First Observations of Volcanic Eruption Clouds From the L1 Earth-Sun Lagrange Point by DSCOVR/EPIC

Volcanic sulfur dioxide (SO2) emissions have been measured by ultraviolet sensors on polar-orbiting satellites for several decades but with limited temporal resolution. This precludes studies of key processes believed to occur in young (similar to 1-3 hr old) volcanic clouds. In 2015, the launch of the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) provided an opportunity for novel observations of volcanic eruption clouds from the first Earth-Sun Lagrange point (L1). The L1 vantage point provides continuous observations of the sunlit Earth, offering up to eight or nine observations of volcanic SO2 clouds in the DSCOVR/EPIC field of view at similar to 1-hr intervals. Here we demonstrate DSCOVR/EPIC's sensitivity to volcanic SO2 using several volcanic eruptions from the tropics to midlatitudes. The hourly cadence of DSCOVR/EPIC observations permits more timely measurements of volcanic SO2 emissions, improved trajectory modeling, and novel analyses of the temporal evolution of volcanic clouds. Plain Language Summary Satellite measurements of sulfur dioxide (SO2) and ash emissions by volcanic eruptions are crucial for assessment of volcanic impacts on climate and mitigation of hazards to aviation. Until recently, the vast majority of such observations were made using satellites in low-Earth (or polar) orbit at altitudes of similar to 700-800 km, which only provide one measurement per day at most latitudes. This precludes studies of dynamic processes in volcanic clouds, which could radically alter their composition and potential impact. Here we report the first measurements of volcanic SO2 emissions from an entirely new perspective: the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory, located at the first Earth-Sun Lagrange point (L1), 1.6 million kilometers from Earth. From L1, EPIC views the sunlit Earth continuously as it rotates and can measure volcanic SO2 hourly from sunrise to sunset, as we demonstrate using several recent volcanic eruptions as examples. EPIC measurements allow us to detect volcanic eruptions sooner, and track their emissions for longer, than was previously possible with a single sensor. Our paper thus demonstrates a new Earth observation paradigm that could revolutionize studies of volcanic cloud chemistry and impacts and potentially reduce the societal impacts of volcanic eruptions.