Schlüsselwörter
(Englisch)
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water vapor; climate; remote sensing; microwave radiometry
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Forschungsprogramme
(Englisch)
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COST-Action ES0604 - Atmospheric Water Vapour in the Climate System
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Kurzbeschreibung
(Englisch)
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Atmospheric water plays a key role in climate. Water vapour and its condensed forms (liquid and ice) exert a profound influence on both, the incoming solar radiation and the outgoing thermal emission of the Earth. Accurate, height-resolved global-scale measurements of atmospheric humidity are difficult to obtain. In the troposphere, the water vapour distribution is extremely variable on almost all scales, and the change in concentration of five orders of magnitude from the ground to the stratosphere means there is no standard instrument that will measure everywhere. Our research aim is the improvement of the accuracy and availability of vertical profiles of atmospheric water vapour from the ground up to the mesosphere This aim shall be achieved by exploration, cross-validation, merging, and refinement of adequate measurement techniques and retrieval techniques. The vision for this project is to pave the way for the realisation of a water vapour profiling “super site” in Switzerland by combining available infrastructure at Bern (IAP, Univ. of Bern) and Payerne (MeteoSwiss).
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Partner und Internationale Organisationen
(Englisch)
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BE, BG, CH, CZ, DK, ES, FI, FR, GE, GR, HU, IE, IT, NO, PL, PT, SE, UK
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Abstract
(Englisch)
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Atmospheric water vapor plays a key role in weather aspects, the radiation balance, atmospheric chemistry and climate. However accurate, height-resolved measurements of water vapor over the whole altitude range, from the ground to the mesosphere (i.e. up to about 70 km altitude) are a challenging task for all available traditional and modern measurement techniques, as the water vapor mixing ratio extends over five orders of magnitude. The assessment of the strengths and weaknesses of different measurement techniques was a key aspect of the COST action 'Atmospheric Water Vapor in the Climate System'. The Swiss contribution to this project, called 'closing the water vapor gap', consist in assessing how water vapor profiles can be retrieved in the troposphere based on broad band measurements of spectral features in the microwave part of the spectrum. A microwave radiometer operated at the observatory for atmospheric research at Zimmerwald near Bern provided the needed data. It was shown that profiles of water vapor can be retrieved up to 8 km altitudes that compare well with balloon soundings. In contrast to the conventional soundings that provide two profiles per day, the remote sensing approach provides three profiles per hour. It further was shown how in situ information from other measuring techniques can be used to constrain optimal estimation retrievals of tropospheric water vapour retrievals from microwave radiometry. Another aspect was put on middle atmospheric water vapor, particularly on the analysis of dynamical phenomena that can be analyzed using water vapor as a tracer. Operating a microwave radiometer at Sodankylä in Finland it was possible to show that air in the polar vortex moves down at a speed of roughly 350meters per day based on measurements of the water vapor profile in the altitude range from 40 to 70km. Two short-term scientific missions were devoted to the possibility of retrieving horizontal wind in the middle atmosphere by a novel Doppler spectro-radiometer and on the determination of atmospheric trajectories to discriminate chemical from dynamical effects.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C08.0021
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