Steps In MTP Post-Campaign Data Analysis

MJ Mahoney
Last Revision: July 15, 2008

6. Fill in LR1, LR2 and Zb in MISSION_RAOBrangeAll.txt and Create the MISSION_RAOBs.RAOB2 File

Before OATnavCOR and a Window Correction Table can be calculated, one file (MISSION_RAOBrangeAll.txt) needs to be filled with sounding extension information, and a second file needs to be created (MISSION_RAOBs.RAOB2). The latter file contains all the radiosondes that were launched before and after an aircraft flies by a radiosonde launch site. Although not essential, it also should contain a few earlier and later sounding to make it more convenient to check during data processing for temporal variability in the sites temperature field. Typically 24 hours before and after flyby should be included; that is, two soundings before and two soundings after the time of closest approach.

The easiest way to enter the sounding extension information (LR1, LR2, and Zb) is to import the MISSION_RAOBrangeAll.txt file (that was created using the MTPbin|Tools| Run Pgm tab in Step 5) into an Excel spreadsheet using the following steps:

Open a blank Excel spreadsheet
On the menu bar, use File/Open to navigate to the MISSION folder
Select All Files so that the MISSION_RAOBrangeAll.txt file will be visible to open
On the Text Import Wizard - Step 1 of 3 select the Delimited option in the Original Data Type frame (rather than Fixed Width) as the file is tab delimited.
Click Next
Check the Tab check box in the Delimiters frame
Click the Finish button

The result of these steps is shown in Figure 1 below. The reason that we import the MISSION_RAOBrangeAll.txt file into a spreadsheet is that is is easier to enter the RAOB extension information into a spreadsheet than into a text file. After this has been done, the spreadsheet will be saved in the mission /RAOB/ folder as MISSION_RAOBrangeAll.xls and it will also be saved as MISSION_RAOBrangeAll.txt; the latter because several programs use this file. I will use the two names interchangeably. Just remember that the xls-file is where editting is done, but that it must always be saved in the txt-file because that's where the programs get their lapse rate extension information.

Figure 1. The PAVE_ROABrangeAll.txt file imported into an Excel spreadsheet.

To figure out which values should be used for LR1, LR2, and Zb, we need to look at the soundings using the program RAOBman. (Recall that in the MISSION_RAOBrangeAll.txt file there are two soundings provided for each flyby to allow for spatial interpolation between two sounding launch sites. Unlike temporal interpolation, which is fully automated, spatial interpolation can only be done manually. Because this is so tedious, spatial interpolation is not currently supported. As a result, the PAVE_RAOBrangeAll.txt file shown in Figure 1 shows redundant information. Once spatial interpolation is implemented, the information in columns E:G and H:J, K and L, and M and N will be different. That's why LR1, LR2 and Zb are labelled LR11, LR12, and ZB1 in columns E:G (for the first RAOB site used in a spatial interpolation), and LR21, LR22, ZB2 in columns H:J (for the second RAOB site used in a spatial interpolation).

It shouldn't be surprising that a number of things need to be done before subsequent calibration steps can be undertaken. In Step 5, we discussed the generation of two binary RAOB files:

the MISSION_All.RAOB2 file, which contains the tens of thousands of radiosondes collected during the campaign and from archives that will be used to calculate retrieval coefficients, and
the smaller MISSION_Campaign.RAOB2 file which contains only radionsondes launched during the campaign that will be used to select template soundings to calculate retrieval coefficients.

Finally, to speed up data processing, we need to create the MISSION_RAOBs.RAOB2 file, which contains only the RAOBs needed for spatial and temporal interpolation. It is a very small subset of the MISSION_Campaign.RAOB2 file. To create this file, we need the information in the MISSION_RAOBrangeAll.txt file that was opened in an Excel spreadsheet (see Figure 1). Since it contains all the radiosonde launch sites that the aircraft flew close to, we can use it to figure out which soundings to put in the MISSION_RAOBs.RAOB2 file. The simplest way to proceed is day by day. We will use the PAVE campaign as an example. The first PAVE test flight was on January 14, 2005, and the PAVE_RAOBrangeAll.txt file shows that three radiosonde launch site were flown close to: Edwards AFB (EDW), Vandenburg AFB (VBG), and Miramar NAS (NKX).

Figure 2. RAOBman Filters tab.

Therefore, as shown if Figure 2, type EDW in the Site text box of the Site frame of the RAOBman Filters tab and depress the Return key or Add button to enter it into the Site list box. Repeat this step for VBG and NKX to obtain the results shown in Figure 2. Then, in the Time frame enter a period of time that includes two sonde launch times prior to takeoff and two after landing. Even though only the sondes immediately before takeoff and after landing will be used (if they exist!), we want two before and after in order to check for temporal variability (as discussed above) and as backups in case the immediately before and after sondes don't exist or burst at too low an altitude.

Figure 3. RAOBman Select tab.

Next depress the Clear List button on the RAOBman Select tab (if necessary), and depress the Search button. The results of the search are shown in Figure 3. Sixteen soundings were found for EDW, VBG and NKX for the requested time window specified on the Filters tab (see Figure 2).

Figure 4. RAOBman Select tab.

Next, for each launch site flyby select the before and after soundings. In the example given in Figure 4, we have chosen sondes that were launch at 0000UT and 0300UT which bracketed the EDW flyby time (just after 0000UT) on January 15, 2005. Make sure that the Plot Multiple Scans check box (near the top middle) is check so that selected soundings will be overlayed in the RAOB plot form (Figure 5).

Figure 5. Two EDW soundings at 0000UT and 0300UT on January 15, 2005.

The two EDW soundings are shown in Figure 5. This would be an example of when there was not a significant temporal variability over a 3 hour period of time throughout most of the temperature field. Since this was a short 4-hour test flight, all the flying time at altitude (where comparisons are made) was between 0000UT and 0300UT. If it was not, an earlier or later sounding would have been needed as well.

If the chosen soundings do not completely cover the flight time period (that is, takeoff to landing), the software will not run properly, since it assumes that before and after soundings always exist in the MISSION_RAOBs.ROAB2 file! Although these two EDW soundings are similar, there are some substantial differences. For example, the temperature at the tropopause near 11 km changed by >4 K. For this reason data near the tropopause should not be used for calculating OATnavCOR (see next step). Another rule of thumb is to avoid regions in the atmosphere where the lapse rate is large, since aircraft altitude excursions will introduce much larger errors than altitude regions where the temperature is nearly isothermal. There are several parameters that can be set when RAOB and MTP retrievals are compared to help mitigate some of these issues, and they will be described shortly.

Figure 6. RAOBman I/O tab.

Before moving on to the next launch site for this flight (NKX), we need to do two things:

Enter LR1, LR2, and Zb information into the PAVE_ROABrangeAll.txt spreadsheet. Examining Figure 5, we see that both soundings got above 30 km, so we set LR1 = 0 K/km (since it will never be needed), Zb = 22 km (because that is where the lapse rate changes or breaks), and LR2 = 2.0 K/km above Zb. Save the file and move on to the next flyby for this flight. By default the txt-file will be saved as Text (Tab Delimited), which is what you want. When we are done, we will also save the file as an Excel file named MISSION_RAOBrangeAll.xls.
Copy these two EDW soundings to the MISSION_RAOBs.RAOB2 file. To do this, make sure that the Random RAOB Output frame of the RAOBman I/O tab has the correct filename; in this case, C:\MTP\RAOB\PAVE\PAVE_Campaign.RAOB2. Also, if this is the first time that file is being written to, make sure that the New File Mode option box is selected on the Random RAOB Output frame; otherwise, the soundings will be appended to an existing file of the same name if there is one. This done, return to the Select tab (Figure 4) and depress the Write button. (Note that by default the WriteAvg check box is not selected. If it was, the average temperature profile of all the soundings in Search list box would be written to the Export Path text box on the Export tab. A Tooltip will tell you where the file is being written.)

Figure 6. RAOBman I/O tab.

We continue like this for the other sounding site flybys for the flights of January 14, 2005, and January 18, 2005, being sure to enter the LR1, LR2 and Zb information into PAVE_ROABrangeAll.txt spreadsheet, and to save the selected soundings that cover the flight time into PAVE_RAOBs.RAOB2. As shown in Figure 6, the I/O tab Random RAOB Output frame Mode option should be changed to Append all binary RAOB writes after the first.

Figure 7. The RAOBman Select tab.

Our next example is for the January 20, 2005 flyby of Miramar NAS (NKX). There were 4 flybys within 10 km of NKX on this 8 hour test flight, which covered the time period 72.43 ks to 96.47 ks UT. Therefore, 200501201200UT, 200401210000UT and 200401211200UT sounding are needed to cover the time period of this flight. These are shown selected in Figure 7, and Figure 8 (below) shows the actual soundings.

Once all the values have been entered, the Excel workbook should also be save as an Excel file, MISSION_RAOBrangeAll.xls using the following steps:

On the menu bar save the file using File/Save As
In the Save As dialog box, change Save As Type to Microsoft Excel Workbook, and click Save

This will save MISSION_RAOBrangeAll.xls.

It is useful as a final step to sort the radiosondes in the MISSION_RAOBs.RAOB2 file into chronological order. (If they were saved chronologically this would not be necessary, but invariably some soundings are not saved (operator error!) and must be added later after they are discovered missing. Believe me, this will happen!) This is easily done on the RAOBman Select tab by closing the currently open RAOB2 file and opening the MISSION_RAOB.RAOB2. Then, on the Select tab depress the Search button. This brings all the soundings into the Search list box. Next, depress the Sort button. This will sort the soundings chronologically. On the I/O tab Random RAOB Output frame Output File text box change the name of the file to MISSION_RAOBs.RAOB2, where the final small "s" indicates that the file has been sorted, and select the New File Mode option. Finally, on the Select tab depress the Write button.

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