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

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... ed. 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.