Temperature measurements in clouds on a centimetre scale Preliminary results

Preliminary results of the temperature measurements in Cumulus mediocris clouds with a new ultra-fast airborne thermometer installed on a motor-glider are presented. The time constant of the thermometer is about 2 × 10−4 s but due to limitations of the recorder the data were conditioned with the use of a 300 Hz low-pass filter and sampled with 999 Hz rate, giving spatial resolution of 3 cm at 30 m/s cruising speed. Records taken whilst penetrating various parts of Cumulus clouds on 23 and 25 August 1994 in the vicinity of Warsaw show a number of unexpected features such as single and multiple sharp jumps of temperature over layers only a few centimetres thick. Measurements of this kind are throwing a new light on the process of mixing in convective clouds.