Interannual variability of winter-time O3 above Kiruna and a comparison of ground-based radiometer measurements in winter 2012/13

The Kiruna Microwave Radiometer (KIMRA) and the Millimetre-wave Radiometer (MIRA 2) are ground-based radiometers for atmospheric research currently operating in Kiruna, Sweden (68N, 20E). Each instrument measures radiation emitted by molecules in the atmosphere while they change their rotational state. These measured spectra were used to retrieve profiles of O3 concentrations in the stratosphere with a resolution of at best 7 km altitude. KIMRA and MIRA 2 offer the advantage of 24-hour measurements every day as the rotational transitions do not rely on sunlight. Due to the movement of the Arctic winter vortex passing overhead, measurements from Kiruna can sample air masses that both lie within and outside of the vortex, depending on the location of the edge of the vortex at a given time. This allows the examination of the gradient in O3 concentrations across the vortex edge but also the evolution of chemical ozone depletion inside the vortex. These measurements of the Arctic stratosphere are essential to monitoring and understanding the changes in Arctic O3 and its relationship with an evolving climate. KIMRA has been operating in Kiruna since 2002, and since the installation of MIRA 2 in November 2012 they have been making simultaneous measurements of O3, providing an excellent opportunity for a comparison. In this contribution I will present the results of a new inversion scheme applied to the data from KIMRA and MIRA 2, which enables the retrieval of atmospheric O3 profiles between approximately 15 - 65 km altitude. I will focus on a comparison of the results from KIMRA and MIRA 2 during winter 2012/13 and present the interannual winter-time variability of O3 above Kiruna over the last several years using the data from KIMRA.