The Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign is the US component of an international experiment in late 2011/early 2012 in the Indian Ocean, the Cooperative Indian Ocean Experiment on Intraseasonal Variability (CINDY2011). The overarching goal of DYNAMO is to expedite understanding of processes key to MJO initiation over the Indian Ocean and to improve simulation and prediction of the MJO. The field campaign will include multiple radars, atmospheric sounding sites, a research aircraft, multiple research vessels, and oceanic measurements.
The three main hypotheses of DYNAMO are: 1) Deep convection can be organized into an MJO convective envelope only when the moist layer has become sufficiently deep over a region of the MJO scale; the pace at which this moistening occurs determines the duration of the pre-onset state, 2) Specific convective populations at different stages are essential to MJO initiation, and 3) The barrier layer, wind- and shear-driven mixing, shallow thermocline, and mixing-layer entrainment all play essential roles in MJO initiation in the Indian Ocean by controlling the upper-ocean heat content and SST, and thereby surface flux feedback
Research under this award is conducted using dropsondes deployed from a NOAA WP-3D research aircraft, which will be based on the island of Diego Garcia. The dropsondes contain a full meterological instrument package and a GPS locator, and provide relatively high resolution measurements of atmospheric temperature, pressure, humidity, horizontal winds, and vertical velocity. The project also makes use of onboard aircraft measurements and data from airborne expendable bathythermographs (AXBTs) and airborne expendable conductivity-temperature-depth (AXCTD) probes, which can be launched from the aircraft along with the dropsondes. The aircraft also has substantial radar assets, and radar work is funded separately by NOAA, and additional funding for aircraft activities comes from the Office of Naval Research. The research considers the interaction between environmental moisture and convection (DYNAMO hypothesis 1) and the role of air-sea interaction (hypothesis 2) in the lifecycle of the MJO. The work on moisture-convection relationships is motivated by recent results showing that the outbreak of organized deep convection in the tropics resembles a non-equilibrium phase transition occurring at a temperature-dependent threshold value of column water vapor. But the moisture-convection relationship is complicated by the role of mid-tropospheric moisture and the fact that areas of shallow convection are prevalent following MJO initiation, as well as the drying effect of convective downdrafts. Work on air-sea interactions seeks to understand how air-sea interactions associated with the MJO in the Indian Oceand differ from their counterparts in the western equatorial Pacific observed during the TOGA-COARE field campaign in the 1990s. Air-sea interactions are expected to be different because large latent heat fluxes occur prior to convection in the Pacific Ocean (fig. 1 of the proposal), associated with MJO-related westerly wind bursts, while in the Indian Ocean the strongest winds (and presumably turbulent fluxes) occur during and after the convective phase of the MJO.
Motivation for this project and more generally for DYNAMO comes from the many ways in which the MJO affects weather and climate worldwide. The MJO regulates the active and break periods of the Asian and Australian monsoon systems, serves as a forcing agent for El Nino events, and, when it propagates into the Pacific ocean, impacts weather over the United States. MJO activity over the Pacific Ocean has a strong influence on hurricane formation in the Gulf of Mexico. Improved prediction of the MJO could thus allow long-lead forecasts (up to two weeks) of its worldwide weather and climate impacts, and research conducted under this project could serve as the basis for such advances in MJO prediction. In addition, this project will provide support and training to a graduate student, thereby promoting the next generation of scientists in tropical meteorology and climate dynamics.
