Characterization of Convective Interactions with Easterly Waves, the Caribbean Low-Level Jet and Central American Topography During OTREC

OTREC 期间与东风波、加勒比低空急流和中美洲地形的对流相互作用的特征

• 批准号: 1758666
• 负责人: Yolande Serra
• 金额: $ 41.03万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2023-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1758666&HistoricalAwards=false
• 关键词: Characterization; Convective; Interactions; Easterly; Waves

This award supports work on the Organization of Tropical East Pacific Convection (OTREC) field campaign. The campaign seeks to understand the formation and development of tropical convective clouds and associated heavy rainfall in the adjacent but distinct regions of the eastern equatorial Pacific and the southwest Caribbean, along with their evolution over the intervening portions of Central America and Colombia. The campaign also examines the genesis and evolution of easterly waves, large westward-moving atmospheric disturbances (wavelengths of about 2,000 km) which occur on a weekly basis in the Caribbean and eastern Pacific. The full set of campaign awards is discoverable on the nsf.gov/awardsearch webpage by a keyword search on "OTREC".Tropical convection plays a critical role in earth's climate system and is also responsible for extreme precipitation and hurricane formation. Easterly waves are of particular interest for weather forecasting given their tendency to spawn hurricanes. More generally, tropical convection is an engine of weather and climate worldwide yet poorly understood and difficult to simulate. Work leading to better representation of tropical convection in weather and climate models can thus lead to better weather forecasts and impact assessments, both for the public and decision makers. Aside from the societal relevance of the science, the campaign includes several education and outreach activities including support for undergraduates to participate in fieldwork and production of short documentary videos for use in classroom teaching and informal science education. In addition, the project builds international scientific collaboration through partnerships with researchers in Costa Rica and Mexico. The project also supports fieldwork participation by three graduate students, and outreach to local students is conducted through short courses at the University of Costa Rica.The eight week OTREC deployment consists primarily of a set of 20 flights in the Gulfstream V (GV) research aircraft maintained by the National Center for Atmospheric Research (NCAR). The campaign uses an airport in Costa Rica for easy access to the equatorial Pacific and southwest Caribbean study regions, and conditions in these regions are sampled using dropsondes and a wing-mounted W-band radar. Dropsondes contain the same instrument package as standard weather balloons, only dropped from an aircraft (in this case from about 40,000 feet) with a small parachute. The radar determines cloud properties such as the relative abundance of ice particles versus liquid droplets, and uses Doppler shift to measure updraft and downdraft speeds in clouds. The aircraft sampling is augmented by observations collected at ground sites in Costa Rica and Colombia.The specific focus of this project is easterly waves, which play a dominant role in the variability of tropical convection and serve as precursors for hurricane formation. Easterly waves in the southwestern Caribbean are generally thought to propagate into the region from West Africa. But it is not clear whether easterly waves in the eastern Pacific originate locally or reintensify after crossing Central America from the Caribbean. Some studies suggest that formation or reintensification occurs through instabilities of strong low-level jets which occur where winds are funneled through gaps in the Central American mountains. Generation and intensification could also happen through interaction with convection, either over Central America or off the Pacific coast of Colombia, regions where a strong diurnal cycle produces episodes of intense convection and rainfall.The role of jet stream instabilities in generating or reinvigorating easterly waves is examined using data from meteorological analyses produced using observations from the OTREC campaign (provided by collaborators at ECMWF). The interaction of easterly waves with convection over Central America is examined using satellite data and surface meteorology stations in Costa Rica. These include GPS receivers already deployed as part of the COCONet network (see EAR-1042906), which record the total precipitable water vapor in the atmosphere. These assets are augmented with an additional 10 GPS ground stations and 10 surface weather stations, as well as two weather balloon launching stations. A key issue to be examined with the surface stations is the timing of the maxima in precipitable water vapor and precipitation, as the lag between the two (i.e. whether precipitation peaks first or precipitable water peaks first) provides valuable information regarding the organization and vertical structure of convection.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项支持热带东太平洋对流组织（OTREC）实地活动的工作。 该活动旨在了解赤道东太平洋和加勒比西南部相邻但不同区域的热带对流云和相关暴雨的形成和发展，沿着它们在中美洲和哥伦比亚中间部分的演变。该活动还研究了东风波的成因和演变，东风波是加勒比和东太平洋每周发生的向西移动的大规模大气扰动（波长约2 000公里）。在nsf.gov/awardsearch网页上以“OTREC”为关键词搜索可获得全套活动奖项。热带对流在地球气候系统中起着至关重要的作用，也是极端降水和飓风形成的原因。 东风波对天气预报特别感兴趣，因为它们倾向于产生飓风。 更普遍地说，热带对流是全球天气和气候的引擎，但人们对它的了解很少，也很难模拟。 因此，在天气和气候模型中更好地体现热带对流的工作，可以为公众和决策者带来更好的天气预报和影响评估。 除了科学的社会意义外，该运动还包括几项教育和宣传活动，包括支持本科生参加实地考察和制作用于课堂教学和非正式科学教育的简短纪录片。 此外，该项目通过与哥斯达黎加和墨西哥的研究人员建立伙伴关系，建立国际科学合作。该项目还支持三名研究生参加实地考察，并通过在哥斯达黎加大学开设短期课程向当地学生进行宣传。为期八周的OTREC部署主要包括由国家大气研究中心（NCAR）维护的湾流V（GV）研究飞机的20次飞行。 该活动利用哥斯达黎加的一个机场，方便进入赤道太平洋和西南加勒比研究区域，并利用下投式探空仪和机翼上的W波段雷达对这些区域的情况进行采样。 投下式探空仪包含与标准气象气球相同的仪器包，只是从飞机上（在这种情况下从大约40，000英尺）用小降落伞降落。 雷达确定云的特性，如冰粒与液滴的相对丰度，并使用多普勒频移测量云中的上升气流和下降气流速度。 在哥斯达黎加和哥伦比亚的地面站点收集的观测资料加强了飞机取样工作。该项目的具体重点是东风波，它在热带对流的变化中起着主导作用，并作为飓风形成的前兆。 加勒比海西南部的东风波通常被认为是从西非传播到该地区的。 但目前尚不清楚东太平洋的东风波是源于当地，还是从加勒比海穿越中美洲后重新加强。 一些研究表明，在风通过中美洲山脉的缝隙汇集的地方，强烈的低空急流不稳定，从而形成或再增强。 生成和强化也可能发生通过与对流的相互作用，无论是在中美洲或关闭的太平洋沿岸的哥伦比亚，一个强大的昼夜周期产生强烈的对流和raining.The急流不稳定性的作用产生或振兴东风波检查使用的数据从气象分析产生的观测OTREC活动（由合作者提供ECMWF）。 利用卫星资料和哥斯达黎加地面气象站研究了中美洲上空东风波与对流的相互作用。其中包括已经作为COCONet网络的一部分部署的全球定位系统接收器（见NOE-1042906），它记录大气中可降水的总水汽量。 这些资产还增加了10个全球定位系统地面站和10个地面气象站，以及两个气象气球发射站。地面观测站要研究的一个关键问题是可降水量和降水量最大值的时间，两者之间的滞后（即是降水量先达到峰值还是可降水量先达到峰值）该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。