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We report on the wind radiometer WIRA, a new ground-based microwave Doppler-spectro-radiometer  specifically designed for the measurement of middle-atmospheric horizontal wind by observing ozone  emission spectra at 142.17504 GHz. Currently, wind speeds in five levels between 30 and  79 km can be retrieved which makes WIRA the first instrument able to continuously measure  horizontal wind in this altitude range. For an integration time of one day the measurement error  on each level lies at around 25 m s<sup>−1</sup>. With a planned upgrade this value is expected  to be reduced by a factor of 2 in the near future. On the altitude levels where our measurement  can be compared to wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF)  very good agreement in the long-term statistics as well as in short time structures with  a duration of a few days has been found.    WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform  spectrometer for the data acquisition. A big advantage of the radiometric approach is that such  instruments can also operate under adverse weather conditions and thus provide a continuous time  series for the given location. The optics enables the instrument to scan a wide range of azimuth  angles including the directions east, west, north, and south for zonal and meridional wind  measurements. The design of the radiometer is fairly compact and its calibration does not rely on  liquid nitrogen which makes it transportable and suitable for campaign use. WIRA is conceived in  a way that it can be operated remotely and does hardly require any maintenance.    In the present paper, a description of the instrument is given, and the techniques used for the  wind retrieval based on the determination of the Doppler shift of the measured atmospheric ozone  emission spectra are outlined. Their reliability was tested using Monte Carlo  simulations. Finally, a time series of 11 months of zonal wind measurements over Bern  (46°57′ N, 7°26′ E) is presented and compared to ECMWF wind data

First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer