Spectrometric measurements of NO2 Slant Column Amount at Stara Zagora Station (42°N, 25°E)

Nitrogen dioxide (N02) is a representative of a family of chemically very active radicals NO,=NO+NO2. These radicals catalytically destroy the ozone and play a significant role in other ozone-destroying catalytic cycles. In the polar night NO2 can deactivate Cl0 by a termolecular reaction to form the reservoir gas ClON02. In this way NO2 restricts the ozone destruction in the polar vortex. NO2 also takes part in heterogeneous reactions, which occur on the surface of polar stratospheric clouds. For the trace gases study and particularly for the nitrogen dioxide a spectrometric instrument GASCOD-BG was installed at the Solar Terrestrial Influences Laboratory - Bulgarian Academy of Sciences , Stara Zagora Department in August 1999. The instrument was developed at the Institute of Atmospheric and Oceanic Sciences at the Council of National Research, Italy, Bologna. The results of the NOa observation for more than two years are presented in this paper.