Metop-B AMSU-A channel 15

[Nigel Atkinson]

Dear all,

Early this morning, the gain of Metop-B AMSU-A channel 15 suddenly dropped to zero. The channel is currently unusable.

If you run atovpp (i.e. if you generate level 1d files for this satellite) then you should disable the use of channel 15, otherwise the brightness temperatures of all AMSU channels will be set to zero. To do this, edit file ppaind.F in directory AAPP/src/preproc/libatovpp, find the line that contains “ELSE IF ( ama1c_h_satid .EQ. 2 ) THEN” and immediately before that insert the following lines

          ELSE IF (ama1_h_satid .EQ. 1) THEN
!
!  For Metop-B do not set bit for channel 15
!
            DO chn = 1, 14
              chanbits = IBSET ( chanbits, bits(chn) )
            ENDDO

Then “make lib; cd ../bin;make bin”.

This change will be included in the next AAPP update.

Note that after the failure the AMSU-A scattering index (difference between observed BT15 and prediction using BT1,2,3 – in ppascat.F) is set to “missing”. So is the result from the Crosby precipitation test which uses BT1 and BT15 (ppacrosby.F).

If this causes problems for you, and you would rather set the outputs to zero instead of missing, edit file pphapcp.F and change the ELSE condition of tests 1 and 2: set Hscatindx(fov,line) = 0.0, scat = .FALSE., Hcrosby(fov,line) = 0.0, crosby = .FALSE.. Similarly for ppapcp.F.

Regards,

Nigel Atkinson

[Anonymous]

Do these changes in calculations of vertical profile in IAPP?

Thanks

[Nigel Atkinson]

University of Wisconsin will need to make an update to IAPP to allow for this failure. I understand this is planned.

Nigel

[Author]

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