OSIRIS temperature data products spans over 22 years

A new upper stratospheric (35–60 km) temperature data product has been produced using OSIRIS limb-scattered spectra that now spans over 22 years. Temperature is calculated by first estimating the Rayleigh scattering signal and then integrating hydrostatic balance combined with the ideal gas law. Uncertainties are estimated to be 1–5 K, with a vertical resolution of 3–4 km. Correlative comparisons with the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) and the Microwave Limb Sounder on Aura (MLS) are consistent with these uncertainty estimates and generally have no regions of statistically significant drift. The temperature data product is publicly distributed as part of the recently released OSIRIS v7.3 data products. An example of the produced data is shown in Figure 1. The technique differs from previous techniques in that multiple scattering is included rigorously in the forward model, with a novel method to estimate the amount of upwelling radiation.

Figure 1: Tropical (20oS to 20oN) monthly zonal mean time series calculated from OSIRIS v7.3 temperature data product.

Chemistry Contribution to Stratospheric Ozone Depletion After the Unprecedented Water-Rich Hunga Tonga Eruption

Following the Hunga Tonga-Hunga Ha'apai (HTHH) eruption in January 2022, stratospheric ozone depletion was observed at Southern Hemisphere mid-latitudes and over Antarctica during the 2022 austral wintertime and springtime, respectively. The eruption injected sulfur dioxide and unprecedented amounts of water vapor into the stratosphere. This work examines the chemistry contribution of the volcanic materials to ozone depletion using chemistry-climate model simulations with nudged meteorology. Simulated 2022 ozone and nitrogen oxide (NOx = NO + NO2) anomalies show good agreement with satellite observations. We find that chemistry yields up to 4% ozone destruction at mid-latitudes near ∼70 hPa in August and up to 20% ozone destruction over Antarctica near ∼80 hPa in October. Most of the ozone depletion is attributed to internal variability and dynamical changes forced by the eruption. Both the modeling and observations show a significant NOx reduction associated with the HTHH aerosol plume, indicating enhanced dinitrogen pentoxide hydrolysis on sulfate aerosol.

OSIRIS data helps to unravel complex behaviour of ozone layer recovery

After decades of depletion in the 20th century, near-global ozone now shows clear signs of recovery in the upper stratosphere.  In the tropical lower stratosphere, ozone is expected to decrease as a consequence of enhanced upwelling driven by increasing greenhouse gas concentrations, and this is consistent with observations. There is recent evidence, however, that mid-latitude ozone continues to decrease as well, contrary to model predictions. We use OSIRIS ozone profile measurements to show that these differences might be related to changes in atmospheric circulation. 

OSIRIS provides a new view of NOx in the Asian Summer Monsoon

Deep convection within the Asian summer monsoon (ASM) transports surface level air into the upper troposphere-lower stratosphere (UTLS). We use the long record of OSIRIS data to reveal a new understanding of the distribution of NOx in the lower stratosphere in the region of the ASM.  These results largely agree with climate model simulations. 

Increased wildfires may slow recovery of Earth's ozone layer

A new study reveals that an expected increase in wildfires due to climate change may lead to chemical reactions that cause destruction of the Earth’s protective ozone layer and slow its ability to recover. As global warming continues, it is likely that the scale and frequency of wildfires will increase, raising questions about how this will impact the planet’s protective ozone layer over time.

2020 Arctic Ozone Hole is Largest Ever Observed

The largest recorded ozone layer hole over the Arctic has been detected by the OSIRIS instrument. Normally, holes of this magnitude form only over the South Pole, as the conditions required to form an ozone hole over the North Pole are rare. The last hole to form over the North Pole was in 2011.

A stable polar vortex formed this year over the North Pole, which allowed the ozone-depleting CFCs to reduce the region's ozone layer without being dissipated by the surrounding atmosphere.

Figure 1 shows ten days of OSIRIS measurements over mid-March at various altitudes. The hole is apparent, especially when compared to all of the March 2018 measurements shown in Figure 2, which represent typical values.

Figure 3 shows OSIRIS ozone profiles from different areas around the Pole, some profiles inside the ozone hole region and others outside for comparison.

Figure 1: The 2020 Northern Ozone Hole. Scatterplot of OSIRIS ozone number density measurements from March 10 to March 20. Compared to 2008 (a typical year) the measurements are very low (cf. Figure 2).
Figure 2: A scatterplot of typical March ozone number density over the North Pole. There are more data points as this plots all the data from March 1 to 31.
Figure 3: A selection of ozone profiles measured by OSIRIS inside and outside of the 2020 North Pole ozone hole. The ozone values are very low around 20km where they should be at their peak value.