Geoffrey Dix jr.
NCAR/MMM
8/15/02
The MER program is written in IDL and is used to create the following:
- Reflectivity Parameter plots
- CAPPIs
MER counts on the following programs and files to execute:
cednex.ct– this is the color table used to produce the reflectivity intensity
get_citation.pro – this program is used to retrieve the aircraft data
get_comp_efield.pro – this program is used to get the efield data
get_micro.pro – this program is used to retrieve the microphysics data
MER uses a setup file whose default name is 'setup' or specified by the user upon program execution as a command-line argument. Here are some examples: MER Execution
The setup file is formatted in the following manner:
description : value
The description cannot have any whitespace characters in it. It is ok that
there is whitespace between the description and the colon, but the actual
description cannot contain any whitespace.
It is also important to note that all filenames assume the current directory.
For this reason, specifying the full paths of any and all filenames is advised.
setup_curr is a sample setup file with a number on each line of the setup file. The following is an explanation of those numbers and each lines' corresponding significance as it pertains to the MER software.
Line 1:
This line points to the name of the file that contains the names of the radar volume files. The radar volume files are expected to be in the same directory as the file that contains their names.
Line 2:
This line points to the name of the file that contains the efield data.
Line 3:
This line points to the name of the file that contains the aircraft data
Line 4:
This line points to the name of the file that contains the microphysics data
Line 5:
This line allows the user to choose between gif images (1) or postscript images (0) Note: There has not been a need for postscript images to this point therefore they have not been tested recently and plot position and plot accuracy cannot be guaranteed.
Line 6:
This line lets the user specify whether he or she is using NEXRAD or WSR74C data. The value can be one or more words and is also used as a label on the plots produced. If using NEXRAD data, the first word must be NEXRAD (all caps).
Line 7:
This line allows the user to decide whether he or she wants to produce MER plots (1) or not (0)
Line 8:
This line allows the user to decide whether he or she wants to produce reflectivity parameter plots (1) or not (0)
Line 9:
This line allows the user to decide whether he or she wants to produce track plots (1) or not (0)
Line 10:
This line allows the user to decide whether he or she wants to produce CAPPIs (1) or not (0)
Line 11:
This line allows the user to decide whether he or she wants to produce efield plots (1) or not (0)
Line 12:
This line allows the user to decide whether he or she wants to produce an ascii reflectivity file (1) or not (0)
Line 13:
This line should be set to 1. If this ever changes it means you are using different radar data and you have lots of work to do to make it work
Line 14:
This line is only relevant if the user is plotting CAPPIs. To plot a CAPPI for every volume scan set this value to 1. If not plotting CAPPIs this value is ignored by the software
Line 15:
This line allows the user to specify the time interval for each plot. The time interval is calculated in seconds. E.g. – for 10min plots this value should be 600
Line 16:
This line allows the user to specify a maximum plotting value for Ez (kV)
Line 17:
This line allows the user to specify a minimum plotting value for Ez (kV)
Line 18:
This line allows the user to specify a maximum plotting value for Emag (kV)
Line 19:
This line allows the user to specify a minimum plotting value for Emag (kV)
Line 20:
This line allows the user to specify a box size (km) to calculate reflectivity averages. The averages are calculated from the aircraft position to the user specified value in the positive x direction, negative x direction, positive y direction, negative y direction and in the positive and negative z direction all the way to max_z and min_z within the box.
Line 21:
This line allows the user to specify another box size (km) to calculate reflectivity averages.
Line 22:
This line allows the user to specify the maximum value (km) of x from the origin
Line 23:
This line allows the user to specify the minimum value (km) of x from the origin
Line 24:
This line allows the user to specify the maximum value (km) of y from the origin
Line 25:
This line allows the user to specify the minimum value (km) of y from the origin
Line 26:
This line allows the user to specify the beginning date of the data (yy/mm/dd)
Line 27:
This line allows the user to specify the beginning time of the data (hh:mm:ss)
Line 28:
This line allows the user to specify the ending date of the data (yy/mm/dd)
Line 29:
This line allows the user to specify the ending time of the data (hh:mm:ss) Note: If the data crosses over midnight to a new day you must add additional time to the previous day. E.g. – The data starts at 18:00:00 and ends at 02:30:00 the next day, the end time would be: 26:30:00
Line 30:
This line allows the user to specify the directory to place all plots in. Note: There must be a trailing slash to specify that directory
Line 31:
This line allows the user to specify the filename of the reflectivity output file. This line is ignored if the user chose not to create an ascii file
All MER Dependency files are expected to be in the same directory as the MER software. After assuring that this is the case and editing the setup file, enter IDL.
At the IDL command prompt type the following:
IDL> .compile mer.pro
IDL> mer, 'setup_curr'
Where setup_curr can be replaced with the name of your setup file
Alternatively you can simply type the following:
IDL> .compile mer.pro
IDL> mer
This assumes your setup file is called ‘setup’
The first or top panel is a plot of the microphysics
The second panel down is a plot of the reflectivity at the aircraft, temperature, and airplane bank angle.
The third panel down is a plot of the vertical curtain of reflectivity along the aircraft track and the aircraft's altitude.
The fourth or bottom panel is a plot of the Ez component of efield for both the K and M matrices and Emag (Ex2+Ey2+Ez2)1/2 calculated for the M matrix.
Reflectivity Parameter Plots
Refl_plot.gif is an example of a Reflectivity Parameter plot produced by the MER software. It has four panels on it.
The first or top panel is the same as the third panel on the MER plot. It is a plot of the vertical curtain of reflectivity along the aircraft track and the aircraft's altitude.
The second panel down is a plot of average reflectivities at 5km and above in a box surrounding the aircraft position (the box only pertains to x and y, not z). There are two user defined box sizes that averages are calculated for.
The third panel down is a plot of the average reflectivities at 5km and above in a 1km box and the maximum reflectivities in both a user defined box and a 15km box.
The fourth or bottom panel is the same as the bottom panel on the MER plot. It is a plot of the Ez component of efield for both the K and M matrices and Emag (Ex2+Ey2+Ez2)1/2 calculated for the M matrix.
Efield Plots
Efield_plot.gif is an example of an Efield plot produced by the MER software. It has five panels on it.
The first or top panel is a plot of the x component of Efield for both the M and K matrices.
The second panel down is a plot of the y component of Efield for both the M and K matrices.
The third panel down is a plot of the z component of Efield for both the M and K matrices.
The fourth panel down is a plot of the calculated Emag (Ex2+Ey2+Ez2)1/2 for both the M and K matrices.The fifth or bottom panel is a plot of Qsca for the M matrix and Slack for the K matrix.
CAPPIs
CAPPI_plot.gif is an example of a CAPPI plot produced by the MER software. It has three panels on it.
The three panels on this plot are CAPPIs at the 4, 7, and 10km layers. They are labeled as such. The one exception is when the aircraft is flying. When the aircraft reaches an altitude of 4km or greater, the aircraft's altitude replaces that of the nearest CAPPI. E.g. - if the aircraft's altitude is 8km, the 7km CAPPI is replaced by an 8km CAPPI.
The aircraft's altitude is calculated by taking the average of it's altitude at the beginning of the volume scan and at the end of the volume scan. The average is then rounded to the nearest integer value and the closest CAPPI is replaced if the average is greater than 4km. The CAPPI replaced by the aircraft altitude is labeled as Flight Level and the altitude of the aircraft.
Airplane Track
ACTrack_plot.gif is an example of an Aircraft Track plot produced by the MER software.
The track shows the aircraft track relative to each volume scan. The track is plotted in both x-y and lat-lon.
ASCII Reflectivity File
ASCII_file.txt is an example of an ASCII reflectivity file produced by the MER software.
The reflectivity file contains reflectivity parameters relative to the aircraft for every second of flight time. The following is a list of the different parameters and an explanation of each.
Param 1 - time:
This parameter specifies the time of the aircraft in seconds from midnight.
Param 2 - time:
This parameter specifies the time of the aircraft in hours, minutes, and seconds.
Param 3 - x_pos:
This parameter specifies the x position of the aircraft relative to the WSR74C radar.
Param 4 - y_pos:
This parameter specifies the y position of the aircraft relative to the WSR74C radar.
Param 5 - z_pos:
This parameter specifies the altitude of the aircraft from MSL.
Param 6 - refl_aircraft_pos:
This parameter specifies the reflectivity value at the position of the aircraft.
Param 7 - sumAll:
This parameter specifies the sum of the column of reflectivity the aircraft is flying in. It is the sum of dbz from MSL to the maximum height measured by the radar.
Param 8 - sum5above:
This parameter specifies the sum of the column of reflectivity the aircraft is flying in at 5km altitude and above (this roughly corresponds to the 0 C level). It is the sum of dbz from 5km to the maximum height measured by the radar.
Param 9 - ave5above:
This parameter specifies the average reflectivity value in the column the aircraft is flying in at 5km altitude and above.
Param 10 - ave5aboveBox_5:
This parameter specifies the average reflectivity value in a user specified box (in this case 5km - evident by the 5 at the end of the parameter label) of 5km in the positive x direction, 5km in the negative x direction, 5km in the positive y direction, 5km in the negative y direction, and at 5km altitude and above. The user specified box size used to calculate this parameter corresponds to Line 20 of the setup file.
Param 11 - ave5aboveBox_2_10:
This parameter specifies the average reflectivity value in another user specified box (in this case 10km - evident by the 10 at the end of the parameter label) of 10km in the positive x direction, 10km in the negative x direction, 10km in the positive y direction, 10km in the negative y direction, and at 5km altitude and above. The user specified box size used to calculate this parameter corresponds to Line 21 of the setup file.
