Intercomparison of atmospheric water vapour measurements at a Canadian High Arctic site

• Published in: Atmospheric Measurement Techniques
• Main Authors: Weaver, Dan, Strong, Kimberly, Schneider, Matthias, Rowe, Penny M., Sioris, Chris, Walker, Kaley A., Mariani, Zen, Uttal, Taneil, McElroy, C. Thomas, Vömel, Holger, Spassiani, Alessio, Drummond, James R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2017
• Subjects: article; Verlagsveröffentlichung; Arctic; Nunavut; Eureka; polar night
• Online Access: https://doi.org/10.5194/amt-10-2851-2017; https://noa.gwlb.de/receive/cop_mods_00009417; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00009374/amt-10-2851-2017.pdf; https://amt.copernicus.org/articles/10/2851/2017/amt-10-2851-2017.pdf

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).