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OAS accession Detail for 0054150
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| accessions_id: | 0054150 | archive |
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| Title: | NODC Standard Product: US Navy Geosat wind/wave data (WWDR) from the Geodetic Mission (NCEI Accession 0054150) |
| Abstract: | This dataset contains a complete copy of the previous NODC CD-ROM for the Wind/Wave Data from the Geodetic Mission (revised) 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., 1988]. 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. Data are in binary format. |
| Date received: | 19880101 |
| Start date: | 19850331 |
| End date: | 19860930 |
| Seanames: | |
| West boundary: | -180 |
| East boundary: | 180 |
| North boundary: | 72 |
| South boundary: | -72 |
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| Submitter: | Cheney, Mr. Robert E. |
| Submitting institution: | US DOC; NOAA; National Ocean Service |
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| 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 dataset 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 (below) 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 (below), 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 altimeter and airborne synthetic aperture radar during the 1988 Norwegian continentenatal shelf experiment, J. Geophys. Res. 96,(C6), 1991. Monaldo, F. Expected differences between buoy and radar altimeter estimates 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 achieved 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: | 12 |
| Keydate: | 2009-05-28 19:42:00+00 |
| Editdate: | 2024-08-28 18:48:22+00 |