QuikSCAT Radiometer (QRad)

Project Description

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. In addition to measuring radar backscatter, SeaWinds simultaneously measures the microwave brightness temperature of the surface, and this passive microwave measurement capability is known as the QuikSCAT Radiometer (QRad). Brightness temperatures (Tb’s) measured by QRad are used to develop an algorithm for remotely sensing rain rate over the ocean. The basis of the algorithm is that the brightness temperature over a raining ocean is greater than that over a clear ocean. Rain can be extracted from the differential (excess) part between the raining and clear ocean Tb.

An empirical relationship is developed using regression analysis of the QRad excess brightness (Tex ) with simultaneously measured rain rates from an independent rain measuring satellite known as the Tropical Rainfall Measuring Mission (TRMM). For QRad, the rain rate algorithm produces two rain products: an instantaneous rain rate, and an average rain rate that is temporally and spatially averaged using instantaneous rain rates from many satellite revolutions.

Examples of the two precipitation rain products are presented below.

Figure1: Qrad and TRMM Microwave Imager (TMI) instantaneous rain rates.

Figure 2: Monthly average rain rate for the month of June 2000.

Sponsors

NASA Jet Propulsion Laboratory

NASA Goddard Space Flight Center

Personnel

Khalil Ahmad

Yanxia Wang

Publications

• Jones, W. L., Zec, J., Mehershahi, , R. and M. Susanj, "A Rain Flag for the Seawinds Scatterometer on Quikscat", 1999 IEEE AP-S Internat. Symp.and USNC/URSI Nat. Radio Sci. Meeting, July 11-16, 1999, Orlando, FL.
  
  
• Jones, W. L. and D. Long, "QRad Radiometer Products", QuikSCAT Calibration/Validation and Early Science Meeting, Jet Propulsion Lab, Pasadena, CA, Nov. 2-4, 1999.
  
  
• Jones, W. L., Susanj, M., Mehershahi, R. and D. Long, "QRad Radiometric Calibration and Special Product", QuikSCAT Calibration/Validation and Early Science Meeting, Jet Propulsion Lab, Pasadena, CA, Nov. 2-4, 1999.
  
  
• Jones, W. L., Susanj, M., Park, J. D. and Mehershahi, R. "A Quality Control Rain Flag using QuikSCAT Radiometric Observations", QuikSCAT Calibration/Validation and Early Science Meeting, Jet Propulsion Lab, Pasadena, CA, Nov. 2-4, 1999.
  
  
• Susanj,Mladen, Jones, W. L., Wang, Y., Zec J., and Jun-Dong Park, "A Rain Flag over Oceans for the SeaWinds Scatterometer on QuikSCAT", AGU Spring meeting, May 30 - June 3, 2000, Wash DC.
  
  
• Jones, W.L., Susanj, M., Zec, J. and J. Park, "Validation of QuikSCAT Radiometer Estimates of Rain Rate", IGARSS'00, July 24-28, 2000, Honolulu, HA.
  
  
• Jones,W. L., Mehershahi, R., Zec, J. and D. G. Long, "SeaWinds on QuikScat Radiometric Measurements and Calibration" IGARSS'00, July 24-28, 2000, Honolulu, HA.
  
  
• Ezraty, R., Jones, W. L. and J. Zec, "On the joint use of QSCAT and QRAD over the Arctic and Antarctic Oceans", IGARSS'00, July 24-28, 2000, Honolulu, HA.
  
  
• Datta, S., Jones, W. L., Kasparis, T. and B. Roy, "Spatial Variability of Surface Rainfall as Derived from TEFLUN-B Dense Rain-Gauge Network and Kennedy Space Center Gauges," AGU Fall meeting, Dec. 15-19, 2000, San Francisco, CA.
  
  
• Wang, Y., Jones, W. L., Park, J. and J. Zec, " Quantitative Rain Rate Estimates over Oceans using QuikSCAT," Oceanology Americas 2001, NASA Oceanography Scientific Conference, April 3-4, 2001, Miami, FL.
  
  
• Jones, W. L., Kasparis, T., Wang, Y. and J. Park, "Global Ocean Rain Rates from QuikSCAT," 7th International Conference on Precipitation, June 30 -July 3, 2001, Samoset Resort, Rockport, ME.

Thesis

• An Algorithm for Measuring Rain over Oceans using the QuikSCAT Radiometer, M. Susanj, Summer 2000.
  
  
• Ocean Brightness Temperature Measurements using the QuikSCAT Radiometer, R. Mehershahi, Fall 2000.
  
  
• A Statistical Algorithm for Inferring Rain Rate from the QuikSCAT Radiometer, Yanxia Wang, Fall 2001.