Abstract
Abstract. Water vapour is a critical component of the Earth system. Techniques to acquire and improve measurements of atmospheric water vapour and its isotopes are under active development. This work presents a detailed intercomparison of water vapour total column measurements taken between 2006 and 2014 at a Canadian High Arctic research site (Eureka, Nunavut). Instruments include radiosondes, sun photometers, a microwave radiometer, and emission and solar absorption Fourier transform infrared (FTIR) spectrometers. Close agreement is observed between all combination of datasets, with mean differences ≤ 1.0 kg m−2 and correlation coefficients ≥ 0.98. The one exception in the observed high correlation is the comparison between the microwave radiometer and a radiosonde product, which had a correlation coefficient of 0.92.A variety of biases affecting Eureka instruments are revealed and discussed. A subset of Eureka radiosonde measurements was processed by the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) for this study. Comparisons reveal a small dry bias in the standard radiosonde measurement water vapour total columns of approximately 4 %. A recently produced solar absorption FTIR spectrometer dataset resulting from the MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water) retrieval technique is shown to offer accurate measurements of water vapour total columns (e.g. average agreement within −5.2 % of GRUAN and −6.5 % of a co-located emission FTIR spectrometer). However, comparisons show a small wet bias of approximately 6 % at the high-latitude Eureka site. In addition, a new dataset derived from Atmospheric Emitted Radiance Interferometer (AERI) measurements is shown to provide accurate water vapour measurements (e.g. average agreement was within 4 % of GRUAN), which usefully enables measurements to be taken during day and night (especially valuable during polar night).
Highlights
Water vapour plays a significant role in the Earth’s atmosphere
This study compared High Arctic water vapour measurements taken by several different instruments located at Eureka, Nunavut
The accuracy of the MUSICA dataset derived from Eureka 125HR spectra is supported by comparisons with coincident measurements taken at Eureka
Summary
Water vapour plays a significant role in the Earth’s atmosphere. It is involved in driving atmospheric dynamics (Hwang and Frierson, 2010) and actively impacts atmospheric chemistry (Shindell, 2001). D. Weaver et al.: Intercomparison of atmospheric water vapour measurements inant effect on climate and radiative forcing (Soden et al, 2002; Dessler et al, 2008). Climate-change-induced shifts to the global hydrological cycle affect atmospheric transport processes, creating and intensifying droughts and flooding (Trenberth et al, 2013). Observations of the Arctic region are sparse and important for understanding how the planet’s atmosphere is changing (ACIA, 2005). This study compares measurements of atmospheric water vapour taken near Eureka, Nunavut, in the Canadian High Arctic
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