The James Holton Symposium


Three dimensional structure of ozone recovery processes in the Antarctic revealed by ground-based and satellite observations in 2003


Kaoru Sato, National Institute of Polar Research, Tokyo, Japan; and Y. Tomikawa, G. Hashida, A. Kadokura, T. Yamanouchi, H. Nakajima, and T. Sugita

An intensive observation campaign was conducted using ozonesondes to elucidate detailed seasonal march of ozone hole formation and ozone layer recovery in the Antarctic. We launched 98 ozonesondes in the time period of the middle of June in 2003 through early January in 2004 at Syowa Station (69.00OS, 39.59OE). The ozone hole in 2003 was one of the largest in the past. The ozone hole was developed fast in the last half of August. Both ozone hole area in which the total ozone is less than 220DU and the amount of the destructed ozone was the largest in the end of September. The ozone hole disappeared in early December. Our observation in the first half period from the middle of June to the middle of October was a part of the first Antarctic MATCH campaign by European research program of QUOBI (Quantitative Understanding of Ozone losses organized by Bipolar Investigations). This is a Lagrangian method to examine the ozone destruction quantitatively by making an ozonesonde observation network consisting of nine stations (Neumayer, Rothera, Dmont d'Urville, Belgrano, Marambio, Amundsen Sott, McMurdo, Davis and Syowa) in the Antarctic. We launched 50 ECC ozonesondes at Syowa Station for the Match campaign. The observation in the second half period was an original observation at Syowa Station to examine ozone layer recovery processes. We launched ozonesondes five times a week until the middle of December except for the days of severe weather condition. Moreover, seven launches of ECC ozonesondes and optical ozonesondes by using high altitude balloons of thin plastic film with a thickness of 6 m were made to observe ozone profiles up to the height of about 40 km. In 2003, a satellite observation of minor constituents including ozone and N2O by ILAS-II was also performed in the period until the end of October covering the whole the ozone hole formation period. We used these ground-based and satellite observation data to examine the Antarctic ozone hole dynamics. By analyzing ozonesonde data at Syowa Station in detail, it is shown that the ozone recovery process is clearly divided into two time periods, namely before the end of October and after. In the first half period, ozone recovery is clear by downward transport due to Brewer-Dobson circulation. This transport is observed even late August when ozone destruction to make the ozone hole is proceeded below. On the other hand, in the last half period, mixing and intrusion of ozone rich air in the middle latitude associated with the polar vortex breaking is the dominant processes, although the transport by B-D circulation remains. An interesting point is that even early December when the ozone hole disappeared, the ozone in the height region around 14 km is not recovered. The height region around 14 km corresponds to "sub-vortex" and is located in the lowermost stratosphere. ILAS-II data was used to examine the downward transport of ozone in October as a function of longitude. The estimate of downward speed is similar to the result from the ozonesonde data analysis at the longitude region of Syowa Station. However, the downward speed depends clearly on longitude. A similar analysis was made for the ILAS-II data of N2O which does not have source and sinks in the focused region and hence used as tracer of B-D circulation. The longitudinal dependence of the downward speed is also clear for N2O. However, the downward speed is faster for N2O than O3. This difference suggests that the photo-chemical destruction process act even on the ozone newly transported by the circulation. The longitudinal dependence of downward motion is considered to be due to amplification of planetary waves observed in October.

Poster Session 1, James Holton Poster Presentations
Monday, 30 January 2006, 2:30 PM-4:00 PM, A302

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