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. Attached to this eMail is the 7th libRadtran Newsletter. The main issue of this Newsletter is to announce the new version, *** libRadtran 1.2 *** which includes some bug fixes and several improvements compared to version 1.1-beta. If you are interested in a closer collaboration with the libRadtran developers, have a look at the attached job offer. The EUMETSAT Fellowship is an exciting opportunity in my group at DLR Oberpfaffenhofen if you are interested and have experience in 1D and 3D radiative transfer, remote sensing, and cloud physics. Please feel free to distribute this information! And now, we wish you all a Merry Christmas and a happy and successful new year! Bernhard Mayer, Ulrich Hamann, 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. 7 * * December 24, 2006 * * Bernhard Mayer (bernhard.mayer_at_dlr.de) * Ulrich Hamann (ulrich.hamann_at_dlr.de) * Arve Kylling (arve.kylling_at_helse-sunnmore.no) * * ### More info: http://www.libradtran.org ### *----------------------------------------------------------------*/ Welcome to the 7th libRadtran Newsletter! Dear libRadtran users, following a long tradition established in 2001, a new version of libRadtran is provided on Christmas Eve! But prior to exchanging the gifts I want to point out two important things: *** If you are interested in a closer collaboration with the libRadtran developers, have a look at the attached job offer. The EUMETSAT Fellowship is an exciting opportunity in my group at DLR Oberpfaffenhofen if you are interested and have experience in 1D and 3D radiative transfer, remote sensing, and cloud physics. *** The list of publications at the libRadtran homepage (http://www.libradtran.org/publications.html) now includes 82 publications using the libRadtran model. With SCOPUS I found actually more than 100 papers not only referencing the uvspec papers but making direct use of the model. Before using SCOPUS, I was not even aware of half of those! Therefore my wish: If you publish something which is based on libRadtran, please let us know! And even better, if it is published not in the "standard journals" (JGR, GRL, JAS, ...) but some place which is not easily accessible for us (e.g. a SPIE conference contribution or a PhD thesis), we would be very happy about a reprint, preferably in electronic form! And now: libRadtran 1.2! The following list shows quite a few changes. Mostly new options but also a few small bug fixes. As usual, we have done a lot of testing, but the number of available options prevents a complete test of all combinations of options. This version of libRadtran was tested under Linux and Solaris but should basically run under all operating systems with a C and a Fortran77 compiler including Mac OSX and Windows. *** Bug fixes: * Fixed a bug in the implementation of the Bodhaine et al. Rayleigh cross section which caused errors of up to 3% in the cross section! Fortunately the error was largest for longer wavelengths where the Rayleigh cross section is small anyway. * The airmass calculations did not work since the last update (the calculations provided only zeros). Only one user complained - the option is probably not used very often. * Small bug: during interpolation of gas number densities tiny but negative numbers occurred. Now these values are automatically corrected to 0 if they are smaller than a -epsilon. * Some fixes to the twostr solver in the thermal spectral range: twostr frequently crashed in thermal calculations and provided nan's as output. After the fix, the twostr solver seems to provide stable results in the solar and the thermal, except for cases of high surface albedo in combination with a cloudy atmosphere (multiple scattering between surface and atmosphere seems to cause trouble). *** New options: * The output of "make" has been cleaned up. If the compilation is started with "make", messages like "compiling ascii.c" etc will be issued instead of multi-column "gcc -xxx " command lines. Warnings and error messages are much better visible that way. To get the full output, use "make VERBOSE=1". Also, the dependencies have been cleaned up so that a file is recompiled if and only if recompilation is really required. * The ice cloud parameterization by Key et al. (2002) has been extended from 0.2 - 5 micron to 0.2 - 100 micron, based on more recent single scattering data provided by Ping Yang. Below 3.4 micron it actually equals the Key et al. (2002) parameterization while from 3.4 - 100 micron new coefficients have been calculated with much higher wavelength resolution and better accuracy. The new ice cloud parameterization should give a reasonably consistent approximation from 0.2 - 100 micron, suitable for spectrally resolved calculations of radiance and irradiance. * Considerable effort has been spent on the calculation of heating rates. Heating rates are now calculated as spectral rather than integrated quantities. They can therefore be treated equivalent to other output quantities with output sum, output integrate, and output_user. In order to activate the calculation of heating rates use 'heating_rate' instead of 'output heating'. * New options in order to convert output units: 'output per_nm', 'output per_cm-1', and 'output per_ck_band' Very useful in particular for thermal calculations. * The water vapour side clouds is usually saturated. 'wc_saturate' and 'ic_saturate' have been added in order to set the water vapour pressure to saturation water vapour pressure inside the cloud. * A new option 'radiosonde' allows to easily include radiosonde data or ECMWF reanalysis. 'radiosonde' expects an input file which contains at least temperature and pressure, and optionally gas densities. This information will be merged with the atmosphere file data. * 'toa' (top of atmosphere) and 'sur' (surface) are now possible zout levels (zout = altitude above ground) * New option zout_sea; same as zout, but relative to sea level rather than above surface. * New output_user options T (temperature), T_d (dew-point temperature), p (pressure), theta (potential temperature), theta_e (equivalent potential temperature), zout_sea (altitude above sea level), number and mass density as well as mass and volume mixing ratio of gases. * Included oxygen absorption cross sections between 108 and 240nm and extended ozone absorption cross section down to 116 nm to allow calculations in the UV-C, including the Schumann-Runge absorption bands and the Lyman-alpha emission line. This is required for calculations in the stratosphere and above. In particular, added - Ackerman [1971] ozone cross section below 185/195nm - Schumann-Runge bands from Minschwaner et al [1992], 175-205nm - Herzberg continuum from Yoshino et al. [1988], 194-240nm - Schumann-Runge continuum from Yoshino et al. [2005], 160-175nm - Schumann-Runge continuum from Ogawa and Ogawa [1975], 108nm-160nm - Lyman-alpha region from Lewis [1983], 121.4nm-121.9 nm The resolution in the Schumann-Runge bands is per default the resolution of the Minschwaner et al. [1992] data, 0.5 cm-1. This amounts to 16000 data points between 175 and 205nm. According to Minschwaner et al. [1993], the Herzberg continuum from Yoshino et al. [1988] has to be added to the Schumann-Runge bands, for consistency (other data give worse results). For a more detailed description watch out for a paper by Nissen et al. which is accepted for publication in ACPD. * The albedo can be specified with a combination of new input options: albedo_map map of surface types albedo_library collection of spectral albedo files latitude, longitude specifies location on the albedo map An albedo map example is enclosed. * The altitude can be specified in a similar manner with altitude_map latitude and longitude An altitude map example is enclosed. * tools/mie can now directly generate the format required by uvspec as input e.g. by 'wc_properties ...'. Also added a new option 'output_user' to tools/mie. * The mie program can now calculate optical properties for gamma and lognormal distributions, in addition to explicitely defined size distributions. * Claudia Emde included a new ice cloud parameterization by Bryan Baum, http://www.ssec.wisc.edu/~baum The parameterization is provided over the spectral ranges from 0.4 to 2.2 microns in the visible and from 100 to 3250 cm-1 in the infrared. The new option is invoked with ic_properties baum The Baum et al phase functions were fitted with 100 Legendre coefficients (as required by disort), determined with a fitting method described in Hu et al. (2000). For an exact description of all features (forward and backscattering peaks and the HALO) more than 10,000 Legendre terms would be required but for most applications the chosen solution is appropriate. Expect small differences around the Halo, slightly larger ones close to the backward directions; even larger differences in the forward direction. The infra-red data is not included in the distribution but can be obtained on request. The high-accuracy data set with 10,000 Legendre coefficients is also available on request. * Claudia Emde provided a new tool pmom to calculate Legendre coefficients for arbitrary phase functions. *** Smaller changes: * Several changes to reduce computational time and memory usage. E.g. cross sections are only read if the concentration of the species is larger than 0 which may reduce computational time by a factor of 2 in a monochromatic case. * Major changes to speedup the Kato routines, introduced by Sina Lohmann: Cross section tables are now only read once instead of again and again for each layer. This saves typically half of the computational time for a kato2 twostr calculation! * All gas densities are now interpolated assuming linear changes of the mixing ratio. * If pressure is scaled, O2 and CO2 are scaled accordingly to conserve their mixing ratios. * Dens_column can be specified for ALL gases in DU or cm-2. * More error checking of uvspec input. Actually, some of the checking might be too tied and if you feel that you should be allowed to do something which uvspec does not allow you to do, please let us know. * Smaller changes in the verbose output - same z-grid for all outputs - atmosphere almost in the format as in the input file - quadrature point number and correlated-k weights - spectral albedo * Added several examples / self checks. The latest version is available at http://www.libradtran.org, as usual. And now, have fun! Bernhard Mayer (bernhard.mayer_at_dlr.de) Ulrich Hamann (ulrich.hamann_at_dlr.de) Arve Kylling (arve.kylling_at_helse-sunnmore.no)