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Lenticular wave clouds are used as a natural laboratory to estimate the linear andmass growth rates of ice particles at temperatures from 2208 to 2328C and to characterize the apparent rate of ice nucleation at water saturation at a nearly constant temperature. Data are acquired from 139 liquid cloud penetrations flown approximately along or against the wind direction.Amean linear ice growth rate of about 1.4 mm s21, relatively independent of particle size (in the range 100–400 mm) and temperature is deduced. Using the particle size distributions measured along the wind direction, the rate of increase in the ice water content (IWC) is calculated from the measured particle size distributions using theory and from those distributions by assuming different ice particle densities; the IWC is too small to be measured. Very low ice effective densities, ,0.1 g cm23, are needed to account for the observed rate of increase in the IWC and the unexpectedly high linear growth rate.




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