CHARTING THE AIR.

Oamaru Mail, Volume XLIV, Issue 14043, 28 April 1920, Page 2

CHARTING THE AIR.

The-rapid'increase in the use of aircraft, . and its .employment in almost every condition of weather, make it im- • perat ice that. more should be known about the movements of the upper atmosphere. • . . The New South Wales Meteorologist. Mr Mares, is keenly interested. Many of the important facts brought to light through aerial exploration during the war. will, in his opinicjn, now be applicable to commercial flying. "The frequent .occurrence of northerly winds over the eastern half, of Australia is fortunate," he says. "Such .undoubtedly provie. {wvaju-r • able aid to ' aviators 'flying " from : we northern to southern parts." He emphasises the fact that a reasonable distance from the mountain slopes should be maintained, as irregularities in the shape of the ground have curious effects on the lower layers ot the air. "Here, in Australia," lie explains, "the flying' weather to be contended with is difficult from that of Europe. \Ye have tropical conditions whiph are so often absent in Europe. The great heat of the interior part of our continent very frequently sets up adverse flying weather. This is due to the convection of the atmosphere." Another interesting fact commented on by Mr Mares is that often two currents of air entirely opposite in direction may be blowing one above the other. „ "The most casual observer ot weather." he points out. "knows this to' be so. for he cannot help noticing that sometimes clouds of high" altitudes aie travelling in another direction as compared with those nearer the earth. "That the charting of the upper air on a comprehensive scale will have a beneficial effect on civil flying isi a fact reco<mised in Europe. Mr Holt Ihomas has "said that the future of commercial airships depends on the charting of the upper wind currents, so that an airship flving at a suitable altitude will be able to increase her rate of travel, and thus overcome to some extent the disadvantage of her comparatively slow speed. . . . • I "Now experiments with the aim to investigate the structure of the upper atmosphere have been carried out in Sydney, and also in Melbourne. A method is bv releasing a sounding balloon. This balloon is generally a little over a. vard in diameter, and filled with hydrogen. The rate of ascent is standard, and, the path is followed with a. special theodolite until the balloon vanishes in the clouds. , "The balloons often carry sensitive instruments carefully protected, which, - when recovered, give valuable information as to barometric pressure, .tem- • perature, and humidity. All the time the ascent is in progress these registrations are being made. ' "The most suitable day to release one of them at Sidney would be when a- north-easterly wind was blowing, and then it would stand a fair chance of being carried inland. Attached to the case is, of course, a note offering the finder a reward 011 rcturnuing it to the Weather Bureau. ■ '

"A 'balloou-sonde,' to use. tlie techr nical name, generally travels miles upwards before the atmosphere pressure is so weak as to cause the gas inside to burst it. Sometimes they have failed to burst, and there as a case on record of a long flight from England to a Bavarian forest."

Mr Mares considers that the adoption of sound ranging may be ranked among the best practical solutions of the problem of gaining knowledge of the air currents. Even with that method, however, the results are only approximately correct, though of value. "A number of explosive charges timed to go off one after another at fixed intervals are attached to a small balloon, of which the rate of ascent is known. The balloon is released, and the successive explosions take place. The direction frpni which the sound travel's and the difference in the time between each explosion gives enough data, when they reach the sounding instruments, to enable a reasonbly accurate estimate of the wind', its speed, and direction at different altitudes, to be calculated.

The results of the soundings throughout the British Isles are-trans-mitted by telegraph, telephone, and wireless to the central office of the Air Ministry, and are forthwith plotted on charts. These charts are studied thoroughly in their relation to the prevailing weather conditions, and much information is thus obtained. A section of air soundings or' chartings is published in tho Times daily. France has aTso half-a-dozen stations in operation, and she intends to equip many more. .An exchange of reports by wireless between England and France is in operation.. Discussing the dependence of aviation on the ■weather, Mr. Ma res states that the-best times for making flights are in the early morning arid ,at evening. The air at these times is "less bumpy than in the middle of the day. "Successful flying,'-'- he explains, "is

more likely with a rising barometer and a low temperature. Clouds then are generally higher ; aud more .detached. Another interestingrthiug;is that temperature 'decreases one degree- in every 300 feet of ascent'up to a certain height-, usually about seven, or eight miles.-. Experiments at the Central Weather Bnreau havo. proved this." 'Mr .Mares refers to the assistance meteorologists can give : to aviators by preparing special forecasts. lii his view it is absolutely necessary that aviators should be armed with a knowledge of the fundamental principles of meteorology. This, he thinks, could be readily acquired, and, .as weather changes .generally occurred.. in. se-. : <Xiieii'c<', : little- in application should he experienced. • ."There is a startling inter-depen-dence of meteorology and aviation,'" concludes Mr Mares. "As a result- of man's fixed determination to-fly, nature has unfolded many of her atmospheric secrets that otherwise iwould have remained undisclosed. The two great sciences must travel down "the future hand in hand."