Time behavior of nitric acid and its influence on polar stratospheric cloud formation and ozone destruction in the winter-spring stratosphere of the Arctic based on Aura MLS observations
O.E. Bazhenov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: ozone, sudden stratospheric warming, polar night, nitric acid, temperature, Aura MLS observations, mixing ratio profile, polar stratospheric cloud evaporation
Abstract
The onset of polar stratospheric cloud (PSC) formation and chlorine activation is so far considered to be the temperature threshold of formation of nitric acid trihydrate T NAT, below which the HNO3 concentration sharply increases in PSC particles. In this paper, we use the data on the minimal temperature, maximal negative deviations of ozone concentration from multiyear average, and maximal nitric acid (HNO3) concentration in the Arctic stratosphere at four sites: Eureka, Canada (EUR); Ny-Ålesund, Norway (NAD); Thule, Greenland (THU); and Resolute, Canada (RES) for calculations of the maximal HNO3 concentrations and the total HNO3 columns. The maximal HNO3 concentrations decrease throughout the winter until late February at all observation sites considered here due to condensation of gas-phase HNO3 on PSC particles. The concentrations start to grow after return of sunlight to polar latitudes due to PSC sublimation and HNO3 export from peripheral areas of the vortex during its deformation. The HNO3 content in the winter-spring stratosphere of the Arctic is an important indicator of the PSC formation and breakup.
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