Observations of precipitation elements in cumulus clouds

Cloud particles of diameters greater than about 100 μ can be sampled from an aircraft by exposing within the cloud a thin aluminium‐foil surface to the airstream and counting and sizing the indentations made on it. A series of flights has been made through cumulus clouds using this technique with the object of obtaining data on the concentrations of these larger particles in clouds of different size and temperature. A series of observations showing the measured concentrations is presented and discussed. Concentrations range from less than 1/m3 in the smaller cumulus clouds up to 1/litre or more in clouds about 1 km thick.