THE WORLD DROUGHT OF 1895-6.

New Zealand Herald, Volume XXXIII, Issue 10085, 21 March 1896, Page 1 (Supplement)

THE WORLD DROUGHT OF 1895-6.

IN RELATION TO LONG • PERIOD PREDICTION FOR NEW ZEALAND. (BXPROF. DOUIiLAS ARCHIBALD, F.R. MKT. soo.] THE PRESENT EMPIRICAL SYSTEM OP DAILY FORECASTS. Prediction from rational principles is universally acknowledged to bathe crucial and only true tost of any science, and meteorology, or the science of the weather, (literally, to meteora, the things above), will only be admitted to tho academy of accurate sciences when it can enable us to confidently look forward to the occurrence of certain prevalent characteristics which have been forecasted on rational principles. The present system of daily forecasting is a meretricious substitute for the real thing, a sacrifice to the popular cry for daily weather, as though, liko daily bread, it could bo served out in slices, and involving as it does chiefly the telegraphing of conditions already in operation ovor places whence moving weather systems may bo expected to arrive, togethor with the drawing of maps which an intelligent child could decipher, has little or no connection with the real science of atmosphoric movements and aerial physics.

FUTILITY OF THIS METHOD FOR LONO PERIOD rORKCASri.NO. Even within its assigned shoft limits of time and space this empirical mothod frequently breaks down, partly because it attempts too definite a forecast, and partly because it ignores a knowledge of the larger movements and conditions which frequently check the normal movements and sometimes affect) tho ontiro world simultaneously.

A notable instance of tho futility of continuing to confine our attention to a mere daily forecast has been furnished by the abnormal prevalent weather not only over our own area, but all over tho world, during the past twelve months. A drought in the Nile rogion which may not improbably affect tho fortunes of the proposed Soudan campaign, a short monsoon over India, which at one timo threatened famine, corresponding with a failure of tho south east trade wind of tho Indian Ocean ; a drought ovor tho Southern United State? no severe as to oxposo the boil of tho Ohio, which has temporarily boon worked for coal, and reduce the American fall at Niagara to a " mere trickleand a drought and heat over Australasia which ha» been unprecedented within historical memory, are enough to show its universality. It is of little use, as some of our Australian meteorologists have lately done, to dwell on tho proximato causes of the local hoat and other conditions introduced by such a widespread " kink '' in the ordinary atmospheric motions. The conditions are universal, so must bo tho causes. Such a widespread abnormal may be taken as an exceptional samplo. Tho more ordinary periods of different species of provalont weather which occur at different seasons though not of such general incidence embrace large areas, and can he forecasted by rational principles with the aid ot cablo news of analogous controlling provalonb conditions over surrounding areas.

INDIA LEADS TUB WAY IV SEASONAL FORECASTING. So far, India has led the van in this departure from the stereotyped daily fore cast, and the success which lias attondod the publication by Mr. Eliot, the head of the weather service there, of long-period forecasts of the summer and winter monsoons, has induced tho Indian Government to vote the establishment of several new observing stations in Persia, togethor with regular cablegrams from tho Seychelles, and ultimately Mauritius. It has been found that the winter weather of India is manufactured, so to speak, in Persia, while the summer monsoon is chiefly dependent on tho south-oast trade wind of the Indian Ocean. If tho latter is strong, a good monsoon for India is the result, and vice vena Forecasting on such a basis is entirely different from tho system pursued in the present daily forecast. Details are disregarded, and only general prevalence is aimed at and achieved. Tho greator importance, however, of such prevalence compared -with daily weather, especially to the farmer and pastoralist, is obvious when we consider that tho result of a season is far more dopondent on the general prevalence or repetition d similar conditions than on the individual weather of a single day.

POSSIBILITY OF SIMILAR FORECASTS FOB AUSTRALASIA. It may be urged that India is exceptionally situated, and that a similar systora of long-period forecasting would not bo equally successful when applied to Australia or Now Zealand.

There are, however, many considerations which show that while the daily weathor of the southern parts of Australia and Now Zealand is more variable than that of the more tropical parts, owing to its dependence upon the frequent storm systems which circulate round the large stationary South Polar permanent cyclone, the general track of such storms is subject to secular as well as seasonal changes of position which persist for months together and cause long periods in the prevalence of their accompanying wind* ana rains over extensive districts, . The storm systems of the northern parks of this country are of a more tropical origin, and are equally subject to long-period variations, sinoo they are connected with the position and development, abnormal or otherwise, of the large pressure belts which bound and control the southeast trade winds of the Indian Ocean and

the Pacific. These latter are known to undergo long period-variations, which result in occasional droughts and floods in Australia as well as in Southern Asia, Africa, and Mid-America. PRESENT DROUGHT COULD HAVE BEEN predicted. A knowledge of the fact that the southeast trade wina of the Indian Ocean was almost in abeyance during 1895, coupled with unusually small baromotric gradients, might have led the Australian meteorologists to infer sluggish equatorial conditions, a lack of seawinds towards the interior of the Australian continent, and consequent abnormal heat and drought; or in any case to have expocted a persistence of such conditions when once they had, been established. Nothing, however, was said about these conditions until all was over and tho mischief dono. This was due partly to absolute ignorance of what had boon going on for months outside tho Australian area, and partly to the paralysing system of empirical daily forecasts.

I'LAN TO SECURE SEASONAL FORECASTS FOR NEW ZEALAND. By an extension of tho prcsont Australasian system to include cable news of prevalent conditions from the Cape, India, China, Samoa, and ho Eastern Pacific archipelago, there is little doubt that New Zealand giving the probable prevalence for seasonal forecasts could„'be constructed, of winds from certain quarters, tho position of storm tracks and the occurrence of more or less rain than the normal, and this without any substantial increase in the oxpense of conducting the daily forecast,, especially if some of the telegrams such as "A cold night at Rotorua,""A gale at Wellington,' "Fine and warm at Nelson," etc., were dispensed with.

THE STORM SYSTEM OF NEW ZEALAND AND ITS CONNECTION WITH OUTSIDE CONDITIONS. The weather over New Zealand is regulated by the seasonal march north and south of the largo pressure bolts of tho Pacific, together with variations in the normal trs cks, number, and intensity of tho storms which move ovor it.

The genoral position of its throe prevailing storm tracks is indicated in t-lio diagram abovo. Without entering into details, it may bp stated that tho north-west and northeast systems prevail mostly in tho sum men', and the south-west mostly in the winter. During tho present summer tho effect of tho abnormal conditions over Australia has resulted in the almost entiro absence of tho two last, and an undue and unprecedented prevalence of north west storms and winds. In consequence tho North Island and a large part of the South Island have shared in the great Australian drought, while Southland alone has enjoyed tho rain brought by wosterly winds which have not been parched by thoir passage over the exceptionally arid region of Australia. The north-oast system, which usually brings us the humidity and warmth from the tropical Pacific, has apparently been pushed eastwards by tho dominant north-wester, while the south-west storms have probably been wasting their supplies over the sen, to the south of Stewart Island. These conditions have prevailed for months, and are obviously connected with tho general disturbance of tho normal conditions, and will only disappear when tho world's weather, and particularly Australian weather, returns to a more normal state of things.

The moral of all this is surely plain. The prevalent weather of New Zealand is intimatoiy bound up with conditions cmbracing large areas nf neighbouring space, and loner period® of time. To be ablo to furnish a prediction of the prevalent weat,herofasea«on, prevalent conditions, particularly over Australia, must be studied, and the probable tracks of tho north-west and south-west storm' laid down by comparison with theory and experience. The occurrence of tho north east storms in tho ab«ence of a dominance of those from the north-west may not improbably be fairly determined by a better knowledge of the con ions prevailing over tho Society Islands, and a sharp watch must be kept upon all pronounced abnormal conditions of long period, like the presont, which affect large portions of the world at the same time, and which cannot affect ono part without indirectly, if not directly, affecting the rost. Wo may erect a boundary against the importation of Japanese boots by a hostile tariff, but wo are bound by natural laws to undergo a frcetrado in weather.

PROBABLE CAUSER OK ORDINARY AND EX-

CKPTION'AIj MINI! period ABNORMAL^, I have not hore attomptcd to enter upon tho complicated question of causes of either t,hoordinary seasonal abnormal weather, or of the present extraordinary world-wide abnormal, but I may indicate that tho goneral belief among modern meteorologists is that the ordinary long period abnormals result from large changes in tho flow chiefly of tho upper atmospheric currents, like those which cause a river to change its course and create a now channel, combined with re-acting marine current and temperature conditions. On the othor hand, thoso larger onos, of which tho present year presonts a notable example, aro probably primarily dim to influences which have a solar or cosmical origin. It is not absolutely necessary, however desirable it may be, 'or us to. know tho exact cause if"we can by help of tho law of persistence of initial conditions, and the present knowledge of atmospheric laws and merits, deduce a fairly rational system of consequences,

Sir Charles Todd remarks in a reoenfc number of the Review of Reviews, that in time he hopes to be able to predict these "heatwaves" (presumably those of long period, like the ono under discussion), and apparently by collecting more data and waiting for "some pcionbist with sufficient leisure to discuss them." I am afraid, under such a system, we might wait until Domoßday. This is an old way of shelving the difficulty, and waiting for soma Newlon to come along and help us out of it. The real plan is not to collect more data in Australia, but for tho meteorologists and Government astronomers (if they can spare the timo) of Australasia to ascertain what is being dono in India and elsewhero, and by establishing bettor communications with the neighbouring ureas to utilise observations from these in conjunction with their own. More local data will chiefly encumber tho bookshelves. A fow more stations over the central parts of Australia and on the New Zealand Alps would certainly bo desirable, but what is far more requisite is that life should bo infused into the oxisting statistical dry bones, and an attempt made to follow on the path of seasonal prediction so successfully pioneered by tho head of tho Indian Meteorological Servico.

Lord Salisbury's hobby, as wo all know, is physical science, and when at Hatfield he spends moat of his time in what ho culls his "den," which consists of a laboratory, a drossing, and a bath room on the ground floor. In this room, according to an interesting * article on "Hatfield House" in Caßaell's Magazine, his lordship himself planned the electric lighting of the house by means of the water power in the River Lea, which flows through a portion of the park. . Lord Salisbury has also applied his scientific talent to the problem of the water supply of Hatfiold, and the town now receives excellent water from the mains in Hatfield Park, In the same room, too, are some interesting suggestions of the skill to which Lord Salisbury has attained in the gentle ark of photography.