Abstract
Edinburgh. Royal Meteorological Society, July 24.—Dr. C. Chree, president, in the chair.—C. K. M. Douglas: Observations of upper cloud drift as an aid to research and to weather forecasting. The condition of the wind near the top of the troposphere in different stages of a cyclone is discussed. The pressure distributions aloft, disclosed by the upper winds, are considered in relation to temperature, as the pressure at considerable heights is largely determined by the temperature of the column of air underneath. There is complete lack of symmetry in the temperature distribution over a cyclone in its earlier stage, with a great contrast in the temperature of the whole troposphere between the “polar”and “equatorial”currents. When the cyclone becomes stationary and fills up, the distribution of temperature and wind in the upper air approaches to symmetry round the centre, and the easterly current on the north side often extends throughout the troposphere. No simple rules for weather forecasting can be drawn up, as the changes in the wind at considerable heights follow rather than precede those near the surface, but observations of high cloud motion are valuable, for they indicate the temperature distribution in the troposphere.—J. S. Dines: Note on the effect of a coast line on precipitation. A convergence effect occurs over a coast line when the wind blows along the coast, the low pressure being over the sea and the high pressure over the land; this may cause precipitation. Under favourable conditions an upward current of 15 feet per minute may be produced over a strip of the earth's surface extending 5 miles on each side of the coast line. A similar effect occurs wherever the pressure gradient varies along a line perpendicular to the isobars, and the following rule is deduced: “In any area where the pressure gradient increases towards the ‘High’ there will be rising air.”—A. E. M. Geddes and C. A. Clarke: Note on turbulence, as exhibited by anemometer records, smoke and cloud formation. The effect of eddy motion is shown near the surface by the records from a pressure tube anemometer. The turbulence and cdnsequent eddy motion depend largely on the nature of the surface over which the air current is travelling. Eddies higher up are shown by smoke from tall chimneys. Higher up, cloud of the stratus order is formed. Smoke eddies and clouds occur when there is little or no convection due to heated air, and therefore their appearance and formation is evidently in accordance with Taylor's theory of eddy motion. Eddies occur at the junction of two currents of different temperature, and fragments of cloud form below the base of the line squall or similar cloud. Cloud intermediate between the normal cirrus and cirro-cumulus types undergoes changes which are at present unexplained. The change of the cirro-cumulus type, regarded as a water-droplet cloud, into the ice-crystal structure of true cirrus is only to be expected at high altitudes and consequently generally very low temperatures, but the reverse process occurs frequently.
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Societies and Academies. Nature 110, 235–236 (1922). https://doi.org/10.1038/110235a0
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DOI: https://doi.org/10.1038/110235a0