404 



NA TURE 



[August 25, 1904 



detail by various weather bureaus, and as at present with- 

 out an)- co-ordination of the results of these bureaus. 



The discussion has also indicated that the south-west 

 monsoon current is a periodic or intermittent extension of 

 the permanent circulation of the south-east trades to the 

 peninsulas of Southern Asia, and also that variations in the 

 strength, volume, and direction of movement of the latter 

 aflect the extension, volume, aqueous vapour contents, and 

 precipitation of the south-west monsoon currents in Burma, 

 India, and Abyssinia. This fact further emphasises the 

 necessity for the co-ordination and systematisation of the 

 work of observation in the Indo-oceanic meteorological 

 province and the continuous and systematic examination 

 and discussion of observations for the whole of that area. 



It is, of course, possible that it may be necessary to extend 

 this work to a larger area than the Indo-oceanic region. 

 For Sir Norman Lockyer and Dr. Lockyer have shown that 

 similar pressure variations to those of Bombay occur over 

 a large portion of the Eastern Hemisphere, and variations 

 of opposite sign (similar to those of Cordova) over a con- 

 siderable part of the Western Hemisphere. 



The Indian Meteorological Department, with the sanction 

 ot the Government of India, is now arranging to collect 

 and tabulate data for the whole area between the Central 

 Asian winter anticyclone and the permanent South Indian 

 Ocean anticyclone, and to utilise the information for the 

 investigation of the causes of the large and general 

 variations of rainfall in Burma and India from year to 

 year. This extension of its labour is recognised as necessary 

 for the improvement of the seasonal forecasts, an important 

 feature of the work of the Department the value and im- 

 portance of which are fully recognised by the Government 

 of India. 



Possibly the practice of the Indian Meteorological Depart- 

 ment in the preparation and issue of long-period or seasonal 

 forecasts is considered to be not only unscientific, but not 

 justified by comparison with facts. Prof. Cleveland Abbe, 

 in his paper on " The Physical Basis of Long-range Weather 

 Forecasts," expresses his opinion that " we are warranted 

 in saying that during the thirteen years (iSSS-igoo) the 

 only real failure has been that of the prediction of the 

 monsoon season of i8go, the year of phenomenally great 

 drought in that country." This opinion is probably more 

 favourable than I should myself give, but it is the opinion 

 of an independent meteorologist eminently qualified to give 

 a judgment in the matter. 



My own opinion with respect to weather forecasts is that 

 there appears to be too strong a desire for absolute accuracy, 

 possibly due to public and newspaper criticism. Certainty 

 is not possible in weather forecasts based on imperfect in- 

 formation, and in which the introduction of a single un- 

 known factor in regions beyond observation — e.g., the upper 

 or middle atmosphere — may completely alter the course of 

 events. Percentages of success are an inadequate measure 

 of the utility of forecasts. To be of real value as estimates 

 of utility they should be calculated rather on the inform- 

 ation required, and which might be reasonably expected, 

 than on that actually given. 



It appears to me that the striving after perfection in 

 short-period forecasts to the exclusion of other claims is 

 impeding the extension and progress of meteorology in 

 other useful directions. It is absolutely essential that 

 officials preparing or utilising forecasts 'should recognise 

 that every forecast is based on imperfect information and 

 experience, and hence that all important forecasts should be 

 expressed as probabilities, and, whenever desirable, an 

 estimate of the value of each probability be given. 



The Government of India desires to' have these seasonal 

 forecasts, and has ordered its Meteorological Department 

 to furnish them. The Government encourages the work, 

 provides the additional means required bv the Department 

 for its proper performance, and issues the forecasts only 

 to those who will use them as probabilities for practical 

 guidance. 



The importance of the work of seasonal forecasting in 

 India may be judged from the following remarks : 



India is almost exclusively an agricultural country, with 

 a population of nearly 300 millions. The material prosperity 

 of practically the whole people is determined bv the amount 

 ;ind dislrihution of the periodic rains. The 'variations in 

 the amount and period of the rains are occasionally so 

 NO. 18 17, VOL. 70] 



great as to produce the most disastrous results in the staple 

 crops over large areas. In 1899, for example, the crops 

 failed more or less completely over an area several times 

 the extent of England. 



There is probably no country where the meteorological 

 problems, of which these rainfall variations form one 

 feature, are of greater interest or more practical importance. 

 The daily weather and rainfall reports are studied during 

 the greater part of the year with the closest attention by 

 the ofTicials, from the Viceroy downwards. 



The Government is hence keenly interested in meteor- 

 ological observation and investigation, and is most anxious 

 to improve its meteorological service and utilise it for 

 practical purposes, of which seasonal forecasting is one of 

 the most important. To give two examples. A reassuring 

 forecast at a critical period, followed by its realisation, 

 might be of the greatest value to the agricultural population 

 of a large province, as well as to the local and Imperial 

 Governments. Again, a statement or forecast the prob- 

 ability of which was, say, at least 10 to i that the rains 

 would fail more or less completely during a season over 

 a large area might enable the Government to carry out 

 early prudential measures for relief in the most economical 

 and effective manner with the means at its disposal. The 

 preparation and issue of seasonal forecasts will hence, I am 

 confident, be in the future, as in the past, one of the most 

 important duties of the Indian Meteorological Department. 



There are several points in connection with weather fore- 

 casting in India which it is desirable should be borne in 

 mind. The first is that weather in India is distinguished 

 rather by the massiveness, intensity, and persistence of 

 abnormal features than by the frequency and rapid succession 

 of important weather changes. It is chiefly on this account 

 that daily weather forecasts, even if they could be com- 

 municated with the necessary rapidity, are of no value to 

 the Indian agricultural population. Also, the empirical 

 knowledge of the significance of the important variations 

 as factors determining or indicating future weather accumu- 

 lates much more slowly than in Europe, and it is hence 

 doubly important that in India the empirical knowledge 

 derived from very limited experience should be, so far as 

 possible, regulated and controlled by theory and scientific 

 knowledge. It should also be remembered that there are 

 large differences between the meteorology of tropical and 

 temperate regions, and also between the relation of crops 

 to weather in India and England. The instincts, habits, 

 beliefs, education of the body of the people in England and 

 India also differ very widely. Hence the possibilities of the 

 practical applications of meteorological science in India 

 cannot be judged from the European standard, and may 

 from that standpoint be unique. 



The possibilities of usefulness of the work of seasonal 

 or long-period forecasting in India are almost unlimited. 

 To be acceptable and useful to the agricultural population 

 of areas liable to drought they should be fairly accurate 

 with respect to the dates of commencement and termination 

 of the periodic rains, their general character, and the prob- 

 able occurrence of prolonged breaks likely to be injurious 

 to the chief food crops. If the forecasts were found to be 

 fairly trustworthy in these respects, it is quite certain that 

 the agricultural population would value them and use them. 

 Indications of a growing belief in the utility and value of 

 this feature of the work of the Department by the people in 

 different parts of India are not wanting. 



The Government of India has sanctioned large changes 

 in its Meteorological Department in order to enable it to 

 carry out the extensions of work that recent experience 

 has shown to be desirable. The Department is kept in 

 touch with scientific opinion and judgment at home through 

 the Observatories Committee of the Royal Society. The 

 relations to other scientific departments in India are main- 

 tained by a special committee termed the Board of Scientific 

 Advice. The scientific staff has been largely increased. 

 The solar physics observatory at Kodaikanal and the 

 magnetic observatory at Bombay have been placed under 

 the Meteorological Department with a view to the complete 

 co-ordination of the departments of scientific investigation 

 for which they are maintained. Observational data for the 

 whole Indo-oceanic area are now being collected and tabu- 

 lated with a view to the early publication of daily and 

 monthly weather reports and charts of that area. 



