Mismo Field Experiment in the Equatorial Indian Ocean*

Abstract

The Mirai Indian Ocean cruise for the Study of the Madden?Julian oscillation (MJO)-convection Onset (MISMO) was a field experiment that took place in the central equatorial Indian Ocean during October?December 2006, using the research vessel Mirai, a moored buoy array, and land-based sites at the Maldive Islands. The aim of MISMO was to capture atmospheric and oceanic features in the equatorial Indian Ocean when convection in the MJO was initiated. This article describes details of the experiment as well as some selected early results. Intensive observations using Doppler radar, radiosonde, surface meteorological measurements, and other instruments were conducted at 0°, 80.5°E, after deploying an array of surface and subsurface moorings around this site. The Mirai stayed within this buoy array area from 24 October through 25 November. After a period of stationary observations, underway meteorological measurements were continued from the Maldives to the eastern Indian Ocean in early December. All observations were collected during an El Niño and a positive Indian Ocean Dipole (IOD) event, which tended to suppress convection in the western Pacific and eastern Indian Ocean in throughout much of November 2006. However, as the IOD began to wane in mid-November, an abrupt change from westerly to easterly took place in upper tropospheric winds in the MISMO study region. By late November and early December, deep convection developed over the central Indian Ocean and eastward movement of large-scale cloud systems were observed. This article describes these variations in detail and how they advance our understanding of the onset of tropical deep convection on intraseasonal time scales.