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

马登-朱利安涛动（DYNAMO）场运动的动力学是2011年底/ 2012年初在印度洋进行的一项国际实验——印度洋季节内变率合作实验（CINDY2011）的美国组成部分。DYNAMO的总体目标是加快对印度洋MJO形成的关键过程的理解，并改进对MJO的模拟和预测。实地考察活动将包括多部雷达、大气探测站点、一架研究飞机、多艘研究船和海洋测量。DYNAMO的三个主要假设是：1)只有当湿层在MJO尺度上足够深时，深层对流才能组织成MJO对流包络；2)不同阶段的特定对流种群对MJO的形成至关重要；3)阻挡层、风切变混合、浅层温跃层和混合层夹带通过控制上层海洋热含量和海温对印度洋MJO的形成起重要作用。根据该合同进行的研究将使用NOAA WP-3D研究飞机部署的下投探空仪，该飞机将驻扎在迪戈加西亚岛。下投式探空仪包含一个完整的气象仪器包和一个GPS定位器，可以提供相对高分辨率的大气温度、压力、湿度、水平风和垂直速度的测量。该项目还利用了机载测量数据，以及机载一次性深海温度仪（axbt）和机载一次性电导率-温度-深度探头（AXCTD）的数据，这些探头可以与下投探空仪一起从飞机上发射。该飞机还具有大量雷达资产，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。研究考虑了环境湿度与对流的相互作用（DYNAMO假设1）和海气相互作用（假设2）在MJO生命周期中的作用。最近的研究结果表明，热带地区有组织的深层对流的爆发类似于发生在温度依赖的柱状水蒸气阈值处的非平衡相变，从而激发了对水分-对流关系的研究。但由于对流层中层水汽的作用和MJO启动后浅对流区普遍存在，以及对流下降气流的干燥作用，使得水汽-对流关系变得复杂。海气相互作用的研究旨在了解印度洋与MJO相关的海气相互作用与20世纪90年代TOGA-COARE野外运动期间观测到的西赤道太平洋的海气相互作用有何不同。海气相互作用预计会有所不同，因为太平洋的大潜热通量发生在对流之前（提案图1），与MJO相关的西风爆发有关，而在印度洋，最强的风（可能是湍流通量）发生在MJO的对流阶段期间和之后。这个项目的动机，更广泛地说，DYNAMO来自MJO影响全球天气和气候的许多方式。MJO调节着亚洲和澳大利亚季风系统的活跃和中断期，充当着厄尔尼诺事件的强迫因子，当它传播到太平洋时，影响着美国的天气。太平洋上的MJO活动对墨西哥湾的飓风形成有很强的影响。因此，对MJO的改进预测可以实现对其全球天气和气候影响的长期预测（长达两周），而在这个项目下进行的研究可以作为MJO预测取得这种进展的基础。此外，该项目将为一名研究生提供支持和培训，从而促进下一代热带气象学和气候动力学科学家。

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.