Periodic Reporting for period 1 - ACRoNNIM (Aerosol and Climate Response to NH3 in the NMMB/BSC Inter-Scale Model)
Reporting period: 2017-09-12 to 2019-09-11
A common approach to treating multiphase chemistry in large-scale atmospheric models is to split individual process across a collection of ‘modules’ that treat, for example, gas-phase chemistry, the partitioning of inorganic species and acid–base chemistry, the partitioning of organic species to the condensed phase, aqueous chemistry in cloud droplets, etc. Progress towards the goal of investigating the multiphase NH3–organics system using results from a recently completed field campaign and a mechanism developed in collaboration with researchers performing laboratory experiments on this system required a rethinking of this approach to treating multiphase chemical systems in atmospheric models. This effort led to the development of the Chemistry Across Multiple Phases (CAMP) framework, which answers several key questions in atmospheric modelling, including:
• How do you describe multiphase atmospheric chemical systems in code in a way that is independent of how a host model treats aerosol systems (e.g. size bins, modes, single particles, etc.)?
• How do you allow a multiphase chemical system to be solved as a single system, thus avoiding artifacts related to operator splitting?
• How do you facilitate the rapid transfer of multiphase chemical knowledge from laboratory results to atmospheric models?
CAMP makes significant progress towards answering these questions in an innovative way.
An important result of the ACRoNNIM project is the development of the CAMP framework. Using modern approaches to software design, CAMP treats comprehensive multiphase chemical systems as a single system and is readily configured at runtime without the significant development efforts typically required to incorporate new multiphase processes into models. It is applicable to a wide variety of models, and has been developed as part of the publicly available PartMC science library (https://github.com/compdyn/partmc) licensed under the GNU General Public License version 2.0. Two papers describing the CAMP framework and its initial deployment in the MONARCH model are in preparation.
The CAMP framework is also designed to facilitate the rapid deployment of new chemical processes to large-scale atmospheric models, and to be applicable to a wide range of users, from atmospheric climate and weather modelers to industry to researchers performing laboratory experiments. Once fully implemented, CAMP will allow experimentalists with little or no software development experience to build human-readable mechanisms describing new chemical processes that they can test in a box model running CAMP to simulate their laboratory results. Once their mechanism is complete, they can provide the same input files to modelers using large-scale atmospheric models running CAMP to rapidly assess the impact of these new mechanisms at the regional or global scale. This will dramatically reduce the current development time involved in incorporating new multiphase chemical processes in different models, thus increasing the capacity for innovation in atmospheric modeling.