About VolArc

Constraining the effects of volcanic aerosol on radiative forcing and stratospheric composition (VolARC) will address the direct radiative effects of volcanic aerosols in the stratosphere. This project aims at:

  1. Quantifying the temporal variability of stratospheric aerosol extinction and particle size distribution (PSD) as well as radiative forcing using available satellite data sets and state of the art modelling capabilities;
  2. Improving current aerosol microphysical modelling capabilities to better link observed SO2 emission and stratospheric aerosol optical depth (SAOD) and thereby constraining volcanic SO2 emission, e.g., of Pinatubo.

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Deseasonalized time series (anomalies) of the maximum of aerosols size distribution (Rmod) retrieved from SCIAMACHY limb data in the tropics (20◦ N–20◦ S).
It can be noticed that there is a distinct increase in "Rmod" in the lower altitudes after most of the volcanic eruptions.

Results from VolArc will improve the understanding of the response of the Earth system to external forcing, facilitate much better prediction of climatic consequences of future volcanic eruptions, and uniquely improve our understanding of the historical record and of key processes relevant to climate change more generally.
In addition, our research will guide the design of instruments needed to adequately observe and document future volcanic eruptions. As a result, society will be in a better position to exploit these natural experiments to test our understanding of the climate system.

VolArc is framed inside VolImpact, which includes 5 different science projects assessing different physical and chemical aspects of volcanic emissions.


annual and zonal mean aerosol optical depth
Simulated annual and zonal mean aerosol optical depth (top) and the resulting radiative forcing from artificial sulfur injections. Differences between blue and yellow lines are related to the model configuration (high vs. low vertical resolution), differences between red and blue lines are due to injections assumed at 30 and 60 hPa, respectively. Figure taken from Niemeier and Schmidt (2017).

Objectives

The overarching research objective of VolARC is to constrain the uncertainty in the scientific understanding of the radiative impact of volcanic eruptions. This overarching objective is addressed by the four science objectives described in detail below:

Objective 1:

Characterization of the variability in stratospheric aerosol particle size distribution

Objective 2:

Development and evaluation of the ICON-ART model to represent aerosol microphysics and stratospheric sulfur chemistry in a nested environment

Objective 3:

Estimate the dependence of size distribution, optical properties and radiative forcing from volcanic aerosols on the way datasets are constructed to allow uncertainty estimates

Objective 4:

Improve understanding of the effect of volcanic eruptions on stratospheric water vapour