GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns

Fernandez, Susana; Murk, Axel; Kämpfer, Niklaus

doi:10.5194/amt-8-2649-2015

Cited by 27 publications

(22 citation statements)

References 30 publications

(29 reference statements)

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“…We have a blackbody target cooled with Peltier elements to 240 K used as the default cold load, and a similar load heated with resistors to 350 K used as default hot load; additionally we have a noise diode used as super-hot load adding circa 300 K, and tipping curves are performed regularly in order to use the zenith sky as an alternative cold load. In Fernandez et al (2015) spectra calibrated with different methods were compared. In this section, we compare the influence of these calibration methods on the retrievals.…”

Section: Comparing the Calibration Methodsmentioning

confidence: 99%

“…A detailed description of the instrument and of the ozone profiles retrieval method can be found in Fernandez et al (2015). The main characteristics of GROMOS-C are summarized in Table 1.…”

Section: Gromos-cmentioning

confidence: 99%

“…3 of Fernandez et al, 2015). Water vapour inhomogeneities in the troposphere are difficult to model and therefore it is important to correct the measured spectra for the tropospheric effect.…”

Section: Ozone Retrievalsmentioning

confidence: 99%

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Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

et al. 2016

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Abstract. Ozone performs a key role in the middle atmosphere and its monitoring is thus necessary.At the Institute of Applied Physics of the University of Bern, Switzerland, we built a new ground-based microwave radiometer, GROMOS-C (GRound based Ozone MOnitoring System for Campaigns). It has a compact design and can be operated remotely with very little maintenance requirements, being therefore suitable for remote deployments. It has been conceived to measure the vertical distribution of ozone in the middle atmosphere, by observing pressure-broadened emission spectra at a frequency of 110.836 GHz. In addition, meridional and zonal wind profiles can be retrieved, based on the Doppler shift of the ozone line measured in the four directions of observation (north, east, south and west).In June 2014 the radiometer was installed at the Maïdo observatory, on Réunion island (21.2 • S, 55.5 • E). Highresolution ozone spectra were recorded continuously over 7 months. Vertical profiles of ozone have been retrieved through an optimal estimation inversion process, using the Atmospheric Radiative Transfer Simulator ARTS2 as the forward model. The validation is performed against ozone profiles from the Microwave Limb Sounder (MLS) on the Aura satellite, the ozone lidar located at the observatory and with ozone profiles from weekly radiosondes. Zonal and meridional winds retrieved from GROMOS-C data are validated against another wind radiometer located in situ, WIRA. In addition, we compare both ozone and winds with ECMWF (European Centre for Medium-Range Weather Forecasts) model data. Results show that GROMOS-C provides reliable ozone profiles between 30 and 0.02 hPa. The comparison with lidar profiles shows a very good agreement at all levels. The accordance with the MLS data set is within 5 % for pressure levels between 25 and 0.2 hPa. GROMOS-C's wind profiles are in good agreement with the observations by WIRA and with the model data, differences are below 5 m s −1 for both.

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Section: Comparing the Calibration Methodsmentioning

confidence: 99%

“…A detailed description of the instrument and of the ozone profiles retrieval method can be found in Fernandez et al (2015). The main characteristics of GROMOS-C are summarized in Table 1.…”

Section: Gromos-cmentioning

confidence: 99%

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Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

et al. 2016

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“…Lobsiger (1987) developed a load-switching technique where the sky, a liquid nitrogen cold load at 80 K, and an ambient load were measured during each observation cycle; several 142.2 GHz instruments use variants of this method (Hartogh et al, 1991;Peter et al, 1998;Hocke et al, 2007;Palm et al, 2010;Moreira et al, 2015). Recently the technique has been developed further by implementing a noise diode and a Peltier cooled load (Fernandez et al, 2015). Parrish et al (1988Parrish et al ( , 1992) developed a sky-switching procedure at 110.8 GHz where the reference zenith beam passes a lossy window at a Brewster angle to compensate for the higher intensity in the signal beam.…”

Section: P Forkman Et Al: Double-sideband 3 MM Receiver Systemmentioning

confidence: 99%

A compact receiver system for simultaneous measurements of mesospheric CO and O<sub>3</sub>

Forkman¹,

Christensen²,

Eriksson³

et al. 2016

Geosci. Instrum. Method. Data Syst.

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Abstract. During the last decades, ground-based microwave radiometry has matured into an established remote sensing technique for measuring vertical profiles of a number of gases in the stratosphere and the mesosphere. Microwave radiometry is the only ground-based technique that can provide vertical profiles of gases in the upper stratosphere and mesosphere both day and night, and even during cloudy conditions. Except for microwave instruments placed at high-altitude sites, or at sites with dry atmospheric conditions, only molecules with significant emission lines below 150 GHz, such as CO, H 2 O, and O 3 , can be observed. Vertical profiles of these molecules can give important information about chemistry and dynamics in the middle atmosphere.Today these measurements are performed at relatively few sites; more simple and reliable instrument solutions are required to make the measurement technique more widely spread. This need is urgent today as the number of satellite sensors observing the middle atmosphere is about to decrease drastically. In this study a compact double-sideband frequency-switched radiometer system for simultaneous observations of mesospheric CO at 115.27 GHz and O 3 at 110.84 GHz is presented.The radiometer, its calibration scheme, and its observation method are presented. The retrieval procedure, including compensation of the different tropospheric attenuations at the two frequencies and error characterization, are also described. The first measurement series from October 2014 until April 2015 taken at the Onsala Space Observatory, OSO (57 • N, 12 • E), is analysed. The retrieved vertical profiles are compared with co-located CO and O 3 data from the MLS instrument on the Aura satellite. The data sets from the instruments agree well with each other. The main differences are the higher OSO volume mixing ratios of O 3 in the upper mesosphere during the winter nights and the higher OSO volume mixing ratios of CO in the mesosphere during the winter. The low bias of mesospheric winter values of CO from MLS compared to ground-based instruments was reported earlier.

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“…The opacity itself can be estimated in different ways. We are applying the same technique as Fernandez et al (2015a) and use the brightness temperature at the wings of the measured spectra, as far away from the ozone rotational transition resonance frequency as possible. In 10 practice we use an average over 10 MHz at the left wing of the spectrum measured by the second spectrometer channel (USRP channel B) depicted in Fig.…”

Section: Tropospheric Correctionmentioning

confidence: 99%

WIRA-C: A compact 142-GHz-radiometer for continuous middle-atmospheric wind measurements

Hagen¹,

Murk²,

Rüfenacht³

et al. 2018

Preprint

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Abstract. Ground-based microwave wind radiometry provides a method to measure horizontal wind speeds at altitudes between 35 and 75 km as it has been shown by various previous studies. No other method is capable of continuously delivering wind measurements in this altitude region.In this paper, we present the WIRA-C (WInd Radiometer for Campaigns) instrument that observes the 142.17504 GHz rotational transition line of ozone with a high spectral resolution using a low noise single side band heterodyne receiver. 5Because the emitting molecules are drifting with the wind, the line is Doppler shifted. Together with the pressure broadening effect, this allows the retrieval of altitude resolved wind profiles.The novel WIRA-C instrument represents the newest development in microwave wind radiometry. The main improvements include the compact structure, lower noise and an advanced retrieval setup. This paper describes the instrument and the data processing with a focus on the retrieval that takes into account a three-dimensional atmosphere and has never been used in 10 ground-based radiometry before. The retrieval yields profiles of horizontal wind speeds with a 12 hour time resolution and a vertical resolution of 10 km for zonal and 10 to 15 km for meridional wind speeds. We give an error estimate that accounts for the thermal noise on the measured spectra and additionally estimate systematic errors using Monte Carlo methods.WIRA-C has been continuously measuring horizontal wind speeds since one year at the Maïdo observatory on La Réu-nion Island (21.4• S, 55.9• E). We present the time series of this campaign and compare our measurements to model data

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GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns

Cited by 27 publications

References 30 publications

Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

A compact receiver system for simultaneous measurements of mesospheric CO and O<sub>3</sub>

WIRA-C: A compact 142-GHz-radiometer for continuous middle-atmospheric wind measurements

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GROMOS-C, a novel ground-based microwave radiometer for ozone measurement campaigns

Cited by 27 publications

References 30 publications

Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

Results from the validation campaign of the ozone radiometer GROMOS-C at the NDACC station of Réunion island

A compact receiver system for simultaneous measurements of mesospheric CO and O&lt;sub&gt;3&lt;/sub&gt;

WIRA-C: A compact 142-GHz-radiometer for continuous middle-atmospheric wind measurements

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A compact receiver system for simultaneous measurements of mesospheric CO and O<sub>3</sub>