Add instrument-specific bias correction to setup, addressing ORAC-CC#44

pre_processing/allocate_channel_info.F90

@@ -75,4 +75,7 @@ subroutine allocate_channel_info(channel_info)
    allocate(channel_info%channel_fm_sea_uncertainty( &
         channel_info%nchannels_total))
 
+   allocate(channel_info%channel_absolute_bias(channel_info%nchannels_total))
+   allocate(channel_info%channel_relative_bias(channel_info%nchannels_total))
+
 end subroutine allocate_channel_info

pre_processing/channel_structures.F90

@@ -20,6 +20,7 @@
 ! 2016/07/01, GT: Added map_ids_sw_to_channel and map_ids_lw_to_channel.
 ! 2016/08/04, GM: Added map_ids_channel_to_sw and map_ids_channel_to_lw.
 ! 2017/07/05, AP: Add NAll to track the total number of channels.
+! 2021/03/09, AP: Add radiance bias corrections.
 !
 ! Bugs:
 ! None known.
@@ -98,6 +99,10 @@ module channel_structures_m
       real(kind=sreal),   dimension(:), pointer :: channel_fm_lnd_uncertainty
       real(kind=sreal),   dimension(:), pointer :: channel_fm_sea_uncertainty
 
+      ! Bias correction for each channel
+      real(kind=sreal,    dimension(:), pointer :: channel_absolute_bias
+      real(kind=sreal,    dimension(:), pointer :: channel_relative_bias
+
    end type channel_info_t
 
 contains

pre_processing/deallocate_channel_info.F90

@@ -49,6 +49,8 @@ subroutine deallocate_channel_info(channel_info)
    deallocate(channel_info%channel_minimum_uncertainty)
    deallocate(channel_info%channel_fm_lnd_uncertainty)
    deallocate(channel_info%channel_fm_sea_uncertainty)
+   deallocate(channel_info%channel_absolute_bias)
+   deallocate(channel_info%channel_relative_bias)
    deallocate(channel_info%sw_rttov_viewone_id)
    deallocate(channel_info%sw_view_ids)
    deallocate(channel_info%lw_rttov_viewone_id)

pre_processing/read_imager.F90

@@ -55,7 +55,8 @@
 !                 instead of IMPF (as previous). The new driver file option
 !                 USE_GSICS enables this to be disabled.
 ! 2018/06/08, SP: New global attribute to store satellite position information
-! 2019/8/14, SP: Add Fengyun-4A support.
+! 2019/08/14, SP: Add Fengyun-4A support.
+! 2021/03/09, AP: Add radiance bias corrections.
 !
 ! Bugs:
 ! None known.
@@ -255,7 +256,15 @@ subroutine read_imager(sensor, platform, path_to_l1b_file, path_to_geo_file, &
       stop error_stop_code
    end if
 
+   ! Bias correction (these are defined in the appropriate setup.F90 routine)
+   do k = 1, channel_info%nchannels_total
+      imager_measurements%data(:,:,k) = channel_info%channel_absolute_bias(k) + &
+           channel_info%channel_relative_bias(k) * &
+           imager_measurements%data(:,:,k)
+   end do
+
    ! Estimate measurement uncertainty
+   ! NOTE: Doing this here as instruments will eventually provide L1 uncs
    do k = 1, channel_info%nchannels_total
       do j = 1, imager_geolocation%ny
          do i = imager_geolocation%startx, imager_geolocation%endx

pre_processing/read_slstr.F90

@@ -16,29 +16,6 @@ module read_slstr_m
 
    implicit none
 
-   ! The calibration of SLSTR is under ongoing revisions, such that the
-   ! application of empirical correction factors is currently required.
-   ! These are taken from the SLSTR User Guide and/or personal communications.
-   real, parameter :: slstr_correction_factor(18) = [ &
-        0.95, & ! Ch1
-        -1.0, & ! Ch2
-        -1.0, & ! Ch3
-        -1.0, & ! Ch4
-        1.10, & ! Ch5
-        1.10, & ! Ch6
-        -1.0, & ! Ch7
-        -1.0, & ! Ch8
-        -1.0, & ! Ch9
-        0.92, & ! Ch10
-        0.93, & ! Ch11
-        0.93, & ! Ch12
-        -1.0, & ! Ch13
-        -1.0, & ! Ch14
-        -1.0, & ! Ch15
-        -1.0, & ! Ch16
-        -1.0, & ! Ch17
-        -1.0 ]  ! Ch18
-
 contains
 
 ! When defined, the offset between the nadir and oblique views is assumed

pre_processing/read_slstr_main.F90

@@ -256,13 +256,7 @@ subroutine read_slstr(infile, imager_geolocation, imager_measurements, &
          stop error_stop_code
       end if
 
-      ! Apply some correction factors
-      if (slstr_correction_factor(band_ids(i)) .gt. 0.0) then
-         imager_measurements%data(:,:,i) = imager_measurements%data(:,:,i) * &
-              slstr_correction_factor(band_ids(i))
-      end if
-
-      ! Other corrections have previously been applied in this code to minimise
+      ! Corrections have previously been applied in this code to minimise
       ! problems with the geolocation, dynamic range, and calibration of SLSTR.
       ! These have been removed at this point, as many are now included in the
       ! L1B files but may still be necessary for earlier data. The main one is