Cloudland: A Study on the Structure and Characters of Clouds

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Сторінка 164 - ... considerable. Hence the interior and most violent portion of a cyclone, always gyrating from right to left in the northern hemisphere, and the contrary in the southern, must always gradually move towards the pole of the hemisphere in which it is. While between the equator and the tropical calm belt, it is carried •westward by the general westward motion of the atmosphere there, but after passing the tropical calm belt, the general motion of the atmosphere carries it eastward, and hence the...
Сторінка 138 - If a body moves in any direction upon the earth's surface , there is a deflecting force arising from the earth's rotation, which deflects it to the right in the northern hemisphere, but to the left in the Southern hemisphere
Сторінка 163 - The motion of a cyclone toward the poles may be accounted for by the principle in § 5. The motion of the equatorial side of a cyclone in either hemisphere is always toward the east, and hence the deflecting force causes a pressure toward the equator, but that of the polar side being always toward the west, the deflecting force causes a pressure toward the pole. Now these deflecting forces being as the sine of the latitude, as may be seen from...
Сторінка 118 - Cirrus moving from South is generally an indication of /Unsettled weather, especially in summer. The temperature is then usually above the mean for the time of year. " Cirrus from South-west indicates unsettled and sometimes stormy weather in winter. In summer it often precedes thunderstorms, but with a high barometric pressure and 'a high temperature it frequently has no disturbing influence, and is then usually replaced by Cirro macula.
Сторінка 118 - Cirrux are held to be of service for forecasting purposes, the following rules by the author may be considered useful and instructive : — "Cirrus moving from North or North-east with a high barometer is a sign of settled weather in summer and of temporarily fine weather in winter. With a low barometer it is a sign of marked improvement in weather.
Сторінка 164 - ... being greater on the polar side, where the deflecting forces which cause it are greatest, its action upon the atmosphere in advance of it is greater than on the equatorial side, where these forces are much less, and hence new portions of the atmosphere are being continually brought into action on the one side, while the resistance of the earth's surface, and the adjacent portions of atmosphere on the other side, are continually overcoming the comparatively weak forces there, and destroying the...
Сторінка 12 - ... which are not caused in this way. The second class of clouds are termed clouds of interfret. Interfret is explained as the action of two air currents on one another, the two currents differing -in velocity, or direction, or both, and producing a wave motion or eddy motion at the surface of contact. " Now if the upper current be colder than the lower, as will usually be the case, and if the lower current contain watervapour near its maximum tension, it is evident that condensation will very likely...
Сторінка 118 - Hast, a rare occurrence, is a sign of fine weather in winter, but of unsettled weather in summer. " Cirrus moving from South-east (but it rarely does so with a low and unsteady barometer) is a sign of improving weather in winter, and in summer frequently indicates coming thunderstorms. " Cirrus moving from South is generally an indication of /Unsettled weather, especially in summer. The temperature is then usually above the mean for the time of year. " Cirrus from South-west indicates unsettled and...

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