svn code to generate new LUTS for you selected instrument can be found here


This is the IDL code required to generate ORAC forward model lookup tables (LUTs). The main routine is in "" and there is a wrapper procedure, in "", for running batch jobs. Besides requiring IDL the code has one external dependency, the so called EODG Mie code [Grainger et al., 2004], a mixture of IDL and Fortran callable through the IDL DLM interface. The code also calls the original Fortran implementation of DISORT [Stamnes et al., 1988] through a DLM interface. For details on the LUTs and the methodolgogy for producing them see McGarragh? and Others, 2016.


The code requires the EODG Mie code available at:

Please consult the README.txt file in the EODG Mie distribution for instructions on compiling the IDL DLM interface to the Fortran Mie code.

Please consult the README.txt file in the disort/ subdirectory for instructions on compiling the IDL DLM interface to the DISORT code.


In order to use this code the IDL_PATH and IDL_DLM_PATH variables must be set to this directory and the various dependencies (eodg_mie/, eodg_mie/dlm-code/, disort/src and dubovik/). These may be set either as an environmental variable or within IDL with the PREF_SET command.

create_orac_lut may be called directly with the procedure in Please see the extensive documentation in the procedure comment header for a description of the required arguments and keyword arguments.

create_orac_lut may also be called with the procedure in In this case the arguments passed are contained in a driver file given directly to create_orac_lut_wrapper as a keyword or contained in the file equal to the CREATE_ORAC_LUT_DRIVER environmental variable. Please see the comment header for create_orac_lut_wrapper for more details.

create_orac_lut requires several input files. Several example input files are contained in the example_driver_files directory. Essentially, there are five different types of files:

  • Instrument definition files: *.inst, which define the channels of a given


  • Pressure profile files: *.dat, which define the atmospheric pressure and

temperature as a function of height.

  • Scattering properties files: *.mie, which define the components, height

distribution and microphysical properties of an aerosol or cloud type/class.

  • LUT definition files: *.lut, which define the axes/grid of the output lookup


  • Gas optical depth files: *.gas, which provide the gas extinction profiles

(due to molecular absorption) for a given channel of a given instrument. These may be produced with MODTRAN. They are optional and required for the ORAC aerosol retrieval but should not be included for LUTs for the ORAC cloud or ash retrievals.

  • create_orac_lut_wrapper files: *.driver, which is used to pass arguments of

create_orac_lut procedure into the create_orac_lut_wrapper wrapper procedure as mentioned above.

Detailed descriptions of these files are in the comment headers of their corresponding read procedures in

In the case of the instrument definition files these can be usually used unchanged but for the other files it is up to the user to use them as templates and modify them according to their requirements.

The set of nine example driver files represent a set of example runs that try to cover all the common code paths and should be used by developers for regression testing. It is recommended that developers reduce the number of output channels in the driver files and the number of output solar zenith angles in the *.lut files to speed up testing. Below is a brief description of each driver file. Though only two instruments, AATSR and MODIS, are covered in these examples/tests, switching instruments is as easy as using a different *.inst file and modifying the channel related driver file inputs accordingly.

aatsr_CCI_A70.driver, aatsr_CCI_A72.driver, aatsr_CCI_A76.driver:

These driver files are a few samples from the full set of 10 driver files for Aerosol CCI retrievals. A70 contains 3 components, A72 contains 4 components, and A76 contains two components. A70 and A72 both have a T-matrix components [Dubovik et al., 2006] whereas A76 has only Mie components. All the components are 'user' defined. Finally, since these examples are for the ORAC aerosol retrieval they include gas absorption.


This driver file is of interest as all three components are from OPAC. Gas absorption is also included.


This driver file example contains 4 components, one that is an OPAC component, two that are user defined Mie components, and one that is a user defined T-matrix component [Dubovik et al., 2006].

modis-aqua_ICE_baum.driver, modis-terra_ICE_baum.driver:

These driver file examples contain a single ice crystal component. The source of the optical properties is that of Baum et al. 2014. Here there are two driver files to emphasize that fact that these ice crystal properties are platform specific.


This example contains a single user defined log-normal mode.


This driver file is for a single single ice crystal component the source of which is optical properties from Baran and Havemann, 2004. Notice that this one is not platform specific.


This driver file is for a single modified-gamma distribution of liquid water droplets and is what is used for the Cloud CCI retrieval.

Please see the comments in the source files themselves for further information.


For questions, comments, or bug reports please email the ORAC developers email list at: devorac@….

If you would like to report a bug please a include sample case that reproduces the bug along with the all the required inputs.

Gareth Thomas, 21/06/2013 Greg McGarragh?, 06/09/2016


  1. J. Baran and S. Havemann. The dependence of retrieved cirrus ice-crystal

effective dimension on assumed ice-crystal geometry and size-distribution function at solar wavelengths. Quarterly Journal of the Royal Meteorological Society, 130(601):21532167, 2004. doi:10.1256/qj.03.154.

Bryan A. Baum, Ping Yang, Andrew J. Heymsfield, Aaron Bansemer, Benjamin H. Cole, Aronne Merrelli, Carl Schmitt, and Chenxi Wang. Ice cloud single-scattering property models with the full phase matrix at wavelengths from 0.2 to 100 mm. Journal of Quantitative Spectroscopy and Radiative Transfer, 146:123–139, 2014.

Oleg Dubovik, Alexander Sinyuk, Tatyana Lapyonok, Brent N. Holben, Michael Mishchenko, Ping Yang, Tom F. Eck, Hester Volten, Olga Munoz, Ben Veihelmann, Wim J. van der Zande, Jean-Francois Leon, Michael Sorokin, , and Ilya Slutsker. Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust. Journal of Geophysical Research, 111:D11208,

  1. doi:10.1029/2005JD006619.

Roy G. Grainger, Jonathan Lucas, Gareth E. Thomas, and Graham B. L. Ewen. Calculation of Mie derivatives. Applied Optics, 43(8):5386–5393, October

  1. doi:10.1364/AO.43.005386.

Gregory R. McGarragh? and Others. The Community Cloud Retrieval for Climate (CC4CL). Part II: Theory and algorithm. 2016. To be submitted to Atmospheric Measurement Techniques.

Knut Stamnes, Si-Chee Tsay, Warren Wiscombe, and Kolf Jayaweera. Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. Applied Optics, 27(12):2502–2509, June

  1. doi:10.1364/AO.27.002502.