Ocean Surface heat fluxes

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Ocean Surface heat fluxes

• Lisan Yu and Robert Weller
• lyu_at_whoi.edu
• rweller_at_whoi.edu
• http//oaflux.whoi.edu

2
Ocean Surface heat fluxes

• A brief introduction of the OAFlux project
• Surface latent and sensible heat fluxes
• the state of the latent and sensible heat
  fluxes in 2005
• its relation to 2004 and to the analysis
  record that starts from 1981
• the long-term trend in latent heat flux
• Surface longwave and shortwave radiations (ISCCP)
• time series of the global averaged long- and
  short-wave radiations (1984-2004)
• Problems of the ISCCP datasets
• Comparisons
• mean pattern comparison with SOC, NCEP1, and
  ERA40
• time series comparison with buoy measurements

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Objectively Analyzed air-sea Fluxes (OAFlux)
website http//oaflux.whoi.edu/

• The project is supported by NOAA Office of
  Climate Observation (OCO) and Climate Change and
  Data Detection (CCDD).
• PIs Yu and Weller, with technical support
  from X.Jin
• It is to develop gridded air-sea heat fluxes
  analysis for the global ice-free oceans for the
  past 50 years
• The development is based on a weighted objective
  analysis that combines surface meteorology from
  satellite retrievals, COADS ship observations,
  and model outputs from atmosphere reanalyses.
• Data currently available online
• Global QLH and QSH on daily/monthly and
  1º-grid for the years 1981-2005.
• Global QLW and QSW (1983-2004) are from
  ISCCP (Bill Rossow).

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OAFlux estimating QLH and QSH
QLH ? Le ce U (qs qa) QSH ? cp cp U (Ts
Ta)
Four independent variables U, Ts, qa, and Ta.

• Input Data Sources
• Atmospheric reanalyses (NCEP/DOE and ERA40)
• Air humidity and temperature at 2m, surface
  wind at 10m, SST, sea level pressure
• Satellite retrievals
• SSMI wind speed and air humidity, AVHRR SST,
  TMI and AMSR-E SST, scatterometer winds

Weighted Objective Analysis produce optimal
estimate for variable fields through combining
data from various sources
Best estimates of daily flux-related variable
fields
COARE bulk flux algorithm 3.0 (Fairall et al.
2003)
Daily latent and sensible heat fluxes
References regarding the methodology and
validation Yu, L., R. A. Weller, and B. Sun,
2004a Improving latent and sensible heat flux
estimates for the Atlantic Ocean (1988-1999) by
a synthesis approach. J. Climate, 17, 373-393.
Yu, L., R. A. Weller, and B. Sun, 2004b Mean
and variability of the WHOI daily latent and
sensible heat fluxes at in situ flux measurement
sites in the Atlantic Ocean. J. Climate, 17,
2096-2118. Yu, L., and R. A. Weller, 2006
Objectively Analyzed air-sea heat Fluxes (OAFlux)
for the global ice-free oceans Trend and
variability during 1981-2005. Submitted to Bull.
Amer. Meteor. Soc.
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State of ocean heat fluxes in 2005
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Difference 2005 -2004
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Changes in oceanic heat fluxes and SST since 1981
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Linear trends 1981-2005
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Variance contributions of ?q and U
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ISCCP Surface longwave and shortwave
radiationsyearly-mean averaged over the global
oceans
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Problems in the ISCCP datasets(1) spatial
structure
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Effect on the EOF analysis
The Atlantic Ocean
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Problems in the ISCCP datasets(2) mean bias
QLWQSW (1984-2002)
Positive downward
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TRITON heat fluxes at (1.5S, 90E) (H. Hase/IORGC)
shortwave
net
sensible
longwave
latent
OAFlux
ISCCP
(provided by Dr. Yoshifumi Kuroda)
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Locations of in situ measurements
All components No QLW x No QLW and
QSW
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Stratus buoy (693 days, 10/08/00 to 08/31/02)
30-day running mean applied
Fluxes comparison statistic based on daily
means --------------------------------------------
--------------------------
QNET QLHQSH
QSWQLW ------------------------------------------
---------------------------- Buoys
50 -110
160 OAFluxISCCP 54 ( 4) -113 ( -3)
168 ( 8) NCEP1 -14 (-64)
-144 (-34) 130 (-30) ERA40
47 ( -3) -124 (-14) 171 (11) --------------
--------------------------------------------------
------
Statistics based on daily means
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Pacific Basin TAO array
The meridionally averaged mean QSW (Sep.1991
Aug.2002) for TAO array, ISCCP, ERA40, NCEP1 and
NCEP2 as a function of longitude
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Atlantic Basin
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Summary

• The OAFlux product 1981-2005 a synthesis of
  satellite observations and NWP reanalyses outputs
  of surface meteorology.
• Surface latent and sensible heat fluxes
• There is a long-term trend in latent heat
  flux. The mean has increased by about 10Wm-2
  since 1981, which amounts to almost 12 change.
• The increasing trend in latent heat flux is
  in concert with the warming trend of global SST.
• Surface longwave and shortwave radiations (ISCCP)
• time series of the global averaged long- and
  short-wave radiations (1984-2004)
• Problems of the ISCCP datasets
• (1) spatial structure is affected by the mean
  drifts in different sensors
• (2) mean bias in the tropical
  oceans Too much net downward QSW