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Aerosol data for better climate modelling

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Stratospheric aerosols play an important role for the climate, since they affect the propagation and absorption of sunlight. This is why climate models have to take them into account as precisely as possible. This is a challenge because these particles of varying size and composition are difficult to characterize. A key problem in the prediction of the evolution of the climate is the decryption of information provided by satellites, and understanding the limits and imperfections of the measurements, in order to translate them into reliable and precise data that can be easily used in climate models.
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Stratospheric aerosols: a major actor of climate

Aerosols perturb the propagation of the solar light by scattering and absorption and have therefore an impact on the radiative budget of the atmosphere. For this reason, they are an important actor of the climate.

The main source of aerosols in the stratosphere is volcanism: during large eruptions, explosive volcanoes send ashes and sulfur gases up to these high altitudes, giving rise to aerosol plumes staying durably in the stratosphere.

It is thus important to include aerosols as accurately as possible in the modelling of climate evolution. This task is particularly challenging.

  • On the one hand, the aerosol composition may vary in time and space, combining different types of particles: volcanic sulfate, particles of oceanic origin, desert dust, meteoritic smoke particles or carbonaceous particles produced by human activities.
  • On the other hand, aerosols present a large variability of particle size depending of the aerosol type, their history, the atmospheric conditions or local particularities of atmospheric dynamics.

Using satellite measurements to constrain climate models

In order to provide the climate modelling community with the most adapted datasets, BIRA-IASB developed data records from satellite experiments, in our case from the GOMOS experiments that covered the period 2002-2012. This important period saw an increase of the stratospheric aerosol load following a succession of tropical volcanic eruptions, while the effect of anthropogenic activities became more visible in the atmosphere.

A challenge, in this work, is to understand as good as possible the information content of the measurements, the limitations of the instrument, measurement principle and retrieval technique, and their impact on the quality and accuracy of the retrieved aerosol parameters.

Another challenge is to translate the knowledge provided by measurements, spread irregularly in time and space, into well-documented, ready-to-use data records for climate models.

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Figure 2 caption (legend)
Evolution in time and altitude of the aerosol extinction, which quantifies the scattering and absorption of the solar radiation by the atmosphere. The upper panel shows a data record derived from measurements of the GOMOS experiment, and the lower panel shows a simulation of the same dataset by the chemistry-climate model EMAC.