Metop-A AMSU-A channel 3

[Nigel Atkinson]

Dear all,

The target view counts for AMSU-A channel 3 on Metop-A have dropped below the lower limit set in AAPP. This channel is degrading quite rapidly now and the noise is above 0.8K. So we recommend that you do not use the data. However, some applications (including atovpp) will require valid brightness temperatures. There are 2 things you can do:

1. If you are processing your own direct broadcast data: Alter the gross limits in the amsua_clparams.dat file, in directory AAPP/src/calibration/libamsuacl. Change line 1462 (warm gross limit) to

10000,14000,14000,14000,8000,8000,14000,14000,14000,14000,14000,14000,14000

and change line 1467 (cold gross limit) to

9000,10000,10000,10000,8000,8000,10000,10000,10000,10000,10000,10000,10000

Then type “make dat” to install the file into the directory AAPP/data/calibration/coef/amsua/. If you have a separate installation directory you should copy it there also.

2. If you are processing level 1c data from elsewhere (e.g. DBNet-RARS data): to prevent atovpp from rejecting all AMSU channels, if channel 3 is bad, edit file AAPP/src/preproc/libatovpp/ppaind.F and change lines 156-158 from

            DO chn = 1, 6
               chanbits = IBSET ( chanbits, bits(chn) )
            ENDDO

to

            DO chn = 1, 2
               chanbits = IBSET ( chanbits, bits(chn) )
            ENDDO
            DO chn = 4, 6
               chanbits = IBSET ( chanbits, bits(chn) )
            ENDDO

Then compile using “make lib; cd ../bin; make bin”.

These changes will be incorporated in the next AAPP update release.

Regards,

Nigel Atkinson

[Author]

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