Added a new inorganic nucleation subroutine to tomas_mod.F90.

[samuelod-atmos]

The nucleation scheme is based on this paper:
https://www.science.org/doi/10.1126/science.aaf2649.

Name and Institution (Required)

Name: Samuel O'Donnell
Institution: Colorado State University

Describe the update

We have added a new inorganic nucleation mechanism to the TOMAS aerosol package. The nucleation mechanisms are based on Dunne et al. (2016; https://www.science.org/doi/10.1126/science.aaf2649), and was originally written by Jeff Pierce at CSU. We have not included the organic nucleation mechanism outlined in Riccobono et al. (2014) which is part of the Dunne et al. (2016) paper.

A new switch has been added (dunn_nuc; 0/1) in order to turn the mechanism off/on, consistent with the existing inorganic nucleation mechanisms. The updated scheme uses sulfuric acid (molecules/cm^3) and ammonia (molecules/cm^3) in a simple power-law function to give the formation rate of small particles. In order to better match observations of new particle formation events at the Southern Great Plains (SGP) observatory, we had to scale up the nucleation mechanism by 1000x for the 15 bin simulation. This updated is relatively untested with TOMAS40, so the 1000x multiplier should be tested with a TOMAS40 simulation.

Expected changes

Overall, nucleation and particle growth is a buffered system, so the nucleation rates should result in little changes to bulk aerosol mass. Ideally, the updated mechanisms should lead to better agreement with observations in terms of new particle formation event frequency, duration, and strength throughout the globe, but we have only tested this at the SGP site so far.

Reference(s)

The work with updates to TOMAS are not published yet.

Related Github Issue

Please link to the corresponding Github issue(s) here. If fixing a bug, there should be an issue describing it with steps to reproduce.

[yantosca]

Also tagging @BettyCroft who has worked with TOMAS more recently