source: trunk/adm/website/motivation.rst @ 154

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.. DESCRIPTION
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.. motivation
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.. TODO
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.. bold is implemented with either ** .. ** and :strong:`..`, but witgh none
.. of these way I manage to mix text and hyperlink
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.. EVOLUTIONS
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.. $Id$
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.. $URL$
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.. - fplod 20120229
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..   * add meta robots constraints
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.. - jv 20120222
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..   * typos 
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.. - jv 20120221
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..   * add full references and doi links when available 
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.. - fplod 20120219
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..   * fix links
..   * add section level
..   * add bold texts
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.. - fplod 20120217
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..   * creation from motivation.odt
..     transform to ReST using odt2sphinx + hand correction (diacritical,
..     ponctuations, short lines, links !!)
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.. meta::
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.. _motivation:

Motivation
==========

Importance of air-sea fluxes in the tropics
+++++++++++++++++++++++++++++++++++++++++++

The tropics play an important role in the earth's climate and energy cycle.
The tropical oceans gain heat from downward shortwave radiation, allowing for
very high surface temperature (above 28°C) in the Indo-Pacific and
Atlantic warm pools.
This high sea surface temperature can cause the atmospheric boundary layer to
destabilize through upward latent and sensible fluxes and by providing
moisture through evaporation, leading to the development of deep atmospheric
convection.
These air-sea interactions are crucial in setting up the Walker circulation,
an essential component of the earth climate.
These interactions are also active through a continuum of time scales, from
diurnal to interannual, and are involved in many tropical climate modes.
At the intraseasonal timescale, for example, air-sea heat fluxes play a
central role in theories of the Madden and Julian Oscillation, and in the
monsoon active and break phases (Sobel et al. 2008).
At the interannual timescale, air-sea momentum fluxes play a key role in the
Bjerknes feedback, a positive feedback between the surface wind signal related
to deep atmospheric convection and its dynamical oceanic response, which is
critical to phenomena like El Niño (e.g. McPhaden et al. 2006) and the Indian
Ocean Dipole (Webster et al. 1999; Saji et al. 1999).
Those examples illustrate how an accurate knowledge of air-sea heat and
momentum fluxes is required to understand the main modes of tropical climate
variability.
**The TropFlux project aims at providing state of the art heat and momentum
fluxes that resolve the main phenomena of the tropical climate, at
intraseasonal (Madden-Julian Oscillation, monsoon active and break phases),
seasonal and interannual (El Niño, Indian Ocean Dipole ...) time scales.**


Why a new air-sea flux product?
+++++++++++++++++++++++++++++++

  * Air-sea fluxes derived from in situ observations are extremely useful
    for establishing reference climatologies, but do not allow resolving 
    intraseasonal variations due to limited data coverage


  * Air-sea fluxes obtained from re-analyses generally suffer from systematic
    biases, and do not perform extremely well for surface shortwave
    fluxes (|pkbetal2011|_)

  * The |oaflux|_ project is a very useful initiative that delivers high-quality surface heat
    fluxes from a synthesis of various re-analyses, satellite observations
    and in situ datasets. Unfortunately, OAFlux does not provide momentum
    fluxes so-far, and the availability of its net heat fluxes is conditioned
    by the availability of high quality
    |isccp|_ shortwave surface fluxes,
    which are only updated once every year or so.

:strong:`The TropFlux project aims at providing timely (i.e. a few months behind
present) estimates of both momentum and net heat flux (and their components).
These fluxes should compare well to the largest observational database of
estimates of air-sea fluxes in the tropics:`
|gtma|_
:strong:`(McPhaden et al. 2010).`


References
++++++++++++++

.. [McPhadenEtAL:Science:2006]_

McPhaden, M.J.,S. E. Zebiak, and, M.H. Glantz, 2006: *ENSO as an integrating concept in Earth science*, Science, `doi:10.1126/science.1132588 <http://dx.doi.org/10.1126/science.1132588>`_

.. [McPhadenEtAL:JC:2010]_

McPhaden, M.J., K. Ando, B. Bourles H.P. Freitag, R. Lumpkin, Y. Masumoto, V.S.N. Murty, P. Nobre, M. Ravichandran, J. Vialard, D. Vousden, and W. Yu, 2010: *The global tropical moored buoy array*, In Proceedings of the "OceanObs'09: Sustained Ocean Observations and Information for Society" Conference (Vol. 2), Venice, Italy, 21-25 September 2009, Hall, J., D.E. Harrison, and D. Stammer, Eds., ESA Publication WPP-306.

.. [SajiEtAl:Nature:1999]_

Saji NH, Goswami BN, Vinayachandran PN, Yamagata T, 1999: *A dipole mode in the tropical Indian Ocean*, Nature, `doi:10.1038/43855 <http://dx.doi.org/10.1038/43855>`_

.. [SobelEtAl:NatureGeo:2008]_

Sobel, A.H., E.D. Maloney, G. Bellon and D.M. Frierson, 2008: *The role of surface fluxes in tropical intraseasonal oscillations*, Nature Geo., `10.1038/ngeo312 <http://dx.doi.org/10.1038/ngeo312>`_

.. [WebsterEtAl:NatureGeo:2008]_

Webster, P. J., Moore, A. M, Loschnigg, J. P, and Leben, R. R, 1999: *Coupled oceanic-atmospheric dynamics in the Indian Ocean during 1997-98*, Nature, `doi:10.1038/43848 <http://dx.doi.org/10.1038/43848>`_