Dear Colleagues, you receive this eMail because you are either a user of the radiative transfer package libRadtran or because we think that you might be interested in this information. Should you not be interested in receiving further information, please let us know. Should you know of anybody who might be interested in libRadtran and whose name is not on the distribution list, please let us also know as well. Attached to this eMail is the first libRadtran Newsletter. The main issue of this Newsletter is to announce the new version, *** libRadtran 0.99 *** And now, we wish you all a merry christmas and a happy and successful new year! Bernhard Mayer and Arve Kylling. ------------------------------------------------------------------ Dr. Bernhard Mayer Bernhard.Mayer_at_dlr.de Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) Institut fuer Physik der Atmosphaere, Oberpfaffenhofen, D-82234 Wessling, Germany. Phone: +49 8153 282568, Fax: +49 8153 281841, Homepage: http://www.bmayer.de ------------------------------------------------------------------ /*---------------------------------------------------------------- * libRadtran Newsletter No. 1 * * December 22, 2001 * * Bernhard Mayer (bernhard.mayer_at_dlr.de) * Arve Kylling (arve.kylling_at_nilu.no) * * ### More info: http://www.libradtran.org ### *----------------------------------------------------------------*/ Welcome to the first libRadtran Newsletter! Since the libRadtran user community is continuosly growing, we feel that it is neccessary to have a medium (a) to announce new versions (b) to inform about identified and fixed bugs (c) to highlight new features Hence, we will send a sporadic Newsletter, whenever new features have been added or bugs have been fixed. The main issue of this Newsletter is the announcement of *** libRadtran 0.99 *** After two years beta status where new options were added and tested continously we decided it's time now to get rid of the beta (which places us in good company because Linux Torvalds usually needs something like two years before he calls a new linux kernel version 'a release'). Removing the beta from the version number does not necessarily imply that this version is free of bugs (which is probably true for any piece of software with more than 100,000 lines of code). However, the number of bugs that we become aware of and fix is rather small. In general we have to distinguish between two types of bugs: Those which cause the model to crash and produce an error message as output, and those which produce erroneous output without warning the user. The first one is not too uncommon, especially since libRadtran is run on various different platforms, but the second class is rather rare, probably something like less than one per year. Here we need the help of all users: If you find a bug, please send us a message including all the relevant information. We cannot guarantee that we will fix the bug immediately, but it will definitely improve the model quality in the long run. Talking about the future: In order to converge towards version 1.0, we plan to (1) add more options, (2) do more testing, and (3) improve the documentation. Before the final 1.0 release, however, there will surely be many small upgrades (there have been 12 upgrades to the original 0.99-beta after it was released two years ago). In this context, please note that libRadtran is pretty much 'application-driven', that is, options are added whenever we need them for our research. *** Features of version 0.99 compared to the old 0.15 *** - New radiative transfer solvers: 1) the old version of disort has been replaced by disort 1.3 2) a new disort version, disort 2, has been added. disort 2 has two big advantages compared to previous disort versions: (a) the number of streams, nstr, and the number of Legendre terms in the phase function are decoupled; this allows much better radiance calculations for detailed scattering phase functions; hence disort 2 is to be preferred whenever radiances are calculated; (b) non Lambertian BRDF is included 3) a polarization-dependent solver, polradtran, has been added; scattering matrices have yet only been implemented for Rayleigh scattering but not for Aerosol and cloud scattering 4) the default pseudo-spherical disort is now in double-precision - libRadtran has been extended from its original wavelength region (ultraviolet and visible) to the solar and thermal infrared. Calculations can either be done line-by-line, or with a correlated k-distribution; three different distributions are provided with libRadtran: 1) Kato et al. [1999] for the shortwave range (0.25 micron - 4.5 micron) 2) Fu and Liou [1992/93] for the shortwave and longwave range (0.25 micron - 100 micron) 3) Kratz [1995] for the AVHRR channels The k-distribution is the most accurate solution (after line-by-line, of course) but it has the drawback that it takes away all the flexibility of user-defined wavelength grids. We are currently working on a solution that restores part of this flexibility. - There is now a variety of options to define aerosol properties, starting from 'aerosol_default' which selects the Shettle et al. [1989] profiles up to the possibility of defining the optical properties explicitely for each layer with 'aerosol_files' - The optical properties of water clouds are calculated either with the parameterization by Hu and Stamnes [1993], or from tables that have been pre-calculated with Mie theory (the tables are separately available from http://www.libradtran.org) - There are several parameterizations for the optical properties of ice clouds. Either the parameterization by Fu (1996), Fu et al. (1998), or the parameterization by Yang et al. (2000), Key et al. (2001), or a pre-calculated Mie-table for ice spheres may be used (the tables are separately available at http://www.libradtran.org) - Non-Lambertian surface reflectance (BRDF) may be specified following the parameterization of Rahman et al. (1993) - Improved documentation: The documentation of libRadtran has been re-organized. It starts now with kind of a cook-book how to use the model for certain questions which is followed by the full list of input parameters. The long description of all the library functions which is not very interesting for most users went into libRadtran_developer.ps. - Options 'verbose' and 'quiet'. 'verbose' will produce an awful amount of information which provides a new means for checking if the model really does what the user had in mind. It is always a good idea to test a new input file first with 'verbose' because that gives you an idea if e.g. the clouds are really there where you want them to be, because 'verbose' uvspec dumps profiles of every species just before they are passed to the rte_solver, The 'quiet' option is only recommended when you are really sure that the input is working properly. - Some new tools: cldprp allows the calculates optical properties of water and clouds; addlevel adds a level to one of the standard atmospheric profiles at a user-selected altitude. - Many many small changes and new input options which are not discussed here in detail. The latest version is available at http://www.libradtran.org, as usual. And now, have fun! Bernhard Mayer (bernhard.mayer_at_dlr.de) Arve Kylling (arve.kylling_at_nilu.no)