Studies on Dew

II. On the Formation of Dew

Abstract

The present paper deals with the relationships between 1) dew formation and meteorological elements, 2) dew amount on leaves and acrylic plate, and the observed dew amounts were compared with the calculated values from the Yamamoto's dew estimation equation based on heat balance. The results obtained were summarized as follows:
(1) Dew formation is related to cloud amount (i.e., net radiation) and wind speed. When the sky was clear (cloud amount less than 3), the dew amount increased from 2.0 to 2.8mgcm^-2hr^-1 accompanied with wind speed increased from 10 to 120cm sec^-1, and in another case, when the sky was cloudy (cloud amount more than 4), the dew amount increased from 0.6 to 1.4mgcm^-2hr^-1 accompanied with wind speed increased from 50 to 190cm sec^-1.
(2) The relationship between the ratio (Y, %) of dew amount on leaves to that on acrylic plate and the difference of the surface temperature (X, °C) between leaves and acrylic plate could be expressed as following equation,
Y=ae^-bX,
where a and b are the empirical constants.
(3) The net radiation on the surface of a body that factorized in the Yamamoto's dew estimation equation was revised. As a result, the calculated values of dew amount were close to the observed values and showed a similar variation tendency and fairly good agreement.