110 MR ROBERT C. MOSSMAN ON THE METEOROLOGY OF 



Cloud amount is still very large over the Weddell Sea, but over Antarctic areas, 

 where the temperature has fallen, skies are clearing. 



In April, pressure has risen everywhere except in the south of the Bellingshausen 

 Sea. The most marked rise is over Graham's Land, over which there is an area of 

 relatively high pressure, dividing the low-pressure systems located to the east and west 

 respectively. In these low-pressure systems the strength of the wind reaches its 

 annual maximum, this being especially the case in the south of the Bellingshausen Sea, 

 where the prevailing easterly winds blow with great force. Indeed, atmospheric 

 conditions are everywhere very disturbed, and especially so in the South Atlantic 

 and the vicinity of Cape Horn. The only marked exceptions to this are to be 

 found over Graham's Land and at Dungeness, where the infrequency of gales 

 is remarkable. 



There is in this month a decided tendency for the winds to veer. Thus at the South 

 Orkneys south-west winds are at their annual maximum, and at South Georgia, Staten 

 Island, and the Falklands the prevailing north-west winds are reduced in favour of 

 west and south-west. On the other hand, at Dungeness, Evangelists Island, and 

 Sandy Point northerly and north-east winds, which are infrequent for these places, have 

 increased, and are at their annual maximum for the two first-mentioned stations. 

 Temperature is now falling rapidly, the fall being greatest at the southern continental 

 stations and least at oceanic stations in the south of South America. At places such as 

 Sandy Point and Ushuaia, which are not specially under oceanic influences, the fall of 

 temperature is also considerable. In this month the isotherms begin to assume their 

 winter shape, and the amount of cloud shows a decided diminution north and south of 

 60° S. lat., where the mixture of warm and cold air currents is most apparent. At 

 Ancud, Point Gallera, and Isle Mocha the increase in rainfall is considerable, the 

 precipitation being four times that of January — the driest month of the year. 



In May, the outstanding feature of the isobaric chart is the reappearance of the 

 Antarctic high in a pronounced form in the south of the Bellingshausen Sea and adjacent 

 continental regions. The south-east wind, although here still the strongest, has greatly 

 diminished in force, and this reduction is shared by winds from other directions. Areas 

 of low pressure are shown m the South Pacific and over the Weddell Sea. North-east 

 winds are virtually absent at Wandel Island, which appears to be more under the 

 influence of the high- than of the low-pressure area. 



South of 60° S. the temperature has fallen from 6° to 8°, the fall being greater 

 on the eastern than on the western side of Graham's Land. At the South American 

 and Island stations the fall is from 3 to 5 degrees, and is greatest, as in the previous 

 month, at places removed from the direct influence of the sea. The mean temperature 

 has fallen to zero F. a little to the south-east of Snow Hill, owing to the continental 

 conditions there prevailing and the northerly extension of the pack. On the other hand, 

 on the Pacific side of Graham's Land, where the oceanic iufiuence is considerable, much 

 higher temperatures prevail. Cloud has very generally diminished, the cloudiest zone 



