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

[摘要] Stratospheric ozone is of major interest as it absorbs most harmful UVradiation from the sun, allowing life on Earth. Ground-based microwave remotesensing is the only method that allows for the measurement of ozone profiles up to themesopause, over 24 hours and under different weather conditions with high timeresolution.

In this paper a novel ground-based microwave radiometer is presented. It iscalled GROMOS-C (GRound based Ozone MOnitoring System for Campaigns), and ithas been designed to measure the vertical profile of ozone distribution inthe middle atmosphere by observing ozone emission spectra at a frequency of110.836 GHz. The instrument is designed in a compact way which makes ittransportable and suitable for outdoor use in campaigns, an advantageousfeature that is lacking in present day ozone radiometers. It is operatedthrough remote control.

GROMOS-C is a total power radiometer which uses a pre-amplified heterodynereceiver, and a digital fast Fourier transform spectrometer for the spectralanalysis. Among its main new features, the incorporation ofdifferent calibration loads stands out; this includes a noise diode and a new type ofblackbody target specifically designed for this instrument, based on Peltierelements. The calibration scheme does not depend on the use of liquidnitrogen; therefore GROMOS-C can be operated at remote places with nomaintenance requirements. In addition, the instrument can be switched infrequency to observe the CO line at 115 GHz.

A description of the main characteristics of GROMOS-C is included in thispaper, as well as the results of a first campaign at the High AltitudeResearch Station at Jungfraujoch (HFSJ), Switzerland. The validation isperformed by comparison of the retrieved profiles against equivalent profilesfrom MLS (Microwave Limb Sounding) satellite data, ECMWF (European Centre for Medium-Range Weather Forecast) model data, as well as our nearby NDACC (Network for the Detection ofAtmospheric Composition Change) ozoneradiometer measuring at Bern.

[学科分类] 几何与拓扑