BTRAM, the Blue Sky Spectroscopy Transmission and Radiance Atmospheric Model, is a fast, fully customizable, line-by-line, layer-by-layer radiative transfer model based on the HITRAN 2008 molecular line database. BTRAM provides line-of-sight transmission and emission spectra for fully customizable atmospheres and gas cells over wavelengths ranging from the visible to the extreme infrared at variable spectral resolution. Running on a PC, BTRAM quickly produces accurate results through a convenient graphical user interface. The product of 5 years of development and testing was released for the first time to a wider community as version 3.0 in January 2007.
Transmission, emission, and opacity are modeled along a line of sight for radiation at wavelengths above 500nm. BTRAM can provide spectral information equally at low and high resolution. The user can specify the spectral resolution of the model and is essentially limited by the computation time. The model spectrum can be convolved with a user-specified instrument line shape.
The user has a choice of modeling radiative transfer through an atmosphere or a gas cell. The Earth’s atmosphere is modeled in three different sections: 0 to 12km, 12 to 30km, and 30 to 50km. Within these sections, atmospheric layers can be customized by the user. Nine pre-defined atmospheric profiles are included, six of these are equivalent to the standard atmospheric models found in FASCODE. The atmospheric model has been successfully validated against FASCODE. Radiative transfer through a gas cell allows users to select a mixture of gases from a list of 37 common gases, or simply to model a short path of atmosphere at constant pressure and temperature.
The particular strength of BTRAM is to provide results fast and through a flexible interface. Simulations can be based on individual parameter selections or on a batch process that iterates through a one-dimensional parameter space at a user-defined interval. The Graphical User Interface allows users to click to zoom into results and auto-scale axes. Commonly used units (cm-1, GHz, μm, nm) are available for the spectral dimension. A comprehensive online help system and a stand-alone user manual are available. Results can be printed and stored in ASCII or the open SPC® data format.
BTRAM runs under the IDL Virtual Machine® on Windows XP, Vista, and Linux. The purchase of third-party software is not required. Installation of the self-contained application is straightforward. Send email to btram@blueskyinc.ca for a license quote. You can also download a one page summary of BTRAM v3.
Download the latest version, BTRAM 3, now.
| Spectral range | λ>500nm, from the visible to the submillimeter |
| Spectral resolution | User selection, <100,000 spectral elements |
| Line database | HITRAN 2008 |
| Pre-defined atmospheric models | Tropical, Mid-Latitude (Summer and Winter), US Standard, Subarctic (Summer and Winter), Antarctic Summer, Chajnantor Winter, Mauna Kea, Antofagasta Summer |
| Available gases | H2O, CO2, CO, CH4, O3, O2, N2O, etc. |
| Compatible operating systems | Linux, Windows XP, Vista |
| System requirements | 30MB of disk space, 256MB RAM required, 1GB RAM recommmended |