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ATMOSPHERE-OCEAN INTERACTION
A strategic research project for the
Geophysical Institute, University of Bergen, with the following
objectives:
- A: To improve the understanding of key
atmosphere-ocean interaction processes at a fundamental level, to
provide a better basis for their representation in models, and to
enhance the accuracy of air-sea flux estimations;
- B:
To
investigate the roles of atmosphere-ocean interaction versus
horizontal atmospheric and oceanic mass and energy transports in
determining
interannual
climate
variability in the Atlantic-Arctic sector.
Project Summary
The project focuses on fundamental problems of atmosphere-ocean
interaction, and provides the opportunity to conduct the following
in-depth investigations within the following subprojects, during a 3-4
year time frame:
- Fundamental
studies of atmosphere-ocean flux processes,
comprising
theoretical and basic process modelling studies of the
air-sea interface;
- Interannual
variability of surface fluxes and ocean heat storage, using
atmosphere-ocean data sets from the past 50 years.
In order to make knowledge on these topics available to the scientific
and broader community at local, national/regional and international
levels, the project also incorporates:
3. Atmosphere-ocean
interaction seminars and information
exchange.
Background
It is necessary for a proper understanding of the global
atmosphere-ocean heat balance, and the spatial distribution and time
evolution of greenhouse gases, to understand quantitatively and on a
fundamental level the phenomena which influence air-sea fluxes of mass,
momentum, and energy. In particular, it is necessary to consider
as a whole the air-sea interface and the boundary layers on both sides
of it, and formulate in a self-consistent way the dynamics, and other
physical and biogeochemical processess, so that continuity is
maintained in the system description as one moves through the lower
atmosphere down into the ocean. In high latitude regions, gale
and storm force winds, are likely to contribute in a major way to the
fluxes, and the coupled system properties are not well understood under
such conditions. Steep and breaking waves are always present when
the wind is strong, and so it is necessary to perform studies that take
them into account. We will therefore study the hydrodynamical and
physical effects of wave
breaking, using suitable theoretical and ad hoc numerical models. The
most important of these effects will be incorporated into a
one-dimensional coupled model for the sea surface and atmospheric and
oceanic boundary layers. The results from the theoretical and model
investigations will be used to improve air-sea flux parameterisations
for momentum, energy, moisture, heat, and mass, in regional and
large-scale three-dimensional coupled models, and to identify critical
parameters to be measured during field investigations.
The global radiation balance requires poleward heat transports of order
1012-1015 watts (W). The relative contributions
from the atmosphere and oceans to this transport vary with latitude,
with ocean transports dominating in low latitudes and atmosphere
transports closer to the poles. The mean, seasonally-varying and
geographically-varying atmospheric heat and moisture transports to high
northern latitudes can be quantified from data and model-assisted
analyses, but the accuracy is limited. Long-term mean estimates of
oceanic heat transports through the ocean basins are also available,
for net transport to the Nordic Seas and the Arctic Ocean), but very
little is known about its interannual variability. Will perturbations
in the oceanic heat transport be compensated by atmospheric heat
transport as suggested by Bjerknes (1964)? Will
perturbations instead be compensated by changing albedo or radiation
temperature, e.g. via sea ice extent or cloudiness? In order to
address these fundamental questions, which are crucial for regional
climate and possibly also for global climate, a combination of insight
into atmosphere and ocean dynamics as well as high latitude air-sea
heat exchange is desirable. Although reliable quantification of
mean seasonally and geographically varying
total surface heat exchange in the Nordic Seas and Arctic Ocean is
difficult, recent advances in modelling tools, the availability of in situ and remote
sensing data, and the usefulness of just a slight
improvement of present large error bars, make the effort worthwhile.
With such a basis, interannual variability can be obtained, which in
combination with regional oceanic heat storage estimated from
hydrography, will give a new basis for understanding interannual
variability and propagation of anomalies.
The figure below shows links
between Atmosphere-Ocean Interaction subprojects. Results from
fundamental studies of key air-sea processes and estimation of
interannual flux variations will be used to improve and tune the
parameterisation of these processes in regional and global-scale
climate and operational models, with distribution of state-of-the-art
information to the scientific community, via publications in journals
and at conference, and by means of this web page, a series of seminars, and
future planned workshops.
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Web page maintained by Alastair D. Jenkins <alastair.jenkins@gfi.uib.no>
© GFI
2006-09-28 |
