A ship-borne imager: determining mesospheric gravity wave activity above the ocean

重力波是大气中的浮力波。它们可以由各种来源产生，例如，流经山区的风或大型天气系统。当它们向上传播时，它们变得不稳定并破裂(类似于海滩上的波浪)，储存它们的能量和动量，推动大气中的环流和温度模式。高度在50公里到90公里之间的区域，也就是所谓的中间层，主要是重力波活动。为了在大气气候模型中准确地再现它们的影响，我们需要观察地球上所有地区的重力波(并确定它们的来源)。由于海洋占地球表面的70%，了解海洋上发生的重力波活动是至关重要的。传统上，卫星观测被用来获得对大气中重力波活动的全球估计，但它们有局限性，因为它们不能看到重力波的整个范围(全频谱)。这项提议旨在最终完成舰载成像仪的开发，该成像仪将允许在詹姆斯·克拉克·罗斯号穿越大西洋往返南极和英国时对中间层进行重力波测量。这些测量将提供一个独特的视角，了解重力波范围与卫星可以观测到的不同部分。船载成像仪将使用一种新的系统，由3个一度视野成像仪(辐射计)和船舶的俯仰和横摇扫描天空。成像器将在约90公里高度的一层气辉层中观测到重力波扰动。气辉是指大气中不同气体层发出的微弱光。当重力波穿过这个气辉层时，它们交替地压缩和稀疏它，导致气辉发射的变化。利用这些观测可以确定重力波的特征。我们建议利用船舶与陆地重力波源的隔离和船舶航线来进行案例研究，并考察对中层重力波场的两个影响：深海大天气系统和地形。

Gravity waves are buoyancy waves in the atmosphere. They can be produced from a variety of sources, e.g. wind flowing over mountains or large weather systems. As they propagate upwards they become unstable and break (similar to waves on a beach) depositing their energy and momentum, driving the circulation and temperature patterns in the atmosphere. The region between 50km and 90km in altitude, known as the mesosphere, is dominated by gravity wave activity. In order to accurately reproduce their effects in atmospheric climate models, we need to observe gravity waves (and identify their sources) from all areas of the planet. As the oceans make up 70% of the Earth's surface it is vitally important to understand the gravity wave activity that occurs over them. Traditionally satellite observations are used to obtain global estimates of gravity wave activity in the atmosphere but, they have limitations in that they cannot view the whole range (full spectrum) of gravity waves. This proposal looks to finalise development of a ship-borne imager that will allow gravity wave measurements of the mesosphere to be made from the R.R.S. James Clarke Ross as it traverses the Atlantic Ocean to and from the Antarctic and the U.K. These measurements will provide a unique insight into a different section of the gravity wave range to that which satellites can observe.The ship-borne imager will use a novel system of 3 one-degree field of view imagers (radiometers) and the pitch and roll of the ship to scan the sky. The imagers will be observing gravity wave perturbations in a layer of airglow at around 90km altitude. Airglow is the term given to the weak emission of light by different gas layers in the atmosphere. As gravity waves pass through this airglow layer they alternately compress and rarefy it, resulting in a variation in the airglow emissions. Using these observations it is possible to determine the characteristics of the gravity waves.We propose to exploit the ships isolation from land-based gravity wave sources and the ships itineraries to do case studies and examine two influences on the mesospheric gravity wave field: large weather systems in the deep ocean and topography.