Atmospheric Sounding Network in the Dynamics of the Madden-Julian Oscillation Project (DYNAMO)

Colorado State University, Fort Collins CO

Investigators

Abstract

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 This award is for planning and implementation of the sounding network for DYNAMO, as well as follow up quality control and analysis. The DYNAMO sounding network will consist of four locations: Gan, Diego Garcia, and two research vessels. The researchers will plan the sounding network for DYNAMO and establish a sounding data monitoring system which will be used for field quality control of the data and preparation of quick-look products. After the campaign, the team will prepare large-scale forcing fields for the DYNAMO modeling community, as well as conduct diagnostic studies involving the divergence and diabatic heating profiles and the boundary layer evolution through the life cycle of the MJO. These tasks will help to address Hypotheses 1 and 2 of the DYNAMO campaign. In addition to the overarching DYNAMO hypotheses, the researchers have identified two others that they plan to test: 1) The pre-onset (moistening or pre-conditioning) phase of the MJO over the Indian Ocean, rather than exhibiting a gradual, steady build-up of moisture in the lower troposphere, is characterized by a stepwise evolution of the moisture field, which is related to the development of distinct cloud populations, and 2) The mixed-layer depth and its properties over the central Indian Ocean vary on the timescale of the MJO and these variations have corresponding relationships to the evolving cloud and precipitation fields observed during DYNAMO. The broader impacts of the research include the involvement of multiple graduate students in the field campaign and data analysis. A successful DYNAMO campaign would lead to improved understanding of tropical convection, the predictability of the MJO, and downstream effects of the MJO on weather in the United States and other areas.