HYDROLOGY OF THE SOUTH ATLANTIC 235 



APPENDIX 



THE WINDS OF THE ATLANTIC OCEAN 

 SOUTH OF 40° S 



By Lieut. R. A. B. ARDLEY, R.N.R. 



The accompanying table is compiled from the meteorological logs of the Research 

 ships 'Discovery', 'William Scoresby', and 'Discovery H', and checked from the 

 Meteorological Charts of the South Atlantic. In that publication, the data given for 

 latitudes south of 45° S are very meagre, since no trade route lies across the higher 

 latitudes of the South Atlantic. The data extracted from the logs of the three ships of 

 the Discovery Committee, covering a period of seven years, give a good general 

 analysis of wind conditions. A favourable indication of the accuracy of the final average 

 is that though each ship's observations were extracted and compiled separately, the 

 resulting averages for latitude agreed fairly well. 



The only other possible source of information concerning oceanic winds in the high 

 latitudes of the South Atlantic would be the logs of the whaling factories voyaging to 

 and from the ice-edge ; but in the writer's opinion the averages here given are reliable 

 and would merely be confirmed by further information. The wind forces are measured 

 on the Beaufort Scale. 



The relatively high average westerly wind force between the parallels of 40 and 50° S 

 is maintained by the almost constant prevalence of fresh to strong breezes in these 

 latitudes. Between 50 and 60' S, the wind forces are generally more erratic. The region 

 with the highest percentage of gales lies between 45 and 55° S. 



The data obtainable are insufficient for compiling an average for easterly winds. Within 

 the latitudes under consideration, easterly winds are usually erratic and of short 

 duration; they blow either as light winds or as brief, violent gales. 



In measuring the average force of the westerly winds all winds with a westerly com- 

 ponent are taken into account, for it is found that winds from the north-west and south- 

 west quadrants are fairly evenly balanced. Almost all the region north of latitude 55° S 

 lies within the northern semicircles of depressions, and the normal wind sequence, 

 subject to minor variation, is north-west, west, south-west. 



South of latitude 55^ S, it will be seen that the percentage of easterly winds grows 

 steadily greater. Probably at the Antarctic Circle the easterly and westerly winds are 

 about balanced, and, south of that, easterly winds would predominate. 



All the observations collected here were made in spring, summer and autumn, but in 

 this great stretch of ocean it is doubtful if the winter winds would show any large 

 deviation from the average. No account is taken of the ice conditions, though probably 

 when the pack is far north a slightly higher percentage of easterly winds and calms 

 would be found. 



