Estimation of the real aperture radar modulation transfer function directly from synthetic aperture radar ocean wave image spectra without a priori knowledge of the ocean wave height spectrum

1994 ◽  
Vol 99 (C7) ◽  
pp. 14291 ◽  
Author(s):  
S. Jacobsen ◽  
K. A. Høgda
Keyword(s):  
Transfer Function ◽  
Wave Height ◽  
Modulation Transfer Function ◽  
A Priori ◽  
Ocean Wave ◽  
Synthetic Aperture ◽  
A Priori Knowledge ◽  
Modulation Transfer ◽  
Wave Image ◽  
Aperture Radar

scholarly journals A Novel Approach to Marine Wind Speed Assessment Using Synthetic Aperture Radar

2006 ◽  
Vol 21 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Todd D. Sikora ◽  
George S. Young ◽  
Nathaniel S. Winstead
Keyword(s):  
Wind Speed ◽  
Synthetic Aperture Radar ◽  
Wind Direction ◽  
A Priori ◽  
Gulf Of Alaska ◽  
Synthetic Aperture ◽  
A Priori Knowledge ◽  
Direction Field ◽  
Aperture Radar ◽  
Priori Knowledge

Abstract This paper describes a product that allows one to assess the lower and upper bounds on synthetic aperture radar (SAR)-based marine wind speed. The SAR-based wind speed fields of the current research are generated using scatterometry techniques and, thus, depend on a priori knowledge of the wind direction field. The assessment product described here consists of a pair of wind speed images bounding the wind speed range consistent with the observed SAR data. The minimum wind speed field is generated by setting the wind direction field to be directly opposite to the radar look direction. The maximum wind speed field is generated by setting the wind direction field to be perpendicular to the radar look direction. Although the assessment product could be generated using any marine SAR scene, it is expected to be most useful in coastal regions where the large concentration of maritime operations requires accurate, high-resolution wind speed data and when uncertainty in the a priori knowledge of the wind direction precludes the generation of accurate SAR-based wind speed fields. The assessment product is demonstrated using a case in the northern Gulf of Alaska where synoptic-scale and mesoscale meteorological events coexist. The corresponding range of possible SAR-based wind speed is large enough to have operational significance to mariners and weather forecasters. It is recommended that the product become available to the public through an appropriate government outlet.

Extreme Waves Detected by Satellite Borne Synthetic Aperture Radar

2002 ◽  
Author(s):  
Susanne Lehner ◽  
Johannes Schulz-Stellenfleth ◽  
Andreas Niedermeier ◽  
Jochen Horstmann ◽  
Wolfgang Rosenthal
Keyword(s):  
Synthetic Aperture Radar ◽  
Wave Height ◽  
Sampling Rate ◽  
Ocean Wave ◽  
Synthetic Aperture ◽  
Extreme Waves ◽  
Sar Images ◽  
Data Set ◽  
Sar Data ◽  
Aperture Radar

Within the last 20 years at least 200 supercarriers have been lost, due to severe weather conditions. In many cases the cause of accidents is believed to be ‘rouge waves’, which are individual waves of exceptional wave height or abnormal shape. I situ measurements of extreme waves are scarce and most observations are reported by ship masters after the encounter. In this paper a global set of synthetic aperture radar (SAR) images is used to detect extreme ocean wave events. The data were acquired aboard the European remote sensing satellite ERS-2 every 200 km along the track. As the data are not available as a standard product of the Europea Space Agency (ESA), the radar raw data were focused to complex SAR images using the processor BSAR developed by the German Aerospace Center. The entire SAR data set covers 27 days representing 34000 SAR imagettes with a size of 5km×10km. Complex SAR data contain information on ocean wave height, propagation direction and grouping as well as on ocean surface winds. Combining all of this information allows to extract and locate extreme waves from complex SAR images on a global basis. Special algorithms have been developed to retrieve the following parameters from the SAR data: Wind speed and direction, significant wave height, wave direction, wave groups and their individual heights. The satellite ENVISAT launched in March 2002 acquires SAR data with an even higher sampling rate (every 100 km). It is expected that a long-term analysis of ERS and ENVISAT data will give new insight into the physical processes responsible for rogue wave generation. Furthermore, the identification of hot spots will contribute to the optimization of ship routes.

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