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Introduction to Geosat Wind/Wave CD-ROM


How to Use this CD-ROM

    The National Oceanographic Data Center is responsible for disseminating Geosat ocean data to the research community. This CD-ROM contains the data from Geosat's Geodetic Mission, March 30, 1985 to September 30, 1986. The data from years 1985 and 1986 are in separate subdirectories of the same name. The naming convention of the files is as follows:

  1. DAY_DDD.YY

    Where: DDD is the year day , 001-365; and YY is the year, 85 or 86.

    The table below gives the format for the integer binary data records, which have a record length of 26 bytes.

  2. Wind/Wave File Data Records
    Field Bytes Content
    1 1-4 Geodetic Latitude in microdegrees
    2 5-8 East Longitude in microdegrees
    3 9-12 Time in seconds from 1985.000...
    4 13-14 Time continued in units of .1 milliseconds
    5 15-16 Significant Wave Height in centimeters
    6 17-18 Radar Cross Section (Sigma Naught) in .01 db
    7 19-20 Attitude Angle in .01 degrees
    8 21-22 Flag Word
    9 23-24 Chelton-Wentz Wind, cm/sec (divided by 1.06)
    10 25-26 Smoothed Brown Wind, cm/sec

    Also included on this CD-ROM is a C-program named WW_SWAB.C. For VAX and PC users, whose computers use "little-endian" byte order, this program will convert the "big-endian" data on this CD to the format used by their machines. This program should be uploaded to their computer and compiled with a command line such as: "cc -O -s -o ww_swab ww_swab.c". The program acts like a Unix "filter", reading from standard in and writing to standard out. A typical usage would be: "ww_swab < orginal.file > swapped.file".

  3. In summary, the files included on this CD-ROM are as follows:

    Root directory:

    1985 subdirectory:

    1986 subdirectory:

  4. Changes from the First Release of Wind/Wave Data

    This CD-ROM constitutes the second release of the Geosat GM Wind/Wave data. Long after the first CD was released, it was discovered that 29 of the first 30 days of data were corrupted (days 90-119, excluding day 109). Each of the affected files had two extra space characters inserted at the ends of records 20165 and 40330, causing the data fields to become misaligned. In the process of repairing this error it became apparent that the record length on the original CD was 27 bytes vs. 26, since a line-feed delimeter had been inserted after each 26-byte record. These unnecessary line-feeds were stripped from all the data files, so that the record length is truly 26 bytes. The space savings from this step made it possible to store all the wind/wave data on a single disc, without compression. By contrast, the original wind/wave files were first compressed with the PKZIP utility before being written to CD-ROM.


Click here for an example listing program that will do byte-swapping if needed for PC or VAX users.

For More Information


Copies of this CD-ROM are available from:


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 micrplsqlve 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 Geosat

altimeter 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 micrplsqlve 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, Micrplsqlve Remote Sensing - Active and

Passive, Vol II, Addison-Wesley Publis. Co., 1982.

Wentz, F. J., L. A. Mattox, and S. Peteherych, New algorithms for micrplsqlve

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


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
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