Generalized Aerosol/Chemistry Interface (GIANT): A community effort to advance collaborative science across weather and climate models

Atmospheric aerosol and chemistry modules are key elements in Earth system models (ESMs), as they predict air pollutant concentrations and properties that can impact human health, weather, and climate. The current uncertainty in climate projections is partly due to the inaccurate representation of aerosol direct and indirect forcing. Aerosol/chemistry parameterizations used within ESMs and other atmospheric models span large structural and parameter uncertainties that are difficult to assess independently of their host models. Moreover, there is a strong need for a standardized interface between aerosol/chemistry modules and the host model to facilitate portability of aerosol/chemistry parameterizations from one model to another, allowing not only a comparison between different parameterizations within the same modeling framework, but also quantifying the impact of different model frameworks on aerosol/chemistry predictions. To address this need, we have initiated a new community effort to coordinate the construction of a Generalized Aerosol/Chemistry Interface (GIANT) for use across weather and climate models. We aim to organize a series of community workshops and hackathons to design and build GIANT, which will serve as the interface between a range of aerosol/chemistry modules and the physics and dynamics components of atmospheric host models. GIANT will leverage ongoing efforts at the U.S. modeling centers focused on building next-generation ESMs and the international AeroCom initiative to implement this common aerosol/chemistry interface. GIANT will create transformative opportunities for scientists and students to conduct innovative research to better characterize structural and parametric uncertainties in aerosol/chemistry modules, and to develop a common set of aerosol/chemistry parameterizations. SIGNIFICANCE STATEMENT: Accurate predictions of atmospheric aerosols and trace gases concentrations in current and future atmosphere are key to determining their effects on human health, weather, and climate. Atmospheric scientists and students currently face major difficulties in developing, maintaining, and using state-of-the-art aerosol and chemistry numerical parameterizations within increasingly complex Earth system models. This article describes the ongoing effort of the Earth system modeling community to build a Generalized Aerosol/Chemistry Interface (GIANT) that will facilitate the use and improve the accuracy of aerosol and chemistry representations within current air quality, weather, and climate models.