OTREC: Organization of Tropical East Pacific Convection

该奖项为题为热带东太平洋对流组织(OTREC)的实地活动的规划和组织活动提供资金。通过颁发奖项，NSF鼓励PI和他的合作者提交一套提案，请求支持每一项不同的竞选活动，这些提案将在以后集体审查。第二轮审查决定了这场运动是否进入实地，以及运动的哪些要素得到了国家科学基金会的支持。OTREC的目标是了解热带对流云的形成和发展，以及与之相关的赤道东太平洋和加勒比海西南地区邻近但不同地区的暴雨。赤道东太平洋海表温度(SST)具有较强的南北温差，从赤道深水上升流产生的“冷舌”向北升高。接近地面的风通常从较冷到较暖的SST方向吹到热带辐合带(ITCZ)，大约在赤道以北4到12度之间。ITCZ是一个狭窄的多云和对流区域，通常被认为是近地面风辐合的结果。但PI假设，在东太平洋ITCZ发现的深层、有组织的对流和强降水还需要其他因素。这些其他因素包括大气稳定性、对流层中层涡度(一个结合了风的旋转和水平切变的术语)和湿热力学，这些因素结合在PI和其他人发展的理论中(例如见AGS-1546698)。相比之下，加勒比海西南部是一个均匀的海温区域，不利于低层风辐合，对流层中层的空气往往非常干燥。这些条件不利于对流，但无论对流形式如何，该运动都试图了解克服对流障碍的机制。一种可能的机制涉及到由邻近的中美洲大陆强迫的大气运动，要么是由于太阳加热的日循环，要么是由于地形的阻挡效应。另一个需要解决的问题是东风波的形成机制，它是热带东太平洋和加勒比海西南部最常见的天气扰动。东风波是一种向西移动的大气扰动，波长约为2000公里，每周出现一次，有时会发展为飓风。大西洋和加勒比上空的东风波一般源自非洲(例如，见AGS-1433764)，但赤道东太平洋东风波的形成机制尚不清楚。OTREC的活动数据将被用来确定机械和热力学机制对这些波的形成和加强的相对贡献。OTREC将使用由国家大气研究中心地球观测实验室维护的湾流V(GV)研究飞机作为其主要观测平台。GV将设在哥斯达黎加，便于进入东太平洋和加勒比海西南部。风、气压、温度和湿度的观测将使用投放探空仪，这种探空仪使用的仪器与标准气象气球基本相同，只是用一个小降落伞从飞机上投放的。将使用安装在机翼吊舱中的W波段雷达进行额外的云量测量，还将为这一行动提议进行地面观测。该运动的一个主要目标是确定与热带对流有关的对流质量通量，因为这一数量在该运动试图检验的对流云发展理论中发挥着核心作用。热带对流在天气和气候中发挥着重要作用，因为它可以产生极端降水，并发展为具有破坏性影响的飓风。它还可以扰乱大气环流，影响远距离的天气和气候，例如可以从厄尔尼诺事件对美国大陆的影响中看到。因此，对热带对流的研究具有社会和科学意义，因为更好地了解热带对流可以改进用于预报每日天气和预测气候变异性和变化的模型。该运动还将通过发展与中美洲研究人员的国际科学伙伴关系产生更广泛的影响，并将为大气科学研究生提供宝贵的教育机会。

This award funds planning and organizational activity for a field campaign titled Organization of Tropical East Pacific Convection (OTREC). By making the award NSF encourages the PI and his collaborators to submit a set of proposals requesting support for each of the various campaign activities, which are reviewed collectively at a later date. This second round of reviews determines whether the campaign goes to the field and what elements of the campaign are supported by NSF.The goal of OTREC is to understand the formation and development of tropical convective clouds and their associated heavy rainfall in the adjacent but distinct regions of the eastern equatorial Pacific and the southwest Caribbean. The sea surface temperature (SST) in the eastern equatorial Pacific has a strong north-south temperature contrast, with temperatures increasing northward from the "cold tongue" produced by the upwelling of deep water along the equator. Winds near the surface generally blow in the direction from colder to warmer SST until they reach the intertropical convergence zone (ITCZ), roughly between four and twelve degrees north of the equator. The ITCZ is a narrow region of cloudiness and convection which is generally regarded as a consequence of wind convergence near the surface. But the PI hypothesizes that other factors are required to produce deep, organized convection and heavy precipitation found in the eastern Pacific ITCZ. These other factors include atmospheric stability, mid-tropospheric vorticity (a term which combines rotation and horizontal shear of the wind), and moist thermodynamics, combined in a theory developed by the PI and others (see for example AGS-1546698).In contrast, the southwest Caribbean is a region of uniform SSTs which do not favor low-level wind convergence, and air at mid-tropospheric levels tends to be quite dry. These conditions are unfavorable for convection yet convection forms regardless, and the campaign seeks to understand the mechanisms through which the obstacles to convection are surmounted. One possible mechanism involves atmospheric motions forced by the adjacent Central American landmass, either by the diurnal cycle of solar heating or the blocking effects of topography.A further issue to be addressed is the formation mechanisms of easterly waves, which are the most frequent weather disturbances in the tropical east Pacific and in the SW Caribbean. Easterly waves are westward-moving atmospheric disturbances with wavelengths of roughly 2,000km which appear on a weekly basis and sometimes develop into hurricanes. Easterly waves over the Atlantic and Caribbean generally originate over Africa (see for example AGS-1433764), but the formation mechanisms for easterly waves in the eastern equatorial Pacific are unclear. OTREC campaign data would be used to determine the relative contributions of mechanical and thermodynamic mechanisms to the formation and intensification of these waves.OTREC would use the Gulfstream V (GV) research aircraft maintained by the Earth Observing Laboratory of the National Center for Atmospheric Research (NCAR) as its primary observing platform. The GV would be based in Costa Rica, allowing easy access to the east Pacific and southwest Caribbean. Observations of winds, pressure, temperature and humidity would be taken using dropsondes, which use essentially the same instrument package as standard weather balloons only dropped from the aircraft with a small parachute. Additional cloud measurements would be taken with a W-band radar mounted in a wing pod, and ground-based observations are also proposed for the campaign. A key objective of the campaign is to determine the convective mass flux associated with tropical convection, as this quantity plays a central role in the theory of convective cloud development which the campaign seeks to test.Tropical convection plays an important role in weather and climate, as it can produce extreme precipitation and develop into hurricanes with damaging impacts. It can also perturb atmospheric circulation in ways that affect weather and climate over long distances, as can be seen for example in the effects of El Nino events on the continental US. Thus research on tropical convection is of societal as well as scientific interest, as better understanding of tropical convection can lead to improvements in models used to forecast daily weather and anticipate climate variability and change. The campaign would also have broader impacts through the development of international scientific partnerships with researchers in Central America, and would provide a valuable educational opportunity for graduate students in atmospheric science.