Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 10 2008 10.5194/acp-8-2643-2008 http://www.atmos-chem-phys.net/8/2643/2008/ http://www.atmos-chem-phys.net/8/2643/2008/acp-8-2643-2008.html http://www.atmos-chem-phys.net/8/2643/2008/acp-8-2643-2008.pdf 2643 2655 2008-05-20 Variability of subtropical upper tropospheric humidity J.-M. Ryoo D. W. Waugh waugh@jhu.edu A. Gettelman Department of Earth and Planetary Science, Johns Hopkins University, Baltimore, MD, USA National Center for Atmospheric Research, Boulder, CO, USA Analysis of Atmospheric Infrared Sounder (AIRS) measurements for five years shows significant longitudinal variations in the winter subtropical upper tropospheric relative humidity (RH), not only in the climatological mean values but also in the local distributions and temporal variability. The largest climatological mean values occur over the central-eastern Pacific and Atlantic oceans, where there is also large day-to-day variability. 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