Numéro |
J. Phys. IV France
Volume 139, December 2006
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Page(s) | 37 - 61 | |
DOI | https://doi.org/10.1051/jp4:2006139005 |
C. Boutron
J. Phys. IV France 139 (2006) 37-61
DOI: 10.1051/jp4:2006139005
Water in the Earth's atmosphere
M. Quante and V. MatthiasGKSS Research Center, Institute for Coastal Research, 21502 Geesthacht, Germany
e-mail: markus.quante@gkss.de
(Published online: 9 January 2007)
Abstract
Water is the key to our existence on this planet and it is involved
in nearly all biological, geological, and chemical processes. Life
on Earth depends very much on the remarkable properties of water.
The availability of freshwater is for many regions one of the key
concerns in connection with global climate change. The atmosphere
contains only about 0.001% of the water available on our planet.
Despite this small amount its horizontal and vertical distribution
plays a key role in the global water cycle and the Earth's climate.
The atmosphere has direct connections to most of the other
reservoirs and steers the redistribution of water between them with
an average turnover time of about 10 days. Evaporation over the
oceans exceeds precipitation and over land evapotranspiration
amounts only to 2/3 of the precipitation reaching the ground.
Consequently, there is a net flux of water from the oceans towards
the continents, of course via the atmosphere, which has the largest
overall volume of fluxes. Water is present in the atmosphere as
solid, liquid, or gas. Water vapour is the most important greenhouse
gas in the atmosphere and, in addition, changes of water phase and
cloud-radiation interaction contribute strongly to the global energy
cycle. Water is also a physically and chemically integral part of
other biogeochemical cycles. Although there have been large efforts
and improvements in recent years, uncertainties in quantifying the
components of the atmospheric water cycle still exist. Observational
capabilities on the global scale are not satisfactory at present,
but the advent of new satellites devoted to the global observation
of precipitation and cloud systems along with dedicated modelling
projects certainly will improve the situation. Progress is urgently
needed to adequately contribute to the answer of one of the central
questions in the context of global warming: Is the hydrological
cycle accelerating?
© EDP Sciences 2006