This web page describes a Window Correction Table (WCT) calibration I performed for the MTP/DC8 instrument for the SOLVE2 mission.  The purpose in preparing this web page is to have a record to refer to later when a similar mission for this instrument is in need of calibration.  Guidance will then be available for analysis procedures and it will also be easier to determine if changes in the instrument's calibration has occurred.

QuickBASIC Programs Used

This section is presented for me to perhaps refer to later when the WCT task is again required for this instrument.

Format changes in raw data's D-line, for "mux" data mostly, were accomodated in the program D2SOLVE2.bas.  In using this program I didn't employ lag/lead parameters (since the goal is simply to produce a RET-file for establishing a new WCT).

Spreadsheet #K3109.WQ2 was used to select 8 RAOB/MTP comparison locations.  Most of them were the "spatial interpolation" type since few RAOB sites were overflown.  RT_TB.bas was used to read RET-files at the appropriate times for producing 5-cycle tx-files for each of the 8 comparison times.

RAOBs were downloaded from the WYO site, http://weather.uwyo.edu/upperair/sounding.html.  A 2-epoch time interval was specificed, leading to SSS.htm RAOB info files that included 2 RAOB soundings.  WYO.bas was used to produce 2 R-files for each site.

The R-files were processed by GAP.bas, then TB.bas, then WCTd.bas, and the dtb-files were imported to spreadsheet #3206C.WQ2 for WCT analysis (the final one used).

Gain Equation

Using the CTS-file and spreadsheet #C3109.WQ2 I established gain equations:  G1 = 14.7 (1 - 0.016 (tMXR - 40)), G2 = 16.8 (1 - 0.016 (tMXR - 40)), and G3 = 17.35 (1 - 0.019 (tMXR - 40)).

Window Correction Table

Here are the "Observed TB minus RAOB-Predicted TB" profiles versus elevation angle for two flights, yielding 18 RAOB/MTP comparisons.  It's the negative of these average plots that is the "suggested WCT."

Figure 1.  Obseved minus predicted TB versus elevation angle for MTP/DC8 Channel #1.

Figure 2.  Obseved minus predicted TB versus elevation angle for MTP/DC8 Channel #2.

Figure 3.  Obseved minus predicted TB versus elevation angle for MTP/DC8 Channel #3.

The corresponding Window Correction Table, WCT, is given below:

      80  -1.44  0.22 -0.15
      55  -0.87 -0.00 -0.00
      42  -0.82  0.03  0.09
      25  -0.19  0.05  0.04
      12  -0.08  0.02 -0.07
       0   0.00  0.00  0.00
     -12   0.15  0.09  0.12
     -25   0.32  0.14  0.11
     -42   0.65  0.16 -0.07
     -80   0.05 -0.31  0.00

Here are a few SE uncertainties for the WCT based on population SEs:

      80   0.44  0.14  0.20
      55
      42
      25   0.18  0.21  0.10
      12
      0
     -12
     -25   0.22  0.14  0.10
     -42
     -80   0.63  0.21  0.17

Here's a formal SE of the WCT based upon the RMS of 18 estimates at each WCT location.

    80    0.53  0.21  0.22
    55    0.41  0.24  0.21
    42    0.33  0.22  0.20
    25    0.19  0.20  0.13
    12    0.14  0.12  0.09
    00    0.06  0.05  0.03
   -12    0.12  0.11  0.07
   -25    0.16  0.14  0.10
   -42    0.21  0.16  0.13
   -80    0.33  0.20  0.17

Some of this table's entries are larger than the previous estimated SE because of the way my estiations were trying to ignore outlier data.

Note:  On June 10 I calculated a WCT that was in error due to my reduction program forcing gains to low values (i.e., 12.5 cts/K for Ch#1)  For comparison I will include here the incorrect WCT:

OLD   80   2.60  0.17 -0.24
      55   2.23  0.04 -0.01
      42   1.14  0.06  0.07
      25   0.42  0.09 -0.01
      12  -0.03  0.04 -0.10
       0   0.00  0.00  0.00
     -12   0.11  0.12  0.12
     -25   0.06  0.18  0.10
     -42   0.04  0.16 -0.08
     -80  -1.23 -0.36  0.01

The corrected WCT (in bold, starting with -1.44, is generally similar to the WCT for CAMEX4, based on the flight date 2001.09.26 (Florida to California).  For that flight I derived the following WCT:

         80 -2.17 -0.66 -0.43
         55 -2.39 -0.86  0.04
         42 -1.83 -0.80 -0.09
         25 -0.97 -0.49 -0.10
         12 -0.68 -0.23  0.00
          0  0.00  0.05 -0.03
        -12  0.68  0.13  0.06
        -25  1.44  0.20  0.08
        -42  2.09  0.46  0.23
        -80  1.51  0.11  0.36

Navigation Outside Air Temperature Offset

The corretion to Outside Air Temperature, OAT, is accomplished by comparing a several-minute average of the DC-8's navigation system's 1 Hz temperatures with a temperature obtained from RAOBs.  The RAOB temperatures are interpolated in pressure altitude, time and space (when using two RAOB sites that straddle the flight track).

Figure 4.  Navigation OAT versus RAOB temperature interpolated in space and time for RAOB site encounters, for flights DC030109, DC030112 and DC030206.

The two flights analyzed to date yield:

    OATnavCOR = -0.15 +/- 0.22 K, N=17 (population SE = 0.93 K).
 

This site opened:  January 22, 2003.  Last Update:  June 30, 2003