Following the Hunga Tonga–Hunga Ha’apai (HTHH) eruption in January 2022, stratospheric ozone depletion was observed in the Southern Hemisphere mid-latitudes and Antarctica during the 2022 austral wintertime and springtime. This eruption injected sulfur dioxide and unprecedented amounts of water vapor into the stratosphere. This work examines and quantifies the chemistry contribution of the volcanic materials to the ozone depletion using chemistry-climate model simulations with nudged meteorology. Simulated 2022 ozone and nitrogen oxides (NOx) anomalies show a good agreement with satellite observations. We find that chemistry only contributes up to 6% and 20% ozone destruction at mid-latitudes wintertime and Antarctic springtime respectively. The majority of the ozone depletion is attributed to the internal variability and dynamical changes forced by the eruption. Both the simulation and observations show a significant NOx reduction associated with the HTHH aerosol plume, indicating the enhanced dinitrogen pentoxide hydrolysis on sulfate aerosol.

The Hunga Tonga Hunga-Ha’apai (HTHH) volcanic eruption on 15 January 2022 injected water vapor and SO2 into the stratosphere. Several months after the eruption, significantly stronger westerlies, and a weaker Brewer-Dobson circulation developed in the stratosphere of the Southern Hemisphere and were accompanied by unprecedented temperature anomalies in the stratosphere and mesosphere. In August 2022 the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument observed record-breaking temperature anomalies in the stratosphere and mesosphere that alternate signs with altitude. Ensemble simulations carried out with the Whole Atmosphere Community Climate Model (WACCM6) indicate that the strengthening of the stratospheric westerlies explains the mesospheric temperature changes. The stronger westerlies cause stronger westward gravity wave drag in the mesosphere, accelerating the mesospheric mean meridional circulation. The stronger mesospheric circulation, in turn, plays a dominant role in driving the changes in mesospheric temperatures. This study highlights the impact of large volcanic eruptions on middle atmospheric dynamics and provides insight into their long-term effects in the mesosphere. On the other hand, we could not discern a clear mechanism for the observed changes in stratospheric circulation. In fact, an examination of the WACCM ensemble reveals that not every member reproduces the large changes observed by SABER. We conclude that there is a stochastic component to the stratospheric response to the HTHH eruption.

The Hunga Tonga-Hunga Ha’apai (HTHH) volcanic eruption in January 2022 injected extreme amounts of water vapor (H2O) and a moderate amount of the aerosol precursor (SO2) into the Southern Hemisphere (SH) stratosphere. The H2O and aerosol perturbations have persisted and resulted in large-scale SH stratospheric cooling, equatorward shift of the Antarctic polar vortex, and slowing of the Brewer-Dobson circulation associated with a substantial ozone reduction in the SH winter midlatitudes. Chemistry-climate model simulations forced by realistic HTHH inputs of H2O and SO2 reproduce the observed stratospheric cooling and circulation effects, demonstrating the observed behavior is due to the volcanic influences. Furthermore, the combination of aerosol transport to polar latitudes and a cold polar vortex enhances springtime Antarctic ozone loss, consistent with observed polar ozone behavior in 2022.

With the COVID-19 pandemic still active, the Boulder Solar Alliance Research Experience for Undergraduates (BSA REU) decided to keep the program remote for a second consecutive year. Our coordination team took lessons learned from the 2020 virtual BSA REU program and adapted the research experience to suit a virtual environment, especially with respect to increased technological support. The primary changes, as well as the reasons for implementing them, are outlined below. Due to the virtual nature of the program, all of the projects relied more heavily on coding. In response, the BSA REU team invested more time and resources in programming tutorials and weekly programming help sessions in Python, IDL, and MATLAB. The participants also faced unequal access to high-quality hardware resources in a remote environment. As a result, students received a technology stipend to help them upgrade their computer and internet resources. Additionally, with an increase in the focus on programming, a higher number of projects in 2021 involved machine learning and data science techniques compared to previous years. However, many of the students were unfamiliar with machine learning (ML) concepts. The coordination team provided an introductory ML lecture and tutorial during boot camp and hosted a weekly ML sub-group meeting to provide support and resources for students involved in ML projects. Finally, without being able to present results in person, it was important to provide an interactive online experience for the poster presentation session. To make the final poster presentation more engaging in a virtual environment, we used Gather Town, an online service where participants create avatars that can interact with the virtual environment. In this presentation, we will discuss how the adjustments to the BSA REU program in a virtual environment, including those listed above, and how we think REU programs can adapt to future remote and hybrid options. We will also discuss what elements of a remote program can be carried forward into an on-site program to enhance the on-site experience.