The Ocean Archive System searches our original datasets as they were submitted to us, not individual points or profiles. If you want to search and retrieve ocean profiles in a common format, or objectively analyzed fields, your better option may be to use one of our project applications. See: Access Data

OAS accession Detail for 0054150, meta_version: 2. Current meta_version is: 12
<< previous |revision: 2| next >>
accessions_id: 0054150 | archive
Title: Wind/Wave Data from the Geodetic Missing (revised, NODC Accession 0054150)
Abstract: This accession contains a complete copy of the previous NODC CD-ROM for the Wind/Wave Data from the Geodetic Missing between March 31, 1985 and September 30, 1986.
The U.S. Navy Geodetic Satellite (Geosat) was designed and built by the Johns Hopkins University Applied Physics Laboratory and launched in March 1985. The primary mission during the first 18 months was to map the marine gravity field for the U.S. Navy. After that mission was completed, the exact repeat mission was started to measure sea surface height, wind speed and significant wave height. Because the first 18 months of data (the Geodetic Mission, or GM) were classified, the wind and wave data were not readily available to the general research community. In 1988 the Navy released the radar backscatter (from which wind speed is derived) and the significant wave height data [Dobson et al., 1987]. This compact disc contains these data. In 1995 the Navy declassified the entire GM dataset, in the form of Geophysical Data Records (GDRs), but the wind/wave data on this disc are still unique in that the derived wind values are not available on the GDRs
Date received: 19880101
Start date: 19850331
End date: 19860930
Seanames: World-Wide Distribution
West boundary: -180
East boundary: 180
North boundary: 72
South boundary: -72
Observation types: derived products, satellite data
Instrument types: satellite sensor - altimeter
Datatypes: WAVE DATA, WIND SPEED
Submitter: Cheney, Mr. Robert E.
Submitting institution: US DOC; NOAA; National Ocean Service
Collecting institutions: Johns Hopkins University; Applied Physics Laboratory, US Navy
Contributing projects:
Platforms: GEOSAT (3290)
Number of observations:
Supplementary information: The radar backscatter from a nadir-pointing radar is related to the wind speed and is directly proportional to the normal incidence Fresnel power reflection coefficient and inversely proportional to the mean square slope of the low pass filtered version of the ocean surface [Brown, 1978]. Using an algorithm, radar cross section can be converted to wind speed. There are two wind speed fields on this disc, one computed using the Chelton-Wentz algorithm [Chelton and Wentz, 1986] and one using the Smoothed Brown algorithm [Goldhirsh and Dobson, 1985]. The data on this disc were extracted to form
the larger Geosat data set in 1988, and at that time these were the two algorithms chosen to compute wind speed. In terms of rms (root mean square) accuracy, the Smoothed Brown is slightly more accurate but has the drawback that it should not be used for wind speeds greater than 14 m/s.

Since 1988 several additional algorithms have been proposed. Appendix B gives three of these algorithms which can easily be used to compute wind speed when using the radar cross section values contained herein. A bibliography is included in Appendix A, and the reader is encouraged to read some of the pertinent papers for further clarification of the differences of these algorithms. A general review can be found in Dobson [1993]. The general accuracy of wind speed measurements from Geosat is 1.8 m/s.

Significant wave height (SWH) data on this disc were derived from an algorithm used onboard the spacecraft during the Geosat mission. The SWH is related to the slope of the returned radar pulse. When there are waves present on the ocean, the surface appears rough causing the leading edge of the pulse to intersect the wave crests before the troughs, which results in a broadening of the pulse shape. As the distribution of wave heights broadens, so does the
returned pulse shape. Thus from this knowledge, an algorithm was developed relating the pulse slope to SWH. SWH is defined to be that wave height for which there is a 33 percent probability of waves higher than that value. In addition, if the probability density of wave amplitudes is assumed to be a Rayleigh distribution, then it can be shown that SWH is 4 times the standard deviation of the surface waves [Borgman, 1982]. In the last few years several papers have been published that indicate the onboard SWH algorithm underestimates SWH [Mognard et al., 1991; Carter et al., 1992; Glazman, 1991]. The user may want to consult these publications before using the SWH data. A bibliography has been included which contains these three papers and many others that have used Geosat SWH and wind measurements.

FOR MORE INFORMATION

Technical questions about reading the CD-ROM or about scientific applications
should be addressed to:

Satellite and Ocean Dynamics Branch
NOAA/National Ocean Service N/OES11
SSMC-4, Room 8307
1305 East-West Highway
Silver Spring, MD 20910-3232
Phone: (301)713-2857
e-mail: rcheney@grdl.noaa.gov

Additional copies of this CD-ROM are available from:

National Oceanographic Data Center
User Services Branch
NOAA/NESDIS E/OC21
1825 Connecticut Ave, NW
Washington, DC 20235
Phone: (202)606-4549
e-mail: services@nodc.noaa.gov

Appendix A: BIBLIOGRAPHY

Barrick, D. E., Rough surface scattering based on specular point
theory IEEE Trans. Ant. and Prop.,AP-16(4) 449-454,1968.
Barrick, D. E., A relationship between the slope probability density
function and the physical optics integral in rough surface
scattering, Proc. IEEE, 36, 1728-1729, 1968, 1968a.
Barrick, D. E., Wind Dependence of quasi-specular microwave sea
scatter, IEEE Trans. Antennas and Propag., AP-22,1135-136, 1974.
Borgman, L.E., Summary of probability laws for wave properties, Proc.
Inter. School of Physics (Topics in Ocean Physics), Edited by A.R.
Osborne and P.M. Rizzoli, North Holland Pub. Co., 1982.
Brown,G.S., Estimation of Surface wind Speeds Using Satellite-Borne
Radar Measurements at Normal Incidence, J. Geosphys. Res., 84(B8),
3974-3978, 1979.
Brown,G.,H.R Stanley,and N. A. Roy, The Wind-speed measurement
capability of space-borne radar altimeters, IEE J. Oceanic
Eng. OE-6(2) 59-63, 1981.
Cardone, V. J. , J. G. Greenwood, and M. A. Roy, On trends in
historical marine wind data, J. Climate, 3, 113-127, 1990.
Carter. D. J. T., P.G. Challenor,and M. A. Srokosz, An assessment of
Geosat wave height and wind speed measurements, J. Geophys.
Res.,97(C7)11383-11392, 1992.
Chelton, D. B. and P. J. McCabe, A review of satellite altimeter
measurement of sea surface wind speed: with a proposed new
algorithm, J. Geophys. Res.90,4707-4720, 1985.
Chelton,D. B. and Wentz,F. J., Further Development of an improved altimeter
wind speed algorithm, 91(C12), 14150-14260, 1986.
Chelton,D. B., WOCE/NASA altimeter algorithm workshop, U. S. WOCE
Tech. Rep. No.2, 1988.
Dobson, E. B.,F. Monaldo, J. Goldhirsh, J. Wilkerson, Validation
of Geosataltimeter derived wind speeds and significant wave
heights using buoy data, J. Geophys. Res., 92(C10), 1987.
Dobson, E. B., Geosat altimeter wind speed and waveheight measure
measurements: The ERM mission, Proceedings of the WOCE/NASA
Altimeter Algorithm Workshop, Corvallis, Oregon, U. S. WOCE
Tech. Rep. No. 2 1987.
Dobson, E.B., Wind Speed from Altimeters - A Review, JHU/APL
S1R-93U-024,1993.
Glazman, R. E. and Pilorz, Effects of sea maturity on satellite
altimeter measurements, J. Geophys. Res., 95, (C3),
2857-2870, 1990.
Glazman, R. E., Statistical problems of wind generated gravity
waves arising in microwave remote sensing of surface winds,
IEE Trans. Geosci. Remote
Sens., 29(1), 135-142, 1991.
Glazman, R. E. and A. Greysukh, Satellite altimeter measurements of surface
wind., J. Geophys. Res., 98, (C2), 2475-2483, 1993.
Goldhirsh, J. and E. B. Dobson, A recommended algorithm for the
determination of ocean surface wind speed using satellite
-borne radar altimeter,Tech. rep. S1R85-005, Appl. Phys. Lab.,
Johns Hopkins Univ., Laurel,Md., Mar. 1985.
Jackson, F.C, W. T. Walton, D. E. Hines, B. A. Walter, C. Y. Peng, Sea
surface mean square slope from K^u- band backscatter data,
J. Geophys. Res. 97(C7), 1992.
Mognard, N. M. and B. Lago, The computation of wind speed and wave
height from Geos 3 data, J. Geophys. Res., 84(B8), 1979.
Mognard, N. M., J. A. Johannessen, C. E. Livingstone, D. Lyzenga,
R. Shuchman, and C. Russell, Simultaneous observations of ocean
surface winds and waves by Geosat radar alimeter and airborne
synthethetic aperature radar during the 1988 Norwegian
continentenatal shelf experiment, J. Geophys. Res. 96,(C6), 1991.
Monaldo, F. Expected differences between buoy and radar altimeter
esitmates of wind speed and significant wave height and their
implications on buoy-altimeter comparisons, J. Geophys. Res., 93,
2285-2302, 1988.
Tournadre,J, and R. Ezraty, Local climatology of wind and sea state
by means of satellite radar altimeter measurements, J. Geophys.
Res., 95(C10),18225-18268, 1990.
Townsend, W. F., An initial assessment of the performance acheived
by the Seasat-1 radar altimeter, IEE J. of Oceanic Eng.
OE-5(2), 1980.
Ulaby, F. T., R.K. Moore, A. D. Fung, Microwave Remote Sensing
- Active and Passive, Vol II, Addison-Wesley Publis. Co., 1982.
Wentz, F. J., L. A. Mattox, and S. Peteherych, New algorithms for
microwave measurements of ocean winds with application to Seasat
and SSM/I, J. Geophys. Res., 91, 2289-2307, 1986.

APPENDIX B: ALGORITHMS TO COMPUTE WIND SPEED FROM RADAR CROSS SECTION

Modified Brown Algorithm
------------------------
6.6 25.5680
6.8 23.7010
7.0 22.0450
7.2 20.5720
7.4 19.2580
7.6 18.0800
7.8 17.0240
8.0 16.0720
8.2 15.2130
8.4 14.4360
8.6 13.7310
8.8 13.0890
9.0 12.4509
9.2 11.7923
9.4 11.1745
9.6 10.5933
9.8 10.0446
10.0 9.52479
10.2 9.03052
10.4 8.55883
10.6 8.10740
10.8 7.67366
11.0 7.25583
11.2 6.85210
11.4 6.46129
11.6 6.08195
11.8 5.71337
12.0 5.35477
12.2 5.00570
12.4 4.66582
12.6 4.33492
12.8 4.01336
13.0 3.70079
13.2 3.39790
13.4 3.10481
13.6 2.82246
13.8 2.55095
14.0 2.29109
14.2 2.10000
14.4 1.90000
14.6 1.59000
14.8 1.40000
15.0 1.15300
15.2 1.09200
15.4 1.03600
15.6 0.98500
15.8 0.93900
16.0 0.89700
16.2 0.85900
16.4 0.82400
16.6 0.79200
16.8 0.76200
17.0 0.73500
17.2 0.71000
17.4 0.68700
17.6 0.66500
17.8 0.64500
18.0 0.62700
18.2 0.61000
18.4 0.59400
18.6 0.57900
18.8 0.56600
19.0 0.55200
19.2 0.54100
19.4 0.53000
19.6 0.51900
19.8 0.50900
20.0 0.50000
20.2 0.49100
20.4 0.48300
20.6 0.47600
20.8 0.46900
21.0 0.46200
21.2 0.45600
21.4 0.45000
21.6 0.44400


Witter-Chelton Algorithm
---------------------------
7.0 20.154
7.2 19.597
7.4 19.038
7.6 18.463
7.8 17.877
8.0 17.277
8.2 16.655
8.4 16.011
8.6 15.348
8.8 14.669
9.0 13.976
9.2 13.273
9.4 12.557
9.6 11.830
9.8 11.092
10.0 10.345
10.2 9.590
10.4 8.827
10.6 8.059
10.8 7.298
11.0 6.577
11.2 5.921
11.4 5.321
11.6 4.763
11.8 4.252
12.0 3.792
12.2 3.378
12.4 3.014
12.6 2.708
12.8 2.447
13.0 2.208
13.2 1.992
13.4 1.818
13.6 1.676
13.8 1.547
14.0 1.419
14.2 1.292
14.4 1.167
14.6 1.056
14.8 0.972
15.0 0.915
15.2 0.873
15.4 0.833
15.6 0.794
15.8 0.755
16.0 0.716
16.2 0.677
16.4 0.637
16.6 0.599
16.8 0.559
17.0 0.520
17.2 0.481
17.4 0.442
17.6 0.403
17.8 0.363
18.0 0.324
18.2 0.285
18.4 0.246
18.6 0.207
18.8 0.167
19.0 0.128
19.2 0.089
19.4 0.050
19.6 0.011


Wu Algorithm
---------------
Radar Cross Section = -4.0 - 10(logbase10[0.009 + 0.012 ln U(sub10)])

Where U(sub10) = U sub 10 = wind speed at 10 meters above the surface
and Radar Cross Section is in decibars.

Note: All algorithms are referenced to 10 meters height above the surface.
Availability date: 19880101
Metadata version: 2
Keydate: 2009-05-28 19:42:00+00
Editdate: 2009-05-28 20:43:11+00