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- Author or Editor: Robert E. McIntosh x
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Abstract
Scatterometer model functions that directly estimate friction velocity have been developed and are being tested with radar and in situ data acquired during the Surface Wave Dynamics Experiment (SWADE) of 1991. Ku-band and C-band scatterometers were operated simultaneously for extensive intervals for each of 10 days during SWADE. The model function developed previously from the FASINEX experiment converts the Ku-band normalized radar cross-section (NRCS) measurements into friction velocity estimates. These are compared to in situ estimates of surface wind stress and direction across a wide area both on and off the Gulf Stream (for hourly intervals), which were determined from buoy and meteorological measurements during February and March 1991. This involved the combination of a local, specially derived wind field, with an ocean wave model coupled through a sea-state-dependent drag coefficient. The Ku-band estimates u∗ magnitude are in excellent agreement with the in situ values. The C-band scatterometer measurements were coincident with the Ku-band NRCSs, whose u∗ estimates are then used to calibrate the C band. The results show the C-band NRCS dependence at 20°, 30°, 40°, and 50° to be less sensitive to friction velocity than the corresponding cases for Ku band. The goal is to develop the capability of making friction velocity estimates (and surface stress) from radar cross-sectional data acquired by satellite scatterometers.
Abstract
Scatterometer model functions that directly estimate friction velocity have been developed and are being tested with radar and in situ data acquired during the Surface Wave Dynamics Experiment (SWADE) of 1991. Ku-band and C-band scatterometers were operated simultaneously for extensive intervals for each of 10 days during SWADE. The model function developed previously from the FASINEX experiment converts the Ku-band normalized radar cross-section (NRCS) measurements into friction velocity estimates. These are compared to in situ estimates of surface wind stress and direction across a wide area both on and off the Gulf Stream (for hourly intervals), which were determined from buoy and meteorological measurements during February and March 1991. This involved the combination of a local, specially derived wind field, with an ocean wave model coupled through a sea-state-dependent drag coefficient. The Ku-band estimates u∗ magnitude are in excellent agreement with the in situ values. The C-band scatterometer measurements were coincident with the Ku-band NRCSs, whose u∗ estimates are then used to calibrate the C band. The results show the C-band NRCS dependence at 20°, 30°, 40°, and 50° to be less sensitive to friction velocity than the corresponding cases for Ku band. The goal is to develop the capability of making friction velocity estimates (and surface stress) from radar cross-sectional data acquired by satellite scatterometers.
Twelve national research organizations joined forces on a 30-day, 6800 n mi survey of the Central and Tropical Western Pacific on NOAA's Research Vessel Discoverer. The Combined Sensor Program (CSP), which began in American Samoa on 14 March 1996, visited Manus Island, Papua New Guinea, and ended in Hawaii on 13 April, used a unique combination of in situ, satellite, and remote sensors to better understand relationships between atmospheric and oceanic variables that affect radiative balance in this climatically important region. Besides continuously measuring both shortwave and longwave radiative fluxes, CSP instruments also measured most other factors affecting the radiative balance, including profiles of clouds (lidar and radar), aerosols (in situ and lidar), moisture (balloons, lidar, and radiometers), and sea surface temperature (thermometers and Fourier Transform Infrared Radiometers). Surface fluxes of heat, momentum, and moisture were also measured continuously. The Department of Energy's Atmospheric Radiation Measurement Program used the mission to validate similar measurements made at their CART site on Manus Island and to investigate the effect (if any) of large nearby landmasses on the island-based measurements.
Twelve national research organizations joined forces on a 30-day, 6800 n mi survey of the Central and Tropical Western Pacific on NOAA's Research Vessel Discoverer. The Combined Sensor Program (CSP), which began in American Samoa on 14 March 1996, visited Manus Island, Papua New Guinea, and ended in Hawaii on 13 April, used a unique combination of in situ, satellite, and remote sensors to better understand relationships between atmospheric and oceanic variables that affect radiative balance in this climatically important region. Besides continuously measuring both shortwave and longwave radiative fluxes, CSP instruments also measured most other factors affecting the radiative balance, including profiles of clouds (lidar and radar), aerosols (in situ and lidar), moisture (balloons, lidar, and radiometers), and sea surface temperature (thermometers and Fourier Transform Infrared Radiometers). Surface fluxes of heat, momentum, and moisture were also measured continuously. The Department of Energy's Atmospheric Radiation Measurement Program used the mission to validate similar measurements made at their CART site on Manus Island and to investigate the effect (if any) of large nearby landmasses on the island-based measurements.
