OBSERVED EPISODIC WARMING AT 86 AND 100 KM BETWEEN 1990 AND 1997 - EFFECTS OF MOUNT-PINATUBO ERUPTION

Along with initial observations, our regular lidar temperature measure ments over Fort Collins, CO (41 degrees N, 105 degrees W) in the rarel y probed mesopause region has resulted in a unique seven-year data set between 1990 and 1997. After the seasonal variations are removed, a c lear episodic warming is observable in the time series of residual tem peratures. Least squares fitting the residual temperatures to an episo dic impact function plus a linear trend shows maximum temperature incr eases 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 c ause for the observed connection between tropical temperatures in a mi dlatitude mesopause region. It is hoped that our lidar observation fro m a single location will stimulate similar investigations at other lat itudes and longitudes.