Collaborative Research: Dropsonde Measurements for Characterizing Lower Troposphere Moisture Variability and Air-sea Interaction over the Tropical Indian Ocean

Madden-Julian Oscillation（MSTO）现场活动的动力学是2011年底/2012年初在印度洋进行的国际实验的美国组成部分，该实验是印度洋季节内变率合作实验（CINDY 2011）。该项目的总体目标是加快对印度洋MJO启动的关键过程的理解，并改进MJO的模拟和预测。现场活动将包括多个雷达、大气探测站、一架研究飞机、多艘研究船和海洋测量。MJO的三个主要假设是：（1）只有当湿层在MJO尺度上变得足够深时，深对流才能组织成MJO对流包层;这种润湿发生的速度决定了预开始状态的持续时间，2）不同阶段的特定对流群体对于MJO的开始是必要的，和3）阻挡层，风和剪切驱动的混合、浅温跃层和混合层卷吸都通过控制上层海洋热含量和SST，在印度洋MJO的形成中发挥着重要作用，从而产生表面通量反馈。该奖项下的研究是使用NOAA WP-3D研究飞机上部署的下投式探空仪进行的，该飞机将以迭戈·加西亚岛为基地。 下投式探空仪包含一个完整的气象仪器包和一个全球定位系统定位器，并提供相对较高的分辨率测量大气温度，压力，湿度，水平风和垂直速度。 该项目还利用机载一次性使用测深温度计和一次性使用电导率-温度-深度探测器的机载测量值和数据，这些探测器可与下投式探空仪沿着从飞机上发射。 该飞机还拥有大量的雷达资产，雷达工作由NOAA单独资助，飞机活动的额外资金来自海军研究办公室。该研究考虑了环境水分和对流之间的相互作用（假设1）和海气相互作用（假设2）在MJO的生命周期中的作用。 最近的结果表明，在热带地区有组织的深对流的爆发类似于一个非平衡相变发生在一个温度依赖的阈值柱水蒸气的工作是出于对水分对流关系。 但是，由于对流层中层水分的作用，以及MJO开始后浅对流区域普遍存在的事实，以及对流下降气流的干燥效应，水分-对流关系变得复杂。海气相互作用方面的工作旨在了解印度洋MJO的海气相互作用与1990年代TOGA-COARE实地活动期间观察到的西赤道太平洋MJO的海气相互作用有何不同。 海气相互作用预计是不同的，因为大的潜热通量发生在太平洋对流之前（建议图1），与MJO相关的西风爆发有关，而在印度洋，（可能还有湍流通量）发生在MJO的对流阶段期间和之后。该项目的动机以及更普遍的MJO的动机来自于许多方面，MJO影响全球的天气和气候。MJO调节亚洲和澳大利亚季风系统的活跃期和中断期，作为厄尔尼诺事件的强迫因子，当它传播到太平洋时，影响美国的天气。太平洋上空的MJO活动对墨西哥湾的飓风形成有很大影响。因此，改进对MJO的预测可以对其全球天气和气候影响进行长期预测（长达两周），在该项目下进行的研究可以作为MJO预测方面取得进展的基础。此外，该项目将为一名研究生提供支助和培训，从而促进热带气象学和气候动力学领域的下一代科学家。

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.