Improved Hurricane Wind Measurements Using QuikSCAT
The SeaWinds microwave scatterometer is a conical-scanning radar that remotely senses ocean surface wind vector from a near-polar orbiting satellite known as QuikSCAT. The measurement geometry is given in Fig. 1. The backscattered energy is collected over the entire conical scan (forward and aft looking) with separate offset pencil beams, vertical or horizontal polarization. The pulse repetition frequency and antenna scan rate have been designed to provide approximately 50% overlap of the instantaneous field of view (IFOV) in both the along track and cross track directions. This sampling can be used to provide four backscatter measurements on a 0.125 deg x 0.125 deg grid (12.5 km) with two forward looks (V-pol & H-pol) and two aft looks (V-pol & H-pol).
The radar backscatter, called the normalized radar cross section , is proportional to the ocean surface wind vector. The variation in azimuth is determined by the radar look direction compared to the wind direction. The largest occurs when the wind direction is towards the radar (upwind) and the minimum occurs for crosswind (90 deg between the radar look and the wind direction). The average value of (over all azimuths) is proportional to wind speed. Thus by measuring at four different azimuths, we can solve for the unknown wind speed and direction. The aim of this project is to develop a geophysical retrieval algorithm that uses QSCAT data to infer wind speed in a hurricane. An example of preliminary QSCAT wind speed results are shown for hurricane Floyd (Sept. 1999) in Fig. 2. Unfortunately part of the storm is obscured by strong rain; but the high resolution of QSCAT can “see between the rain bands” to measure the surface winds.
Ian Stuart Adams
- Jones, W. L. and Zec, J., "Evaluation of Rain Effects on NSCAT Wind Retrievals", Oceans 96, Sept. 23-26, 1996, Ft. Lauderdale, FL.
- Jones, L., Park, J.D., Zec, J., Donnelly, J., Carswell, J., McIntosh, R. and Yueh, S. "Ku-Band GMF at High Wind Speeds", QuikSCAT GMF Workshop, Brigham Young Univ., March 5, 1998, Provo, UT.
- Alhumaidi, S., Jones, L., Syed, F., Devan, V., Shah, K., and Brown, R. "Conical Scanning Microwave Scatterometer Geophysical Performance Simulation", Southeastcon'98, April 1998, Orlando, FL.
- Park, J.D., Zec, J., Jones, W.L., Donnelly, J., Carswell, J., McIntosh, R.E. and Yueh, S. "An Improved Neural Net Geophysical Model Function for High Wind Speeds", Spring AGU, June 1998, Boston, MA.
- Jones, L., Park, J.D., Zec, J., Donnelly, J.R., Carswell, J.R., McIntosh, R.E., and Yueh, S. "An Improved NASA Scatterometer Geophysical Model Function for Tropical Cyclones", IGARSS'98, July 1998, Seattle, WA.
- Jones, W.L., Zec, J., Park, J.D., Donnelly, W.J., Carswell, J.R., McIntosh, R.E., Cardone, V.J., Cox, A., Pierson, W.J., and Sylvester, W.B. "An Improved NASA Scatterometer Geophysical Model Function for Tropical Cyclones", QuikSCAT Sci. Meeting, August 10-13, 1998, Kona, HA.
- Zec, J. and Jones, W. L., "Tropical Cyclone Geophysical Model Function for Ocean Surface Wind Retrievals from NASA Scatterometer Measurements at High Wind Speed ", IGARSS'99, July 1999, Hamburg, Germany.
- Cardone, V. J., Pierson, W. J., Jones, W. L., Cox, A., Zec, J., Sylvester, W. B., and Park, J. D., "NASA Scatterometer High Resolution Winds for Hurricane Lili," IGARSS'99, July 1999, Hamburg, Germany.
- Jones, W. L., Zec, J., Cardone, V. J., and W. J. Pierson, "NASA Scatterometer Measurements of Ocean Surface Winds in Tropical Cyclones", Oceans'99, Sept. 1999, Seattle, WA.
- Alhumaidi, Sami M. and W. Linwood Jones, "A Novel Approach to Retrieving Wind Vectors from the NSCAT Scatterometer", SPIE Proc. AeroSense 2000, April 24-29, 2000, Orlando, FL.
- Zec, Josko and W. Linwood Jones, "Scatterometer-retrieved Hurricane Wind Direction Ambiguity Removal using Spiral Dealias", IGARSS'00, July 24-28, 2000, Honolulu, HA.
- Jones, W. L., Zec, J., Park, J. D. and Yanxia Wang, "Review of NSCAT Hurricane Research and Application to SeaWinds," SeaWinds Performance in Extreme Winds and Ambiguity Removal and Directional performance Workshop, Jet propulsion Lab, Aug. 29-30, 2000, Pasadena, CA.
- Eubanks, C., Jones, W. L., Zec, J., Carswell, J. R. and S. S. Chen, " Improved Hurricane Wind Measurements using QuikSCAT," Oceanology Americas 2001, NASA Oceanography Scientific Conference, April 3-4, 2001, Miami, FL.