EarthCARE Satellite Enhances Air Travel Safety by Monitoring Volcanic Plumes

The recent eruption of Anak Krakatau, which began on September 4, 2023, has underscored the critical importance of real-time satellite monitoring for aviation safety. As the European Space Agency's EarthCARE satellite orbited above, it captured detailed vertical profiles of various constituents within the volcanic plume, delivering essential insights not just for climate studies, but also for the safe navigation of air traffic.

Located in Indonesia's Sunda Strait, Anak Krakatau, meaning "Child of Krakatoa," has been comparatively active since its emergence in the early 20th century. While its recent activity lacks the catastrophic force of the 1883 Krakatoa eruption—which generated a devastating tsunami—the current eruption still disrupted thousands of flights, stranding hundreds of thousands of passengers globally. This disruption highlights how even eruptions that seem minor can have substantial repercussions for air travel.

Volcanic ash poses serious risks to aircraft, including potential engine damage and decreased visibility in the cockpit due to window abrasion. Additionally, gases like sulfur dioxide can contaminate cabin air. To manage these risks, a global network of nine Volcanic Ash Advisory Centres (VAACs) exists, each overseeing specific geographic areas to provide timely aviation warnings. The Darwin VAAC, operated by the Australian Bureau of Meteorology, is responsible for the region around Anak Krakatau. This organization has rapidly integrated EarthCARE’s unique lidar data into its monitoring arsenal, augmenting its capabilities with advanced satellite observations.

EarthCARE is equipped with a suite of four sophisticated instruments, including the atmospheric lidar (ATLID), cloud profiling radar (CPR), multispectral imager (MSI), and broadband radiometer (BBR). These instruments work together to offer a holistic view of clouds and aerosols, critical for understanding Earth’s energy balance and the interplay of various atmospheric components.

Specifically, ATLID utilizes a specialized laser that emits ultraviolet light toward Earth, measuring the light that scatters back to the satellite. This technology provides crucial data on the altitude and concentration of aerosols, including various types—ash, smoke, sulfate, sea salt, and desert dust. An image captured from Copernicus Sentinel-3 and overlaid with EarthCARE's instrument data can illustrate the flight levels most commercial aircraft travel at, typically around 35,000 feet.

Analysis of the measurements collected during the Anak Krakatau eruption reveals the composition of the volcanic plume, distinguishing between different aerosol types. The MSI captured images in false color, where purple areas highlight ash and bright green indicates sulfur dioxide gas. The vertical view from ATLID and CPR shows various aerosol layers; however, it also identifies areas of uncertainty, such as regions obfuscated by thick sulfate layers where detection is limited.

Experts like Robin Hogan from the European Centre for Medium-Range Weather Forecasts (ECMWF) noted that while the CPR is less sensitive to smaller particles, it effectively identified larger ash aggregates up to 6 kilometers from the eruption site, potentially rewriting assumptions about ash behavior and dispersion distances post-eruption.

Helen Dacre from the University of Reading pointed out that observations confirming the persistence of larger ash particles in the atmosphere could refine volcanic ash dispersion models, essential for aviation and environmental predictions. While more investigations are needed to clarify the details in some regions of the data, the imperative remains clear: aviation authorities must heed these warnings and avoid flying through hazardous areas.

Andy Prata from BOM emphasized the value of ATLID in forecasting, helping to verify the plume's altitude and ensuring that guidance for aircraft was accurate as it moved westward at approximately 15 kilometers above sea level. The multi-faceted nature of volcanic plume interactions—ash, gases, and ashes complicate the aviation landscape, yet real-time data from EarthCARE allow meteorologists to understand these dynamics better.

Shannon Mason from ECMWF articulated the rapid evolution of volcanic events and the importance of having immediate data to appropriately inform aviation safety measures. The timely observations enabled scientists to analyze the plume’s structure quickly, aiding in precise decision-making for aviation advisories. Following a major eruption, long-term impacts are often observed, as demonstrated by historical eruptions like Krakatoa's, which had global cooling effects lasting over a year due to stratospheric sulfate injections.

Going forward, EarthCARE will continue to enhance our understanding of volcanic eruptions and their long-range effects on air travel and climate. Recent data has already contributed to modeling the global transport of volcanic aerosols, demonstrating EarthCARE’s vital role in both immediate and extended atmospheric conditions. The satellite’s capabilities not only protect aviation but provide crucial insights into how such natural events affect Earth's overall radiation balance.