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Images, data, and information for the Southern Hemisphere

1994 Antarctic TOMS and MERRA Ozone

Daily progression

The daily progression through the 1994 ozone hole season of the various ozone statistics, comparing 1994 to the climatology of all other years. Clicking a link will bring up, in a new window, a PDF vector plot or a plain-text ASCII data file that is suitable for input into any program.

ozone hole area

The ozone hole area is determined from total ozone satellite measurements. It is defined to be that region of ozone values below 220 Dobson Units (DU) located south of 40°S. Values below 220 DU represent anthropogenic ozone losses over Antarctica.

ozone minimum

The minimum ozone is found from total ozone satellite measurements south of 40°S. No interpolation of missing values is performed. This means that the actual minimum value on a day may be estimated too high, especially in the polar night region.

ozone mass deficit

The ozone mass deficit is determined from total ozone satellite measurements. It combines the effects of changes in area and depth. It is the total amount of mass that is deficit relative to the amount of mass present for a value of 220 Dobson Units (DU).

Data description

The depth and area of the ozone hole are primarily governed by the amounts of chlorine and bromine in the Antarctic stratosphere. Very low temperatures are needed to form polar stratospheric clouds (PSCs). Chlorine gases react on the surface of these PSCs to release chlorine into a form that can easily destroy ozone. The chlorine and bromine chemical catalytic reactions that destroy ozone need sunlight. Hence, the ozone hole begins to grow as the sun is rising over Antarctica at the end of the winter.

The ozone hole begins to grow in August and reaches its largest area in depth from the middle of September to early October. In the early years (before 1984) the hole was small because chlorine and bromine levels over Antarctica were low. Year-to-year variations in area and depth are caused by year-to-year variations in temperature. Colder conditions result in a larger area and lower ozone values in the center of the hole.

Data source

The data for 1979–1993 are from the TOMS instrument on the NASA/NOAA Nimbus-7 satellite.

The data for this 1993–1994 are from the TOMS instrument on the Soviet-built Meteor-3 satellite.

The data for 1996–October 2004 are from the NASA Earth Probe TOMS satellite.

The data from November 2004 on are from the OMI instrument (KNMI / NASA) onboard the Aura satellite. They are the OMTO3d that have been processed in a manner similar to the TOMS data from earlier years.

The ozone minimum is determined only from data actually contained in the processed satellite data. To calculate the ozone hole area and mass deficit, we fill in missing areas (bad orbits and polar night) from an atmospheric model. MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context. Since these data are from a reanalysis, they are not up-to-date. So, we supplement with the GEOS-5 FP data that are also produced by the GEOS-5 model in near real time.

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