A GCM Study of Volcanic Eruptions as a Cause of Increased Stratospheric Water Vapor

Abstract

Abstract Recent general circulation model (GCM) experiments have shown that idealized climatic perturbations that increase the temperature of the tropical tropopause region can cause larger than expected surface temperature increases. This is because the extra water vapor that is transported into the stratosphere acts as a positive radiative forcing agent. Since major volcanic eruptions in the Tropics also perturb temperatures in the region of the tropical tropopause, evidence is sought for the existence of such a mechanism by comparing model simulations and observations of the period following the eruption of Mount Pinatubo in 1991. Lower-stratosphere temperature perturbations are simulated using a GCM of intermediate complexity, and increases in water vapor concentration are found in the lower stratosphere that decay slowly in the years following the peak temperature increase. Such increases are consistent with the limited observations that exist over this period, as well as earlier work done with simpl...