VARIATIONS OF TROPOSPHERIC HCL AMOUNTS OVER NORTHERN SWEDEN

Unexpectedly large variations of tropospheric HCl zenith column amount s were observed over Kiruna, Northern Sweden, in the arctic winters of 1991/92 and 1992/93. Trajectory calculations prove a strong dependenc e of tropospheric HCl variation on the origin of the air mass observed . This effect cannot be explained by different altitudes of the tropop ause caused by dynamical processes. Polar maritime air contains 0.67 /- O.11 x 10(15) more HCl molecules cm(-2), in terms of tropospheric z enith column amounts, than maritime midlatitudinal air. The latter con tains 0.39 +/- 0.16 x 10(15) more HCl molecules cm(-2) than continenta l air from midlatitudes. The HCl loading of arctic air is comparable t o that of maritime polar air, except for one measurement on January 28 , 1993, which showed significantly less tropospheric HCl. Tropospheric chlorine activation, along with ozone destruction in the troposphere, is considered a candidate for explanation. Furthermore, HCl strongly correlates with CH2O.