Procedure

          At present most complete ozone datasets are provided by different ozonesondes and satellite instruments. While ozonesonde measurements are limited to certain locations and times, satellites have a big advantage of collecting data everyday and nearly globally. However, most of the satellite ozone data in the past were not as accurate as the ground-based ozonesonde measurements. That is why a Canadian instrument OSIRIS (Optical Spectrograph and Infrared Imager System) recently launched on the Odin satellite is very beneficial for the ozone studies worldwide (http://osirus.usask.ca). OSIRIS measures stratospheric ozone profiles (from 10 to 48 km) since November 2001 and has an advantage of high quality data and nearly global coverage: between 600 and 900 profiles daily, much more than most other satellites.

          OSIRIS stratospheric ozone profiles are regularly retrieved by scientists at the Institute of Space and Atmospheric Studies, University of Saskatchewan. I was already familiar with these data from my Science Fair project in 2004, which was focused on the tropospheric ozone studies with OSIRIS and TOMS (Total Ozone Mapping Spectrometer). A complete OSIRIS ozone database is available in Saskatoon, and I asked permission from Prof. E.J. Llewellyn, Head of the Infrared Aeronomy Group, to use them for my work. OSIRIS Team members also helped me to open and read the data files, as well as sort and extract certain ozone values.

          I selected several geographic regions that represent different geographic locations and latitudes. As I learned from one my previous Science Fair project in 2004, the average ozone amount changes significantly with latitude. It is usually higher near the Poles and lower around the equator. To better represent different latitude ranges, the following locations (also shown in Figure 6) were chosen:

1. Canada.
          Latitude: 45°N to 60°N, Longitude: 60°W to 130°W.

2. Australia
         Latitude: 15°S to 35°S, Longitude: 110°E to 150°E.

3. Canada’s mirror location in the Southern hemisphere, “Region #3”:
          Latitude: 45°S to 60°S, Longitude: 60°W to 130°W.

4. Australia’s mirror location in the Northern hemisphere, “Region #4”:
          Latitude: 15°N to 35°N, Longitude: 110°E to 150°E.

5. Central Africa.
         Latitude: 10°N to 10°S, Longitude: 110°E to 150°E.

Schematic Locations of Five Chosen Regions
Figure 6. Schematic locations of five chosen regions

          First, OSIRIS ozone profiles were selected in each of these regions and the total column ozone (TCO) was calculated from each profile as a sum of all ozone concentrations between 10 and 48 km.

        Second, these TCO have been averaged on a daily basis from January 1, 2002, until December 31, 2004. Scientists from the Infrared Aeronomy Group, University of Saskatchewan, helped me greatly with these two steps.

          Third, daily averaged TCO were plotted for: a) every region each year and b) every region for all years in a row.