Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 21, 779-790, 2017
https://doi.org/10.5194/hess-21-779-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
08 Feb 2017
The residence time of water in the atmosphere revisited
Ruud J. van der Ent1 and Obbe A. Tuinenburg2 1Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands
2Department of Environmental Sciences, Copernicus Institute for Sustainable development, Utrecht University, Utrecht, the Netherlands
Abstract. This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9 ± 0.4 days (uncertainty given as 1 standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-T) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4–5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days less than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. In the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation, we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8–10-day traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view of the characteristics of the turnover of water in the atmosphere in time and space.

Citation: van der Ent, R. J. and Tuinenburg, O. A.: The residence time of water in the atmosphere revisited, Hydrol. Earth Syst. Sci., 21, 779-790, https://doi.org/10.5194/hess-21-779-2017, 2017.
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Short summary
This research seeks out to answer a fundamental question about the functioning of the water cycle in the atmosphere: how much time does a water particle spend in the atmosphere? Based on state-of-the-art data, we derive a global average residence time of water in the atmosphere of 8–10 days. We further show in this paper how the residence time of water varies in time and space. This serves to illustrate why it is so difficult to make weather predictions on timescales longer than a week.
This research seeks out to answer a fundamental question about the functioning of the water...
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