Ivan, Lisette and Justin;
a first study within the ERSIN/PCS

This set of images was obtained from the ERS-2 Scatterometer Fast Delivery data.

The data were distributed less than three hours after sensing to European and North American meteorological centers for assimilation into their weather forecast model.

The three color components of the images (R, G, B) have been modulated with the signals of the three Scatterometer antennas after a spatial re-sampling and a normalization with an empirical model of sea backscattering to avoid the incident angle effect.

The scatterometer provides not only a large amount of wind measurements of homogeneous quality to the meteorologists, but also detailed information on very intense structures such as cyclones.

The detailed structure of the cyclone Lisette is clearly shown; in particular one can note the sensitivity of each Scatterometer' s antenna to the wind direction. The famous cyclone's eye where the wind speed falls dramatically is clearly visible at the near range of the swath. Two plots show the mid antenna sigma naught and the wind speed evolution across the cyclone's eye.

For the cyclone Justin the Scatterometer had covered only half of the structure of the tropical cyclone; due to the position of the cyclone's eye in the far range of the swath.

In this case the meteorological institutes have estimated for the sustained wind speed increases up to 90 knots (165 km/h). It is interesting to note that even at this wind speed the direction is very well captured by the Scatterometer. This is a clear indication that the physical phenomena allowing the wind to be measured (basically the sea surface roughness) are still there and that there is no saturation of the sea surface under the wind stress. The under-estimation of the wind speed retrieved by the scatterometer is due to the model used into the ground processing (CMOD-4) that is not well calibrated at such wind speed.

Typhoon Ivan: October 16th,1997 01:12:45 utc

Typhoon Ivan: Sigma Naught Along Track: node # 9 (ESRIN/PCS)

Typhoon Ivan: Wind Speed Along track: node # 9 (ESRIN/PCS)

Go to the text

Cyclone Lisette February 27th, 1997 07:25:06 utc

Cyclone Justin: 16 March 1997 23:33:45