A new Nephoscope, and its use

[摘要] Ekholm's, Besson's, Fineman's, Marvin's, Vettin's, Finkes, Strachey's, Galton's, Clement Lay's and some other's nephoscopes have respective superiority and defect. The present instrument is comparatively good for routine observations. It consists of a plane mirror mounting on an azimuth circle, which carries a bridge with a movable eye piece, as shown in fig. 1. The eye piece slides along the horizontal beam of bridge with a constant height above the surface of mirror. The equatíon of cloud motion for this instrument is V/H=m/t, where V is the true velocity of a cloud mass, H its height, m the distance on the mirror travelled by the image of cloud, and t is the time of the travelling, by taking t. suitably, i.e. t=10 seconds for H=1000 metres t=20 seconds for H=2000 m and so on, we have the formula V=m. The scale of m on the mirror shows at once the velocity in metre-per-second. In these respects the nephoscope is just convenient as that of Marvin's. Besides, our instrument has a scale along the bridge showing the altitude of cloud above borizon, hence we can very easily read off the azimuth and altitude of the cloud. We use such sheets of paper in which azimuth lines and altitude circles are printed with blue ink. The radii of altitude circles is proportional to their tangents and hence the point entered in this diagram represents at once the position at the level of cloud. If we enter the points for successive readings of the cloud, then we can trace a line (nearly always straight) which shows the motion of cloud and the locality of fiamament through which the cloud passed. Fig. 2 and fig. 3 show examples of such diagrams before and after a storm. We can get some idea on the local character of the upper current by constructing such a diagram every day.For clouds passing very near the zenith we use an incl_??_ned small mirror with angle of elevation of 15°. But in practice we scarecely find any use of this auxilialy mirror.Very easily and accurately we can measure the angles for halo, corona, rainbow and alied phenomena, with this instrument.

[学科分类] 大气科学