Frequently Asked Questions

On this page are frequently asked questions (FAQ) by users of the HITRAN and HITEMP databases and the software in the HAWKS (HITRAN Atmospheric Workstation) compilation.
Is there any cost to obtain HITRAN? The HITRAN database and its associated compilation are free. One can obtain information for accessing the files from an anonymous ftp-site by filling out the HITRAN questionnaire/request form located in this web-site.
Are the line positions in HITRAN in vacuum or air? The transitions (line positions) in the HITRAN database are given in vacuum wavenumber (cm-1). The intervals for the IR and UV cross-sections are likewise given in wavenumber.
What are the units of intensity in HITRAN? The units for intensity in HITRAN are cm-1/( molecule × cm-2 ) at the standard HITRAN temperature of 296 K. This unit has been chosen for its convenience for input to transmission and radiance modeling computer codes. An illustration of the definition of intensity, line position, and half-width is given in Fig. 1 in the Appendix to the article on the 1996 Edition of HITRAN in the Journal of Quantitative Spectroscopy and Radiative Transfer vol. 60, pp. 665-710 (1998). A reprint is located in the documentation section of the HITRAN web-site.
How does one convert intensity units between different databases? An example of converting the intensities from either the Jet Propulsion Laboratory or Cologne Database for Molecular Spectroscopy databases to HITRAN units is provided in the short Guide for Unit Conversion.
Does HITRAN model the atmosphere? HITRAN is a database, not a “simulation” code. It provides a suite of parameters that are used as input to various modeling codes, either very high-resolution line-by-line codes, or moderate spectral resolution band-model codes. These codes are based on the Lambert-Beers law of attenuation and may include many more features of modeling, for example line shape, scattering, continuum absorption, atmospheric constituent profiles, etc.
Then what does the software included with HAWKS do? The software included with the HITRAN compilation allows the user to perform the basic operations on the database, namely filtering by means of wavenumber or wavelength, molecule, isotopologue, band system, etc; plotting the line-by-line or cross-section data; and various other database management functions. One can also import portions of HITRAN into familiar spreadsheet programs to perform various analyses.
The software, JavaHAWKS, has been hanging up. What is wrong? JavaHAWKS has not been updated for any new molecules, isotopologues, or bands that have been introduced after the 2004 edition of HITRAN. So as long as you do not use it in a mode that encounters these additional items, then it is OK.
  A whole new internet-based software system for HITRAN is under development at the Institute of Atmospheric Optics in Tomsk, Russia. You can access this program by going to HITRAN on the Web.
Are the data in HITRAN observed or calculated? The parameters in HITRAN are sometimes direct observations, but often calculated. These calculations are the result of various quantum-mechanical solutions. The goal of HITRAN is to have a theoretically self-consistent set of parameters, while at the same time attempting to maximize the accuracy. References for the source are included for the most important parameters on each line of the database.
What is “HITRAN-PC”? HITRAN-PC is a commercial software product that uses the HITRAN database to calculate molecular absorption and to model attenuation in the atmosphere or laboratory conditions. It was developed for easy use on a PC by Professor Dennis Killinger and Dr. William Wilcox at the University of South Florida (Killinge@chuma.cas.usf.edu) and is distributed by the Ontar Corporation (http://www.ontar.com).
What does the value “-1” mean for the lower-state energy? There are some lines in HITRAN (only for H2O and CH4 at this time) where we were unable to fully identify the transition (but whose position and intensity are known). These lines come from measurements made at 296K. It was decided long ago that we would nonetheless put these lines in HITRAN. A “flag” for these lines was to set the lower-state energy to “-1.”. You will also notice that the lower-state quanta for these lines are incomplete. The E″ = -1 flag is used by some transmission/radiance programs (FASCODE, for example) to allow calculations of transmission as long as the temperatures are not far from 296K. The algorithms make decisions on how to handle this situation.
I have been unable to access the ftp-site for the HITRAN files. What can I do? A small fraction of users have not been able to access the HITRAN data because their computers are not properly registered with a Domain Name Server, a prerequisite for accessing our anonymous ftp server. As an alternative, you can obtain the HITRAN compilation files via the regular web-site at: http://www.cfa.Harvard.edu/HITRAN/HITRAN2012/
You will then be prompted for a Username and Password. The latter are obtained by filling out the HITRAN request form.
My browser strips the .gz file extension from the compressed files in the HITRAN ftp-site. What should I do? Some browsers strip the ".gz" extension from the HITRAN files, but still save them as gzipped files. Users can simply add ".gz" to the file name when the dialog box appears, or download the file(s), rename to *.gz, and then uncompress them.