Observed episodic warming at 86 and 100 km between 1990 and 1997: Effects of Mount Pinatubo eruption

Abstract

Along with initial observations, our regular lidar temperature measurements over Fort Collins, CO (41°N, 105°W) in the rarely probed mesopause region has resulted in a unique seven-year data set between 1990 and 1997. After the seasonal variations are removed, a clear episodic warming is observable in the time series of residual temperatures. Least squares fitting the residual temperatures to an episodic impact function plus a linear trend shows maximum temperature increases occurring in 1993 with magnitudes of 9.0±1.7 K and 12.9±1.8 K, at 86 km and 100 km, respectively. By association, we attribute the Mount Pinatubo eruption in June, 1991, as the most probable primary cause for the observed warming, supporting a connection between tropical stratospheric aerosol and temperatures in a midlatitude mesopause region. It is hoped that our lidar observation from a single location will stimulate similar investigations at other latitudes and longitudes.