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EO in orbit: Scientific webinars -


  • Type: Webinar
  • Date:
  • Time: 11:00 a.m. to noon
  • Duration: 1 hour
  • Cost: Free
  • Location: Virtual
  • Language: English
  • Target audience: Companies, general public, educational institutions, media, not for-profit organizations, scientists, government


During this event, two young postdoctoral fellows from the University of Saskatchewan will present their scientific advances, funded by the Canadian Space Agency (CSA)'s Sun-Earth system science research grants to analyze satellite data.

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  1. A Canadian View of Stratospheric Trace Gas Trends
  2. Assessment of the stratospheric aerosol properties measured by the MAESTRO instrument onboard the ACE satellite

A Canadian View of Stratospheric Trace Gas Trends

11:00 a.m. ET

  1. University of Saskatchewan: Kimberlee Dubé, Susann Tegtmeier, Adam Bourassa, Daniel Zawada, Doug Degenstein
  2. University of Toronto: Kaley Walker, Patrick Sheese
  3. National Center for Atmospheric Research (Boulder, CO): William Randel

The Canadian instruments OSIRIS and ACE-FTS have been monitoring the stratosphere from space since and respectively. Their observations have been invaluable for studying stratospheric composition over the last two decades. One thing that has become clear during this time is that gases in the northern hemisphere (NH) are changing in opposite directions from gases in the southern hemisphere (SH). This hemispheric asymmetry is thought to be caused by changes in the large-scale stratospheric circulation associated with rising greenhouse gas emissions.

To assess if the ozone layer is recovering from its destruction by ozone-depleting substances (ODSs) during the 20th century, it is necessary to isolate the ozone changes caused by ODSs from the ozone changes caused by changing circulation. This talk focuses on one possible technique: using N2O, a long-lived trace gas with a tropospheric source, as a proxy for stratospheric circulation in the model used to calculate ozone trends. By using the N2O proxy, we show that negative ozone trends above ~30 hPa in the NH can be explained by change in stratospheric circulation, but that negative ozone trends at lower levels cannot, and are possibly due to some other phenomena.

Assessment of the stratospheric aerosol properties measured by the MAESTRO instrument onboard the ACE satellite

11:30 a.m. ET

Sujan Khanal, University of Saskatchewan

The Atmospheric Chemistry Experiment (ACE, also known as SCISAT-1) is a Canadian satellite mission that was launched into a low Earth orbit in . Its primary payload consists of two instruments, the Fourier Transform Spectrometer (FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO).

This presentation will focus on the MAESTRO, which measures the transmission of the sunlight passing through the atmosphere based on the solar occultation technique. These measurements are used to estimate the stratospheric aerosol properties such as aerosol extinction and particle size. They provide valuable information about the impact of major volcanic eruptions and wildfires in our climate. In this presentation, the information content of MAESTRO observations will be discussed by comparing it with measurements from other stable, well-calibrated satellite instruments. Further, the regions in the stratosphere where the aerosol particle size retrieved by the MAESTRO is most reliable will be identified.

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