6. Oblateness versus Diameter (Full Screen)

 

 

 

The full screen representation of the diagram "Oblateness versus Diameter" can be selected from the Main Screen by moving the mouse cursor on top of the according diagram icon and doubleclick with the left mouse button. The results presented in this diagram are the geometrical mean of the ratios heigth / width of a raindrop's front and side view. Strictly speaking these results are not really the raindrop's oblateness, but only an approximation.

 

6.1 Menu Buttons

 

button: RUN

Pushing this button draws the diagram for the given filter settings. A dot is set for each drop at the corresponding (equivolumetric sphere diameter, oblateness) position. The mouse cursor changes its appearance to an hourglass cursor in Run-mode, and the RUN button toggles to be the STOP button. Drawing can be terminated by pressing the STOP button.

 

button: MAIN

Pushing this button returns control to the Main Screen.

 

button: HELP

Pushing this button displays a help window.

 

button: COMP

If this button is pushed, graphs taken from the literature and showing relations between equivolumetric sphere diameter and drop oblateness will be drawn.

button: GRID

Pushing this button draws ten yellow crosses into the Oblateness versus Diameter diagram, indicating the nominals of the calibration sphere values. The ten crosses correspond to the following diameters: 0.5, 1, 2, 3, 4, 5, 6, 7, 8 and 10 mm. This menu option allows a quick and easy check of the calibration status of the instrument.

 

button: N(H/W)

Pushing this button invokes the Oblateness Distribution analysis.

 

button: Calibrate

Pushing this button allows the user to make a software adjustment to the measurement result. Previously selected output_data will be processed and written to 2 files named corr_in.dat and corrfact.dat.

6.2 Diagram Header

 

The diagram header contains information on filter settings and also includes the following fields:

 

 

6.3 Comparison with Literature Models

 

The graphs taken from the literature for oblateness versus equivolumetric sphere diameter are:

 

6.3.1 Drop Oblateness after Pruppacher and Beard (1970)

 

For big D H/W(D) is given as:

 

 

where D is the equivolumetric sphere diameter in mm. For small D here the graph is drawn as H/W(D)=1.

 

6.3.2 Drop Oblateness after Poiares Baptista (1992):

For big D H/W(D) is given as:

 

 

where D is the equivolumetric sphere diameter in mm. For small D here the graph is drawn as H/W(D)=1.