地面风和上层海洋变异相关的马登-朱利安振荡的海气耦合中尺度预报系统模拟
Surface Wind and Upper-Ocean Variability Associated with the Madden- Julian Oscillation Simulated by the Coupled Ocean-Atmosphere Mesoscale Prediction System.
关键词:荡;季节变化,热带地区;人工卫星;大气模式
摘 要:Simulation of surface wind and upper-ocean variability associated with the Madden-Julian oscillation (MJO) by a regional coupled model, the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS), is evaluated by the comparison with in situ and satellite observations. COAMPS is configured for the tropical Indian Ocean domain with the horizontal resolution of 27 km for the atmospheric component and 1/8 deg for the ocean component. A high-resolution nested grid (9 km) for the atmospheric component is used for the central Indian Ocean. While observational data are assimilated into the atmospheric component, no data are assimilated into the ocean component. The model was integrated during 1 March-30 April 2009 when an active episode of large-scale convection associated with the MJO passed eastward across the Indian Ocean. During this MJO event, strong surface westerly winds (approximately 8 ms-1) were observed in the central equatorial Indian Ocean, and they generated a strong eastward jet (approximately 1 ms -1) on the equator. COAMPS can realistically simulate these surface wind and upper-ocean variations. The sensitivity of upper-ocean variability to the atmospheric model resolution is examined by the COAMPS experiment without the high-resolution nested grid. The equatorial jet generated in this experiment is about 20weaker than that in the first experiment, which significantly influences upper-ocean salinity and temperature. The large diurnal warming of SST during the suppressed phase of the MJO is also adequately simulated by the model. Weak winds during this period are mostly responsible for the large SST diurnal variation based on the comparison with the spatial variation of surface forcing fields.