Abstract

A flexible treatment for gas- and aerosol-phase chemical processes has been developed for models of diverse scale, from box models up to global models. At the core of this novel framework is an "abstracted aerosol representation" that allows a given chemical mechanism to be solved in atmospheric models with different aerosol representations (e.g., sectional, modal, or particle-resolved). This is accomplished by treating aerosols as a collection of condensed phases that are implemented according to the aerosol representation of the host model. The framework also allows multiple chemical processes (e.g., gas- and aerosol-phase chemical reactions, emissions, deposition, photolysis, and mass-transfer) to be solved simultaneously as a single system. The flexibility of the model is achieved by (1) using an object-oriented design that facilitates extensibility to new types of chemical processes and to new ways of representing aerosol systems; (2) runtime model configuration using JSON input files that permits making changes to any part of the chemical mechanism without recompiling the model; this widely used, human-readable format allows entire gas- and aerosol-phase chemical mechanisms to be described with as much complexity as necessary; and (3) automated comprehensive testing that ensures stability of the code as new functionality is introduced. Together, these design choices enable users to build a customized multiphase mechanism, without having to handle pre-processors, solvers or compilers. Removing these hurdles makes this type of modeling accessible to a much wider community, including modelers, experimentalists, and educators. This new treatment compiles as a stand-alone library and has been deployed in the particle-resolved PartMC model and in the MONARCH chemical weather prediction system for use at regional and global scales. Results from the initial deployment to box models of different complexity and MONARCH will be discussed, along with future extension to more complex gas--aerosol systems, and the integration of GPU-based solvers.

Highlights

  • A flexible treatment for gas- and aerosol-phase chemical processes has been developed for models of diverse scale, from box models up to global models

  • To evaluate the Chemistry Across Multiple Phases (CAMP) framework, we set up three box model simulations that shared the same gas-phase chemistry and aerosol–gas partitioning, but differed in their aerosol representation

  • This paper presents results from the first phase of a three-part development plan for CAMP: a flexible treatment for multiphase chemistry in atmospheric models

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Summary

Introduction

Decades of progress in identifying increasingly complex, atmospherically relevant mixed-phase physicochemical processes 20 have resulted in an advanced understanding of the evolution of atmospheric systems. A fully integrated framework is needed for the treatment of mixed-phase chemical processes with scalable complexity and applicability to various representations of aerosol systems (e.g., modal, sectional, or particle-resolved) Such a framework remains to be developed and a first step toward such a comprehensive system is the focus of this paper. CAMP has been designed to separate the specification of multi-phase chemical mechanisms from the implementation of specific solvers, and to be usable by a variety of host models. It has been designed for scalability of chemical complexity through use of a standardized JSON format for specify115 ing multi-phase chemical systems at runtime CampCore objects can pack and unpack themselves onto a memory buffer for parallel computing applications

Abstraction of a chemical mechanism
Processes
Parameters
JSON mechanism description
External ODE solver
Workflow and CAMP solving functions
Testing
Host models
MONARCH atmospheric chemistry model
PartMC
Results
Box model results
480 5.1 Summary
Optimization, porting to GPUs, and future development
Full Text
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