1. VIEW_HYD, main screen

 

VIEW_HYD.EXE is the interactive display and analysis program for the hydrometeor data files.Various modes and display criteria may be selected by the user. The display may be controlled by mouse or by keyboard input. Single hydrometeor data may be written to an ASCII file.

 

 

 

1.1 General Information on interactive graphics mode

 

1.1.1 User Interface

 

In each of the two graphic modes (Run- and Stand-by mode) the following items allow user interaction:

 

1.1.1.1 Buttons

Buttons are pushed by moving the mouse cursor on top of the button icon and pressing the left mouse button. Each button is assigned to a function key. Thus, buttons can also be pushed by using the keyboard. The function key which has to be pressed to push a particular button is displayed right next of the button icon.

 

1.1.1.2 Input Fields

Input fields are used to enter numerical values. If an input field is selected, the current value of the field is highlighted. A cursor appears at the end of the input line and the field may be edited.

 

"Backspace" key

            Deletes the character left from the cursor position.

"Delete" key

            Deletes the character right from the cursor position.

 

 

1.1.1.3 Diagram Views

On the Main Screen some diagram views can be seen. A diagram can be selected by

moving the mouse cursor on top of the diagram icon and double click with the left mouse button. On this action a separate window will be opened with a more detailed view and depending on the kind of view also with more work options.

 

1.1.2 Run- and Standby-mode

 

Generally two graphic modes are available:

 

1.1.2.1 Run-mode

 

In Run-mode VIEW_HYD.EXE continuously displays data read from the specified V*.HYD file, meaning that the current display is continuously updated. At start-up time VIEW_HYD.EXE  automatically switches to the Main Screen in Standby-mode. First you have to load a valid V*.HYD File by opening the File-Dialog. After the file is opened  the user may change to the Run-Mode by pressing the Run-Button (or F1-key on keyboard). The Run-mode may be stopped by pushing the STOP button, which then toggles to be the RUN button. The current display is set to Standby-mode.

 

 

1.1.2.2 Standby-mode

In Standby-mode VIEW_HYD.EXE does not continuously read the data file and update the

display, but the user may do menu selections, change parameters or just study the diagram presented on the screen. Standby-mode may be left by pushing the RUN button, which then toggles to be the STOP button.

 

 

 

 

On the upper half of the screen five diagram views are arranged showing the following diagrams:

 

·        Rainrate versus Time

·        Drop Size Distribution

·        Velocity versus Diameter

·        Horizontal Velocity

·        Oblateness versus Diameter

 

Two further diagram views show the front  and the side view of the currently displayed hydrometeor. In the middle of the screen a virtual top view of the measuring area is represented. A window in the lower left of the screen presents some information about the currently displayed hydrometeor. Finally, a control panel is located on the right half of the screen. It contains filter options and control buttons.

 

1.2.1 Control Panel

 

 

1.2.1.1 Buttons

 

button: STOP

In this mode VIEW_HYD.EXE continuously displays data read from the specified data file,

meaning that drop by drop is displayed and all the above mentioned windows are updated. In Run-mode the cursor appears in hour-glass design. Run-mode may be stopped by the STOP or by the QUIT button. If STOP has been pushed VIEW_HYD.EXE switches to Standby-mode.

All the Main Screen options are open to the user in Standby-mode, the STOP button

itself then toggles to be the RUN button. If in Run-mode the end of the time window is reached the button will be toggled to RUN.

 

button: RUN

The RUN button activates the Run-mode. If RUN has been pushed, this button toggles to be the STOP button. The windows in the Main Screen are reset, meaning that all figures are cleaned.

 

 

 

button: STEP +

In Standby-mode this button is used to step through the hydrometeor file entry by entry. Every time button STEP + is pressed, the next hydrometeor is displayed and the windows are updated.

 

button: RESET

In Standby-mode the RESET button resets all windows of the Main Screen and in addition sets the file position pointer to the start of the time window. The start time may be defined via menu by the user, the default value depends on the setting made in the Options-Dialog.

 

button: SCALE

The SCALE button allows to toggle the scale of various displays (10 and 20 mm resp. 8 and 16 mm in maximum size).

 

button: HELP

Displays this document.

 

button QUIT

Terminates VIEW_HYD.EXE.

 

button DEFAULT FILTER :

By pressing this button, the default filter settings, which were saved under the section File à Options, were restored and displayed in the control panel.

 

list-control HYDROMETEOR-TYPE:

By help of this control you can change the type of hydrometeor you want to display in the diagram windows. This is only possible, if you have classified the concerning file.

Choosable types are: all, not classified, rain, melting, snow, hail, manual, invalid.

 

1.2.1.2 Filter Options

 

Filters allow the user to sort out certain hydrometeors of special interest for being displayed. At startup time default values are presented, they may be changed by the user. In order to edit filter parameters, move the mouse cursor to the filter field and press the left mouse button.

 

Name of Filter Remark

 

Time window

Determines the time period for which data are to be displayed.

Diameter

Only hydrometeors whose equivolumetric sphere diameter is within the given filter limits will be evaluated.

Velocity 

Only hydrometeors whose velocity is within the given filter limits will be evaluated.

Oblateness

Only hydrometeors whose oblateness is within the given filter limits will be evaluated.

Pixel system A:

Only hydrometeors whose front view centre pixel is within the given filter limits will be evaluated.

Pixel system B:

Only hydrometeors whose side view centre pixel is within the given filter limits will be evaluated.

 

All this filter-settings and some additional settings could be permanently saved in the Options-Dialog: (File à Options)

 

 

 

Tip Size:                    size of optional rain-tip in mm

Window Title:            user customizable information which will be displayed in the window header

 

1.2.1.3 Area Display Mode

 

The measuring area could be viewed in 2 different modes:

 

It is possible to change the viewing mode by checking the radio button while being in the running mode.

 

 

1.2.2 Windows on the Main Screen

 

1.2.2.1 Measuring Area Window

 

The Measuring Area Window, placed in the middle of the VIEW_HYD.EXE - Main Screen represents a virtual top view of the measuring area. The blue borders represent the user defined limits. Via Filter Pixel System in the filter settings this area could be shrinked. Hydrometeors hitting the border of the virtual measuring area in the Sensor Unit are not evaluated by VIEW_HYD.EXE (nevertheless they are contained in the V*.HYD files). This results in a decrease of the effective measuring area for bigger hydrometeors.

An example is given: For 10 mm diameter spheres, the effective measuring area is not around 100 * 100 mm² any longer but only around 90 * 90 mm². The size of the effective measuring area for an individual hydrometeor is displayed in the information window.

The Measuring Area Window can be set to one of the following representation modes:

 

 

1.2.2.3 Information Window

 

 

Some information on the currently visible hydrometeor can be found in the information window. In addition some general information is displayed:

 

Time

Time (Hour, minute, second and milliseconds) when the hydrometeor encountered the measuring area.

Eq. Diameter

Equivolumetric sphere diameter in mm.

Velocity

Vertical fall velocity in m/s.

Oblateness

Oblateness of the drop. Note that side and front view is considered in the calculation of oblateness. See "Oblateness versus Diameter" for further details.

Hor. Velocity

Horizontal velocity is derived from the difference between the centre pixel position in the first line and the centre pixel position in the last line of a particular drop's shadow data. Horizontal velocity is composed of an absolute velocity value and a movement direction. The velocity value is displayed in m/s. The movement direction is given in relation to the distrometer's alignment and denotes the direction where the drop comes from. (The graphiucs however indicates where the drop goes to). The reading 10 m/s, 45° denotes a drop moving towards cameras A and B. See "Horizontal Velocity" for further details.

Wind Sensor

The horizontal velocity measured by the wind sensor at the time given in the first line (plus/minus 3 seconds) is displayed in the same notation as in the line above the derivation of the distrometer measurement.

If wind sensor data are not available this is marked by ----------

Temperature

The temperature measured at the time given in the first line (plus/minus 3 seconds) is presented in deg C.

If temperature data are not available this is marked by ----------

Type

Type of hydrometeor can manually be set in the “Front/Side View Full Screen” display

 

Area

This is the size of the effective measuring area for the currently shown particle, which has to be used for determination of rainrate and dropsize distribution. This value depends on the size of the virtual measuring area in the Sensor Unit, on the current filter settings and on the size of the hydrometeor.

V*.HYD

In this line the hydrometeor data filename is given. The two numbers at the right hand side of this line indicate the position of the presently displayed hydrometeor and of the length of the file.

 

 

 

1.2.3 Diagram Views on the Main Screen

 

Diagram views serve two purposes. First, they show diagrams which continuously are updated. Second, they can be used as menu buttons. Doubleclicking in one of the diagram views brings up a full screen view of the selected diagram.

 

 

 

Diagram view: Rainrate versus Time

The integration interval used for calculating the rainfall rate for this diagram is not a time interval, but a rainfall quantity. The diagram is updated each time total rainfall exceeds a multiple of 0.1 mm. The rainfall rate over the past 30 minutes, counted from the occurrence time of the most recent exceeding of the 0.1 mm limit, is represented.

 

Diagram icon: Drop Size Distribution

The diagram is updated each time total rainfall exceeds a multiple of 0.1 mm, thus forming the integration interval for calculating the drop size distribution. The diameter class width is set to a value of 0.25 mm.

 

Diagram icon: Velocity versus Diameter

This diagram shows hydrometeor vertical fall velocity versus equivolumetric sphere diameter. A dot is set for each hydrometeor at the corresponding (diameter, velocity) position. The diagram is updated on each hydrometeor. In Run-mode this diagram is cleared whenever total rainfall exceeds a multiple of 0.1 mm.

 

Diagram icon: Horizontal Velocity

Horizontal velocity is derived from the difference between the centre pixel position in the first line and the centre pixel position in the last line of a particular drop's shadow data. This difference in centre pixel positions is made visible by drawing a "drop axis" into the front/side view of a drop. This results in an approximation method to determine the drop's horizontal velocity. It should be pointed out, that the horizontal velocity may be precisely calculated, whenever the drop's views are divided into two identical halves. A dot is set for each hydrometeor at the corresponding (velocity, direction) position. The diagram is updated on each hydrometeor. In Run-mode this diagram is cleared whenever total rainfall exceeds a multiple of 0.1 mm.

 

Diagram icon: Oblateness versus Diameter

This diagram shows drop oblateness versus equivolumetric sphere diameter. A pixel is set for each drop at the corresponding (diameter,oblateness) position. The diagram is updated on each drop.

Oblateness is calculated by forming the geometric mean value of the two height/width ratios, which can be computed from drop front and drop side view. In Run-mode this diagram is cleared whenever total rainfall exceeds a multiple of 0.1 mm.

 

Diagram icons: Front View / Side View

These diagrams show the drop views as seen from each camera system. Note that "drop axes", used for deriving horizontal velocity values, are drawn into the drop views. These “drop axes” only approximately indicate the real axes of bodies of revolution.