Due to unfavourable weather conditions during the measurement campaign in 1999
only on few days in the end of February and at the beginning of March ClO was
measured. No chlorine activation coul be detected which is consistent with the
relative high temperatures in the lower stratosphere this winter.
Upper graph: ClO spectrum measured on 25 February 1999, 8:01 - 12:02 o'clock.
Lower graph: Retrieved ClO vmr profile. There is no lower ClO layer at an altitude
of at about 20 km which would be typical for chlorine activation.