p-TOMCAT chemistry schemes

This page describes the chemistry schemes available to use with p-TOMCAT.

IMPORTANT! Do not confuse the chemistry version number with the model version number. The model version number will always be referred to as vM.N (e.g. v1.0) whereas the chemistry (ASAD) files will be referred to as cM (e.g. c1). It's possible to use different chemistry schemes with the same model version (or vice versa except where noted).

Evaluations using these ratesfiles can be found from the p-TOMCAT home page.

Chemistry Scheme Files

For each chemistry scheme, either download the zip file with all files or each individual file. You need to download all the files listed in that row. Note that some chemistry schemes require nupdate changes to either ASAD or p-TOMCAT nupdate libraries.

Chemistry version Chemical species Bimolecular ratefile Termolecular ratefile Photolysis ratefile Dry deposition velocities Wet deposition velocities ASAD updates p-TOMCAT updates Zipfile
c1 - Original UNITOM scheme chch.d ratb.d ratt.d ratj.d depvel.d henry.d none none c1.zip
c2 - Updated c1 scheme chch.d ratb.d ratt.d ratj.d depvel.d henry.d c2_update none c2.zip
c3 - c2 with isoprene                  


Available Chemistry Schemes

This is a summary of the chemistry schemes currently available with p-TOMCAT. The required files for each scheme can be obtained below.

c1 scheme
This is the original species as used in UNITOM. The list of reactions is also the same as used in UNITOM. Most of the rates are the same except Fiona updated some of the reaction rates to the IUPAC 2000 assessment. These ratefiles were never evaluated at the time, but have been recently (2005) using p-TOMCAT.

c2 scheme
(recommended)
This has the same list of species as in c1 chemistry. This is the recommended scheme for use with p-TOMCAT. When new assessments are released or relevant kinetic data published, these ratefiles will be updated.

The changes to the chemistry scheme to date are:

  • Kinetic data for all reactions was updated by Paul Young based on current (March 2005) IUPAC data and MCM data. See notes in the updated ratefiles for more information.
    • In addition, the O(1D) + N2 rate was updated following Ravishankara et al (2002) which reviewed several recent measurements for this reaction.
  • Reaction rates computed explicitly by bimol.f and trimol.f in ASAD have also been updated.

Note that this job includes an update to the ASAD library to alter bimol & trimol and change ASAD to work with 4 products in the ratb.d and ratj.d files.

A new version of the drydep.d file was released with this version, updated by Paul Young. The dry deposition velocity for ozone over water and snow/ice has been reduced to 0.04 from 0.07 (from Ganzeveld and Lelieveld 1995). The old drydep.d file had an incorrect value that was too high and could not be traced back to any publication. Reducing the value improves the model comparison with data over Antarctica.

A new version of the wet deposition file henry.d was also released with this version. The wet deposition velocities were updated by Paul Young. See the comments in this file for details of the publications used.

Note that c2 chemistry required p-TOMCAT v1.1 or higher.


c3 scheme (in preparation)
This is based on the c2 scheme but includes the Mainz Isoprene Mechanism. This scheme is currently under test and will be available in the near future.