3.
Drop Size Distribution (Full Screen)
The full screen
representation of the diagram "Drop Size Distribution" can be
selected from the Main Screen by moving the mouse cursor on top of the
according diagram icon and doubleclick the left mouse button.
3.1
Determination of DSD graph
In order to obtain
the drop size distribution from the distrometer measured raindrop data, drops
have to be classified into drop size classes. The equivolumetric diameter of
each drop is used as a classification parameter. Since the drop size
distribution is the number of drops per unit volume and per unit size, for unit
size class the following quotient has to be summed up:
where:
A ... effective measuring area of drop
Dt ... time integration interval
v ... velocity of drop
Therefore the
number of drops per unit volume and per unit size for a particular size class
is computed as:
where:
Dt ... integration time interval (sec)
DD ... width of size class (mm)
Aj ... effective measuring area of drop j (mē)
vj ... velocity of drop j (m/s)
i ... denotes drop size class
j ... denotes single drop
Mi ... number of drops in class i measured during Dt
Di ... diameter of class i
3.2
Menu Buttons
button: RUN
Pushing this
button starts calculation of the drop size distribution using the present
setting of the integration interval. The integration interval can be a time
interval, a rainfall quantity, or a number of drops. Every time the RUN button
is pushed, a new Drop Size Distribution diagram is drawn. The mouse cursor
changes its appearance to an hourglass cursor during calculations, and the RUN
button toggles to be the STOP button.
button: MAIN
Pushing this
button returns control to the Main Screen.
button: HELP
Pushing this
button displays a help window.
button: Delta -
This button
decreases the drop size class width.
Possible values:
0.05, 0.10, 0.15, 0.20, 0.25 mm.
button: Delta +
This button
increases the drop size class width.
Possible values: 0.05,
0.10, 0.15, 0.20, 0.25 mm.
button: INTEGR.
Pushing this
button allows to select an integration interval mode (time, rainfall quantity,
or number of drops, full time range) for the computation of the drop size
distribution. In addition to the integration mode the interval size can be
entered. The current integration interval mode is highlighted in the diagram
header.
button: COMP
If this button is
pushed, the measured DSD is compared with a Marshall - Palmer - DSD of the same
rainrate.
button: DEFAULT
This button
restores the default integration criterias.
button: RESET TIME
This button causes
the file-pointer set to the beginning of the time interval.
3.3
Diagram Header
The diagram header
contains information on filter settings and also includes the following fields.