XII. Some anomalies in the winds of Northern India, and their relation to the distribution of barometric pressure

Abstract

In the 13 years which have elapsed since Mr. Blanford published his paper on the Winds of Northern India, very great additions have been made to our knowledge of the meteorology of the country. The carefully organised system of observations, commenced in Bengal and the North-Western Provinces, has been extended to include the whole of India, and placed under the direction of Mr. Blanford himself, aided by local officers in all the larger provinces. Verified instruments have been supplied to all the stations, and the elevations of these above sea-level have been determined by connecting them with the lines of spirit-levelling, carried inland from the coast, in various directions, by the officers of the Great Trigonometrical Survey; or, where this was impracticable, by spirit-levelling to some of the trigonometrical stations of the Survey. In this way, trust worthy and intercomparable series of barometric observations, extending over ten years or more, have been obtained for all the more important stations. At the same time, the diurnal variations of the barometer at certain selected stations have been determined by long-continued series of hourly observations, with the object of enabling us to reduce the readings made in the ordinary way (usually at 10 a. m. and 4 p. m.) to time daily means. Simultaneously with the collection of this immense quantity of accurate and reliable barometric data, observations have been made of temperature, humidity, cloud, wind, and rain. Latterly also barometric and wind charts of the Bay of Bengal have been prepared from observations made on board ships navigating those waters. During these 13 years, the winds prevailing over the Indian continent and the Bay of Bengal, and their relations to the distribution of pressure at sea-level, have been discussed from time to time, both in their normal aspects for each month or season and in their abnormal or disturbed conditions during the passage of storms. The latter conditions in particular have been very fully described by Mr. Eliot in his numerous reports on cyclones in the Bay of Bengal, while the former have been noticed in the annual reports on the meteorology of India, in occasional papers appearing in the ‘Indian Meteorological Memoirs,' and latterly in a broad and general review in Mr. Blanford’s great monograph on the Rainfall of India.