Using CATS Near-Realtime Lidar Observations to Monitor and Constrain Volcanic Sulfur Dioxide (SO2) Forecasts

An eruption of the Italian volcano Mt. Etna on December 3^rd, 2015 produced a large sulfur dioxide (SO₂) and sulfate aerosol cloud that travelled across Asia, eventually reaching North America.  The Ozone Profiler and Mapping Suite (OMPS) aboard the National Polar-orbiting Partnership (Suomi-NPP) satellite observed the horizontal transport of the SO₂ cloud. Vertical profiles of the co-located sulfate aerosols were observed between 11.5km - 14km by the new Cloud Aerosol Transport System (CATS) space-based LIDAR aboard the International Space Station (ISS).  Backward trajectory analysis estimates the altitude of the SO₂ cloud much lower, at 7 – 12km.  Eulerian model simulations of the SO₂ cloud constrained by CATS measurements produced more accurate dispersion patterns compared to those initialized with the back trajectory only height estimate.  The near-realtime data processing capabilities of CATS is unique, and this work provides a first time usage of these observations to monitor and model volcanic clouds.