1Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden
2Institute of Environmental Physics, University of Bremen, Bremen, Germany
3Met Office Hadley Centre, Exeter, UK
4Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK-ASF), Karlsruhe, Germany
5Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
6The Swedish Institute of Space Physics, Kiruna, Sweden
7Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
8Atmosphere and Ocean Research Institute, University of Tokyo, Tokyo, Japan
Received: 25 Jul 2012 – Discussion started: 20 Aug 2012
Abstract. We compare measurements of integrated water vapour (IWV) over a subarctic site (Kiruna, Northern Sweden) from five different sensors and retrieval methods: Radiosondes, Global Positioning System (GPS), ground-based Fourier-transform infrared (FTIR) spectrometer, ground-based microwave radiometer, and satellite-based microwave radiometer (AMSU-B). Additionally, we compare also to ERA-Interim model reanalysis data. GPS-based IWV data have the highest temporal coverage and resolution and are chosen as reference data set. All datasets agree reasonably well, but the ground-based microwave instrument only if the data are cloud-filtered. We also address two issues that are general for such intercomparison studies, the impact of different lower altitude limits for the IWV integration, and the impact of representativeness error. We develop methods for correcting for the former, and estimating the random error contribution of the latter. A literature survey reveals that reported systematic differences between different techniques are study-dependent and show no overall consistent pattern. Further improving the absolute accuracy of IWV measurements and providing climate-quality time series therefore remain challenging problems.
Revised: 06 Nov 2012 – Accepted: 13 Nov 2012 – Published: 20 Nov 2012
Buehler, S. A., Östman, S., Melsheimer, C., Holl, G., Eliasson, S., John, V. O., Blumenstock, T., Hase, F., Elgered, G., Raffalski, U., Nasuno, T., Satoh, M., Milz, M., and Mendrok, J.: A multi-instrument comparison of integrated water vapour measurements at a high latitude site, Atmos. Chem. Phys., 12, 10925-10943, doi:10.5194/acp-12-10925-2012, 2012.