Data were provided by J. Cappelen (Danish Meteorological Institute), D. Kiktev (Russian Hydrometeorological Institute), R. Ray (National Climatic Data Center), M. J. Salinger [NIWA New Zealand: Asia–Pacific network (APN) data], L. Vincent (Environment Canada), and P. Zhai (China Meteorological Administration). C. K. Folland provided useful comments. This work was supported by the U.K. Government Research Program and this paper is U.K. Crown Copyright.
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