Height Adjusting the Wind Speed From the TAO Buoy Array to 20 Meters

This page explains how the TAO Buoy data was adjusted for use in the
FSU Pacific Pseudostress Analyses beginning with January 1996 for the
Research Quality Product, and January 1998 for the Quick Look
product. The daily mean TAO Buoy data can be obtained from PMEL.

Quick Facts about the WOCE SAC Products

Introduction

December 1998

This is an important note to all who are using the FSU tropical
Pacific monthly pseudo-stress products.

We have altered the processing of data for these analyses and this
change may affect your research/operational efforts. We apologize for
the late notice regarding these changes (they have been in effect for
~10 months).

Our revised data processing recognizes daily TAO mean wind
observations as originating from 4-m above the ocean surface and
adjusts them to 20-m height (nominal ref height) before they are used
in our analysis. From this point we use the same grid and analysis
techniques - only the treatment of TAO wind data are different.

The end result is stronger winds in the 10S to 10N band, and
especially in the 120-135W and 170W-180 regions.  This amplification
of the winds due to the height adjustment is not uniform in space or
time (due to atmospheric stratification effects) and thus makes
interpretation more interesting.

These changes went into effect for the 1998 quick-look analyses. We
are nearing completion of a manuscript providing a detailed
examination of the impacts of the TAO adjustments on our products
based on comparisons of our original analyses and a revised set of FSU
pseudo-stress products for the tropical Pacific for the period of
January 1996 through Dec 1997.

We are interested in receiving any feedback on these changes and
impacts on prediction/analysis efforts.

A PDF form of the poster presented recently at the Climate Diagnostics
Workshop (Nov 1998) describes a preliminary analysis of the revised
wind fields (http://www.coaps.fsu.edu/~legler/LeglerCDWPoster.pdf).

The revised data files (same format as our regular FSU products) are
found in our FTP site (www.coaps.fsu.edu) as
a compressed tar file /pub/jns/fsu9697.tar.

SUMMARY of FSU Tropical Pacific Monthly Mean Pseudo-Stress Products
1996-1998

1996 Quick-look		Research-Quality 	Research-Quality(ADJ) 
1997 Quick-look					Research-Quality(ADJ)
1998 Quick-look(ADJ)				Research-Quality(ADJ) - 
						   To be released 1999
                                                                  
Background

The TAO array consists of approximately 70 ATLAS and current meter
moorings in the Tropical Pacific Ocean, telemetering oceanographic and
meteorological data in realtime via the Argos satellite system. We
removed the TAO data transmitted via GTS and replaced it with daily
averages obtained from PMEL. All buoys measure the following
meteorological variables:
                                         wind speed
                                        wind direction
                                       relative humidity
                                        air temperature

Adjustment Process

The TAO data are then adjusted using the Bourassa-Vincent-Wood method
(Bourassa, et al. 1998) and configured as follows:

     BVW model in the local wind-wave equilibrium condition.

     Fairall's approximation (Fairall, et al., 1996a) of sea surface
     humidity (98%).

     Convective parameterization is set to 1.25.

     Wind sensor height 4m measured, 20m adjusted.

     For unstable conditions, Benoit (1977) parameterization was used,
     and for stable condtions, Beljaars and Holtslag (1991)
     parameterization was used.

     Monin-Obukhov length scale is calculated as described in Liu, et
     al. (1979). Momentum roughness length model from Bourassa, et
     al. (1998).

     Heat and moisture roughness length parameterization from
     Brutsaert (1982) and Smith (1988, 1992).

References

Beljaars, A. C. M., and A. A. M. Holtslag, 1991: Flux parameterization
over land surfaces for atmospheric models. J. Appl. Meteor., 30,
327-341.

Benoit, R., 1977: On the integral of the surface layer
profile-gradient functions. J. Appl. Meteor, 16, 859-860.

Bourassa, M. A., D. G. Vincent, W. L. Wood, 1998: A flux
parameterization including the effects of capillary waves and sea
state. J. Atmos. Sci., in press.

Brutsaert, W. A., 1982: Evaporation into the Atmosphere. Reidel, 299 pp.

Fairall, C. W., A. A. Grachev, A. J. Bedard, and R. T. Nishiyama,
1996a: Wind, wave, stress, and surface roughness relationships from
turbulence measurements made on R/P FLIP in the SCOPE experiment. NOAA
technical memorandum ERL ETL-268, Environmental Technology Laboratory,
NTIS order number PB96-181334INZ, 37 pp.

Liu, W. T., K. B. Katsaros, J. A. Businger, 1979: Bulk
Parameterization of Air-Sea Exchanges of Heat and Water Vapor
Including the Molecular Constraints at the Interface. J. Atmos. Sci.,
36, 1722 - 1735.

Smith, S. D., 1988: Coefficients for sea surface wind stress, heat
flux, and wind profiles as a function of wind speed and
temperature. J. Geophys. Res., 93, 15467 - 15472.

 ___________, R. J. Anderson, W. A. Oost, C. Kraan, N. Maat,
J. DeCosmo, K. B. Katsaros, K. L. Davidson, K.  Bumke, L. Hasse, and
H. M. Cadwick, 1992: Sea surface wind stress and drag coefficients:
the HEXOS results.  Bound.-Layer Meteorol., 60, 109-142.

Further information on WOCE-MET Web pages can be obtained by mailing:
wocemet@coaps.fsu.edu.

Last Modified: Tue, 15 Dec 1998