What’s New

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RTTOV v13.0

RTTOV v13.0 was released in November 2020 by the NWP SAF. The main new features of RTTOV v13.0 compared to v12.3 are:

  • Clear-sky/general simulation updates:
    • New optical depth coefficient files are available based on an updated (“v13 predictor”) optical depth parameterisation and trained on LBLRTM v12.8. For visible channels this includes a new parameterisation for Rayleigh extinction which can optionally be excluded from simulations.
    • The geometric altitude of each input pressure level is now available as an output in the radiance structure.
    • Updates to allow for new polarisation in sensors like TROPICS with a fixed, but uneven mixture of H- and V-pol in each channel.
  • RTTOV-SCATT MW scattering simulations
    • RTTOV-SCATT allows simulations with an arbitrary number of hydrometeor types and optionally with separate cloud fraction profiles per hydrometeor.
    • RTTOV-SCATT provides a new radar reflectivity simulation capability.
    • New approximate treatment of polarised scattering.
    • New scattering property tables with improved microphysical representation of cloud ice, snow and graupel optical properties.
  • Visible/IR scattering simulations:
    • Visible DOM simulations can optionally include full Rayleigh multiple scattering.
    • Updated cloud liquid water optical properties based on updated refractive index dataset.
    • A parameterisation of cloud liquid water effective diameter has been implemented for use with the CLW “Deff” visible/IR optical properties so that input Deff values are not mandatory: the parameterisation is used where the input clwde(:) profile values are zero.
    • For visible/IR cloud simulations, the surface-space and level-to-space cloud extinction transmittances (on the surface-satellite path and excluding gas absorption) are output in the new tau_total_cld and tau_levels_cld members of the transmission structure.
    • MFASIS simulations may now be run simultaneously (in the same call) as IR scattering simulations.
  • Surface emissivity and reflectance updates
    • The CAMEL 2007 IR atlas now provides standard deviations from the CAMEL climatology rather than the older UWIRemis standard deviations.
    • For the UWIRemis and CAMEL 2007 IR emissivity atlases, the emissivity PC scores and eigenvectors are now optional outputs from the rttov_get_emis subroutine.
    • The profile skin specularity variable introduced in RTTOV v12.3 for use with the do_lambertian option has been moved into the rttov_emissivity structure so that it can vary per-channel. This is now also an active variable in the TL/AD/K.
    • The diffuse reflectances used by RTTOV for downward emitted and downward scattered radiation are available as an output in the rttov_reflectance structure. The value used for the diffuse reflectance can optionally be specified by the user for visible/near-IR channels.
    • New coefficients are available based on LBLRTM v12.8 in ASCII format as well as netCDF.
    • Emissivities are now input on centroid (predictor) wavenumbers which is consistent with the way PC-RTTOV works.
    • HTFRTC now supports RTTOV’s IREMIS sea surface emissivity model.
    • Optimisation of the HTFRTC direct and K models.
  • Technical updates:
    • The GUI has been updated to work with Python3, and to support new RTTOV features including all new options, input of surface specularity, and input/output of diffuse surface reflectance.
    • The Python/C++ wrapper has been updated to support new features including the RTTOV-SCATT updated passive and new active simulation capabilities.
    • Optimisation of the MFASIS model, which improves performance in the direct/TL/AD/K.
    • Optimisation of the RTTOV-DOM AD/K models.

RTTOV v12.3

RTTOV v12.3 was released in March 2019 by the NWP SAF. The main new features of RTTOV v12.3 compared to v12.2 are:

  • Clear-sky/general simulation updates:
    • New CAMEL climatology atlas for IR emissivities: emissivity data based on 2000-2016 climatology, improved treatment of snow, and includes emissivity standard deviations computed from multi-year climatology.
    • New option to switch between fixed or parameterised effective angle for downwelling radiance with the Lambertian surface option.
    • A new specularity profile skin variable has been added which specifies the weighting for a linear combination of specular and Lambertian downwelling radiances with the Lambertian surface option.
    • A new subroutine has been added which makes it easy to use scaled copies of the RTTOV reference profiles for optional trace gases in simulations.
  • Visible/IR scattering simulations:
    • MFASIS has been modified to allow for variable water vapour in affected sensor channels (currently applies to SEVIRI 0.8 micron channel) which greatly improves the fit to the training data.
    • An updated parameterisation of the Baran ice cloud property database has been added for visible/IR cloudy simulations which is more spectrally consistent and extends the parameterisation to the far-IR.
    • A new option opts%rt_ir%grid_box_avg_cloud has been added. If false (the default) then input cloud concentrations for visible/IR cloud simulations should represent the concentration of cloud in the cloudy fraction of the layer (the behaviour of previous versions of RTTOV). If the option is true cloud concentrations for visible/IR cloud simulations should be layer grid-box-average values (consistent with RTTOV-SCATT), which is commonly the quantity output by GCMs. This does not affect simulations with explicit cloud optical properties.
    • A new executable has been created which enables the generation of custom aerosol optical property (scaercoef) files for use with RTTOV.
    • All RTTOV trace gases may now optionally vary in the simulation; ozone is now optional.
    • Options to calculate overcast radiances and simple cloud (as RTTOV does).
    • Option to supply emissivities; IR emissivity atlas interface has been updated to work with HTFRTC.
    • Support for all RTTOV gas units options, do_lambertian option with new specularity profile variable, and the plane_parallel option.
    • Multi-threaded simulations via parallel interfaces enabled.
  • Technical updates:
    • The wrapper has been updated to support the new options, the specularity profile variable, and to enable simulations with user-generated aerosol optical property files.
    • The GUI has been updated to support the new code options, the new specularity profile variable, and to enable choice among the available emissivity atlases.

RTTOV v12.2

RTTOV v12.2 was released in April 2018 by the NWP SAF. The main new features of RTTOV v12.2 compared to v12.1 are:

  • Clear-sky/general simulation updates:
    • New option for solar sea surface BRDF model.
    • New options for MW cloud liquid water (CLW) absorption calculations: new permittivity parameterisations and new option to perform calculations on user levels rather than coefficient levels.
    • MW optical depth coefficient files now contain band correction coefficients.
    • New option to carry out calculations on radiances instead of brightness temperatures.
    • New optional output structure containing information required to perform all-sky emissivity retrievals. A new subroutine is included which carries out the retrieval calculation.
    • New options for CLW permittivity in Mietable generation code (same options as for CLW absorption) and updated Mietable files using new recommended option.
    • New options for non-spherical particles in Mietable generation code from ARTS single-scattering database.
    • New OpenMP parallel interface to RTTOV-SCATT.
  • Visible/IR scattering simulations:
    • New option to use MFASIS fast visible cloud scattering parameterisation.
    • New cloud liquid water optical properties parameterised in terms of particle effective diameter.
    • Explicit cloud/aerosol optical properties are optionally active variables in the TL/AD/K models.
    • New scaercoef files containing optical properties for 9 CAMS aerosol species.
  • Principal Components simulations:
    • New PC-RTTOV coefficients enabling all variable trace gases (except SO2) and aerosol simulations using OPAC aerosol properties.
    • The HTFRTC interface has been rewritten for easier compilation and to improve performance.
  • Technical updates:
    • Python wrapper is now compatible with both Python 2 and 3. The wrapper has also been updated to enable MFASIS simulations and to work with the new CAMS aerosol species.
    • The RTTOV GUI has been updated to enable MFASIS simulations, to work with the new CAMS aerosol species, and to work with the new PC-RTTOV trace gas and aerosol files.
    • Build system updated to make it easier to compile against an external LAPACK library if desired.

RTTOV v12.1

RTTOV v12.1 was released in February 2017 by the NWP SAF. The main new features of RTTOV v12 compared to v11.3 are:

  • Visible/IR scattering updates:
    • Discrete Ordinates Method multiple-scattering solver for clouds and aerosols: there are independent options available for the treatment of scattering for thermal emission and solar radiation.
    • Ice optical properties from the SSEC database replace the old Hexagonal/Aggregate ice shapes.
    • Baran2014 ice parameterisation extended to visible/near-IR wavelengths.
    • New option to supply cloud and aerosol inputs as mass mixing ratios (kg/kg).
  • Surface emissivity and BRDF updates:
    • New MW sea surface emissivity model, TESSEM2, intended for use with ICI.
    • New IR sea surface emissivity model including wind speed and Tskin dependency.
    • Improved treatment of sea surface reflectance for solar radiation.
    • Updated TELSEM MW land surface and sea-ice emissivity atlas (TELSEM2).
    • Updated CNRM MW land surface emissivity atlas.
    • New IR land surface emissivity atlas (CAMEL).
    • More flexible interface to land surface emissivity and BRDF atlases allowing data from multiple atlases, for multiple months and/or instruments to be initialised and used concurrently.
  • Other scientific updates:
    • New visible/IR coefficients based on updated training profiles applicable to whole satellite era (1970-202x) with contemporary reference (background) profiles for CO2, N2O and CH4. Coefficients supporting variable ozone and CO2 are available for all visible/IR sensors.
    • New coefficients available allowing SO2 as an optional trace gas.
    • Updated non-LTE bias correction.
    • New PC-RTTOV coefficients including non-LTE bias correction.
    • New option to call HT-FRTC PC RT model (available separately through the NWP SAF website) through RTTOV interface.
  • Technical updates:
    • Python/C++ wrapper now supports all visible/IR/MW clear-sky and scattering simulation types (direct and K models) and use of BRDF and emissivity atlases.
    • RTTOV GUI has been updated to support new RTTOV capabilities.
    • Improved consistency in subroutine interfaces and derived type naming.
    • Optimisation of gas optical depth calculation in particular for v9 predictors with all trace gases.

RTTOV v11.3

RTTOV v11.3 was released in September 2015 by the NWP SAF. A list of the main new features of RTTOV v11.3 compared to RTTOV v11.2 is given below:

  • Technical changes
    • New Python and C++ interface to RTTOV: allows much RTTOV functionality to be called directly from Python or C++.
    • Updates to the RTTOV GUI including new 1DVar functionality.
    • New option to specify input units for gas profiles (ppmv over moist air, ppmv over dry air, kg/kg over moist air).
    • PC-RTTOV can now be run for all surface types (requires new PC coefficient files available on the website).
    • IR emissivity and BRDF atlases now also available in HDF5 format with much reduced file size due to compression, and avoids the need for compiling against the netCDF library.
    • Example programs simplified and new examples added for IR cloudy simulations and RTTOV-SCATT.
    • Four new subroutines which can be used to allocate any or all input/output arrays and structures for the RTTOV direct, TL, AD and K models simplifying code which calls RTTOV.
    • New interactive script to make compiling RTTOV easier.
    • New interactive script to download coefficients from website.
    • RTTOV libraries no longer have minor version numbers in their names.
  • Scientific Changes
    • Option to treat surfaces as Lambertian reflectors for the downwelling surface-reflected emission can now be applied to IR as well as MW sensors.
    • Option to supply ocean surface foam coverage fraction to FASTEM instead of using the internal foam parameterisation.
    • Improved treatment of snow in land surface BRDF atlas (requires a new eigenvector data file to be downloaded from the website).
    • IR emissivity atlas has new option to include a correction for zenith angle (requires new additional atlas data files available on the website)

RTTOV v11.2

RTTOV v11.2 was released in June 2014 by the NWP SAF. A list of the main new features of RTTOV v11.2 compared to v11.1 is given below:

  • Technical changes
    • RTTOV v11.2 reproduces RTTOV v11.1 radiances for identically configured simulations (bug fixes notwithstanding).
    • Code rewritten in places to improve readability and maintenance.
    • Test suite profile sets are now based on the six US76 standard atmospheres.
    • Code has undergone optimisation for scalar architectures, particularly the solar sea surface reflectance calculation, IR scattering code, and PC-RTTOV.
    • Coefficient I/O in HDF5 format now allows channel selection.
    • RTTOV GUI is supplied with the RTTOV package: this allows users to run the direct and K models and visualise the results.
  • Scientific changes
    • New interpolation options are available which eliminate the jaggedness observed in temperature Jacobians under certain circumstances.
    • New option for profile extrapolation at top of atmosphere based on regression limits.
    • New FASTEM-6 option which has improved treatment of azimuthal dependence.
    • Updated Baran ice optical property parameterisation for cloudy IR simulations.

RTTOV v11.1

RTTOV v11.1 was released in May 2013 by the NWP SAF. A brief overview of the main new features of RTTOV v11 is given here.

  • Technical changes
    • RTTOV v11 reproduces RTTOV v10 radiances for identically configured simulations.
    • Code rewritten in places to improve readability and maintenance.
    • Test suite has been extended to allow all aspects of RTTOV to be configured via input files or via the commandline.
    • Code has undergone optimisation for scalar architectures, particularly the direct and K models and the IR emissivity atlas.
    • Capability to read and write coefficients in HDF5 format.
    • Capability to convert mietables to binary format.
  • Scientific changes
    • Coefficients based on a new set of 54 levels.
    • Capability to simulate visible/near-IR channels.
    • New land surface bi-directional reflectance function (BRDF) atlas.
    • Capability to correct for non-local thermodynamic equilibrium effects.
    • PC-RTTOV may now be run for clear-sky and cloudy profiles over sea.
    • Option to specify scattering parameters explicitly for aerosol and cloudy IR simulations.
    • New ice particle parameterisation for cloudy IR simulations.
    • Two new aerosol particle types: a new volcanic ash type derived from measurements of the Icelandic eruption in 2010, and an Asian dust type.
    • New option to treat the surface as a Lambertian reflector for the reflected down-welling radiance calculation.
    • Capability to account for variable cell pressure in SSU sensors.
    • Improvements to MW scattering code including capability to supply hydrometeor profiles in units of kg/kg.