Satellite TV-based Ozone and OH Observations using Radiometic Measurements (STO3RM)

这项概念验证研究的目的是确定新的遥感观测的可行性，这种观测将首次在短时间尺度上捕捉地球平流层、中间层和较低热层的化学变化，而这些变化是无法使用其他技术测量的。这样的观测将填补我们在理解太阳可变性与空间天气、大气化学和全球气候系统之间联系方面的主要差距。政府间气候变化专门委员会第五次评估报告(IPCC AR5)强调了该项目所针对领域的重要性，该报告指出，需要“评估气候变化对大气辐射强迫的影响--以及中间层在大气辐射强迫中的作用”。臭氧和羟基自由基是中上层大气中的重要痕量气体，对太阳强迫以及在高纬度与空间天气有关的地磁活动作出强烈反应。来自太空的高能粒子在地球磁场的引导下进入高纬度的大气层。关于这种高能粒子沉淀的重要问题仍然没有解决。这些变化包括中上层大气中的主要化学变化是什么，以及这些变化是如何与下面的大气层耦合的？在地磁风暴之后，高能电子沉淀(EEP)进入极地中间大气，引起电离反应，产生奇数氮和奇数氢物种，特别是OH。这些活性化学物质参与了臭氧的短期和长期催化破坏，改变了大气的辐射和热结构，影响到地球表面的温度。EEP非常频繁地发生，可能比强大的太阳质子风暴的脉冲但高度零星和已被充分研究的影响对大气产生更重大的影响。由于在20-100公里的高度测量迅速演变的大气化学成分，特别是臭氧和氢氧化物，一直很难估计EEP对大气的影响。由于微波电子技术的显著进步，商业卫星电视广播成为可能，使从地球静止轨道发射的36000公里以上的微弱信号能够通过廉价的屋顶碟子接收。我们建议在地面微波辐射计中采用高灵敏度的Ku波段卫星接收器技术来测量臭氧和OH。大气的微波光谱包含了来自11.072 GHz发射线和13.44GHz OH发射线的臭氧信息。Ku波段微波辐射测量将使用灵敏的外差探测技术与高分辨率射频分析相结合，对这些大气信号进行精确、定量的表征。我们将使用基于计算机的算法来研究如何将接收器灵敏度提高十倍，以实现对臭氧和OH的空间和时间分布的详细测量。拟议的仪器将是坚固的、半自主的，并连续进行观测，这些观测非常适用于EEP、大气动力学、行星尺度环流、化学输送以及这些过程在全球气候模式中的表示，最终导致数值天气预报的进展。它们将为日益稀疏的卫星测量提供一种低成本、可靠的替代办法，延长长期数据记录，并为校准和验证科学卫星数据提供“地面真实”数据。这项工作涉及NERC的三个研究主题(大气物理和化学；气候和气候变化；工具、技术和方法)，并将建立英国在微波遥感和大气信息检索方面的专业知识。

The aim of this proof-of-concept study is to determine the feasibility of new remote sensing observations that will capture, for the first time, detailed changes in the chemistry of the Earth's stratosphere, mesosphere, and lower thermosphere on short timescales that cannot be measured using other techniques. Such observations would address major gaps in our understanding of the links between solar variability & space weather, atmospheric chemistry, and the global climate system. The importance of the areas targeted by this project are highlighted by the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5) which states the need to 'assess climate change impact on - and the role of the mesosphere in radiative forcing of the atmosphere'.Ozone and hydroxyl radical (OH) are important trace gases in the middle and upper atmosphere that respond strongly to solar forcing and, at high latitudes, geomagnetic activity associated with space weather. Energetic particles from space are guided by the Earth's magnetic field into the atmosphere at high latitudes. Important questions about this energetic particle precipitation remain unresolved. These include what are the key chemical changes in the middle and upper atmosphere and how are these changes are coupled to the atmospheric layers below? Following geomagnetic storms, energetic electron precipitation (EEP) into the polar middle atmosphere causes ionisation reactions that generate odd nitrogen and odd hydrogen species, in particular OH. These reactive chemicals take part in both short-duration and long-term catalytic destruction of ozone that modifies the radiative and thermal structure of the atmosphere, affecting temperatures down to the Earth's surface. EEP occurs very frequently and potentially has a more significant impact on the atmosphere than the impulsive but highly sporadic and well-studied effects of powerful solar proton storms. It has been difficult to estimate the effect of EEP on the atmosphere because of the challenge of making measurements of rapidly-evolving atmospheric chemical composition, in particular ozone and OH, at altitudes of 20-100 km.Commercial satellite TV broadcasting is possible due to remarkable advances in microwave electronics, enabling weak signals transmitted over 36,000 km from geostationary orbit to be received by inexpensive rooftop dishes. We propose incorporating the highly-sensitive Ku-band satellite receiver technology in ground-based microwave radiometers to measure ozone and OH. The microwave spectrum of the atmosphere contains information about ozone from an emission line at 11.072 GHz and from OH at 13.44 GHz. Ku-band microwave radiometry will allow precise, quantitative characterisation of these atmospheric signals using the sensitive heterodyne detection technique combined with high-resolution radiofrequency analysis. We will use computer-based algorithms to investigate how ten-fold improvements in receiver sensitivity will allow detailed measurements of the spatial and temporal distributions of ozone and OH. The proposed instruments would be robust, semi-autonomous, and operate continuously making observations that are highly applicable to studies of EEP, atmospheric dynamics, planetary scale circulation, chemical transport, and the representation of these processes in global climate models, ultimately leading to advances in numerical weather prediction. They would provide a low cost, reliable alternative to increasingly sparse satellite measurements, extending long-term data records and also providing "ground truth" data for calibrating and validating scientific satellite data. The work is relevant to three NERC research subjects (Atmospheric physics and chemistry; Climate and climate change; Tools, technology & methods) and will build UK expertise in microwave remote sensing and atmospheric information retrieval.