12

3.  FEATURES  OF  STORM  SURGES

Some  characteristic  parameters  (calculated  for  each  particular  storm  surge)  define  the
features  of  storm  surges  threatening  the  coasts  and  constitute  the  basis  of  the  storm  surge
definition  provided  in  chapter  1.
These  parameters  include  the  maximum  sea  level  recorded  during  the  surge  and  the  mean
daily  reference  level  indicator,  which  is  a  highly  useful  parameter  in  routine  operational
forecasting.  The  latter  is  determined  by  the  surplus  (above  the  multi-year  mean  sea  level)  of
surface  water  accumulated  off  the  southern  coast.  Other  important  parameters  are  the
duration  (persistence)  of  the  high  levels,  and  the  persistence  of  levels  above  the  warning  and
alarm  levels  (560  cm  and  580  cm  at  Swinoujscie).
3.1  Maximum  sea  levels
The  highest  sea  levels  in  the  area  under  review  were  observed  during  storm  surges;  the  700
cm  level  was  exceeded  at  the  Wismar  station  in  November  1995,  at  a  level  of  702  cm.  During
the  same  storm,  Swinoujscie  (661  cm)  and  Warnemünde  (660  cm)  reported  the  highest
levels  of  the  1976-2000  period.  By  contrast,  the  highest  level  in  Sassnitz  was  observed  in
January  1992,  at  636  cm,  and  in  Kotobrzeg  in  November  1988  (642  cm).

frequency  in  %
—N>  N>  CO
О  СЛ  О  СЛ  О  СЛ  О

Г

II

n

II

1

I

1

1

r

ln

1

■

■

550  560  570  580

590  600  610  620  630  640  650  660  670  680
maximum  sea  level  in  cm

690  700  710

■  Wismar  DWamemünde  DSassnitz

Fig.  3.1.  Frequency  distribution  of  maximum  sea  levels  observed  during  storm  surges  at
Wismar,  Warnemünde  and  Sassnitz  in  1976-2000
The  frequency  distribution  of  maximum  sea  levels  (analysis  of  sea  levels  at  the  German
stations  in  1976-2000)  is  presented  in  Fig.  3.1.  Maximum  sea  levels  (during  storm  surges)  at
the  Wismar  station  were  observed  most  frequently  (about  20%)  in  the  610-620  cm  range.  At
Warnemünde,  about  21%  of  maximum  levels  were  within  the  590-600  cm  range.  At  Sassnitz,
up  to  52.1%  of  the  maximum  sea  levels  ranged  between  570  and  590  cm.
The  frequency  distribution  of  maximum  sea  levels  (reported  at  Swinoujscie  and  Kotobrzeg
during  storm  surges  in  1976-2000)  is  presented  in  Figs.  3.2.  and  3.3.,  in  comparison  with  the
1950-1975  period.  In  both  periods,  i.e.  1950-1975  and  1976-2000,  the  maximum  sea  levels
ranged  mostly  from  570-590  cm;  at  Swinoujscie,  the  percentage  was  48%  in  the  former
period  and  52%  in  the  latter,  compared  to  about  53%  and  49%,  respectively,  at  Kotobrzeg.  At