Iris Publishers- Open access Journal of Agriculture and Soil Science | Role of Stratospheric Temperature and Humidity in Occurrence of 2011 Spring Ozone Anomaly in the Arctic and on the Northern Territory of Russia Using Aura OMI/ MLS Observations 

Authored by Oleg E Bazhenov

In March-April 2011, the М-124 ozonometer observations recorded an anomalous decrease in the level of the total ozone (TO) content over Tomsk. The decrease reached 30% as compared to multiyear average. The paper studies the temperature, humidity, and ozone anomalies, recorded in March 2011 by the Aura OMI/MLS instrumentation in the stratosphere of Arctic latitudes and on the northern territory of Russia. Their relation to the decrease in the ozone concentration over Tomsk in April 2011 is analyzed. It is hypothesized that the Arctic phenomena are the result of ozone loss due to heterogeneous reactions on the surfaces of particles in polar stratospheric clouds after a return of sunlight during spring. Supposedly, irreversible growth of water vapor content at heights of ozone maximum in the second half of March had raised the temperature threshold for formation of PSCs that persisted until late March; this probably promoted the chlorine activation and, thereby, delayed the chlorine deactivation, resulting in even greater overall ozone losses during March 2011. The subsequent midlatitude phenomena seem to be due to synoptic-scale export of the ozone-depleted humid Arctic air masses.
Present-day estimates indicate that the total ozone (TO) column has a positive trend since 2000 at most latitudes, but this trend is not statistically different from zero in many regions [1]. The meteorological conditions in 2010-2011 were unusual for the Arctic and resulted in record-low ozone. If analogous conditions were to arise again in the Arctic while stratospheric chlorine loading remains high, similar severe chemical ozone losses would take place again. A stable stratospheric polar vortex was extremely long-lived in the winter-spring of 2010-2011 in Arctic. The transport barrier at the edge of polar vortex in February-March was the strongest in the last 30 years [2]. The temperatures below TNAT~195 K (the temperature threshold for formation of polar stratospheric clouds (PSCs) Ia) persisted until late March in the altitude interval of 15-23 km [2]. The temperature in the Arctic stratosphere in March 2011 was the second least in the period of 1979-2011, and the Arctic polar vortex was the third or fourth longest of the satellite era [3].
Unusually weak tropospheric planetary wave driving allowed the vortex to remain strong, stable, and cold for an extended period, with its mid-April breakup date one of the latest in the satellite era. Daily minimum temperatures were only moderately low (i.e., rarely below ice PSC formation thresholds), but the cold region was uncommonly long lasting and vertically extensive, leading to a winter-mean vortex fractional volume of air with the potential for PSC formation that was the largest ever observed in the Arctic [2]. An irreversible cooling speeded up diabatic subsidence of air masses from overlying layers which, in particular, had led to ever growing abundance of water vapor, produced in high layers by methane oxidation and explaining qualitatively the positive water vapor anomaly [4].

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