reaching three and two weeks.