On the nature of persistent stratospheric clouds in the Antarctic

Thin, persistent very high clouds called “Stratospheric Cist” were reported at Maudheim base (71°03’S, 10°56’W) during the 1950–51 austral winters. The nature of these clouds, whether they are H2O or dust, is of importance in the proposed sink for stratospheric moisture in the Antarctic winter. Results are presented from analyses of unpublished daily cloud reports and daily upper air measurements from the Maudheim expedition. The results reveal strong evidence that the “Stratospheric Cist” were stratospheric ice clouds. Given this identification, an upper limit of 6–7 ppm can be assigned to the water vapor mixing ratio in the lower stratosphere for the 1950–51 Antarctic winters.