ISEO – 27 July 2010
MODAL ANALYSIS APPLIED
TO THE STUDY OF THE INTERNAL WAVE
STRUCTURE OF ISEO LAKE
GIULIA VALERIO
Università degli Studi di Brescia
QUESTION - How does a so complex bathymetry affect the internal
wave structure in lake Iseo?
distance [m]
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
elevation [m] (10:1)
350
300
250
200
150
100
50
0
-50
-100
-150
-200
-250
Csanady (1972) - Bäuerle (1994) - Wang et al. (2000) - Fricker and Nepf (2000) - Lemmin and Mortimer (2005) - Antenucci
and Imberger (2001) - Gomez-Giraldo et al. (2006) - Rueda et. al (2003) - Shimizu et al. (2007) – Okely et al. (2010)
NUMERICAL APPROACH - Modal model
• Linear
 1 2
 t  t    V1  0

  2    V  0
2
 t
 V
 1  V1   gh111    0
0
 t

 V2  V   gh    gh  
2
2 1
1
2 2
2
 t
• Separation in time and space
 Eigenvalue problem
i  x, i     x, i   0
Mortimer (1974) - Lemmin and Mortimer (2005) - Shimizu et al. (2007) – Shumizu and Imberger (2008) – De la Fuente et
al. (2008)
MODEL  EXPERIMENTAL APPROACH - Field activity
• Forced waves - dominant mode 1
• Locations of the monitoring stations
• Influence of spatial variability of wind
field on modes excitation
•Poincarè waves trapped
around the island
• Sampling strategy for temperature
mapping
www.rmso.com.au
Becker and Miles (1991) – Strub and Powell (1986) - Rueda et al. (2005) - Strub (1986)- Laval et al. (2003), Pan et al.
(2002) - Shimizu et al. (2007) - Bäuerle (1994) - Okely et al. (2010)
FIELD ACTIVITY  MODEL
• General agreement of the main basin scale motion (Cfr 17/7 T3; 18/7
T17)
• Problems in phase capturing in the south (Cfr olaris)  non-uniform
wind distribution?
• Excitation of vertical modes > 1 (Cfr 20/7 T22) necessity number of
layers > 2 when the upper layer is shallow
• Non-linearity of the singnal  limitations of the linear model
Thanks for your attention!