Time Variation of Updraft and Water Content in Small Cumulus Clouds

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Abstract
Observations in small cumuli of depth 1.5–2 km indicate that at any given height above cloud base the average turbulent velocity and liquid water content remain more or less constant for periods of up to 20 min or so during the central part of the cloud lifetime. A region can often be identified near the upshear side of the cloud in which the updraft persists with little change in magnitude for periods of 10–15 min. Outside this region there are large fluctuations in the vertical velocity and when averages are taken over the full visible width of the cloud no consistent pattern is observed. Abstract Observations in small cumuli of depth 1.5–2 km indicate that at any given height above cloud base the average turbulent velocity and liquid water content remain more or less constant for periods of up to 20 min or so during the central part of the cloud lifetime. A region can often be identified near the upshear side of the cloud in which the updraft persists with little change in magnitude for periods of 10–15 min. Outside this region there are large fluctuations in the vertical velocity and when averages are taken over the full visible width of the cloud no consistent pattern is observed.