Observed Perturbations of the Earth's Radiation Budget: A Response to the El Chichón Stratospheric Aerosol Layer?

Abstract

The Earth Radiation Budget experiment, launched aboard the Nimbus-7 polar-orbiting spacecraft in late 1978, has now taken over seven years of measurements. The dataset, which is global in coverage, consists of the individual components of the Earth's radiation budget, including longwave emission, not radiation, and both total and new-infrared albedos. Starting some six months after the 1982 eruption of the El Chichón volcano, substantial long-lived positive shortwave irradiance anomalies were observed by the experiment in both the northern and southern polar regions. Analysis of the morphology of this phenomena indicates that the cause is the global stratospheric aerosol layer which formed from the cloud of volcanic effluents. There was little change in the emitted longwave in the polar regions. At the north pole the largest anomaly was in the near-infrared, but at the south pole the near UV-visible anomaly was larger. Assuming an exponential decay, the time constant for the north polar, near-infrared anomaly was 1.2 years. At mid- and low latitudes the effect of the El Chichón aerosol layer could not be separated from the strong reflected-shortwave and emitted-longwave perturbations issuing from the El Niño/Southern Oscillation event of 1982?83.