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					  Using Satellite Altimetry
for Storm Surge applications

        Ole B. Andersen
Overview
Coverage
Three related parameters.
         Sea surface height
         Wave height
         Wind Speed.




2   DTU Space, Technical University of Denmark   ESA Storm Surge Conference,
                                                   Hamburg, September, 2010
3   DTU Space, Technical University of Denmark   ESA Storm Surge Conference,
                                                   Hamburg, September, 2010
 Altimetric Observations
Accurate ranging to the sea surface is
Based on accurate time-determination


                               Typical ocean waveforms
                               Registred at 2000 Hz
                               (every 3 meters)

                               Averaged into 20 Hz /1 Hz
                               (300 m / 7 km averaging).

                               SWH from slope of leading edge

                               σ0 / windspeed from returned power



 4   DTU Space, Technical University of Denmark                     ESA Storm Surge Conference,
                                                                      Hamburg, September, 2010
     Observations:

3(4) ongoing missions
            JASON-1
            JASON-2
            ENVISAT
            GFO ?????


Near Real time altimetry
       4-6 hours , ~5-7 cm acc.


                              Repeat        Track     Inclination
Satellite
                              Period       spacing     Coverage
GEOSAT/GFO                    17 days      163 km    108°(+/-72°)

ERS/ENVISAT                   35 days      80 km     98° (+/-82°)

                              10 Denmark
TOPEX/JASON Technical University of days
    5  DTU Space,                          315 km       66.5° Storm Surge Conference,
                                                            ESA
                                                              Hamburg, September, 2010
                              Sampling: ”Short-term”.




         95% correlation between Altimetry and tide gauge in Aberdeen
6   DTU Space, Technical University of Denmark          ESA Storm Surge Conference,
                                                          Hamburg, September, 2010
                                               Satellite observations


Brown type return:

Sea Level
Wind Speed
Wave height

Example:
 Hurricane
 Katherina
 August 2006




   7   DTU Space, Technical University of Denmark                 ESA Storm Surge Conference,
                                                                    Hamburg, September, 2010
                  Introduction to the North Sea
                                   Norway        Marginal Sea to the North Atlantic.
                                                 Counterclockwise mean circulation
                                                 External surges generated by wind
                                                        forcing.



                                                     = Water level recorders




8   DTU Space, Technical University of Denmark                   ESA Storm Surge Conference,
                                                                   Hamburg, September, 2010
    Characteristic time scales from Tide Gauges




Courtesy of Hoyer and Boewitz.

    9   DTU Space, Technical University of Denmark   ESA Storm Surge Conference,
                                                       Hamburg, September, 2010
10   DTU Space, Technical University of Denmark   ESA Storm Surge Conference,
                                                    Hamburg, September, 2010
11   DTU Space, Technical University of Denmark   ESA Storm Surge Conference,
                                                    Hamburg, September, 2010
                 Correlations, Water level recorders
        Autocorrelation                                        Crosscorrelation

                                        Short timescales,
                                         ~10-60 Hours
                                        Tidal residuals at
                                         12, 24 hours:
                                         shallow water tides
                                        Counterclockwise
                                         propagation of sea
                                         level anomalies




12   DTU Space, Technical University of Denmark                ESA Storm Surge Conference,
                                                                 Hamburg, September, 2010
                                             Predicting




             Method                                 Correlation   RMS diff. (cm)
             T/P only                                  0.53            20
             In situ only                              0.62            19
             2-dim model, interior                                     20
             2-dim model, at coast                     0.92            18
             Regression model                          0.68            13



Results curtesy of J. Hoyer, DMI, Denmark
  13   DTU Space, Technical University of Denmark                       ESA Storm Surge Conference,
                                                                          Hamburg, September, 2010

				
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