Impact of Atmosphere–Ocean Coupling on the Predictability of Monsoon Intraseasonal Oscillations*

Abstract

The impact of air–sea coupling on the predictability of monsoon intraseasonal oscillations (MISO) has been investigated with an atmosphere–ocean coupled model and its atmospheric component. From a 15-yr coupled control run, 20 MISO events are selected. A series of twin perturbation experiments have been conducted for all the selected events using both the coupled model and the atmosphere-only model. Two complementary measures are used to quantify the MISO predictability: (i) the ratio of signal-to-forecast error and (ii) the spatial anomaly correlation coefficient (ACC). In the coupled model, the MISO predictability is generally higher over the Indian sector than that over the western Pacific with a maximum of 35 days in the eastern equatorial Indian Ocean. Air–sea coupling significantly improves the predictability in almost the entire Asian–western Pacific region. The mean predictability of the MISO-related rainfall over its active area (10°S–30°N, 60°–160°E) reaches about 24 days in the coupled... Abstract The impact of air–sea coupling on the predictability of monsoon intraseasonal oscillations (MISO) has been investigated with an atmosphere–ocean coupled model and its atmospheric component. From a 15-yr coupled control run, 20 MISO events are selected. A series of twin perturbation experiments have been conducted for all the selected events using both the coupled model and the atmosphere-only model. Two complementary measures are used to quantify the MISO predictability: (i) the ratio of signal-to-forecast error and (ii) the spatial anomaly correlation coefficient (ACC). In the coupled model, the MISO predictability is generally higher over the Indian sector than that over the western Pacific with a maximum of 35 days in the eastern equatorial Indian Ocean. Air–sea coupling significantly improves the predictability in almost the entire Asian–western Pacific region. The mean predictability of the MISO-related rainfall over its active area (10°S–30°N, 60°–160°E) reaches about 24 days in the coupled...