The 15 January 2022 eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano (20.5°S, 175.4°W) injected a record amount of water directly into the stratosphere. This study attempts to quantify this impact on the temperature, as well as the subsequent changes to the stratospheric circulation, during the months following the eruption based on reanalysis fields. The extreme nature of the temperature, wind, and circulation changes are tracked through comparisons of the first six months of 2022 with the previous 42 years. Examination of the data assimilation process shows that at 20 hPa the thermal observations are forcing significant cooling, compensating for the absence of the excess stratospheric moisture in the model used for the reanalysis. In response to this cooling the atmosphere adjusts by creating strong westerly winds above the temperature anomaly and large changes to the downward and poleward mean meridional circulation.
Extreme perturbations in the stratospheric winds and temperatures are linked to a volcanic eruption
Hunga Tonga-Hunga Ha’apai eruption effects are unique in the stratospheric record
Data assimilation can track temperature and wind perturbations, even when some physics is missing
While the stratosphere (15-55 km) region of the atmosphere contains the ozone layer, it is typically very dry, especially when compared to the troposphere. However, the remarkable eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano on 15 January 2022 injected a record amount of water directly into the stratosphere. Winds in the stratospheric soon carried this excess water vapor around the globe to all longitudes and spread the water vapor in latitude as well. Since water vapor can cool to space more rapidly than the stratospheric air, enhanced cooling in the stratosphere is expected. This study quantifies this cooling, as well as the subsequent changes to the stratospheric circulation, during the months following the eruption. The extreme nature of the stratospheric temperature, wind, and circulation changes are tracked through comparisons of the first six months of 2022 with the previous 42 years. Details of the stratospheric perturbations in latitude and pressure are presented for June 2022, where anomalously low temperatures are found at near 20 km altitude from 60°S to 30°S. In response to this cooling the atmosphere adjusts by creating strong westerly winds above the temperature anomaly and large changes to the downward and poleward mean meridional circulation. Stratospheric Circulation Changes Associated with the Hunga Tonga?Hunga Ha'apai Eruption - Coy - Geophysical Research Letters - Wiley Online Library