Six years of dew observations in the Negev Desert, Israel

Dew measurements taken at the desert site of Sede Poker for nearly 6 years are analysed. The instrument used is a Hiltner-type dew balance. Several parameters describing various aspects of dew formation are discussed. The total monthly amount of dew and the distribution of the number of dew nights per month shows two maxima (in September and in December-January) and two minima (in April and November). The average dew deposit per dew night behaves differently: the most striking feature of this quantity is the appearance of distinct summer and winter regimes, with the winter having more dew per dew night. With respect to the total monthly dew hours, the year appears to be divided in half: first, the 6 months from August to January, with an average of 145 h per month, and second, the 6 months from February to June, with 80 h per month. The average duration of dew per dew night appears to follow very closely the length of the night: there is a clear maximum of dew duration in December (9.7 h) and a clear minimum in July (5.5 h). Finally, the rate of dew accumulation is found to have a distinct dry season regime and a winter, rainy season regime. (C)1996 Academic Press Limited