Characteristics of surface water at Weather Ship J 333 



function, such as sound speed or surface conccntraiion of dissolved oxyyen. CDuld be 

 shown in the same manner by including the appropriate family of isopleihs. 



For lack of information, the accuracy of the observations is not discussed here. 



The frequency distribution in Fig. 1 is self-evident, but some aspects are note- 

 worthy. There is no apparent correlation between temperature and salinity at 

 Weather Ship J. The frequency distribution of salinity is symmetric, but those of 

 temperature and specific-volume anomaly are very asymmetric. 



The peak frequency of temperature occurs near the minimum temperature. This 

 pattern reflects the annual variation, which has a blunt minimum and a sharp maxi- 

 mum. Presumably the explanation is to be found, at least in part, in the deep, per- 

 sistent winter mixed layer of large heat capacity in contrast with the shallow, change- 

 able summer mixed layer. 



The two-dimensional frequency distribution contains a suggestion of a waist at 

 middle temperatures and of a secondary peak at higher temperatures. Whether 

 these features will remain if the series is extended over more years is uncertain. 



It seems likely that the pattern of annual frequency distribution of water tempera- 

 ture at Weather Ship J is characteristic of a large region in middle latitudes, but some 

 very different patterns can be expected for other regions. As found by HhssfcLBhRG 

 (1943, p. 14), SiPLE (1949-1952), and Feussner (1952, Abb. 4), the annual frequency 

 distributions of air temperature at some land stations in middle latitudes show a 

 rather symmetric bimodal pattern. 



The annual frequency distribution of temperature is an economical expression 

 of the temperature climate and might well be used more widely. The three references 

 above are the only ones the author has found that employ this method. 



The extreme range of temperature in the present series is 7-9 C,* while thediff'erence 

 in mean temperature between the warmest and coldest month is only 4-5 C. The 

 frequency of temperatures below IOC and above 15 C, hence outside the range of 

 0-5-C classes containing monthly means, is 17 per cent. It is clear that monthly 

 mean temperatures, which are often the only statistics presented in climatological 

 summaries, give but a faint picture of temperature conditions. 



A welcome departure from the usual adherence to monthly means is off"ered by 

 several series of oceanic Monthly Meteorological Charts published by the Meteoro- 

 logical Office, London. These charts include upper and lower 5-percentiIe isotherms 

 of both air and water temperature, based on 2-degree quadrangles. The preparation 

 of these charts must have entailed compiling further statistics that would be of 



interest if published. 



The temperature-salinity diagram is but one of the oceanographic and meteoro- 

 logical class that has been called characteristic diagrams (Montgomery, 1950). 

 all of which would be suitable for the representation of frequency distributions. 



Acknowledgements— The author wishes to lecord his benefit and pleasure from 

 discussing this subject with Mr. John D. Cochrane, Mr. Arnold Court, and Dr. 

 John B. Leighly. 



* With access to all data, Frankcom (1954) reports the extremes at Station J as maximum 17-8 C 

 and minimum 7-8 C. 



REFERENCES 



Brooks C E P and Carrutmrs, N. (1953), Handbook of statistical methods in meteorology. 

 London, Her Majesty's Stationery Office, M.O. 538, 412 pp. 



