The Formation of Hurricanes in the South Pacific and the Outbreaks of Cold Air from North Polar Region

[摘要] The purpose of this paper is to bring out, largely by means of observational material, outstanding features concerning the formation of hurricanes in the south Pacific. Because these data were few, fairly marked hurricanes had to be chosen for study, so that a sufficient number of observations might be obtained within one and the same hurricane. While the conclusions reached may have been influenced by this particular selection of cases, it is believed that the results are generally applicable.Now take up the storminess of the south pacific, longitude 160°E to 140°W, by island groups. It will be seen that the hurricane season(1)extends from December to April, inclusive. During this five month period about 90-95 per cent of the recorded storms have occurred. After making conservative allowance for the incompleteness of the record, and counting all gale-producing storms, not only true hurricanes, it appears that on the average fully a dozen tropical cyclones occur annually in the south Pacific.Tropical storms form most frequently in the south Pacific when the thermal equator is farthest south. The season when they are most frequent occurs during the winter and the early spring of the northern Hemisphere. The outbreaks of the cold air from the morth polar region move southward and surge against the Equatorial Front in the southern Hemisphere. But it is the opinion of the author that the hurricane in the south Pacific do not show any warm sector at the surface to the south of the hurricane. On account of the distribution of land and sea over the surface of the earth, both northern and southern air masses generally arrive at the Equatorial Front after a long journey over water. Both masses are there fore warm and humid in the surface layer.The occurrence of the outbreak of cold waves in the north Pacific from China to Kamtchatka inclusive is considered in Table 1. It is based on the data obtained from the weather maps analysed by the Central Meteorological Observatory, Tokyo, Japan.Table 1. Annual Frequency of Cold Waves in the North Pacific 1933-1939. The cold wave season extends from December to April, inclusive. During this five-month period about 20 cold waves have occured. After making allowance for the imcompleteness of the record of hurricanes in the south Pacific and the completeness of the record of cold waves in the north Pacific, it appears probable that the formation of hurrjcanes in the south Pacific is somewhat related to the outbreak of cold waves in Siberia.Utilizing this method for the hurricane in the south Pacific of the 8th to the 12th February, 1932, in which(2) there are appropriate data, a marked outbreak of cold air from the north polar region which moved southward and surged against the Equatorial Front in the southern Hemisphere is proved. The results are generally applicable for the hurricane of the 27th December, 1932, to 5th January, 1933, (1)and the hurricane of the 28th January to the 3rd February, 1936.(2)The work of S. Li(3)shows that the formation of typhoons in the North Pacific is somewhat related to the outbreak of cold waves in Australia. The conclusions stated above agree with that Li had to say regarding the formation of tropical cyclones in 1936.

[学科分类] 大气科学