Impact of the Hunga Tonga volcanic eruption on stratospheric composition

The explosive eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano on 15 January 2022 injected more water vapor into the stratosphere and to higher altitudes than ever observed in the satellite era. Here, the evolution of the stratospherically injected water vapor is examined as a function of latitude, altitude, and time in the year following the eruption (February to December 2022), and perturbations to stratospheric chemical composition resulting from the increased sulfate aerosols and water vapor are identified and analyzed. The average calculated mass distribution of elevated water vapor between hemispheres is approximately 78% Southern Hemisphere (SH) and 22% Northern Hemisphere in 2022. Significant changes in stratospheric composition following the HTHH eruption are identified using observations from the Aura Microwave Limb Sounder satellite instrument. The dominant features in the monthly mean vertical profiles averaged over 15° latitude ranges are decreases in O3 (-14%) and HCl (-22%) at SH midlatitudes and increases in ClO (>100%) and HNO3 (43%) in the tropics, with peak pressure-level perturbations listed. Anomalies in column ozone from 1.2-100 hPa due to the HTHH eruption include widespread O3 reductions in SH midlatitudes and O3 increases in the tropics, with peak anomalies in 15° latitude-binned, monthly averages of approximately -7% and +5%, respectively, occurring in austral spring. Using a 3-dimensional chemistry-climate-aerosol model and observational tracer correlations, changes in stratospheric composition are found to be due to both dynamical and chemical factors.

Sensitivity of stratospheric ozone to the latitude, season, and halogen content of a contemporary explosive volcanic eruption

We present a systematic evaluation of the perturbation to the stratosphere from an explosive volcanic eruption injecting sulfur dioxide into the atmosphere, as a function of latitude, season, and injection gas halogen content in a chemistry-climate state representative of the present day (modeled as year 2025). Enhancements in aerosol surface area density and decreases in stratospheric ozone are observed for a period of years following all modeled scenarios, with volcanic eruptions near the equator impacting both hemispheres relatively equally, and eruptions at higher latitudes reducing the thickness of the ozone layer more substantially in the hemisphere of the eruption. Our simulations reveal that there that are significant seasonal differences when comparing the stratospheric impact of a volcanic eruption occurring in summer versus winter, and this holds true regardless of whether volcanic halogen gases (Cl, Br) are co-injected with sulfur dioxide. If an explosive halogen-rich eruption were to occur, there would be substantial ozone losses in both hemispheres, regardless of latitude or season, with recovery potentially exceeding 4 years.

Australian wildfires depleted the ozone layer

Various mechanisms initiated by wildfires thinned the stratospheric ozone layer

Determination of stratospheric aerosol microphysical properties from independent extinction and backscattering measurements with a Raman lidar

An algorithm that permits the retrieval of profiles of particle mass and surface-area concentrations in the stratospheric aerosol layer from independently measured aerosol (particle and Rayleigh) and molecule (Raman or Rayleigh) backscatter signals is developed. The determination is based on simultaneously obtained particle extinction and backscatter profiles and on relations between optical and microphysical properties found from Mie-scattering calculations for realistic stratospheric particle size distributions. The size distributions were measured with particle counters released on balloons from Laramie, Wyoming, between June 1991 and April 1994. Mass and surface-area concentrations can be retrieved with relative errors of 10-20% and 20-40%, respectively, with a laser wavelength of 355 nm and with errors of 20-30% and 30-60%, respectively, with a laser wavelength of 308 nm. Lidar measurements taken within the first three years after the eruption of Mt. Pinatubo in June 1991 are shown. Surface-area concentrations around 20 µm(2) cm(-3) and mass concentrations of 3 to 6 µg m(-3) were found until spring 1993.