ERS-2 successfully targets China's Typhoon Matsa


MERIS view of Matsa
 
The Medium Resolution Imaging Spectrometer (MERIS) aboard Envisat acquired this image of Typhoon Matsa above the East China Sea on 4 August 2005 in Reduced Resolution Mode - providing a spatial resolution of 300 metres. An ERS-2 C-band scatterometer acquisition made the same day showed the wind fields powering the storm

Typhoon Matsa
 
A map of the wind field at the heart of Typhoon Matsa, using data acquired at 02:09:38 UTC on 17 August 2005 by the C-band scatterometer on board ESA's ERS-2 spacecraft. The map indicates wind direction and also wind velocity - the more lines on each bar, the highest the velocity. The data provides insight into the pressure system powering the hurricane. Click on the high resolution version to see technical details.


 
ECMWF analysis for 4 August 2005 00UTC for mean sea-level pressure (contours) and 10-m surface wind (cream streamlines), along with ERS-2 scatterometer winds (cyan: assimilated, red: rejected, grey: thinned) and in-situ surface observations (green: assimilated, white: rejected).

Matsa landfall
 
Strike probability map for Typhoon Matsa, starting from the ECMWF analysis of 4 August 2005 00UTC and incorporating C-band ERS-2 scatterometer data. ECMWF operates a so-called 'Ensemble Plotting System' (EPS) in which, in addition to the operational high-resolution forecast (OPER), 51 other alternatives forecasts are made at a lower resolution. One of these forecasts, the control (CTRL) is run from the same starting point but at lower resolution; the other 50 members of EPS are each run from slightly perturbed starting points with perturbed physics models - between them representing uncertainty in the initial state and errors built in to ECMWF's non-perfect physics models. Both contribute to incorrect forecasts and so are incorporated into the probability forecast. The idea is that all these members together provide an error bar for the OPER run - the larger the spread, the less certain the result. The probabilities range from 0.05 (one out of 20) to 1 (one out of one), so the numbers in the legend should be divided by ten or 100.

ERS in orbital configuration
 
The follow-on from ERS-1, ESA's ERS-2 Earth Observation satellite remains operational more than a decade after its 1995 launch. Its payload includes a unique C-band scatterometer that can measure wind fields at the heart of storms of hurricanes, even through clouds and heavy rain.



Release date: 26 October 2005