Séminaire
High-latitude winter warming after strong equatorial volcanic eruptions caused by circulation changes associated with the anomalously positive phase of Arctic Oscillation is a subject of active research during recent decade. But severe winter cooling in the Middle East observed after the Mt. Pinatubo eruption of 1991, although recognized, was not thoroughly investigated. These severe regional climate perturbations in the Middle East cannot be explained by solely radaitive volcanic cooling, which suggests that a contribution of forced circulation changes could be important and significant. To better understand these dynamic mechanisms we study the El Chichón and Pinatubo regional volcanic impacts using Geophysical Fluid Dynamics Laboratory global High Resolution Atmospheric Model (HiRAM) with the effectively "regional-model-resolution" of 25-km. We focused on the winter and summer seasons and conducted multiple regression analysis to delineate effects of different factors that include volcanic radiative forcing, shift of ITCZ, Indian Monsoon, Arctic Oscillation, and ENSO.