Introduction

The following graphs show how well the MTP/ER2 MP-file profiles agree with RAOBs.  They are taken from the ferry flight of 2000.01.14, from Massachusetts to Sweden.  The MP-file has a creation date of 2000.02.01, so I assume ti uses the window correction table (CAL-file) that I recommended January 25.

Things to Look For

1)  Most graphs show the "archive average" T(z).  It is useful to compare the MTP retrieved T(z) with the archive average, as the difference shows the effect of the MTP "observables."  One hopes that in all cases where the RAOB profile differs greatly from the archive average that the MTP profile "moves from the archive average profile to somewhere close to the RAOB profile."  When that happens, the "observables" are "doing their job."  In 4 out of 5 comparisons this is the case - comparison #4 doesn't quite behave the right way at 21 to 26 km.

2)  Is there a persistent pattern, such as a kink, in all MTP profiles that are not borne out by ROABs?  I think there's an "artificial inversion layer" with its base at the flight altitude in all 5 cases.  This is surprising, since the window correction table was based on these same 5 RAOB comparisons.  This should be looked into.

3)  Is there a persistent offset of OAT with respect to the interpolated RAOB temperature at flight level?  Not really.  The MTP retrieved OAT averages 0.5 K warmer than RAOB.  If the -0.6 K OATnavCOR that I recommended (based on two flights) was used, then I would expect the MTP temperatures to be 0.4 K colder than RAOBs for this flight (since for this flight the NAV OATs were 0.2 K warmer than RAOBs).  Thus, the MTP OAT's seem to be 0.9 K warmer than expected if NAV OATs were used to set gains and -0.6 K OATnavCOR was used.  Since I don't know what was done during data analysis I cannot determine if the OATs are consistent with expectations.

ROAB/MTP Comparisons

Conclusions

1) The persistent shape of "an inversion layer with a base fixed to the flight altitude" is unexplained, so I suggest that a check be made of the window correction table used for reducing this data.  It should be:

               60   0.78   0.01
        44   0.28  -0.02
        30  -0.10  -0.50
        18   0.46  -0.01
         9   0.73   0.42
         0  -0.20   0.12
        -9  -0.33  -0.66
       -21   0.74   0.60
       -37   0.49   0.36
       -58   0.30   0.17

2) The MTP OAT is 0.9 K warmer than expected if OAT NAV was used to set the gains and -0.6 K was used for OATnavCOR.  If MMS was used to set the gains, and if -0.8 K for OATmmsCOR was used, then for this flight, then MTP OATs should have been 2.3 K warmer than RAOBs (versus 0.5 K warmer).  If gain equations were used for the gains, then I would not know what to expect.  Since I don't know what gain calibration procedure was used I cannot determine if a problem exists.  However, the slight difference of MTP and RAOB temperatures at flight altitude for this flight may be a problem worth pursuing.

Aside from these two poitns, the MTP T(z) data looks good.

This site opened:  February 4, 2000.  Last Update: February 4, 2000