ISSN:
1420-9136
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Summary In Northern Bohemia 33 research flights were made during which concentration of giant condensation chloride nuclei was measured up to a height of 3,500 m above the earth's surface. Chloride particles were determined by traces left by them in a sheet of gelatine with silver nitrate (Liesegang circles). The actual size of the particles was obtained by comparison of particles of a known size, falling in a sedimentation tube, with images in the sensitive sheet, and the result was adapted to the analysis of samples during the flight. For each level at which a sample was exposed the spectrum of the sizes of nuclei was determined. During the year the average concentration of the giant chloride nuclei at a height of 100 m above the earth was 7.3×10−3 cm−3. At greater heights concentration of the nuclei decreased successively, so that at 2,000 m it was only 0.3×10−3 cm−3 and above the level of 3,000 m the nuclei occurred sporadically, on the whole. Under the influence of atmospheric exchange the concentration of the nuclei in the boundary layer up to 1,000 m above the earth's surface changes considerably both during the day and during the year. The highest concentration occurs at a height of several hundred metres above the earth in the winter month, at the morning and evening hours, i.e. during a more stable temperature lapse rate. From the established concentrations of the nuclei relation between the turbulent diffusion coefficient and the height above the earth was determined. Its average value during the year increases up to a height of 300 to 400 m above the earth. Above this level it decreases roughly according to the relation ofK∼z −6/7. The exponent changes not only with temperature stratification (with the time of day and year), but also with the average wind speed. For sodium-chloride particles of 2.5μ in diameter the maximum value of turbulent diffusion coefficient (at level of 400 m), reaches about 18×103 cm2 sec−1 while the minimum value is about 5×103 cm2 sec−1 (above 2,000 m).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02113401
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