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<br />. <br /> <br />Fig. 2.22 shows the dew point depression present in the <br /> <br />environment surrounding the cloud at the flight level. Since the flight <br />temperature was typically -lOoC, dew point depressions colder than <br />-200C are close to the cooling limit of the instrument, so still <br /> <br />. <br /> <br />greater depressions may have existed in same cases. The figure shows <br /> <br />. <br /> <br />that the probability is about constant to find all dew point <br /> <br />depressions from 0 to 200C. The potential for evaporative cooling <br /> <br />varies with the dew point depression, and evaporative cooling plays a <br /> <br />. <br /> <br />role in downdraft formation as well as possible enhancement of primary <br /> <br />nucleation. <br /> <br />2.12: <br /> <br />Cloud 1 i fetime. <br /> <br />The lifetime of the clouds can be <br /> <br />. <br /> <br />characterized by the rate of decay of liquid water content with time <br /> <br />after the first aircraft penetration. For the HIPLEX-l clouds, this <br /> <br />. <br /> <br /> 25 '100 <br /> 20 80 <br /> ~ <br />a: 15 60 LIJ <br />LIJ > <br />CD ~ <br />::E <br />:::> 40 ..J <br />Z 10 :::> <br /> :IE <br /> :::> <br /> u <br /> 5 20 <br /> 0 0 <br /> 0 4 8 12 16 20 <br /> DEW POINT DEPRESSION <br /> <br /> <br />. <br /> <br /> <br />. <br /> <br />. <br /> <br />The observed values of the dew point depression in the <br />Fig. 2.22: <br />environment upwind of the clouds of 1978. <br /> <br />. <br /> <br />32 <br /> <br />. <br />