NSFGEO-NERC: Equatorial Line Observations (ELO) Field Campaign during the International Years of Maritime Continent Program: Oceanography and Atmospheric Perspective

海洋大陆（MC，印度洋和西太平洋之间的地区）温暖的浅海和多山的岛屿对通过该地区传播的大气扰动构成了挑战。这些扰动中最大的是马登-朱利安涛动（MJO），这是一种由云层和降水组成的广阔包络层，形成于印度洋，缓慢地向东移动，一直移动到赤道太平洋中部。MJO影响着全球大部分地区的天气和气候，对美国的影响包括墨西哥湾的飓风形成和加州因大气河流而引发的洪水。MJO的缓慢演变和广泛影响激发了人们对MJO预测的兴趣，而MC对预测提出了挑战，因为模型难以预测哪些事件将穿过该区域，哪些事件将在该区域内消散。因此，对MJO影响进行长期预报的必要性使人们有兴趣了解MC与MJO相互作用的机制，并作为它们进入赤道太平洋的看门人。该项目是赤道线观测（ELO）野外活动的一个组成部分，旨在了解影响MJO传播的当地MC过程。该活动是美国、英国和印度尼西亚研究人员的一个联合项目，在该项目中，利用海上滑翔机在苏门答腊西海岸沿赤道进行海洋观测，并在苏门答腊和婆罗洲之间的卡里玛塔海峡停泊。在苏门答腊岛东部和婆罗洲西海岸的陆地观测补充了海洋观测，计划于2018年11月至2019年2月部署。ELO是在世界气象组织主持下组织的更大的国际努力“海洋大陆年”的一部分。该运动的目标是假设影响MJO通过MC传播的三个因素。首先是大气扰动与底层海洋之间的相互作用。在MC内部海域的大量降雨产生了浅层的淡水，这些淡水可以通过到达表面的阳光变化、风驱动的蒸发和其他因素迅速升温和冷却。海洋表面温度的变化反过来又会影响云量和降水，该项目旨在了解这种海气耦合如何影响向东传播的大气扰动。第二种是MJO与对流耦合开尔文波（CCKWs）的相互作用，后者是较小的赤道天气扰动，向东传播的速度比MJO快，被认为是MJO的“基石”。pi假设，在预报模式中看到的MJO通过MC传播的表示问题与该地区CCKW活动的较差模拟有关。第三是CCKWs与MC降水日循环的相互作用，因为强降水通常发生在苏门答腊和婆罗洲的中午之后，而在分隔它们的Karimata海峡的早晨。岛屿之间的距离使得在一天的雨天经过苏门答腊岛的CCKW很可能及时到达婆罗洲，赶上第二天的最大降水。PI假设与岛屿日循环同步的CCKWs接收的额外冷凝加热有利于它们的生长和与MJO的进一步相互作用。鉴于MJO的全球影响以及改进MJO相关预报的潜力，这项工作具有社会和科学价值。这项工作还促进了大气科学和业务预报方面的国际能力建设，因为它是与印度尼西亚伙伴合作开展的。该活动涉及来自美国，英国和印度尼西亚的博士生，从而为该研究领域提供未来的劳动力发展。

The warm shallow seas and mountainous islands of the Maritime Continent (MC, the region between the Indian Ocean and the western Pacific) pose a challenge for atmospheric disturbances propagating through the area. The larges of these disturbances is the Madden-Julian Oscillation (MJO), a broad envelope of clouds and precipitation that forms in the Indian Ocean and moves slowly eastward as far as the central equatorial Pacific. The MJO affects weather and climate over much of the globe, with US impacts including hurricane formation in the Gulf of Mexico and flooding in California due to atmospheric rivers. The slow evolution and widespread impacts of the MJO have spurred interest in MJO prediction, and the MC presents a challenge to forecasting as models have difficulty predicting which events will transit the region and which will dissipate within it. The desirability of long-range forecasts of MJO impacts has thus lead to an interest in understanding the mechanisms through which the MC interacts with the MJO and serves as a gatekeeper for their entry into the equatorial Pacific.This project is one component of the Equatorial Line Observations (ELO) field campaign, which seeks to understand the local MC processes that influence MJO propagation. The campaign is a joint project between researchers in the US, Great Britain, and Indonesia in which oceanic observations are taken along the equator using sea gliders off the west coast of Sumatra and moorings in the Karimata Strait between Sumatra and Borneo. The oceanic observations are complemented by land-based observations in eastern Sumatra and on the west coast of Borneo, with deployment scheduled between November 2018 and February 2019. ELO is part of a larger international effort known as the Years of the Maritime Continent, organized under the auspices of the World Meteorological Organization.The campaign targets three factors which are hypothesized to influence MJO propagation through the MC. The first is interactions between atmospheric disturbances and the underlying ocean. Abundant rainfall over the internal seas of the MC produces a shallow surface layer of fresh water which can be warmed and cooled rapidly by variations in sunlight reaching the surface, wind-driven evaporation, and other factors. Variations in sea surface temperature can in turn influence cloudiness and precipitation, and the campaign seeks to understand how this air-sea coupling affects eastward propagating atmospheric disturbance.The second is the interaction of the MJO with convectively coupled Kelvin waves (CCKWs), which are smaller equatorial weather disturbances which propagate eastward at a faster rate than the MJO and are regarded as its "building blocks". The PIs hypothesize that the problems with the representation of MJO propagation through the MC seen in forecast models are related to poor simulation of CCKW activity in the region.The third is the interaction of CCKWs with the diurnal cycle of precipitation in the MC, as intense precipitation generally occurs after noon over Sumatra and Borneo but in the morning over the Karimata Strait separating them. The distance between the islands is such that a CCKW passing over Sumatra during the rainy part of the day is likely to arrive at Borneo in time for the precipitation maximum on the following day. The PI hypothesizes that the extra condensational heating received by CCKWs which are synchronized with the island diurnal cycles could favor their growth and further interaction with the MJO.The work has societal as well as scientific value given the worldwide impacts of the MJO and the potential for improvement of MJO-related forecasts. The work also promotes international capacity building in atmospheric science and operational forecasting, as it is conducted in collaboration with Indonesian partners. The campaign involves PhD students from the US, Great Britain, and Indonesia, thus providing future workforce development in this research area.