Water vapor and SST variations associated with equatorial waves over the tropical Indian Ocean

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) conducted a field experiment in October-December 2006 aboard the R/V Mirai, focusing on the initiation of convection in the MJO in the central equatorial Indian Ocean, and named this project MISMO. The present study examines the water vapor and SST variations observed during MISMO.

Main results of the present study are as follows.

(1)GPS-derived precipitable water and radiosonde-derived vapor mixing ratios (and precipitation system number ) show prominent 3-4-day-variations.

(2)Meridional wind also exhibits the 3-4-day cycle.

(3)It is suggested that the 3-4-day variations are associated with "mixed Rossby-Gravity (MRG) wave".

(4)The vertical structure of the MRG wave is shallow in the convectively suppressed period, while it is deepened in the active phase.

(5)Convective activity is also controlled by the MRG wave as well as water vapor.

(6)Diurnal variations of the sea surface temperature (SST) are prominent during the light wind condition.

(7)The surface wind strength and the zonal wind show 6-8-day-variations.

(8)It is suggested that The zonal wind variations are associated with “Equatorial Rossby (ER) wave (n=1)".