Abstract: Volcanic aerosols affect weather, air quality and aviation safety up to several days after the unset of an eruption. Timely response and efficient mitigation actions require accurate volcanic aerosol forecasts. Operational forecast systems often use simple parameterizations (e.g. constant emission profiles) and configurations (e.g. offline coupling) for their ash dispersion forecasts. Moreover, they neglect the impacts of aerosol dynamics and aerosol–radiation interactions on the evolution on the volcanic clouds in the atmosphere. This approach may lead to large errors and shortcomings in the forecasts.

In this seminar, I discuss how detailed treatments of eruption plume, aerosol dynamics and aerosol-radiation interactions within an online fully-coupled model system affect the volcanic aerosol forecasts. As case study, I focus on Raikoke eruption in Kuril Islands in June 2019 mainly because of the complexity of eruption dynamics and the availability of detailed observation data. The simulations are performed using the ICON-ART (ICOsahedral Nonhydrostatic with Aerosols and Reactive Tracers) model system with new features to include 1) the 1D volcanic plume model FPLUME to calculate the eruption source parameters and emission profiles online, 2) the mixing and aging of volcanic aerosols due to aerosol dynamics and 3) aerosol-radiation interactions. The numerical experiments are performed by switching these features on and off and validated against the observation data from AHI (Advanced Himawari Imager), CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), and OMPS-LP (Ozone Mapping and Profiling Suite-Limb Profiler). 

The results highlight the advantage of online eruption plume and mass eruption rate calculations in case of eruptions with complex dynamics like Raikoke 2019. Compared to the simulation with constant profile and eruption rate, the error in very fine ash mass (ash with diameter d<30 µm) prediction is reduced by 28%. Moreover, while aerosol dynamics enhance the ash fallout by 50% through particle growth, aerosol-radiation interaction leads to plume rise up to 5 km within 4 days. This shows, for the first time, how cumulative effects of aerosol dynamics and aerosol–radiation interaction improve the accuracy of volcanic aerosol dispersion forecasts.

Bio: Dr. Ali Hoshyaripour is a senior scientist at Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT). He earned his master’s degree in Civil and Environmental Engineering from University of Tehran, Iran, in 2009. Then he moved to Germany and received his PhD in Earth System Sciences from the University of Hamburg in 2013 under supervision of Matthias Hort. In his dissertation, Ali investigated the physicochemical processing of volcanic ash in the eruption plume with focus on the iron mobilization mechanisms.

After completing his PhD, Ali joined Guy Brasseur’s working group at Max Planck Institute for Meteorology to develop a high-resolution air quality forecast and analysis system for South America. In 2015, he received a research grant from the German Research foundation (DFG) to continue his investigations on the interface of atmospheric sciences and volcanology through studying the physical chemistry of volcanic eruption plumes. Since 2017, he works at Bernhard Vogel’s group at KIT and focuses on modeling the aerosol processes and interactions with ICON-ART model system. His primary focus is on natural aerosols and their implications for weather forecast, renewable energy, air quality and aviation.