Seminar

Abstract

Sulfur dioxide (SO₂) emissions from strong volcanic eruptions are an important natural cause for climate variations. We applied our new Lagrangian transport model Massive-Parallel Trajectory Calculations (MPTRAC) to perform simulations for three case studies of volcanic eruption events. This covers eruptions of the Grimsvotn, Iceland, the Puyehue-Cordon Caulle, Chile, and the Nabro, Eritrea, in May and June 2011. We used SO₂ observations of the Atmospheric Infrared Sounder (AIRS/Aqua) to initialize the simulations and to validate the results. Next to validating the new model, the main goal of our study was a comparison of simulations with different meteorological data products. We considered three reanalyses (ERA-Interim, MERRA, and NCAR/NCEP) and the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis.

Overall, SO₂ distributions from the simulations compare well. Transport deviations and the critical success index (CSI) are calculated to evaluate the simulations quantitatively. During the first 14 days after the eruptions we found closest agreement and best performance for the ERA-Interim and MERRA simulations (CSI ranges of 19-25% and 15-24%, respectively). NCAR/NCEP also provided good results (15-20%), despite its notably lower spatial resolution. Lower CSI values for the ECMWF analysis (6-21%) suggest that high spatial resolution does not necessarily lead to better performance of transport simulation with MPTRAC. The different data assimilation procedures, forecast models, and observations used by the centers seem to have larger influence on the quality of the wind data in the upper troposphere and lower stratosphere.