Current version: v12.1, February 2017
Given an atmospheric profile of temperature, water vapour and, optionally, trace gases, aerosols and hydrometeors, together with surface parameters and a viewing geometry, RTTOV computes the top of atmosphere radiances in each of the channels of the sensor being simulated.
The core of RTTOV is a fast parameterisation of layer optical depths due to gas absorption which is described in the RTTOV v7 Science and Validation Report. In addition, RTTOV also optionally computes the Jacobian matrix which describes the change in radiance for a change in any element of the state vector assuming a linear relationship about a given atmospheric state. For a brief mathematical overview of radiative transfer modelling see this page.
More recent versions of the software have extended its capabilities in numerous ways. Since version 11, RTTOV has had a built-in GUI which allows the user to modify an atmospheric/surface profile, run RTTOV for a given instrument, produce radiances and brightness temperatures and display instantaneously the results. It is also possible to calculate Jacobians, run PC-RTTOV and perform a basic 1DVar retrieval. All this functionality is demonstrated in the EUMETSAT/ECMWF NWP SAF Satellite Data Assimilation course.
The most recent version of RTTOV is v12.1, released in February 2017.
Some example applications of using RTTOV software are given on the RTTOV applications page.
Obtaining RTTOV (and optionally HT-FRTC)
RTTOV is available to licensed users free of charge. To become a licensed user of RTTOV, please register with the NWP SAF (or login if you have already done so) and add RTTOV to your list of software preferences. Older versions of RTTOV are available to download to maintain compatibility with certain software but are not supported by the NWP SAF.
It is recommended (though not mandatory) to compile RTTOV against the HDF5 library (v1.8.8 or later required). This enables the use of HDF5 format coefficient files (the preferred format for hyperspectral sounders), the land surface emissivity and BRDF atlases, and the RTTOV GUI.
In order to compile the RTTOV GUI or to call RTTOV from Python scripts you must also have f2py (part of NumPy) installed.
The GUI has additional requirements which are given in the GUI user guide.
Optionally, one may also download the HT-FRTC fast radiative transfer code developed by the Met Office, for which an RTTOV interface exists to expose a limited subset of its full functionality. HT-FRTC is also available to licensed users free of charge by adding it to ones list of software preferences. It is also necessary to download the training data (supplied in netCDF format and consequently HT-FRTC must be linked against NetCDF libraries as explained in the installation guide) from the RTTOV downloads page.
Documentation and Resources
Instructions for compiling and running the most recent version of RTTOV may be found on the RTTOV v12 homepage. The User Guide also contains comprehensive details of the new features in RTTOV v12 and the changes from RTTOV v11. Further documentation including the RTTOV v12 Science and Validation Report can be found on the RTTOV v12 documentation page.
Resources (coefficients, atlases, etc.) compatible with RTTOV v12 can be accessed from the downloads page.
- RTTOV v11 is still supported by the NWP SAF, but where possible please update to v11.3 and apply any fixes for known bugs before reporting any issues. Coefficients and emissivity/BRDF atlases for RTTOV v11 remain available for download. RTTOV v12 optical depth coefficient files can be converted for use with v11 using an executable which is compiled with RTTOV v12.
- Resources and documentation for RTTOV v10 and earlier can be found on the archived old site.