Papers by Christine Gommenginger
A comprehensive theoretical model of radar backscatter from the ocean surface is discussed. It co... more A comprehensive theoretical model of radar backscatter from the ocean surface is discussed. It combines alternative models of the interaction between the wind and the sea surface, and different descriptions of the ocean waveheight spectrum of wind seas, with two alternative scattering theories, namely the composite-surface model and the integral equation method. The effects of swell, limited fetch, and perturbations
The Southampton Oceanography Centre ocean retracker, initially designed for ERS-1 altimeter data,... more The Southampton Oceanography Centre ocean retracker, initially designed for ERS-1 altimeter data, has been updated for RA-2 Envisat waveform data, in order to be used to retrieve some geophysical parameters such as, the significant wave height, the backscatter power and the range. The algorithm, based on the Maximum Likelihood Estimation, is capable of obtaining those parameters, assuming both linear and non-linear conditions. The use of the non-linear case, allows us to estimate additional parameters, such us the skewness, which relates to the nonlinearity of the wave field (i.e. peakier crests/flatter troughs) and a crossskewness term, with no clear physical significance. In the present work, we have retrieved the significant wave height and the range from RA-2 Envisat 18 Hz waveforms using the SOC ocean retracker. First results show that the linear MLE model retrieves parameters consistent with those in RA-2 SGDR records. This work is part of an ESA study for the exploitation of the Envisat radar altimeter individual echoes and S-band data for ocean, coastal zone, land and ice/sea-ice altimetry (RAIES).
Remote Sensing of Environment, 2016
Before the advent of radar altimeters our understanding of the world's climate was based on a few... more Before the advent of radar altimeters our understanding of the world's climate was based on a few instruments moored off the coats of Europe, Japan and North America and visual observations taken from merchant ships. This information was patchy and in many cases of poor quality. It was difficult to relate what was happening at one location with another. The advent of the radar altimeter has changed all that. We had a series of satellite instruments that made consistent measurements of significant wave height across the globe. Initial work concentrated on simply mapping the wave climate and investigating means and seasonal variation. However with longer records came the ability to look at inter-annual variability. It had been known since the late 70's that wave heights measured at a few sites around the North East Atlantic had shown a dramatic increase. It was only the combination of spatial and temporal sampling from the altimeter that allowed us to discover the extent of the changes and how they related to the North Atlantic Oscillation index. Of course it is not only the mean wave conditions that are important, extreme waves are of vital interest to naval architects and the designers of offshore structures. Being able to estimate extreme waves from altimeter data enables us for the first time to establish what extreme conditions might be in any part of the world. At present we do not exploit the spatial nature of the altimeter data in our estimation of the extremes but this is an active research area.
The Southampton Oceanography Centre ocean retracker, initially designed for ERS-1 altimeter data,... more The Southampton Oceanography Centre ocean retracker, initially designed for ERS-1 altimeter data, has been updated for RA-2 Envisat waveform data, in order to be used to retrieve some geophysical parameters such as, the significant wave height, the backscatter power and the range. The algorithm, based on the Maximum Likelihood Estimation, is capable of obtaining those parameters, assuming both linear and non-linear conditions. The use of the non-linear case, allows us to estimate additional parameters, such us the skewness, which relates to the nonlinearity of the wave field (i.e. peakier crests/flatter troughs) and a crossskewness term, with no clear physical significance. In the present work, we have retrieved the significant wave height and the range from RA-2 Envisat 18 Hz waveforms using the SOC ocean retracker. First results show that the linear MLE model retrieves parameters consistent with those in RA-2 SGDR records. This work is part of an ESA study for the exploitation of the Envisat radar altimeter individual echoes and S-band data for ocean, coastal zone, land and ice/sea-ice altimetry (RAIES).
• Records from the Atlantic around the UK which are most influenced by in- flowing Atlantic water... more • Records from the Atlantic around the UK which are most influenced by in- flowing Atlantic waters reveal a general pattern of low salinity in the mid-late 1970s, followed by three decades of quite large inter-annual variability, probably closely associated with changes in the atmospheric circulation (North Atlantic Oscillation). Salinity records from the Faroe-Shetland Channel and the Ellett Line indicate
Most people are generally aware of the fact that the GPS receivers used on boats and airplanes us... more Most people are generally aware of the fact that the GPS receivers used on boats and airplanes use signals transmitted by a constellation of satellites to determine their locations. What is less obvious is that the same signals are constantly being scattered off the surrounding seas and land, and these signals contain valuable and varied information on the Earth's environment.
HIGH FREQUENCY SPECTRAL TAILS and SSB 10 3 10 2
Canadian Journal of Remote Sensing
Canadian Journal of Remote Sensing
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Papers by Christine Gommenginger