  CORRELATION OF CYCLONES AND ANTICYCLONES AND THE WEATHER. A. Cyclones.—Prepare a piece of tracing paper as shown in Fig. 52, making the diameter of the outer circle about 1000 miles A. Draw a line on the tracing paper enclosing the average area of cloud (including rain and snow), and a second line enclosing the average area of precipitation (rain or snow). B. Determine the percentages of clear, fair, cloudy, and stormy observations for each division of the tracing paper, i.e., (a) for the eight sectors of the large circle; (b) for the whole of the small circle; and (c) for the portion of the diagram between the circumference of the inner circle and the circumference of the outer circle. Fig. 52. C. Write out in general terms a description of the weather distribution in cyclones as illustrated by your own investigation. B. Anticyclones.—This exercise is done in the same way as the preceding one, except that anticyclones are substituted for cyclones. The association of fair weather with anticyclones and of stormy weather with cyclones is one of the most important lessons learned from a study of the weather maps. The great areas of high and low pressure control our weather. On land, where daily weather maps are so easily accessible, a glance at the map serves in most cases to give a fairly accurate idea of the position and extent of cyclones and anticyclones, and hence also of the distribution of weather. At sea, on the other hand, the navigator has no daily weather maps to refer to, and his knowledge of the weather conditions which he may expect must be gained from his own observations alone. Of these local observations, the pressure readings are by far the most important. A falling barometer usually means the approach of a cyclone, with wind, or storm, or both. A rising |
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