Conference Paper

Validation of Parametric Hurricane Models by ENVISAT ASAR

Conference: SEASAR 2006
Source: DLR


In the past decade several satellite borne synthetic aperture radars (SAR) have been put into orbit. A synthetic aperture radar (SAR) not only records the intensity of the returned signal, but also the phase history of the backscattered radar signal and is processed to high spatial resolution images. To observe the structure of tropical cyclones at the sea surface RADARSAT 1 and ENVISAT ASAR Scan SAR images (400 x 400 km coverage) are the preferred datasets used. Together with optical imagery that yield information on the cloud tops they yield the possibility to investigate the three dimensional structure of tropical cyclones. The intensity images are calibrated and information on wind speed is derived. In addition sea surface features relating to cloud structure and rain rate are analysed. We give an assessment on the possibility to retrieve wind speed from SAR using the CMOD algorithms.

In addition we have been investigating the following features in SAR images of hurricanes:

- Wavelength and Direction of Boundary layer rolls for information of mixed boundary layer depth - Radius of maximum wind speed - Sea State in terms of wavelength and -direction

These image parameters are related to parametric models of hurricanes and validated by aircraft measurements from the national hurricane center (NHC). The work aims at the improvement of prediction of the cyclone track, intensity and sea state in such high wind speed conditions.

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Available from: Antonio Reppucci, Sep 30, 2015
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    ABSTRACT: The high spatial resolution and large coverage of satellite-based synthetic aperture radars (SAR) offers a unique opportunity to derive mesoscale wind fields over the ocean surface, providing high resolution wind fields near the shore. For this purpose, algorithms were developed and tested using the ScanSAR aboard the Canadian satellite RADARSAT-1, operating at C-band with horizontal polarization in transmit and receive. Wind directions are extracted from wind-induced streaks visible on most SAR images. Wind speeds are derived from normalized radar cross sections (NRCS) using empirical models. The models were developed for scatterometers (SCAT) operating at C-band with vertical polarization and must be modified for horizontal polarization. Several available C-band polarization ratios were considered, including theoretical and empirical forms. To verify and improve the algorithm, wind speeds were computed from several RADARSAT-1 ScanSAR images and compared to colocated measurements from the SCAT aboard the European remote sensing satellite ERS-2 and to the results of the Danish high resolution limited area model (HIRLAM). Using the colocated measurements, the polarization ratio was estimated and applied to improve the wind retrieval algorithm. In addition, the main error sources in SAR wind field extraction are discussed with respect to the RADARSAT-1 ScanSAR data. Sensitivity studies were performed under different atmospheric situations using the modified C-band model to compute the errors due to wind direction and inaccuracies in NRCS
    IEEE Transactions on Geoscience and Remote Sensing 10/2000; 38(5-38):2122 - 2131. DOI:10.1109/36.868871 · 3.51 Impact Factor
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    ABSTRACT: This article reviews several microwave instruments employed in research and analysis of tropical cyclones (TCs), typhoons, and hurricanes. The instruments discussed include scatterometers, microwave radiometers, synthetic aperture radars (SARs), and rain radar from space. Examples of the particular contribution by one or more of these instruments in analysis of several storms illustrate the comprehensive new views provided by the SeaWinds scatterometers, the detailed high-resolution wind field provided by RADARSAT-1 SAR, particularly inside and in the vicinity of hurricane “eyes,” and the presence of secondary flows in the region between rainbands in TCs. The high spatial resolution of precipitation data from the Tropical Rainfall Measuring Mission's rain radar, combined with scatterometer or SAR data, give a significant improvement in the details that can be seen from space, at the surface, and in the precipitating areas of TCs. The microwave instruments provide a penetrating view below the upper level cirrus clouds.
    Journal of Oceanography 01/2002; 58(1):137-151. DOI:10.1023/A:1015884903180 · 1.27 Impact Factor