Abstract
Abstract. Stratospheric aerosols play an important role in the climate system by affecting the Earth's radiative budget as well as atmospheric chemistry, and the capabilities to simulate them interactively within global models are continuously improving. It is important to represent accurately both aerosol microphysical and atmospheric dynamical processes because together they affect the size distribution and the residence time of the aerosol particles in the stratosphere. The newly developed LMDZ-S3A model presented in this article uses a sectional approach for sulfate particles in the stratosphere and includes the relevant microphysical processes. It allows full interaction between aerosol radiative effects (e.g. radiative heating) and atmospheric dynamics, including e.g. an internally generated quasi-biennial oscillation (QBO) in the stratosphere. Sulfur chemistry is semi-prescribed via climatological lifetimes. LMDZ-S3A reasonably reproduces aerosol observations in periods of low (background) and high (volcanic) stratospheric sulfate loading, but tends to overestimate the number of small particles and to underestimate the number of large particles. Thus, it may serve as a tool to study the climate impacts of volcanic eruptions, as well as the deliberate anthropogenic injection of aerosols into the stratosphere, which has been proposed as a method of geoengineering to abate global warming.
Highlights
The study of stratospheric aerosols has traditionally been a separate activity to that of tropospheric aerosols, inter alia because of different observing methods and observing systems
In this article we have presented a newly developed sectional stratospheric sulfate aerosol (S3A) model as part of the LMDZ atmospheric general circulation model
A strength of our model is that it can readily be coupled to other components of the IPSL climate model to perform climate studies
Summary
The study of stratospheric aerosols has traditionally been a separate activity to that of tropospheric aerosols, inter alia because of different observing methods and observing systems. The volcanic aerosol forcing is important to simulate the temporal evolution of the climate system over the last millennium in general, and over the instrumental period (1850 to the present day) in particular This was initially done by prescribing the amount and properties of stratospheric aerosols as (timevarying) climatologies derived from observations. Bins, whereas it is difficult, if not impossible, in the modal approach to assess the uncertainty induced by the assumption of pre-defined aerosol modes with a pre-defined shape This does not mean that the aerosol sectional scheme will always be superior, as in the end, it will be subject to the same computational trade-off as other models, and the relatively large cost of the sectional approach may limit the horizontal or vertical resolutions of the atmospheric model.
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