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Documentation
Algorithm for Surface Air-Sea Fluxes:
We used the COARE 3.0b algorithm to compute bulk air-sea fluxes,
including latent and sensible heat flux, net heat flux, and other
associated fluxes including evaporation, evaporation minus precipitation,
sensible heat flux due to rain, buoyancy flux,
and wind stresses.
These flux data are available for display and delivery at
hourly, daily, 5-day, monthly, and quarterly resolution from
http://www.pmel.noaa.gov/tao/oceansites/flux/.
The COARE 3.0b algorithm is detailed in
Fairall, C.W., E. F. Bradley, J. E. Hare, A. A. Grachev, and J. B. Edson,
2003: Bulk Parameterization of Air-Sea Fluxes: Updates and Verification
for the COARE Algorithm. J. Climate, 16, pp 571-591.
We downloaded the fortran version of the software from
ftp://ftp.etl.noaa.gov/user/cfairall/bulkalg/cor3_0/.
Implementation of this algorithm by the TAO Project
of NOAA/PMEL was guided by
Cronin, M.F., C. Fairall, and M.J. McPhaden, 2006: An assessment of buoy
derived and numerical weather prediction surface heat fluxes in the
tropical Pacific. J. Geophys. Res., 111, C06038, doi:10.1029/2005JC003324.
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Temporal Resolution
Hourly:
To compute high resolution fluxes, we use hourly averages for all input
data, in addition to using the warm-layer and cool-skin corrections
which are built into the COARE 3.0b algorithm. To provide the best
possible estimates of the high resolution surface fluxes we compute them
only at times when there is a complete set of input data. The only
exception to this is for sea level pressure. Fluxes are insensitive
to sea level pressure, so at times when hourly sea level pressure data
are not available, we use a value from the ICOADS sea level pressure
climatology, at the nominal location of the buoy.
We provide two hourly flux data sets, one using absolute wind speed as
input to the COARE algorithm, and the other using wind speed relative to
10 m ocean currents. There are fewer moorings from which relative
vis-a-vis absolute wind speed can be computed, but at these sites flux
estimates are slightly more accurate (see below). Note that net shortwave
radiation is independent of wind speed.
Hourly Qnet is computed using the net shortwave
radiation and net longwave radiation output from the COARE v3.0b
algorithm. This is done so that the net heat flux includes
any effects of the warm layer and cool skin corrections of
the COARE 3.0b algorithm.
Daily:
As for hourly fluxes, we provide two daily flux data sets, one using
absolute wind speeds and the other using relative wind speeds. The
cool skin, warm layer calculation is turned off for calculations
using daily averages. Therefore, daily averaged net shortwave
radiation, net longwave radiation, and sensible heat due to rain are
all independent of wind speed.
To assess the sensitivity of the latent and sensible heat fluxes and
wind stress to the use of relative wind speeds compared to absolute wind
speeds, we computed the differences between these two daily data sets at
mooring sites in the Pacific, Atlantic and Indian Oceans where 10 m
current velocity data were available. The results are summarized in the
following tables:
To minimize biases in flux estimates from using daily rather
than high resolution wind speeds, all daily wind speeds are
corrected prior to input into the bulk algorithm using an
estimate of the mesoscale gustiness computed from high
resolution data (Cronin et al. 2006).
5-Day, Monthly, and Quarterly Averages:
5-Day, monthly, and quarterly averages of surface fluxes are computed
from daily fluxes which use absolute wind speed as input.
Input Data Quality:
For all of the flux calculations, we use only data with the
highest two levels of data quality from the TAO, TRITON,
PIRATA, and RAMA arrays.
Climatologies for Surface Fluxes:
The surface heat flux climatologies, which are shown in time series
displays and used to compute anomalies, are based on the monthly
Objectively Analyzed Air-Sea Fluxes (OAFlux) from Woods
Hole Oceanographic Institution. These include latent and
sensible heat fluxes, evaporation, net shortwave and
longwave radiation, and net heat flux. The climatology for
E-P was computed by subtracing the Xie and Arkin rain
climatology (1997) from the OAFlux evaporation
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