Ceilometer data on the Japanese icebreaker Shirase

Ceilometer data on the Japanese icebreaker Shirase during the annual Antarctic expedition. Observations were made on 10 voyages, from one departed Tokyo in November 2010 to another departed in November 2019. / After leaving Tokyo, Shirase returns to Tokyo by almost the same route via Fremantle in Australia, Syowa Station in Antarctica, and Sydney in Australia. Departure from Tokyo is mid-November, arrival at Syowa Station is around the end of December, departure is mid-February, and return to Tokyo is mid-April. / The ceilometer emits light vertically upward and measures the intensity of backscattered light from the atmosphere as a vertical profile. When there is an optically thick cloud above, it is recognized as a cloud base because of strong backscattering from the cloud particles there, and its height is recorded. When it is a thick cloud, the measured value cannot be obtained beyond it because the light does not reach above it due tothe light attenuation. In the absence of such thick clouds, the data represents the vertical profile of the amount of scatterers (cloud particles, precipitation particles, and other relatively large visible objects).