Author Topic: 2010 Southern Hemisphere Winter Stratospheric Ozone Hole  (Read 1871 times)

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Offline Downlinerz2

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2010 Southern Hemisphere Winter Stratospheric Ozone Hole
« on: April 18, 2011, 11:44:06 PM »
   Here is the summary and what is to be expected from the report on the 2010 Ozone hole in the Southern Hemisphere.  I only include the last part of it.  If you want to read it all here is the link:
   http://www.cpc.ncep.noaa.gov/products/stratosphere/winter_bulletins/sh_10

III. Summary

The 2010 ozone hole has contrasting characteristics for the SH winter and spring months. The winter months (July and August) were warmer than average due to several poleward eddy heat flux pulses that occurred in June, July and early September. These pulses caused the temperatures in the entire stratosphere to be warmer than average. These warmer temperatures were unfavorable for Polar Stratospheric Clouds. As a result, additional weeks were required before sun light illuminated the colder regions and initiated the heterogeneous ozone destruction chemistry. The peak ozone hole size for 2010 of 20.6 million square kilometers was smaller than in most recent years. From mid-September onward, there was very little poleward eddy heat flux. As a result, the SH polar vortex remained very stable as did the area of the ozone hole. The slow progression of the transition from winter to summer circulation patterns meant that the lower stratospheric polar vortex did not break up until late-December. As a result, the vanishing dates of the ozone hole and the SH polar vortex were later than any previous year.

IV. What is to be expected

Observations of chlorofluorocarbons and of stratospheric hydrogen chloride support the view that international actions are reducing the use and release of ozone depleting substances (WMO, 1999; Anderson et al., 2000). However, chemicals already in the atmosphere are expected to continue to impact the atmospheric ozone amounts for many decades to come. The Antarctic Ozone Hole is expected to continue for decades. Antarctic ozone abundances are projected to return to pre-1980 levels around 2060-2075, roughly 10-25 years later than estimated in the 2002 Assessment. The projection of this later return is primarily due to a better representation of the time evolution of ozone-depleting gases in the Polar Regions. In the next two decades, the Antarctic Ozone Hole is not expected to improve significantly (WMO, 2007). Further, changing conditions (i.e. meteorological, solar, and volcanic aerosols) that modulate ozone can complicate the task of detecting the start of ozone layer recovery. The eruption of the Pinatubo volcano provided an example of such a complication in the 1990s. Based on an analysis of 22 years of South Pole ozone vertical profile measurements, Hofmann et al., (2009) suggested that, according to indicators such as the September ozone loss rate at 14-21 km and ozone loss at the upper limits of the ozone hole (22-24 km), the beginning of recovery of the Antarctic Ozone Hole had not yet begun and may not be detected for some time. An intriguing aspect of recent observations of the Antarctic stratosphere had been the apparent trend towards a later breakup of the vortex in years since 1990, relative to the 1980s. The size and duration and size of the 2008 and 2010 Ozone Hole is attributed in part to meteorological conditions. A full explanation of such meteorological anomalies is not yet available. Continued monitoring and measurements, including total ozone and its vertical profile, are essential to achieving the understanding needed to identify ozone recovery.
 
     Mark





 

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