24
3 Basics of Geophysical Fluid Dynamics
3.5.7 Creation of an Animated GIF File
The “convert” program of ImageMagick can be used to convert the sequence of GIF
file into a single animated GIF file For example, a sequence of GIF f les named
img1001.gif, img1002.gif, img1003.gif, etc. can be composed in an animated GIF
fil (named anim.gif) by entering:
convert -delay 10 img*.gif anim.gif
in the Command Prompt window. The “-delay” option specifie the time lapse
between frames in milliseconds. After moving the resultant animated GIF fil to
another safe location, individual GIF frame file should be immediately deleted to
free up space on the computer.
3.5.8 Phase Speed
The phase speed of a wave is given by the ratio between wavelength and wave
period:
c =
λ
T
(3.3)
With this phase speed, Eq. (3.2) can be rewritten as:
A(x, t) = A o sin
2π
λ
(x − ct)
.
(3.4)
A positive c makes the wave propagating into the positive x-direction, whereas a
negative c makes it running into the opposite direction.
3.5.9 Dispersion Relation
The length and period of waves in fluid are in general not independent of each
other. Instead of this, there is a relation between wave period and wavelength called
the dispersion relation. The form of this relation varies with the situation. Waves
of a wavelength long compared with the flui depth behave much differently from
waves of a wavelength short compared with the flui depth. Section 4.2.5 presents
the dispersion relation for long surface-gravity waves.
3 Basics of Geophysical Fluid Dynamics
3.5.7 Creation of an Animated GIF File
The “convert” program of ImageMagick can be used to convert the sequence of GIF
file into a single animated GIF file For example, a sequence of GIF f les named
img1001.gif, img1002.gif, img1003.gif, etc. can be composed in an animated GIF
fil (named anim.gif) by entering:
convert -delay 10 img*.gif anim.gif
in the Command Prompt window. The “-delay” option specifie the time lapse
between frames in milliseconds. After moving the resultant animated GIF fil to
another safe location, individual GIF frame file should be immediately deleted to
free up space on the computer.
3.5.8 Phase Speed
The phase speed of a wave is given by the ratio between wavelength and wave
period:
c =
λ
T
(3.3)
With this phase speed, Eq. (3.2) can be rewritten as:
A(x, t) = A o sin
2π
λ
(x − ct)
.
(3.4)
A positive c makes the wave propagating into the positive x-direction, whereas a
negative c makes it running into the opposite direction.
3.5.9 Dispersion Relation
The length and period of waves in fluid are in general not independent of each
other. Instead of this, there is a relation between wave period and wavelength called
the dispersion relation. The form of this relation varies with the situation. Waves
of a wavelength long compared with the flui depth behave much differently from
waves of a wavelength short compared with the flui depth. Section 4.2.5 presents
the dispersion relation for long surface-gravity waves.