76 



NATURE 



[August 19, 1920 



odd numbers are usually not utilised), but no one 

 thinks that an accuracy of ii^"^ is thereby claimed, 

 and everyone knows that the exposure of the anemo- 

 meter and the turbulence of the wind cause larger 

 variations with space and time than ii^^. The scale 

 1-72 was adopted for the following reasons : Nearly 

 all the observations of wind in the upper air are made 

 by theodolites graduated in degrees and read to tenths 

 of a degree (or exceptionally to minutes). The direc- 

 tion, of the upper wind is obtained in degrees. Divi- 

 sion of the number so obtained by 5 leads to the 

 scale 1-72. It is much simpler than division by \i\, 

 which would lead to the scale 1-32. Moreover, the 

 variation of wind direction with height cannot be 

 indicated with sufficient precision by a scale 1-32. 

 Also, the general practice in scientific work is to 

 specify directions m degrees, and the practice is 

 extending both at sea and in the air. The scale 1-72 

 is the most precise two-figure scale which is readily 

 converted into degrees. 



Whatever method is used for obtaining wind direc- 

 tion at the surface, the result can be telegraphed in 

 the scale 1-72 without difficulty; if only the eight 

 principal directions (N., N.E., E., etc.) are used, 

 then only the corresp>onding numbers of the scale 

 (72, 9, 18, etc.) will be used. 



(3) Prof, van Everdingen objects to the use of 

 two figures for reporting "weather." The need 

 for an .extension of the existing one-figure code 

 has been apparent for a long time. A meteoro- 

 logist at headquarters requires from a reporting 

 station sufficient information to enable him to 

 say with precision and certainty what the weather 

 was at the station at the tim€ of report. With 

 the pre-war code for international exchange this was 

 not done. A few drops of rain or a little drizzle 

 were reported by the same figure as the most torren- 

 tial downpour. A few flakes of snow or some fine ice- 

 crystals w^ere reported by the same figure as the 

 heaviest snowstorm. No figure was provided for hail 

 or sleet, and no indication given of the thickness of 

 a fog (in past weather). A sky nearly covered with 

 thin, white clouds at 20,000 ft. or 30,000 ft. was 

 described by the same figure as the darkest, gloomiest 

 day of the year. All this was due to the restriction 

 of the pre-war code to one figure. It was not due 

 to failure on the part of pre-war meteorologists to 

 recognise the phenomena which ought to be recorded 

 and the need for differentiation of intensity. Trac- 

 tically the whole of the phenomena for which provi- 

 sion is 7nade in the ninety-five figures of the code of 

 Annexe G are included in the '' hydrometeors " for 

 which provision was made in Appendix I. of the 

 fourth meeting of the Internahiorial Meteorological 

 Congress at Vienna in 1874. Annexe G merely makes 

 provision for reporting by telegram, at the time when 

 it is of direct use, the information which the Con- 

 gress at Vienna arranged should be written down 

 and reported in monthly returns for later scientific 

 investigation. As to the observer being puzzled, there 

 will alwavs be some occasions when he is required 

 to use intelligence in deciding which number to 

 select, whether the single-figure pre-war code is in 

 use or the fuller two-figure code. The difficulty is 

 minimised for him in Annexe G by arranging that all 

 occasions on which precipitation occurs shall be 

 reported by a number greater than 50. We have 

 not found in actual practice the troubles which Prof, 

 van Everdingen fears. 



The severest criticism is directed against the in- 

 clusion of detailed codes in the Convention. Holland 

 signed the International Convention for the Safety of 

 Life at Sea in 19 14; that Convention included detailed 

 codes for meteorological reports. Meteorology is 



NO. 2651, VOL. 105] 



more vital to the safety of life in the air than even 

 ice reports to the safety of life at sea. The latter 

 were made obligatory in 1914. 



No one questions the competence of the Inter- 

 national Meteorological Committee to fix the details 

 of a code. That Committee must be in substantial 

 agreement on the details of any code before it can 

 be made generally obligatory. But at present the 

 urgent need is for the trial of a scheme by the 

 nations of Western Europe which is capable of being 

 extended to the whole globe. The scheme of Annexe G 

 is the only one in the field which provides both the 

 general forms for meteorological messages and the 

 detailed specifications necessary' for reports to be made 

 and interpreted in the confidence that their meaning 

 is clear and definite, and that the information which 

 they contain meets the present needs of an organised 

 meteorological service. * E. Gold. 



8 Hurst Close, N.W.4,'July 25. 



(i) Col. Gold is not too well informed about the 

 history of the International Meteorological Com- 

 mittee. The introduction of improvements in the 

 reports and codes has often given rise to animated 

 discussions ; for example, when barometric tendency 

 was introduced. It is true that the opponents re- 

 mained friends, and that the minority co-operated in 

 carrying out the resolutions, but that was a reason 

 not to insist upon the introduction of a resolution 

 which had been adopted bv 7 votes against 6. 



(2) There is at present no unity in European 

 meteorology ; it is no use to quarrel about who dis- 

 turbed it; discussion of various systems by a com-, 

 petent body is the only way to restore it. 1 am very 

 glad that the British weather reports for aerial naviga- 

 tion have modified already part of the codes of 

 Annexe G. This certainly is a step towards reconcilia- 

 tion. 



(3) The minutes of the meeting of members of the 

 pre-war International Meteorological Committee held 

 in London in July, 1919, at which both Col. Gold 

 and I were present, contain a collection of codes 

 almost identical with that of Annexe G. Col. Gold is 

 right when he says that Annexe G was not discussed 

 then, but that makes very little difference. 



(4) Every standard station can report cloud motion 

 or pilot-balloon observations. I am glad to state that 

 cloud motion has now been introduced in regular 

 British reports. 



(5) The reading of the theodolite is accurate enough, 

 but the direction of upper wind derived from the 

 results is, in general, not accurate to less than 10°. 

 A scale 1-36 is used in Holland and elsewhere. For 

 scientific use a more accurate indication may be 

 useful ; for practical purposes it is useless. 



(6) I only object to the way in which the two 

 figures are combined for reporting weather; exten- 

 sion of the space for description of weather is wel- 

 come. 



(7) My remarks referring to numbers to be used 

 by observers in reporting phenomena are based on 

 the practice we actually have had with the British 

 reports. 



(8) Annexe G can have its trial at the present moment 

 if the Powers who signed it care. There are several 

 other systems and codes being tried bv various coun- 

 tries, and when these have had their course we shall 

 be in a better position to decide what the present 

 needs of an organised meteorological service are and 

 how thev can be met. E. van Everdingen. 



Koninklijk Nederlandsch Meteorologisch 

 Instituut, De Bilt, August 9. 



