What’s New

To comment or to suggest future enhancements to RTTOV, please contact the helpdesk.

RTTOV v14.0

RTTOV v14.0 is currently undergoing final review before planned release in early January 2025. The main new features of RTTOV v14.0 compared to v13.2 are:

  • General simulation updates:
    • Revise the input profile structure so that all input variables (temperature, gases, scattering inputs) are provided on the same vertical grid. This improves consistency with NWP model fields.
    • New option to output overcast BTs in addition to existing overcast radiances.
    • New option to enable UV/VIS/NIR Jacobians in terms of reflectance (now the default) instead of radiance.
    • New diagnostic output structure containing per-profile outputs, including geometric heights of pressure half- and full-levels, and computed effective hydro fraction.
    • Improved user-level routines for checking inputs to RTTOV before running full simulations.
    • Improved notification to users via the radiance%quality(:) output when input values are clipped by various parameterisations within RTTOV.
    • Zeeman coefficients based on v13 predictors enabled.
    • Default values of various options have changed since RTTOV v13.
  • Surface emissivity and reflectance updates
    • Emissivity and reflectance inputs/outputs refactored into a single new rttov_emis_refl data structure.
    • Enable full user control over diffuse reflectance at all wavelengths in the same way as for emissivity and BRDF.
    • Diffuse reflectance is added to BRDF from sea sun-glint model for VIS channels to allow for consistency in treatment of ocean colour/sub-surface scattering.
    • USGS water reflectance datasets extended to the UV (used for sea surface reflectance).
    • Enable fully flexible heterogenous surface capability: users can specify surface and near-surface properties for multiple surfaces per profile, and the properties are combined before the radiance solver is called.
    • Implement interface to CAMEL v3 IR land surface emissivity atlas datasets.
    • Enable optional return of nearby land IR emissivity/BRDF within a user-specified distance if atlas has no data at the original location.
    • Emissivity retrieval output structure generalised for dynamic emissivity retrievals in clear-sky cases, and for Chou-scaling solver in addition to delta-Eddington, and for all cloud overlap options.
  • Scattering simulations:
    • Scattering for MW sensors now run through the main RTTOV interface in a very similar way to IR sensors from a technical perspective (the separate RTTOV-SCATT model no longer exists).
    • Delta-Eddington solver implemented within RTTOV for infrared and microwave sensors.
    • Radar solver implemented in RTTOV, and passive radiances are computed alongside radar reflectivities.
    • Cloud overlap options formerly in RTTOV-SCATT available as additional options in RTTOV.
    • Consistent unit conversions applied for hydrometeor concentrations in the UV/VIS/IR and MW.
    • Allow separate units selection for hydrometeors and aerosols.
    • UV/VIS/IR hydrometeor optical properties made fully flexible allowing any combination of particle types to be used in the same simulation (as implemented in earlier RTTOV versions for aerosols and MW hydrometeors).
    • Explicit optical property inputs can be used for MW simulations as well as UV/VIS/IR.
    • Explicit optical property phase functions and Legendre coefficients are no longer active variables in the TL/AD/K.
    • Tang et al modification to Chou-scaling solver implemented to improve accuracy particularly for hydrometeor simulations with ice clouds in the far-IR.
    • MFASIS-NN updates include improved accuracy by better treatment of water vapour and heterogenous surfaces, and code optimisation.
  • PC-RTTOV:
    • New PC coefficients for IASI, IASI-NG, and Hamming apodised MTG-IRS supporting simulations over all surface types, with all trace gases, and optionally with either the NLTE correction, aerosol scattering, or hydrometeor scattering.
    • Input profiles for PC-RTTOV simulations are no longer modified when the apply_reg_limits option is true. Values falling outside the limits are still flagged via the radiance%quality(:) output as for standard RTTOV simulations.
  • Wrapper:
    • Python and C++ interfaces fully updated with respect to the changes in RTTOV.
    • Enable return of explicit optical property Jacobians through wrapper.
    • Enable user specification of radar K inputs so that the full Jacobian matrix can be computed for radar simulations.
    • Add wrapper interface to the rttov_aer_clim_prof subroutine.
    • Add a new StoreEmisRefl option and accessor functions to obtain surface emissivity/reflectance values used in the simulations so that the input emissivity/reflectance values are not overwritten.
    • Rename Options, Atlas, and Profiles C++ source files with Rttov prefix to avoid potential name clashes/confusion with unrelated external libraries.
    • Technical improvements to the C++ interface.
  • GUI
    • The RTTOV GUI is now a pure Python application that uses the pyrttov interface.
    • The GUI now supports MW scattering simulations.
    • The GUI no longer supports PC-RTTOV simulations.
  • Technical updates:
    • Numerous updates to the RTTOV Fortran interface to improve clarity and consistency. This includes significant changes to the rttov_options structure, updates to various module and subroutine names and subroutine interfaces, and other variable and derived type name changes.
    • HDF5 has been replaced by netCDF4 for large coefficient files and emissivity/BRDF atlas files. HDF5 is no longer an explicit dependence.
    • New subroutine rttov_wmo2rttov_sat_id that maps WMO satellite IDs to RTTOV platform/satellite ID pairs.
    • Reduce the number of memory allocations done within RTTOV to decrease run-time.
    • Allow external allocation of all “trajectory” (internal state) data structures for single-threaded runs. This can improve performance in cases where many calls are made to RTTOV and the parallel interface is not used.
  • Capabilities removed:
    • Surface implicitly lies on bottom pressure half-level so RTTOV v14 cannot be called for profiles on fixed pressure levels with a separate surface pressure that is independent from the pressure levels.
    • FASTEM-1/2/3/4 and TESSEM2 microwave sea surface emissivity models.
    • JONSWAP wave spectrum option for solar sea BRDF model.
    • Solar single-scattering solver for clouds/aerosols.
    • MFASIS-LUT fast visible solver for clouds based on look-up tables.
    • HTFRTC Principal Components based model.
    • Deprecated options removed: grid_box_avg_cloud, dtau_test, reg_limit_extrap, spacetop.
  • Coefficient file compatibility:
    • RTTOV v14 can read all ASCII RTTOV v13-compatible optical depth coefficient files.
    • Binary/Fortran unformatted optical depth coefficient files must be regenerated using RTTOV v14.
    • HDF5 optical depth coefficient files cannot be read by v14: it is recommended to download the corresponding netCDF4 file from the RTTOV v14 coefficients download page.
    • All other aerosol/hydrometeor optical property files and MFASIS-NN and PC-RTTOV coefficient files are mutually incompatible between v13 and v14: you must download new files from the RTTOV v14 coefficients download page.

RTTOV v13.2

RTTOV v13.2 was released in December 2022 by the NWP SAF. The main new features of RTTOV v13.2 compared to v13.1 are:

  • Visible/IR scattering simulations:
    • New MFASIS-NN (neural network) solver for visible/near-IR cloud simulations. The solver is selected by setting opts%rt_ir%vis_scatt_model=4 and is used in conjunction with new neural network coefficient files that can be downloaded from the RTTOV coefficients web page.
    • New option opts%rt_ir%rayleigh_depol to enable use of modified phase function accounting for molecular depolarisation in Rayleigh single and multiple scattering.
    • New capability to generate aerosol optical property files based on a subset of species from the ICON-ART model (users can request files for any VIS/IR sensor via the NWP SAF helpdesk).
  • RTTOV-SCATT MW scattering simulations
    • Alternative physically-based polarisation treatment which applies to cross-track scanners as well as imagers. This is selected via the new opts_scatt%pol_mode option and requires an additional input file that can be downloaded from the RTTOV coefficients download page.
    • Use highest temperature bin in optical property tables (previously was not used): this results in changes to outputs.
    • Hydrotable generation updates:
      – Increase number of mass density points and number of temperature points in hydrotables, reduce precision to mitigate file size increase
      – New PSD options (Abel and Boutle, Illingworth and Blackman)
      – Experimental new version of Bauer (2001) melting layer over 273 – 277 K temperature bins.
  • General simulation updates:
    • New option opts%rt_all%use_tskin_eff to enable optional input of per-channel effective skin temperatures in emissivity(:)%tskin_eff to be used instead of single profile skin temperature.
    • New option opts%config%opdep13_gas_clip which can be used to disable the clipping of negative individual gas optical depths resulting from the v13 predictor regression. This can mitigate convergence failures in some operational assimilation systems. Standard deviation of impact on BTs is well below 0.01 K although maximum impact is of order 0.1 K.
    • Add a new strictly_illegal optional argument to the rttov_user_options_checkinput subroutine to enable checking only for strictly illegal settings and suppress errors for “dubious-but-harmless” settings.
    • The rttov_scale_ref_gas_prof subroutine now provides the option to interpolate in log(pressure) instead of pressure.
    • Add new subroutine rttov_calc_solar_angles to populate a profiles structure with solar zenith and azimuth angles given profile date, time, lat, lon values.
    • Add new subroutine rttov_calc_geo_sat_angles to populate a profiles structure geostationary satellite zenith and azimuth angles given profile lat, lon values and the sub-satellite longitude.
    • Not a new feature, but previously undocumented: the option opts%dev%do_opdep_calc can be set to false to turn off the gas optical depth calculation in RTTOV. The simulations are then run with zero gas optical depths. This may be useful for certain scattering applications. The option is available in the Python/C++ wrapper.
    • Added qmin_kgkg and qmax_kgkg constants to the rttov_const module which give strict min/max values for input water vapour concentrations in kg/kg over moist air.
  • Surface emissivity and reflectance updates
    • New SURFEM-Ocean MW sea surface emissivity model: neural network parameterisation of new PARMIO physical reference emissivity model simulating all Stokes components for channels in the range 0.5 – 700 GHz. This is specified by setting opts%rt_mw%fastem_version=7 but this is a different model to FASTEM.
    • Stokes 3/4 emissivity calculations have been implemented for FASTEM-6 based on the FASTEM-3 parameterisation. FASTEM-6 can now be used for all sensor channels below ~200GHz, including polarimetric sensors.
    • FASTEM-3 relative wind direction bug fix (see FASTEM-3 bug dated 11/02/2022 in bug fix table linked below) is implemented on a switch opts%rt_mw%fastem3_rwd_fix, default true. Set to false to revert to previous behaviour (for users whose systems are tuned to the incorrect version and require continuity).
    • Additional TL/AD/K bug fixes in FASTEM-3. These only occur for zenith angles above 60 degrees which means they are not relevant for current MW sensors.
    • The BRDF atlas now extrapolates at constant value to short wavelengths which provides basic BRDFs for UV sensors (atlas to be updated with improved UV support in a future release).
  • GUI
    • The GUI has been updated to support new features including MFASIS-NN simulations, and other new RTTOV options.
    • New options are provided for installing a Python environment for the GUI including a requirements.txt file and a Dockerfile: see the GUI user guide for details.
  • Wrapper
    • The Python/C++ wrapper has been updated to support the new features including MFASIS-NN, the new polarisation treatment in RTTOV-SCATT, the per-channel effective skin temperautre inputs, and other new RTTOV options.
  • Technical updates:
    • Fix AD/K issue whereby shared AD/K routines (primarily RTTOV-SCATT, but also the v13 predictor optical depth regression) can run in the wrong mode under certain conditions. There is a new optional adk_switch argument to rttov_scatt_ad and rttov_parallel_scatt_ad which can be used to explicitly specify an AD (0) or K (1) run. If omitted, the pre-existing behaviour pertains. For the problem to occur, it requires that some profiles passed in are not simulated for any channels which means that it should not affect most users.
    • Fix issue whereby MW simulations fail if some channels are deactivated by having the channel validity flag in the rtcoef file set to zero. (Not issued as a bug fix as there are simple workarounds and no current or recent MW rtcoef files have this flag set to zero for any channels).
    • Code updated for new DrHook type jphook.

RTTOV v13.1

RTTOV v13.1 was released in November 2021 by the NWP SAF. The main new features of RTTOV v13.1 compared to v13.0 are:

  • Initial support for UV simulations: basic support for UV simulations is implemented and this will be developed further in future releases.
  • MFASIS has been updated:
    • improved treatment of mixed-phase clouds. This update also changes simulated radiances with MFASIS for profiles containing any ice cloud (not only for profiles with mixed-phase layers).
    • capability to simulate 1.6 µm channels for supported sensors. New MFASIS LUT files are available on the coefficient download web page: these are not compatible with RTTOV v13.0 and earlier.
  • The overcast and radiance2 outputs are now calculated for thermal channels in aerosol simulations when the Chou-scaling solver is used. The radiances include the effect of aerosols. For solar-affected short-wave IR channels, solar radiation is not included even when the addsolar option is enabled.
  • New subroutines rttov_get_sea_emis and rttov_get_sea_brdf which can be used outside of RTTOV to obtain surface emissivities and reflectances from the internal RTTOV sea surface models.
  • New option opts%rt_all%transmittances_only to carry out transmittance calculations only (no radiances, and no surface emissivities or reflectances). This is more efficient if only transmittance outputs are required. Applies only to the direct model.
  • Maximum allowed Tskin value over land increased to 1250 K to allow for lava/fires/etc.
  • For SSU PMC shift simulations, the CO2 cell pressures are now initialised with the nominal values from the coefficient file. Previously they were uninitialised.
  • New constants added to rttov_const for the indices of the RTTOV-SCATT hydrometeors in the NWP SAF hydrotables (hydro_index_rain, hydro_index_snow, etc): these can be used in place of hard-coded literal indices in user code for futureproofing.
  • The RTTOV GUI has been updated to better support UV and VIS-only sensors.
  • Minor technical updates to improve the C++ wrapper core and example code to conform to common C++ coding conventions and use recommended techniques.

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.
  • HTFRTC
    • 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.
  • HTFRTC
    • 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.
  • RTTOV-SCATT:
    • 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.