Abstract
Measurements of low amounts of precipitable water vapor by millimeter wave spectroscopy: An intercomparison with radiosonde, Raman lidar, and Fourier transform infrared data
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy
Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy
Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy
Dipartimento di Ingegneria e Fisica dell'Ambiente, Università della Basilicata, Potenza, Italy
Istituto di Fisica Applicata “Nello Carrara,” CNR, Florence, Italy
Istituto di Fisica Applicata “Nello Carrara,” CNR, Florence, Italy
Dipartimento di Fisica, Università di Roma “La Sapienza,” Rome, Italy
Dipartimento di Fisica, Università di Roma “La Sapienza,” Rome, Italy
Istituto di Metodologie per l'Analisi Ambientale, CNR, Potenza, Italy
CETEMPS, Dipartimento di Fisica, Università di L'Aquila, L'Aquila, Italy
Department of Physics and Astronomy and Institute for Terrestrial and Planetary Atmospheres, State University of New York at Stony Brook, Stony Brook, New York, USA
Observations of very low amounts of precipitable water vapor (PWV) by means of the Ground-Based Millimeter wave Spectrometer
(GBMS) are discussed. Low amounts of column water vapor (between 0.5 and 4 mm) are typical of high mountain sites and polar
regions, especially during winter, and are difficult to measure accurately because of the lack of sensitivity of conventional
instruments to such low PWV contents. The technique used involves the measurement of atmospheric opacity in the range between
230 and 280 GHz with a spectral resolution of 4 GHz, followed by the conversion to precipitable water vapor using a linear
relationship. We present the intercomparison of this data set with simultaneous PWV observations obtained with Vaisala RS92k
radiosondes, a Raman lidar, and an IR Fourier transform spectrometer. These sets of measurements were carried out during the
primary field campaign of the Earth Cooling by Water vapor Radiation (ECOWAR) project which took place at Breuil-Cervinia
(45.9°N, 7.6°E, elevation 1990 m) and Plateau Rosa (45.9°N, 7.7°E, elevation 3490 m), Italy, from 3 to 16 March 2007. GBMS
PWV measurements show a good agreement with the other three data sets exhibiting a mean difference between observations of
9%. The considerable number of data points available for the GBMS versus lidar PWV correlation allows an additional analysis
which indicates negligible systematic differences between the two data sets.
Received 15 January 2008; accepted 29 May 2008; published 31 July 2008.
Citation: (2008), Measurements of low amounts of precipitable water vapor by millimeter wave spectroscopy: An intercomparison with radiosonde, Raman lidar, and Fourier transform infrared data, J. Geophys. Res., 113, D14314, doi:10.1029/2008JD009831.
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