The Application of Millimeter Wave Spectroscopy to Ground-Based Remote Sensing of the Atmosphere.

摘要

A new ground-based millimeter wave radiometer, SP´EIR, was designed as part of an observation system to detect and monitor ozone-related trace gases in the Arctic stratosphere. SP´EIR is designed to operate in the frequency range 265-280 GHz and measure the atmospheric spectra of ozone, nitrous oxide, nitric acid, and chlorine monoxide, from which vertical profiles of the gas concentrations can be retrieved. The observation system was characterised and simulated to determine its capability while operating at its intended location at Eureka, Nunavut (80°N). The altitude ranges and resolution of the retrieved profiles were determined, as well as the most significant sources of error in the profile of each gas. Optimal estimation statistics were compared to inversions of 500 simulated spectra. The results are in good agreement but showed that nonlinearities in the forward model, if not accounted for, can cause errors of 5- 10% when constructing climatologies or analyzing trends with the trace gas profiles. A sensitivity study was performed to quantify the effects that uncertainties in the spectral parameters of molecules have on ground-based measurements at 265-280 GHz, and recommendations are made for new laboratory measurements.;An inversion scheme was created to retrieve ozone profiles from measurements made by KIMRA (Kiruna Microwave Radiometer) and MIRA 2 (Millimeter Wave Radiometer 2), two ground-based millimeter wave radiometers in Kiruna, Sweden (68°N). The resulting profiles in winter/spring 2012/2013 were compared to each other, and to those from ozonesondes and the satellite instrument Aura MLS (Microwave Limb Sounder). The Kiruna instruments are biased low compared to the ozonesondes and generally agree with MLS. A significant oscillatory bias was found in KIMRA profiles and is attributed to standing wave features in the spectral measurements. Winter-time KIMRA ozone from 2008-2013 was used to investigate the natural variability of ozone above Kiruna. A persistent local minimum at approximately 35 km altitude is observed in winter-time ozone profiles and may be due to an effect of the polar vortex edge.