DOMINION'S WEATHER.

New Zealand Herald, Volume LXIX, Issue 21133, 16 March 1932, Page 8

DOMINION'S WEATHER.

CLIMATE NOT CHANGING. ; A HISTORICAL SURVEY. CONDITIONS IN AUCKLAND. Of recent years science, which is no Respecter of persons, has chosen at times to give the. lie direct to those who never lire of talking about " the good old 'days." The latest case in which the £' good old days " are revealed to be very largely mythical concerns the weather. New Zealand's climate, it is frequently stated, is not what it used to be. All that is needed is a sudden cold snap or an unusually prolonged spell of wet weather for the elders to shake their heads and say that " they never had ,weather like that in the good, old days." IThey say that shell-fire during the war upset all climatic conditions or they lay the blame at the door of wireless telegraphy and telephony. They may be chocked to learn that the Government meteorologist, Dr. E. Kidson, is definitely of the opinion that during the last 70 years there have been no persistent phanges of temperature in New Zealand. In a recent issue of "The New Zealand 'Journal of Science and Technology," Dr. Kidson, in an article headed " Mean [Temperatures in New Zealand," gives [what is really a historical survey of the Dominion's weather since the time when first an effort was made to gather meteorological statistics. Defective Exposure. " On plotting the data for all stations, both past and ' present, on a map, Dr. Kidson says, " certain values immediately stand out as abnormal. In particular, nearly all the older records givo Tiigh mean temperatures. It would be easy to assume that there has actually been a fall in mean temperature during the past 70 years and the large proportion of our population which is convinced that the climate is becoming colder .would see in this the confirmation of their views. " But it seems safe to assume that the high temperatures of the early records are due to defective exposure. The abnormally high values are confined to Btations which were in existence prior to 1880. We know that the thermometer screens used in the early days were not as efficient as the present type. In the daytime they used to heat the air they (contained, so that the thermometers gave a higher temperature than that of the surrounding air. There was an opposite effect at night, but it was not so marked. The oid screens, therefore, tended to give readings that were, in the main, too -fcigh." Effect of Wellington's Wind. Di\ Kidson quotes actual observations in Auckland in support of his argument. The observations from 1868 to March, •1883, gave a mean temperature of 59.4 degrees. There was then a change in site and a new screen was used. Ihe mean at the new site was 58.9 degrees, a drop of .5 degrees. The first site was over 100 ft. higher than the second, and with the allowance for altitude, the temperature should have been .3 degrees lower. 'Actually, defects in the exposure of the thermometers at the first station were responsible for a reading which was .8 degrees too high. " In Wellington, the almost continual wind tends to produce uniform conditions," Dr. Kidson says. "It would also minimise the errors due to defective screens. The meteorological station has been in four sites prior to the present one, and, when the standard allowance is made for difference in altitude, the means from each of these sites agree to ,within a tenth of a degree. These observations seem, therefore, to point Conclusively to the absence of any persistent changes of temperature." Auckland Temperatures. Other views have been formed by Dr. Kidson from a close study of the records. For instance, he says, the temperature at Auckland would appear to he well established, but short records from Riverhead and the Waipoua Forest to the north indicate temperatures between two and three degrees lower. His conclusion is that, even on the narrow Auckland peninsula, temperatures were considerably higher on the east than on the west side, and that Auckland had an abnormally Jiigh temperature for its latitude. This high temperature was believed to fce due to the presence of large areas of shoal water near the city. A considerable amount of the sun's heat would penetrate to the bottom in the shallow water; It would be absorbed and would then be jconserved by the overlying water. " Owing to the fact that Auckland is Surrounded to a large extent by water," Dr. Kidson says, " the annual variation in temperature is consequently small and the changes are later than elsewhere. [February is as warm as January and [August is almost as cold as July. InverCargill is near the coast and in a locality where there is plenty of air movement Jdue to westerly winds. But, though it is much farther south than Auckland it has a rather larger temperature variation. iThis is due to the effect of the land to the north of it, shown also by the fact that January is considerably warmer than February, while July is considerably polder than August. " The relation between sunspots and ;weather is a subject which attracts considerable attention. On the whole, temperatures tend to be above- norma! at sunspot maximum, but by no means inyariabJy so. The tendency for low temperatures at sunspot minimum is much more marked, but still more definite is One for temperatures to fall at about the second year after sunspot maximum. Rainfall also tends to be low at this period."

One particularly interesting observation la that drought years in Australia tend to be cold years in New Zealand, with low lainfall over the greater part of the jccuntry. The reverse is the case in wet years.