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TEMPORAL AND SPATIAL VARIABILITY OF MAJOR FLOODS AROUND EUROPEAN COASTS

Ziel



THE PHYSICAL STUDY OF STORM SURGES AND RESPONSIBLE MECHANISMS WILL COMPRISE THE FOLLOWING STEPS
A. CHOISE AND PREPARATION OF DATA TO BE USED IN THE STUDY.
EIGHT OR MORE LOCATIONS IN THE AEGEAN AND ONE OR TWO REFERENCE LOCATIONS IN THE NIAN SEA WILL BE ADEQUATLY CHOSEN TO STUDY THE STORM SURGES IN THE AEGEAN.FOR THESE SITES HOURLY DATA OF SEA-LEVEL HEIGHT FOR THE EIGHTEEN MONTH PERIOD JULY 1980-DEC. 1982, WILL BE TYPED INTO THE LABORATORY OF METEOROLOGY COMPUTER.FOR THE SAME PERIOD, HOURLY VALUES OF ATMOSPHERIC PRESSURE AT SEA-LEVEL, FROM A CHOISE METEOROLOGICAL STATIONS WILL ALSO BE TYPED INTO THE SAME COMPUTER.FINALLY THE METEOROLOGICAL CHARTS PRODUCED BY THE "EUROPAISCHER WETTERBERICHT" WILL BE USED TO COMPUTE THE GEOPOTENTIAL HEIGHT OF 500MB SURFACE AND THE GEOSTROPHIC WIND.
THESE FOUR DIFFERENT KINDS OF DETAILED TIME SERIES WILL BE THE BASE FOR THE STUDY OF THE STORM SURGES IN THE AEGEAN.
B. ANALYSIS OF DATA IN TIME DOMAIN.
DETAILED PLOTS OF THE DATA SERIES WILL BE PRODUCED IN ORDER TO FIND :1. THE STORM SURGE EVENTS THAT OCCURED DURING THE EIGHTEEN MONTH PERIOD SELECTED.2. THE HEIGHT OF THE SURGES AT THE DIFFERENT LOCATIONS.3. THE DIRECTION AND SPEED OF PROPAGATION OF SURGES IN THE AEGEAN.4. QUALITATIVE RELATION OF STORM SURGE EVENTS TO ATMOSPHERIC PRESSURE AT SEA-LEVEL, GEOSTROPHIC WIND, AND GEOPOTENTIAL FLUCTUATIONS OF THE 500MB SURFACE. THIS WILL ALLOW TO OUTLINE THE BASIC FACTORS RESPONSIBLE FOR THE STORM SURGES.
CROSS-CORRELATION COEFFICIENTS OF SEA-LEVEL WITH ATMOSPHERIC PRESSURE AND WIND WILL ALSO BE COMPUTED IN TIME DOMAIN.
C. ANALYSIS OF DATA IN FREQUENCY DOMAIN.
SPECTRAL AND CROSS SPECTRAL (GAIN, PHASE, COHERENCE) ANALYSIS OF THE DATA SETS WILL BE PERFORMED. THIS ANALYSIS WILL SHOW THE ENERGY CONTENTS OF EACH SIGNAL IN THE FREQUENCY BAND 0.01CPD-0.5CPD. IT WILL ALSO PERMIT TO TEST THE HYPOTHESIS MADE CONCERNING THE GEOPOTENTIAL OF THE 500MB SURFACE, THAT IS, THIS SIGNAL CONTAINS MOSTLY LOW FREQUENCY BAROTROPIC FLUCTUATIONS. IN THAT CASE THE BAROTROPIC FLUCTUATIONS WILL BE SUBTRACTED FROM THE ORIGINAL SURFACE PRESSURE SIGNALS THUS GIVING THE PART OF THE SIGNAL WHICH IS EXPECTED TO BE MOST RELATED TO SURGES.
CONSIDERING THE SEA-LEVEL AS THE OUTPUT OF A LINEAR SYSTEM WHOSE INPUTS ARE THE SEA-LEVEL ATMOSPHERIC PRESSURE (EVENTUALLY CORRECTED FOR THE BAROTROPIC FLUCTUATIONS) AND THE GEOSTROPIC WIND, A MULTIPLE REGRESSION OF THE SYSTEM'S OUTPUT TO ITS INPUTS WILL BE PERFORMED. THESE COMPLEX COEFFICIENTS WILL BE THE MODELLING PARAMETERS OF THE ANALYTICAL MODEL OF STORM SURGES.

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