Meteorology: India (basic data compiled during the British Raj)

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Meteorology of India: record from 1909

singular interest mFirst, on account of its variety and con- trasts.

General Meteorology of India

THE area dealt with in the present chapter includes the whole of India proper, with Burma and Baluchistan. It is not a self- contained area, as its meteorology depends very largely upon the oceanic area to the south and also, to a slighter extent, upon the regions to the north and northwest, more especially Central Asia and the Persian area or plateau. The object of this chapter is not only to give a statement of the larger seasonal weather changes, but also to indicate, so far as at present possible, their relation to each other, and their co- ordination to meteorological conditions and actions in the neighbouring areas of land and sea.

India probably presents a greater variety of meteorological conditions, actions, and features than any area of similar size in the world. The normal annual rainfall varies from 460 inches at Cherrapunji in the Assam hills, and from between 300 and 400 inches (probably) at suitably exposed positions on the crests of the Western Ghats and the Arakan and Tenasserim hills, to less than three inches in Upper Sind.

The largest rainfall actually measured in India in one year was 905 inches, at Cherrapunji in 1861, while at stations in Upper Sind it has been nil. A rainfall exceeding 25 inches within twenty-four hours is of occasional occurrence, and falls exceeding 15 inches are comparatively frequent. At one period of the year parts of India are deluged with rain ; at another persistent dry weather with clear skies prevails for weeks or months. During the rains the air is almost supersaturated with moisture in some of the coast districts and in the hills, while in the hottest weather it is occasionally so dry in the interior that the methods employed for calculating humidity in Europe have given negative and hence impossible results.

The coasts are occasionally visited by cyclones fiercer and more concentrated than have probably ever occurred in Europe. These bring up storm-waves that sweep over the low coast lands of Lower

Bengal or the deltas of the Mahanadi, Godavari and Kistna, destroying the crops, and drowning the inhabitants by tens of thousands.

In one season of the year India is the scene of the most wonderful and rapid growth of vegetation ; in another period the same tracfc becomes a dreary brown sunburnt waste, with dust-laden skies and a heated atmosphere that is almost unendurable even by the natives of the country.

The transition from the latter to the former phase over the greater part of the interior often occurs in a few days. In one year the rains may be so distributed as to cause a severe and extensive famine over several Provinces, necessitating for months afterwards the continuous relief of millions of the population ; in another the meteorological conditions may be so favourable that the crops far more than suffice for the normal food demand.

India again presents a noteworthy combination of tropical Secondly, and temperate region conditions. Tropical heat, heavy and ^| n ^" frequent rain, and fierce cyclones are prevalent at one period tropical

of the year : while moderate temperature and rain, with shallow ancl tem " . , . . , , . - L perate re-

extensive storms conditions resembling those of South-eastern gi on con- Europe obtain at another. ditions. In the third place India is par excellence the area in which Thirdly the contrast of what are termed monsoon phases or conditions a * a is exhibited most strongly over a large area. These conditions nounced

are the prevalence of dry land winds, with little cloud and monso p n conditions, ram, during one half of the year, and of winds of oceanic origin, with high humidity, much cloud and frequent rain, during the other half.

The work of meteorological observation was begun by the Initiation East India Company at the end of the eighteenth century. ai y e " e t Observatories of the first rank were established at Madras in of meteoro- 1796, at Simla in 1840, at Bombay in 1841, and on the 1( ?& ical Dodabetta Peak (Nilgiris) in 1847.

The observatories at tion and Simla and Dodabetta were closed after a few years' work, but inquiry in those of Bombay and Madras have been continued until the present time and have furnished most valuable series of observations. Observations (chiefly of temperature and rain- fall) were also taken at many hospitals, but in many cases these were carelessly recorde^l and are of little scientific value. The progress of meteorological inquiry in England, and its utilization for the purposes of storm warning after the Crimean War, suggested the commencement of systematic meteorological observation in India.

Isolated and independent Meteorological Departments were started by four of the Provincial Governments -in Bengal in 1865, in the United Provinces in

1864, in the Punjab in 1865, and in the Central Provinces in

1868. The Bengal Meteorological Department was initiated chiefly for the purpose of conveying warnings to the port of Calcutta ; the other three for supplying information to the local medical authorities, in the hope thafcit might enable them to trace out the relations between weather and disease. These local departments were of some service in collecting meteoro- logical data, but they were found to be of little use for the investigation of the larger phases and changes of weather in India. The Government of India accordingly decided to im- penalize the system, and sanctioned the necessary arrangements for the extension of the work of observation to the whole of India,for the adoption of uniform met hods of observation, and for Present the systematic discussion of the observations as a whole. The tion^oHhe I" 1 ? 6 *" Department thus formed was placed under the control

Meteoro- of a scientific officer with full powers to carry out the sanctioned logical reforms. This change was effected in 1874-5, and the present ment. system has thus been in operation for thirty years. At the end of 1902 the following observatories were in existence :

A magnetic and meteorological observatory at Bombay (of the first rank). A solar physics, magnetic, and meteorological observatory at Kodaikanal, on the Palni hills in Southern India (of the first rank).

An astronomical and meteorological observatory at Madras (of the first rank). A central meteorological observatory (of the first rank) at Calcutta (Alipore), where all instruments are tested before

issue and their corrections to the India standards deter- mined.

231 meteorological observatories (of the second and third rank) maintained by the Government of India or by Native States working in co-operation with the Govern- ment. Twenty-three of these are mountain observatories situated at elevations exceeding 5,000 feet, the highest being those at Leh in Kashmir (elevation 11,503 feet), at Kyelang (10,087), and the (Shaur Peak (11,200) in the Punjab.

2,390 rain-gauge stations, recording and reporting rainfall only.

The gazetted staff of the Department includes in addition to its head, who is Director-General of Indian observatories the Directors of the Kodaikinal and Colaha observatories and the First Assistant Meteorological Reporter to the Government of India (all of whom are whole-time officers) ; the Provincial Meteorological Reporters at Allahabad, Bombay, Calcutta, and Madras, of whom the three latter issue Provincial Daily Weather Reports ; and an Assistant Meteorological Reporter in charge of the Alipore central observatory. The five officers last mentioned are half-time officials, who hold other appoint- ments in the Educational or Telegraph departments ! .

For many years the Indian region, including India proper, India not Burma, the Arabian Sea, and the Bay of Bengal, was considered JJJ^J** as an independent meteorological area, in which the weather logical was supposed to be determined chiefly, if not solely, by the area - conditions within that area. It was assumed that India was protected on the north by the lofty barrier of the Himalayas, and on the west by the moderately high range of the Sulaimans, from the cold winds coming from northern regions, and that it was only exposed to the influence of equatorial sea currents.

The presence of this northern mountain barrier does un- doubtedly exercise a very considerable influence on the meteorology of India and more especially of the Indo-Gangetic plain ; for a comparison of the temperature data of Northern India with those of the south and centre of the United States in the same latitudes indicates that the intervention of the Hima- layas increases the temperature of the Indo-Gangetic plain from 3 to 5 above what it would have been if a low-level plain had extended northwards to the Arctic regions. Nevertheless, as will be seen later on, meteorological conditions in India generally are very largely determined by outside influences.

The physiographical and geographical features of India are Physio- of great importance, in so far as they modify more or less futures considerably the lower air movement, and hence the distribution of India, of temperature, pressure, humidity, and rainfall ; and it is necessary to bear them in mind in any scientific discussion of the meteorological conditions and actions of that country.

India is the middlemost of three great Asiatic peninsulas which project southwards into the Indian Ocean, and which are more or less dependent on that ocean for their broader meteorological features. It t consists of a peninsula proper (to the south of latitude 22 N. or the Tropic of Cancer), and of a broad low alluvial plain the axis of which runs east and west.

1 KoU by Editor. The constitution and present efficiency of the Indian Meteorological Department are due mainly to two men who have successively been at its head Mr. H. F. Blanford and Sir John Eliot, K.C.I.E., the Utter of whom has contributed the material for the present chapter.

The Peninsula is of comparatively low elevation and has a backbone of hills, near the west coast, from which the land slopes slowly eastwards 1 . To the north of the Peninsula is the low plateau of Central India, gradually falling to the ex- tensive Indo Gangetic plain, which nowhere rises, except in the immediate neighbourhood of the hills, above 800 feet.

To the north of this extensive plain is the lofty continuous barrier of the Himalayan mass, the central axial range of which averages over 20,000 feet in elevation. Farther north is the elevated Tibetan plateau, an extensive area 2,000 miles in length from east to west and 200 to 500 miles in breadth from north to south, averaging over 10,000 feet in altitude.

The continent thence falls northwards by a succession of slopes to the Arctic Ocean, to which it presents a vast low unbroken plain similar in general character to that of the corresponding plain in North America. Any general air movement on the Tibetan plateau would, if it extended into the plains of Northern India, have to rise 10,000 feet and then be preci- pitated in cascade form over the Indian hills.

There is no evidence of any such general movement in the lower atmo- spheric strata. Actual observations indicate that the air motion over the Western Himalayas is mainly an interchange between the hills and plains due to local actions and conditions, and is not the continuation of general air movements over Central Asia, or the Indian Ocean and its two arms, the Arabian Sea and the Bay of Bengal. Any such general air movement is confined to the middle and higher atmospheric strata.

Again, the north-west frontier of India proper consists of a series of hill ranges running north and south, forming the escarpment of a plateau stretching westwards for at least 1,000 miles into Western Persia. The average elevation of these ranges north of Jacobabad is at least 6,000 feet, and of the greater part of th

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