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

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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.