ISSN:
1420-9136
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract An automatic condensation nuclei counter was developed for the concentration range of about 1 to 400 particles per cubic centimeter. After expansion, the water droplets are photographed when they are still suspended in the air so that the counter can be considered an absolute one. The volume in which the droplets are counted is determined by the size of the picture of the droplets as a function of their distance from the focal plane. To eliminate any effect of decreasing pressure with altitude, the cloud chamber is filled with clean air prior to expansion to about half an atmosphere above ambient pressure. This counter was used to obtain vertical profiles of condensation nuclei up to altitudes of 27 km with high altitude balloons. A total of seven profiles was obtained over a period of about one year at 47° N over the United States. Because of the restrictions in the range of the meter no data could be obtained below 5 km. The profiles show the following main features: 1. Although there are pronounced fluctuations in the individual flights the average nuclei concentration of 200 to 300/cm3 remains fairly constant from 5 km to the tropopause. 2. Above the tropopause, which is on the average of 12 km, the nuclei concentration decreases rapidly by a factor of ten at 15 km and by a factor of hundred at 19 km. Above 20 km, the lower limit of the counter range of l/cm3 is reached. 3. These general features are fairly constant over the year. Data for the lower stratosphere byWigand (1919) andWeickmann (1955) indicate a sharp decrease from concentrations of 2000 to 3000/cm3 at ground to about 100/cm3 at 5 km. If it is assumed that the discrepancy of a factor of 2 to 3 at 5 km is due to the different time, location, and methods used in these observations, all data can be combined into a complete average profile from the ground to 27 km. This composite profile shows then the following three characteristic layers: 1. Pronounced decrease of the nuclei concentration by about 2 orders of magnitude from 0 to 5 km. 2. Almost constant concentration from 5 to 12 km. 3. Pronounced decrease of the concentration by about 2 orders of magnitude from 12 to 20 km. It is shown in the discussion that the decrease in layer 1 is primarily due to washout, supported by coagulation. The small decrease in concentration in the upper troposphere, layer 2, indicates that both washout and coagulation must be fairly inefficient at these altitudes. The decrease in layer 3 forces to the conclusion that the nuclei in the stratosphere are of tropospheric origin. In the stratosphere, coagulation and sedimentation become important because of long stratospheric residence times of about 1/2 to 1 year. Calculations show, that coagulation is predominantly responsible for the decrease with altitude. The concentrations in the stratosphere are also compared with data deduced from observations of mother of pearl clouds and the electrical conductivity in the stratosphere.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02000630
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