Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site
- 1Department of Physics, University of Toronto, Toronto, Ontario, Canada
- 2Institute of Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology, Karlsruhe, Germany
- 3NorthWest Research Associates, Redmond, Washington, USA
- 4Department of Physics, Universidad de Santiago de Chile, Santiago, Chile
- 5Department of Earth and Space Science and Engineering, York University, Toronto, Canada
- 6Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
- 7Cloud Physics and Severe Weather Research Section, Environment and Climate Change Canada, Toronto, Ontario, Canada
- 8Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
- 9Earth Observing Laboratory, National Center for Atmospheric Research, Boulder, Colorado, USA
- 10School of Civil Engineering, University of Queensland, Brisbane, Australia
- 11Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
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).