DRY YEARS

Rotorua Morning Post, Volume 1, Issue 100, 18 December 1931, Page 2

DRY YEARS

N.Z. DROUGHT INTERESTING SUMMARY PREPARED BY DR. KIDSON MIGHT BE MUCH WORSE The present summer has started with the apparent intention of being hot and dryyindeed, some distric'ts are already complaining of drought. Hence a memorandum on "Dry Years in New Zealand," prepared by Dr. E. Kidsoii, Director" of Meteorological Serviees, is of interest at the present time. Referring to last year, he remarks that 1930 was a very dry year, and at various times and in different districts considerable inconvehience and even finaneial loss resulted. In particular, hydro-electric schemes, especially in the South Island, suffered from unprecedented shortage of water. "It is interesting, therefore, to discover what the rainfall deficieneies amou'nted to, and how they compared with those in other dfy years. From about 1864 to 1880 rainfall was recorded at quite a number 'of stations in New Zealand, but between 1881 and 1893 the fecords were extremely few in number. From 1894 onwards an increase Commenced but it Was not until about 1900 that observers became sufficiently nume.roiis and well distributed to enable charts showing the distribution of rainfall over the whole Dominion to be drawn. Nevertheless, it se.ems certain that none of the earlier years, as far back at least as 1864, was as dry at 1914." Over most of the North Island the rainfall deficieneies in 1914 exceeded 10 inches. ' Indeed, for the North Island as a whole, and especially for the Auckland Province, 1914 was undoubtedly the driest year hitherto recorded. It was also very dry in Nelson and Marlborough. In Canterbury conditions were much more nearly normal, while in Otago a large area received more than the average rain. On the west coast of the South Island, though the rainfall was below average, the departures did not amount to a large percentage of the annual falls. Australia's Drought It is a very interesting fact, says Dr. Kidson, that in 1914 Australia suffered from the severest drought in its history. The characteristic of the year was that storm systems were very poorly developed, and there was a relative absence of the northerly winds which bring warm, moist air from low latitudes. It is this air of a northerly origin that is the source of most of our heavy rain, and in the Auckland Province this is especially the case. Westerly Winds were fairly strong, which accounts for the shortage being less important about Cape Egmont and in western districts of the South Island. There were heavy rains in these areas in autumn and spring, 'the periods when the- westerlies are at their ctrongest. The altitude of the ranges is so greas that heavy rains are c.aused by the cooling due to uplift of the air that is foreed over them, e.ven if it is initially dry. In Canterbury and Otago most of the rain comes with south-westerly wihds. The year 1914 followed a Very pronounced sunspot minimum. In Australia the drought broke in 1915. Depressions gradually became more vigorous, and a very wet period, which eontinued through 191.6 and 1917, commenced. In New Zealand the changes Were similar in kind, but occurred somewhat later; 1915 was still dry over most of the North Island, but became wet on the west coast of the South Island. The most important feature of the year, however, was that east'erh districts, experienced a very dry time. In Marlborough arid most of Canterbury it was much more severe than any recorded either before or since. The principal characteristic of the weather in 1915 was the strong development of the anti-cyclones, many of which crossed New Zealand. Cyclones Were few in n'umber, and moved rather fast, and there was a relative absence of southerly winds. Rainfall was below normal at many places in 1912 and 1913, and there is no doubt that the period from 1912 to 1915 was the driest experienced in the Dominion. The next very dry year was 1919. There was little to choose between it and 1914 for dryness so far as the North Island was concerned. The northern portion of the South Island also was dry, but over the southerft half the rainfall was • mainly abovfe normal. ' The year 1919 appears to have been similar to 1915 in that the cyclones ; that crossed New Zealand were few in number and not very vigorous. A- good deal of anti-cyclonic weather was experienced also. There was, however, much more westerly and south-westerly wind over the South Island, depressions of the westerly type being fairly well developed in the south, but having poor northward extensions. In Australia though the drought was not so general as in 1914, in Victoria and New South Wales it was extrfemely severe. Dry Years and Sun-spots For the country as a whole 1930 proved to be the driest year of all. This was especially the case with regard to the western districts of the South Island. It is not ' surprising that the Lake Coleridge hydro-electric scheme suffered severely. The year was as" dry as any of the earlier ones also in eastern. districts north of Hawke's Bay towards East Cape. Otherwiso the North Island did not suffer so severely as in 1914 and 1919. A few heavy and rather local falls raised the totals very considerably in Taranaki, so that the deficits were not especially large "there.. Small areas about Auckland and in southern Hawke's Bay, most of the Canterbury Plains, and a part of southern Otago, had rather more than the average falls. ' ••'•Both 1919 and 1930 followed sunspot maxima by about two years. New Zealand seems to be liable to a very dry ■ bpell at about this time. As r'egards the type of weather, the two years were very different. Cyclones

were numerous in 1930, and the weather was stormy. The westerly wind drift was, however, unusually weak. There were few of the pronounced type of V-depression which has a well-developed trough extending in a northerly direction, and which tendS to bring general rains to New Zealand. The year 1930 differed from the other years in that it was a wet year in Australia, although a series of dry years had preceded it. Each of the years mentioned above was cold, except 1915, which was very slightly warmer than usual. New Zealand Lucicy When New Zealand has a dry year, the effects are not so disastrous as the effects of a drought in Australia for instance. "The strength of New Zealand's position from a climatic point of view," remarks Dr. Kidson on the point, "is well illustrated by her experiences in these, the driest years she has experienced. In none of them did the primary producer suffer anything approaching disaster. Taking the country as a whole, 1930 was a good year for the man on the land. Losses, certainly were experienced in some districts, but in others conditions were unusually favourable. We are fortunate in having large areas which receive about the optimuni amount of rainfall for the growth of good pastures. In the area of low rainfall the reliability is high and a large part falls in spring and summer, when it is most needed. Again there is a tendency for variations'in the eastern districts of the South Island, which contaih some of our richest country, to be opposite in character to those in the remainder of the Dominion."