Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Alan Robock

Alan Robok will work with Jen Kay on his project to analyze the impacts of volcanic eruptions on seasonal and interannual time scales using the Community Earth System Model Large Ensemble and the Decadal Prediction Large Ensemble project. Following a large tropical volcanic eruption, the resulting latitudinal gradient of stratospheric heating, ozone depletion, and surface temperature patterns produce a stronger polar vortex in the Northern Hemisphere, with a positive mode of the Arctic Oscillation in the winter, and winter warming of Northern Hemisphere continents. The exact mechanism by which this winter warming is produced by volcanic eruptions, and whether volcanic eruptions are even involved, is still a matter of research.  And because insolation reductions cool land more than the ocean, summer monsoons, which are driven by the land-ocean temperature gradient, are weaker following volcanic eruptions. He will examine the predictability arising from large volcanic eruptions, considering the state of the climate at the time of the eruptions, to compare the forced response with the noise that comes from natural chaotic variability, to see whether it is possible to issue a seasonal forecast with any skill after a large volcanic eruption.