Abstract. CO serves as a tracer for dynamics in the polar winter middle atmosphere. This work presents the retrieval and the characterization of ground-based CO measurements from the winters 2008/2009 and 2009/2010 by the Kiruna microwave radiometer KIMRA, located in northern Sweden (67.8 • N, 20.4 • E). Furthermore, the dataset is used for an extensive comparison to the recent satellite instruments MLS on Aura, ACE-FTS, and MIPAS on Envisat.The vmr profiles are retrieved using the optimal estimation approach. A detailed analysis of the averaging kernel functions is carried out, showing sensitivity of the measurements between 40 and 80 km altitude, a vertical resolution of 16 to 22 km, as well as a residual influence of the region up to 130 km altitude. An error assessment reveals a total error of the retrieved profile that increases with altitude and is approx. ±0.1 ppmv at 50 km altitude and ±3 ppmv at 80 km altitude. The main contributions to this total error arise from the measurement noise and the uncertainty of the used temperature profiles. The expected dynamical features of the polar winter middle atmosphere are qualitatively identified in the retrieved time series, but are not quantitatively analyzed here.The dense MLS dataset is used to investigate the influence of the collocation criteria on the satellite comparison, showing that relaxing the distance criterion causes a high bias for MLS. The comparison including the other instruments is difficult because of the small number of coincidences. However, Correspondence to: C. G. Hoffmann (christoph.hoffmann@iup.physik.unibremen.de) it suggests that there is a general agreement between KIMRA and the satellite instruments below 65 km altitude, but a high bias for KIMRA above this altitude. Furthermore, the shape of the KIMRA profile appears to be systematically different from the satellite profiles.

Abstract.This manuscript introduces the OZORAM ground-based millimeter wave radiometer. The instrument is deployed to the high Arctic (79 • N, 12 • E) for measurements of O 3 in the upper stratosphere and lower mesosphere.The publication describes the status of OZORAM in the end of 2010. OZORAM is able to provide profile information between 30 and 70 km altitude in time intervals of 1 h.To establish applications of the data and to investigate instrumental biases, the results from September 2008 till summer 2010 are compared to O 3 profiles derived from measurements of two instruments onboard polar orbiting satellites, MLS onboard EOS-AURA and SABER onboard TIMED. The agreement is within 10% in the middle and upper stratosphere and 30% in the lower mesosphere. The deviation shows systematic and oscillating features which are, however, constant during the period of comparison.The data set is therefore suitable for studies of mesospheric and stratospheric response to changes in dynamics or due to solar influences on climate.

Abstract. This paper presents the Alpine Radiometer Intercomparison at the Schneefernerhaus (ARIS), which took place in winter 2009 at the high altitude station at the Zugspitze, Germany (47.42 • N, 10.98 • E, 2650 m). This campaign was the first direct intercomparison between three new ground based 22 GHz water vapor radiometers for middle atmospheric profiling with the following instruments participating: MIRA 5 (Karlsruhe Institute of Technology), cWASPAM3 (Max Planck Institute for Solar System Research, Katlenburg-Lindau) and MIAWARA-C (Institute of Applied Physics, University of Bern). Even though the three radiometers all measure middle atmospheric water vapor using the same rotational transition line and similar fundamental set-ups, there are major differences between the front ends, the back ends, the calibration concepts and the profile retrieval. The spectrum comparison shows that all three radiometers measure spectra without severe baseline artifacts and that the measurements are in good general agreement. The measurement noise shows good agreement to the values theoretically expected from the radiometer noise formula. At the same time the comparison of the noise levels shows that there is room for instrumental and calibration improvement, emphasizing the importance of low elevation angles for the observation, a low receiver noise temperature and an efficient calibration scheme.The comparisons of the retrieved profiles show that the agreement between the profiles of MIAWARA-C and cWAS-PAM3 with the ones of MLS is better than 0.3 ppmv (6 %) at all altitudes. MIRA 5 has a dry bias of approximately 0.5 ppm (8 %) below 0.1 hPa with respect to all otherCorrespondence to: C. Straub (corinne.straub@iap.unibe.ch) instruments. The profiles of cWASPAM3 and MIAWARA-C could not be directly compared because the vertical region of overlap was too small. The comparison of the time series at different altitude levels show a similar evolution of the H 2 O volume mixing ratio (VMR) for the ground based instruments as well as the space borne sensor MLS.

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