Spectral response functions (SRFs) and MW passbands
If you have information on updates or corrections to any of the spectral response function or pass band information below, please let us know either on the RTTOV forum or via the NWP SAF Helpdesk.
All coefficient files for a particular instrument (e.g. those based on different predictor versions or supporting different variable gases) use the same SRF data.
The channels for each instrument are listed in the coefficient file order. You can confirm the RTTOV channel order by looking at the coefficient file headers or by using the rttov_coef_info.exe tool.
The README_SRF section is copied from the coefficient files at the top of each page linked below.
Spectral response functions for VIS/IR coefficient files
Spectral response data for MW coefficient files
Full spectral response function data are available for a subset of microwave sensors. The corresponding optical depth coefficient files include “_srf” in the filenames.
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Pass band data for MW coefficient files
Most MW coefficient files are based on “top-hat” (or “box-car”) spectral responses. These are defined in plain ASCII “filter files”.
Key for MW pass band filter files:
Two records for each channel
Fields in record 1: channel, polarisation, no-of-offsets, bandwidth (MHz)
Fields in record 2: central frequency (GHz), offset1 (GHz), offset2 (GHz)
Notes
(1) Polarisation – this refers to the treatment of surface emissivity:
0: Average of vertical and horizontal polarisation i.e. 0.5(H+V)
1: Nominal vertical at nadir rotating with view angle QV
2: Nominal horizontal at nadir rotating with view angle QH
3: Vertical V
4: Horizontal H
5: +45 minus -45 (3rd stokes vector) S3
6: Left circular – right circular (4th stokes vector) S4
7: Uneven, fixed, channel-specific mixture of V and H
(2) no-of-offsets
0: one passband channel
1: two sideband channel
2: four sideband channel
(3) Bandwidth is for each passband