Title A closer look at Arctic ozone loss and polar stratospheric clouds
Author Harris, N.R.P.; Lehmann, R.; Rex, M.; von der Gathen, P.
Author Affil Harris, N.R.P., University of Cambridge, European Ozone Research Coordinating Unit, Cambridge, United Kingdom. Other: Alfred Wegener Institute, Germany
Source Atmospheric Chemistry and Physics, 10(17), p.8499-8510, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2010
Notes In English. Published in Atmospheric Chemistry and Physics Discussions: 10 March 2010, http://www.atmos-chem-phys- discuss.net/10/6681/2010/acpd-10-6681- 2010.html ; accessed in May, 2011. 51 refs. GeoRef Acc. No: 310411
Index Terms aerosols; altitude; clouds (meteorology); polar stratospheric clouds; ions; ozone; photochemical reactions; polar regions; polar atmospheres; pressure; solar radiation; stratosphere; temperature; Arctic region; polar regions; atmosphere; atmospheric transport; chemical reactions; chlorine monoxide; chlorine nitrate; clouds; denitrification; hydrochloric acid; hypobromite; inorganic acids; nitric acid; nitrogen dioxide; partition coefficients; photochemistry; photolysis; three-dimensional models; transport
Abstract The empirical relationship found between column-integrated Arctic ozone loss and the potential volume of polar stratospheric clouds inferred from meteorological analyses is recalculated in a self-consistent manner using the ERA Interim reanalyses. The relationship is found to hold at different altitudes as well as in the column. The use of a PSC formation threshold based on temperature dependent cold aerosol formation makes little difference to the original, empirical relationship. Analysis of the photochemistry leading to the ozone loss shows that activation is limited by the photolysis of nitric acid. This step produces nitrogen dioxide which is converted to chlorine nitrate which in turn reacts with hydrogen chloride on any polar stratospheric clouds to form active chlorine. The rate- limiting step is the photolysis of nitric acid: this occurs at the same rate every year and so the interannual variation in the ozone loss is caused by the extent and persistence of the polar stratospheric clouds. In early spring the ozone loss rate increases as the solar insolation increases the photolysis of the chlorine monoxide dimer in the near ultraviolet. However the length of the ozone loss period is determined by the photolysis of nitric acid which also occurs in the near ultraviolet. As a result of these compensating effects, the amount of the ozone loss is principally limited by the extent of original activation rather than its timing. In addition a number of factors, including the vertical changes in pressure and total inorganic chlorine as well as denitrification and renitrification, offset each other. As a result the extent of original activation is the most important factor influencing ozone loss. These results indicate that relatively simple parameterisations of Arctic ozone loss could be developed for use in coupled chemistry climate models.
URL http://www.atmos-chem-phys.net/10/8499/2010/acp-10-8499-2010.pdf
Publication Type journal article
Record ID 65007186