EVALUATION OF ERA40 OCEAN SURFACE FLUX SPINS

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Re-analysis single source of a consistent and
homogeneous data set for surface heat and
momentum fluxes
Oceanic model forecasting skills depends on
surface heat fluxes
EVALUATION OF THE ERA-40 SEA SURFACE HEAT FLUXES
SPINS (1989 to 1991 gt 93) S. Ramos Buarque, H.
Giordani, G. Caniaux and S. Planton
Météo-France, Centre National de Recherche
MétéorologiqueThis work has been funded by the
European Union Framework V project ERA-40
(EVK2-CT-1999-00027)
Distribution of surface heat budget components
strongly different on ocean and on continents
1987-gt 91 TOVS, Cloud Motion Winds and
SSM/I 1991 Pinatubo eruption
Les Ateliers de Modélisation de lAtmosphère,
CNRM -Toulouse, France 17-19/12/2002
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ERA-40 assimilation system
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Short-range flux ?identical solar
warmingStep06 ? Step12 the sun is not
located at the same spot on the Earth the RMS
reflect geographical disparitiesStep18 and
Step24 integrated solar warming covers a
larger extends on the Earth and geographical
disparities are reducedStepgt 24 the
geographical disparities are newly introduced.
Methodology
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ERA-40 fluxes follows as is model production ?
model run defined by its Time and its Step
and are archived with Time00, 12 Step0,
6, 12, 18, 24, 30, 36 Time06, 18 Step0,
6 Methodology is based on differences between two
as is interval with the same Time Tk
?time kept Tr ? time rejected or common period
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Bias between global averaged fluxes according to
Tr06, 12, 18, 24, 30 hours and Tr00 for all
seasons. Tr06, 18, 30 correspond to 21 hours
UTC while Tr12, 24 correspond to 15 hours UTC.
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• Latent Heat
• Global differences betweenTr06, 30 and Tr00
  in boreal summer

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• Sensible Heat
• Global differences betweenTr06, 30 and Tr00
  in boreal summer

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• Solar Radiation
• Global differences betweenTr06, 30 and Tr00
  in boreal summer

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• Thermal Radiation
• Global differences betweenTr06, 30 and Tr00
  in boreal summer

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• Regional behaviors
• Turbulent Fluxes
• Borest and Kuroshio gt bi-modal behaviour with
  greatest RMS during DJF and MAM
• Tropical Pacific gt greatest during JJA but
  instability along the year

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• Radiative Fluxes
• Solar flux all regions merged gt highest RMS
  agrees with maximum sun exposition
• Infrared flux 2 W/m² lt RMS lt 6 W/m² for all
  regions

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ERA-15 assimilation system
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? ERA-15 spins are mostly larger than ERA-40
ones? ERA-40 shows a great decrease of spins in
middle latitudes? ERA-40 have a more organized
evolution of spins than ERA-15 along the meridian.
Conclusions
Latent Heat Flux? spin-up increases with time,
levelling off after 24 hours? most of spins
range between 10 and 10 W/m2 but its may exceed
locally 50 W/m2 - large spots of spin-up
corresponds to week relative spins? local
values of spin-up are greater than spin-down
ones.Sensible and Radiative Fluxes? spins reach
a good stability after 6 hours.
Latent Heat flux in Tropical Pacific ? greatest
RMS instability increases with time, levelling
off after 24 hours This result seems drive the
global spin-up stability.Turbulent fluxes in
Kuroshio? bi-modal behaviour with greatest RMS
during DJF
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Applications Global results may help
oceanographers to use surface heat fluxes
physically coherent with the atmospheric
circulation with the intention to constraint
oceanic models. The location of systematic
regional biases can help to explain some drifts
in ocean simulations and bias in ocean heat
transports. The methodology is adapted to model
intercomparisons.
Perspectives ERA-40 and ERA-15 fluxes are being
used to force the oceanic model ORCA 2 degrees.
Impacts of ERA-40 fluxes obtained from spins
methodology on oceanic simulations are going to
be investigated.
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