Winds, waves, clouds & meteors in the mesosphere

风、浪、云

• 批准号: NE/E007384/1
• 负责人: Nicholas John Mitchell
• 金额: $ 42.59万
• 依托单位: University of Bath
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE007384%2F1
• 关键词: Winds; waves; clouds; meteors; mesosphere

The mesosphere is that part of the atmosphere at heights of about 50 to 100 km. Unlike the lower atmosphere, the general circulation of the mesosphere is powered, or 'driven' by atmospheric waves. These waves are generated in the lower atmosphere, from where they ascend into the mesosphere and break, rather like waves breaking on a beach. The breaking of these waves transfers energy and momentum into the mesosphere and drives a unique atmospheric circulation. In this circulation, air rises over the summer polar regions of the Earth, crosses the equator and then converges and descends over the opposite, winter, pole. The entire descending air of the mesosphere eventually ends up in the stratosphere, carrying with it chemicals and 'smoke' particles deposited by meteors - thus connecting the mesosphere very directly to the underlying stratosphere and troposphere. The 'meteor smoke' appears to act as the nuclei on which condense the ice crystals of ghostly high-altitude summertime polar mesospheric clouds (also known as noctilucent clouds). However, the clouds also require very cold temperatures of below 150 K (- 123 degrees C) in order to form. These low temperatures are only achieved as a result of the cooling of the air as it rises over the summer polar region in the wave-driven circulation. Larger-scale waves and atmospheric tides then modulate this circulation and so modulate the occurrence of the clouds. This means that winds, waves, polar mesospheric clouds and meteors are all intimately connected, and that attempts to understand one mean understanding the others. This project will use sophisticated meteor radars and airglow cameras to investigate the waves and tides of the mesosphere and to study how it couples to the underlying layers of the atmosphere. The cameras, technically 'airglow imagers', record the emissions from faintly glowing layers in the mesosphere. Bright ripple patterns in these layers reveal the presence of atmospheric waves. The cameras are operated by Utah State University and so our project is a trans-Atlantic collaboration. The meteor radars will measure the drifting of meteors carried by the flow and so reveal the winds, large-scale waves and tides of the mesosphere. The radars will also measure the flux of meteors into the atmosphere and can even measure the temperature of the atmosphere. Our goal is to discover how the large-scale waves and tides interact with the small-scale waves responsible for driving the circulation. Do these waves modulate the wave driving process, and if so how? These observations will be carried out at two very different sites. One is Rothera in the Antarctic and the other is Bear Lake in the USA. The contrasting behaviour of the atmosphere over these two site will help reveal how the polar atmosphere differs from elsewhere on the Earth. Our results will be used by colleagues at University College London who are developing a mathematical model of the atmosphere. We will make collaborative measurements with the NASA AIM (Aeronomy of Ice in the Mesosphere) satellite to study polar mesospheric clouds over the Antarctic and to investigate how waves and tides modify the occurrence, brightness and variability of these mysterious clouds. This satellite is due to launch in late 2006. We will also work in a collaborative project with groups from the USA, Argentina and Canada to install a new type of meteor radar in Argentina. This new radar will be optimised to directly measure the wave driving of the mesosphere. Finally, we will compare our measurements made in the Antarctic to measurements made by an identical radar at exactly the same latitude in the Arctic. These measurements will help reveal how and why the mesosphere differ over the two polar regions.

中间层是大气的一部分，高度约为50至100公里。与低层大气不同，中间层的环流是由大气波驱动的。这些波是在低层大气中产生的，从那里它们上升到中间层并破碎，就像海浪在海滩上破碎一样。这些波的破裂将能量和动量转移到中间层，并驱动一种独特的大气环流。在这种环流中，空气在地球的夏季极地地区上升，穿过赤道，然后在相反的冬季极地聚集并下降。中间层的整个下降空气最终到达平流层，携带着由流星沉积的化学物质和“烟雾”颗粒，从而将中间层非常直接地连接到下层的平流层和对流层。“流星烟雾”似乎扮演着核的角色，在核上凝结着阴森的高空极地中间层云（也被称为夜光云）的冰晶。然而，云也需要非常低的温度，低于150 K（- 123摄氏度）才能形成。这些低温只是由于空气在夏季极地地区的波浪驱动环流中上升而冷却的结果。更大规模的波浪和大气潮汐调节了这种环流，从而调节了云的出现。这意味着风、波浪、极地中间层云和流星都是密切相关的，试图理解其中一个意味着理解其他的。这个项目将使用复杂的流星雷达和气辉相机来调查中间层的波浪和潮汐，并研究它是如何与底层大气耦合的。这些相机，技术上称为“气辉成像仪”，记录中间层中微弱发光层的辐射。这些层中明亮的波纹图案揭示了大气波的存在。摄像机是由犹他州立大学操作的，所以我们的项目是跨大西洋合作的。流星雷达将测量由气流携带的流星的漂移，从而揭示中间层的风、大规模波浪和潮汐。这些雷达还将测量进入大气层的流星流量，甚至可以测量大气层的温度。我们的目标是发现大尺度波浪和潮汐如何与驱动环流的小尺度波浪相互作用。这些波浪是否调节了波浪的驱动过程，如果是，又是如何调节的？这些观测将在两个非常不同的地点进行。一个是南极的罗瑟拉，另一个是美国的熊湖。这两个地点大气的对比行为将有助于揭示极地大气与地球上其他地方的不同之处。我们的研究结果将被伦敦大学学院的同事使用，他们正在开发一个大气的数学模型。我们将与美国国家航空航天局（NASA）的AIM（中间层冰航空学）卫星合作测量，研究南极上空的极地中间层云，并调查波浪和潮汐如何改变这些神秘云的出现、亮度和变化。这颗卫星定于2006年底发射。我们还将与来自美国、阿根廷和加拿大的团体合作，在阿根廷安装一种新型流星雷达。这种新雷达将经过优化，可以直接测量中间层的波驱动。最后，我们将把我们在南极的测量结果与在北极完全相同纬度的同一雷达的测量结果进行比较。这些测量将有助于揭示两极地区的中间层是如何以及为什么不同的。

项目成果

Evaluation of estimated mesospheric temperatures from 11-year meteor radar datasets of King Sejong Station (62°S, 59°W) and Esrange (68°N, 21°E)

• DOI: 10.1016/j.jastp.2019.105148
• 发表时间: 2019-12
• 期刊: Journal of Atmospheric and Solar-Terrestrial Physics
• 影响因子: 1.9
• 作者: H. Kam;Y. Kim;N. Mitchell;Jeong‐han Kim;Changsup Lee

Interannual variability of mesopause zonal winds over Ascension Island: Coupling to the stratospheric QBO

阿森松岛中层顶纬向风的年际变化：与平流层 QBO 的耦合

• DOI: 10.1002/2013jd020203
• 发表时间: 2013
• 期刊: Atmospheres
• 作者: De Wit R

The 5-day wave in the Arctic and Antarctic mesosphere and lower thermosphere

• DOI: 10.1029/2009jd012545
• 发表时间: 2010-01
• 期刊: Journal of Geophysical Research
• 作者: K. Day;N. Mitchell

Southern Argentina Agile Meteor Radar: System design and initial measurements of large-scale winds and tides

• DOI: 10.1029/2010jd013850
• 发表时间: 2010-09
• 期刊: Journal of Geophysical Research
• 作者: D. Fritts;D. Janches;H. Iimura;W. Hocking;N. Mitchell;R. Stockwell;B. Fuller;B. Vandepeer;J. Hormaechea;C. Brunini;H. Levato

Comparison of Mesospheric Winds From a High-Altitude Meteorological Analysis System and Meteor Radar Observations During the Boreal Winters of 2009-2010 and 2012-2013

• DOI: 10.1016/j.jastp.2016.12.007
• 发表时间: 2017-02
• 期刊: Journal of Atmospheric and Solar-Terrestrial Physics
• 影响因子: 1.9
• 作者: J. McCormack;K. Hoppel;D. Kuhl;R. D. Wit;G. Stober;P. Espy;N. Baker;P. Brown;D. Fritts