Dear Colleagues, you might think it's still summer. A very hot summer, indeed! At least in Germany. However, Christmas is around the corner. Only 4 months to go from today! And as usual, around Christmas time, a new libRadtran release is made available! Attached to this eMail you find the 16th libRadtran Newsletter. The main issue of this Newsletter is to announce the new release libRadtran-2.0 The beta version of 2.0 has been released about one year ago. Since then we have not discovered any major bugs and therefore we now remove the "beta" from the version number. We hope that you are now used to the new syntax and that you also find it more logical and easier to understand compared to the old syntax. There is one major change between version 2.0-beta and version 2.0: The REPTRAN absorption parameterization based on representative wavelengths is now used by default because it provides correct molecular absorption properties for the full spectral range, from the UV to the far IR. This change implies that you may get different results for the same input files. Below about 500 nm the differences should be very small, because REPTRAN uses the same absorption cross sections as were previously used by default. For larger wavelengths you will now get improved results compared to previous libRadtran versions. The old default molecular absorption settings can still be enabled using the option 'mol_abs_param crs'. 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! Best wishes, Claudia Emde, Arve Kylling, Josef Gasteiger, Robert Buras and Bernhard Mayer. /*---------------------------------------------------------------- * libRadtran Newsletter No. 16 * * August 24, 2015 * * Bernhard Mayer (bernhard.mayer_at_lmu.de) * Claudia Emde (claudia.emde_at_lmu.de) * Robert Buras (robert_at_buras.eu) * Arve Kylling (arve.kylling_at_gmail.com) * Josef Gasteiger (josef.gasteiger_at_lmu.de) * * ### More info: http://www.libradtran.org ### *----------------------------------------------------------------*/ The main issue of this Newsletter is to announce the new release libRadtran-2.0 which will be remembered as the Summer Holidays Release 2 (SHR2). As always the new release includes several new features, bug fixes, and most probable several new bugs. Please help us to find and fix them! *** Major changes: * The new default molecular absorption parameterization is REPTRAN (coarse resolution, 15 cm-1). This has the big advantage, that absorption by water vapour, oxygen, and all relevant trace gases is now included automatically without having to specify a molecular absorption parameterization. This implies that libRadtran 2.0 will give slightly different results for the same input compared to previous versions. If different, the new results are more accurate than before. Below 500 nm the differences are very small because REPTRAN uses the same molecular absorption cross sections as the previous default. * A new ice optical properties parameterization has been included. It is based on single scattering data by Yang et al. Reference: P. Yang, L. Bi, B. A. Baum, K.-N. Liou, G. Kattawar, and M. Mishchenko. Spectrally consistent scattering, absorption, and polarization properties of atmospheric ice crystals at wavelengths from 0.2 ??m to 100 ??m. J. Atmos. Sci., pages 330-347, 2013 Bulk optical properties have been generated from the single scattering properties assuming gamma size distributions. The parameterization is available for the full spectral range from 200 nm to 100 micrometers. It includes 9 habits and 3 degrees of roughnesses which can be selected by the user. Arbitrary mixtures of habits and roughnesses may be generated using the "profile_" options. In order to use the parameterization you need to download additional data from the libRadtran website. * The BRDF for planetary and lunar surfaces by Hapke 1993 has been included. Reference: Hapke, B.: Theory of reflectance and emittance spectroscopy, New York: Cambridge University Press, 1993. *** User contributions: This year we have obtained two contributions by libRadtran users which have been included into the package: * New version of "tzs" solver by Luca Bugliaro. "tzs" is a fast solver which calculates radiances in the thermal spectral range without scattering. The new version allows to include "black" clouds, i.e. clouds that emit blackbody radiation at a user specified altitude. * Jethro Betcke included the option "aerosol_king_byrne", which scales the aerosol optical depth according to King and Byrne (1976): Reference: King, M. D. and Byrne, M.: A Method for Inferring Total Ozone Content from the Spectral Variation of Total Optical Depth Obtained with a Solar Radiometer, J. Atmos. Sci., 33, 2242???2251, 1976. *** Bug fixes: * 'output_process integrate' did not give correct results for the calculation of brigthness temperatures in version 2.0-beta. * The MYSTIC standard deviation was wrong for REPTRAN calculations. * Polarized surface reflection has not been correct in spherical geometry (MYSTIC solver). * The Ambrals BRDF was not correct for non-zero azimuth angles