An improved vertical correction method for the inter-comparison and inter-validation of integrated water vapour measurements
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Published:2022-10-10
Issue:19
Volume:15
Page:5643-5665
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Bock OlivierORCID, Bosser PierreORCID, Mears CarlORCID
Abstract
Abstract. Integrated water vapour (IWV) measurements from similar
or different techniques are often inter-compared for calibration and
validation purposes. Results are usually assessed in terms of bias
(difference of the means), standard deviation of the differences, and linear
fit slope and offset (intercept) estimates. When the instruments are located
at different elevations, a correction must be applied to account for the
vertical displacement between the sites. Empirical formulations are
traditionally used for this correction. In this paper we show that the
widely used correction model based on a standard, exponential, profile for
water vapour cannot properly correct the bias, slope, and offset parameters
simultaneously. Correcting the bias with this model degrades the slope and
offset estimates and vice versa. This paper proposes an improved correction
method that overcomes these limitations. It implements a multiple linear
regression method where the slope and offset parameters are provided from a
radiosonde climatology. It is able to predict monthly mean IWVs with a bias
smaller than 0.1 kg m−2 and a root-mean-square error smaller than 0.5 kg m−2 for height differences up to 500 m. The method is applied to the
inter-comparison of GPS IWV data in a tropical mountainous area and to the
inter-validation of GPS and satellite microwave radiometer data. This paper
also emphasizes the need for using a slope and offset regression method that
accounts for errors in both variables and for correctly specifying these
errors.
Funder
Centre National de la Recherche Scientifique
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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