摘要：1. Introduction The Second Japanese Antarctic Expedition, which was held during the Antarctic summer 1957-58, failed to establish the relief to Syowa Base;thus the Base was left unoccupied since 14th February, 1958 until 15th January, 1959, when 3 rd expedition succeeded in sending a new wintering team. The major cause of the failure of the 2 nd expedition was due to the unfortunate weather and ice conditions. In this report the results of the meteorological analysis related to the operation of the expedition are given. The meteorological observations were made every three hours on board m/s Soya throughout her voyage. The fundamental data, taken at the Antarctic region, are given in the appendix of this report. Weather charts were prepared twice a day for the synoptic hours of 0600 z and 1200 z. This work was performed mainly by three meteorologists, who were the ship's crew, being assisted by four meteorologists of the expedition, who were appointed as wintering members. 2. Characteristic features of the weather experienced in the 2 nd expedition Brief summaries of the weather experienced on board Soya in the 2nd expedition are given in Table 1. It is obvious that Soya met remarkably worse conditions in this expedition than in the previous Ost) expedition. Through the synoptic analysis, it is concluded that the area around Li.itzow-Holm Bay was apt to be infested with cyclones in the early summer, corresponding to the stationary existence of the anticyclonic ridge covering Enderby Land. The ridge prevented the eastward movement of circum-polar cyclones, deviating their directions to SE or SSE and drawing them into Li.itzow-Holm Bay. Soya then encountered frequent storms on the way to Syowa Base, when she was crossing the packice zone. Tracks of cyclones in the early summer are given m Fig. 2, comparing with those of the previous year. As is seen in the sequence chart, Fig. 3, the weather became much improved in the latter half of the summer, but the ice conditions affected by the stormy weather in the early summer remained unfavourable and prevented us from establishing the relief to the Base in spite of the powerful cooperation of U.S. Navy icebreaker, "Burton Island'' . 3. Weather situations corresponding to the stages of the operation With respect to the development of the operation, the period is expediently divided into several stages, as is seen in Table 2, for each of which the summarized weather situation is given. 4. Stormy weather from 14 th to 20 th December, 1957 A cyclone had generated at 54° S, 25°E along the westerly trough on 14th December and moved east developing rapidly. Corresponding to the development of the cyclone, the anticyclonic ridge extended northward covering Enderby Land and the pressure gradient became sharp at the Antarctic coastal region from 30°E to 50°E (Fig. 4). Moreover another well-developed cyclone proceeded from the South Atlantic Ocean into the above area on 1 8 th, and the stormy weather succeeded for a week from 14th to 20th, when Soya was sailing south traversing the South Indian Ocean. The stormy weather prevented Soya from assembling the Beaver aeroplane which was to be used for the ice reconnaissance flight of a wide area. Soya was thus obliged to meet ice neither knowing the accurate distribution of pack-ice nor finding any lead in it. As far as we could observe on board Soya or with short flights by helicopters, the north edge line of the closed pack-ice was much undulated this year, while it was almost a straight line in the previous year as is seen in Fig. 6. Such an irregular distribution of this year seems to be caused by the very local but strong gale accompanied with a secondary depression which had generated off Prince Olav Coast on 15th. The existence of this secondary depression is certified by the sequence chart of Syowa Base as is seen m Fig. 5. Unfortunately Soya dashed into the dosed pack-ice at a point where the ice edge projected north, and she had to try to cross the pack-ice zone at its widest portion. 5. Severe storm from 31st December to 1st January A cyclone which had been moving east along the latitude 66° 8 developed rapidly after it crossed 20°E meridian and theradius of storm was estimated as about 650 km at 0600 GMT 1 st January. Then the cyclone, being obstructed by the anticyclonic ridge east of Enderby Land, turned its course toward SE and proceeded into Liitzow-Holm Bay, where it broke up into several centers filling gradually (see Fig. 7). As is listed m Table 3, Soya met a north easterly gale which continued for two days and the heavy hammocked ice paralysed her in the midst of the closed pack-ice. 6. Storm on 9th-12th January A cyclone 1s generated at the east of Sandwich Island on 4th January and moved ESE developing gradually. The cyclonic activity reached its maximum at 60° S, 2 °W on 6th morning. Then the cold front occluded and the cyclone became a type of upper cold vortex, turning its course toward SSE. At that time the polar anticyclone increased in its intensity covering Enderby Land and a powerful ridge was formed centering around 50°E meridian. Then the pressure gradient between the ridge and the cyclone became so sharp that the severe storm set upon over Liitzow-Holm Bay (see Fig. 8 and Table 4). This storm gave a fatal blow to the operation. When the storm was over on 12th afternoon, Soya was found to be completely stuck in the hammocked ice field, the diameter of which was estimated over 60km, and it became clear that Soya would not be able to approach Syowa Base on the prearranged date. 7. Succession of storms from 27 th to 30th January Liitzow-Holm Bay and the whole neighbourhood was attacked by three successive moderate cyclones from 27th to 30th January. General pressure pattern was similar to the case of foregoing sections 4 and 5. According to the strengthened meridional circulation, the cyclone took southerly or southeasterly courses and stagnated in the Liitzow-Holm Bay, decaying there (see Figs. 9, 10 and Table 5). Prior to the attack of cyclones, the ice field around Soya had showed a sign of dissociation and Soya had been trying to escape from the -ice, but, the storms accompanying the cyclones ·caused the escape to be delayed for at least 4 days. On the other hand, successive north- ·easterly gales brought Soya, together with the surrounding ice, to the west of Point Cook, where the coherence of ice floe became loose according to the divergent motion of wind and ·Ocean current. Thus Soya could recover her ·Own ability and be released from ice on 6th February. 8. Weather on 12th-14th February Having been released from ice, Soya tried again -to approach Syowa Base under the support of " Burton Island ", but, it was all that she could ,do to find a runway on the polar fast ice at -the distance of 144 km from Syowa Base. And the rescue of the wintering learn was performed by air transport on 10th and 11 th, and 3 members of the relief party were sent to the Base on 12th morning. These operations were favoured by the comparatively improved weath- . er. Although a weak Antarctic front existed stationarily along the coast line, ceiling and visibility,vere enough for the flights. But the weather was getting worse on 12th with the approach of a small depression which had been generated along the Antarctic front (see Fig. 11), and the air transport was obliged to be stopped m the afternoon. The depression brought a moderate storm lasting 2 days. Then, Professor NAGATA, the leader of the expedition, decided to suspend the operation under following judgement of existing circumstances. 1) Stable weather, needed for the establishment of the relief by air, seemed to be hopeless for days ahead. 2) The open lead, in which Soya and Burton Island were anchored, was becoming narrow and it might be dangerous to stay there pending the recovery of the weather. 3) The decrease of the temperature wasting near. 4) If the ship should be stuck in ice at the present position, the escape might be very difficult. 5) It was bet to escape from ice without delay and to make another attempt of air transport from the open water outside the pack ice zone. According to the above judgement, Soya and Burton Island took action to escape from the ice as soon as the 3 members were taken back to Soya by plane on the evening of the 14th. 9. Weather at the last stage of the operation A cyclone, which was generated in the vicinity of Boubet Island on 16th February, turned its course to SE at about 55° S, 15°E pointing to Liitzow-Holm Bay rapidly developing. Soya, having get away from ice area on 17 th, tried to retire to the northern sea to let the cyclone go past. Yet, she met severe storm on 19 th-20th as is seen m Table 6 and Fig. 12. She retired as far as 62° S, 43 °E, then sailed back to the ice edge line on 24th February to reopen the air transport. But unfortunately the sea surface was so rough that the plane could not start out. Thus all the attempts ended in failure and the relief was given up. The inspection of the recording paper of the automatic climatological station, which had been left at the unoccupied Base and was withdrawn by the 3 rd expedition, indicates that it was almost calm and fair· ·weather on 22nd and 23 rd February as is seen m Fig. 13, when Soya was retiring to north. It is a matter for regret that the above two favourable days could riot be utilized for the operation. If Soya1st and 2nd expeditions, we have learned that the so-called Antarctic front is apt to be formed along the pack-ice line off Liitzow-Holm Bay. With respect to the mechanism of the front, following cases can be pointed out: 1) Occlude front remains after the filling of cyclones, which had proceeded into LiitzowHolm Bay from northern sea and stagnated there. 2) When the outbreak of the Antarctic continental airmass occurs and gradually weakens, the forgoing airmass gets warm and moist at the relatively warm sea surface, changing m characteristic to the transitional airmass. Then the boundary of the succeeding fresh airmass and· the forgoing transitional one becomes distinct with the weakening of the outbreak, finally forming a front. In almost all the cases the contrast of the weather at the both side of the front is conspicuous;i. e. at the north side of the front the sky is usually covered with lower cloud often with some precipitation and reduced visibility, while at the southside the cloudiness is much less and visibility better. Tables 7 and 8 give the comparison between the cloud amount observed at Syowa Base, south side of the front, with that observed on board Soya, operating at the north side of the front. Such a condition reduces the air operation from the pack-ice zone to Syowa Base crossing the Antarctic front. In rare case, when the anticyclonic ridge extends over Queen Maud Land after the passage of a well-developed cyclone, the sky is clear at the pack-ice zone. But such a condition can not last more than 24 hours, after when the weather becomes gloomy by the formation of Antarctic front. 11. A,erial operation and weather In the 2nd expedition, air transport was the only way to coniact Syowa Base. The activity of the airplane was reduced not only by weather but also by the runway condition. Although our Beaver plane was equipped with floats and skis it was difficult to find either open water or an ice floe wide enough for a take-off run. As IS seen in Table 9, the actual flights were made at the utmost possible limit as far as the weather and the runway condition permit. The last flight, made on 14th February to rescue 3 members, was carried out under the worst conditions. On that day the visibility was less than 2 km and the ceiling was about 200 meters and the plane flew skimming the top of ice-bergs, being troubled by white out. 12. Drift of pack-ice by wind Soya, stuck in the closed pack-ice, was drifted to WSW for about 3e,weeks. The relation between the drifted course and the correspondent wind vector is researched by using the accurate position determined by astro fixing. As is seen in Table 10 and Fig. 15, the deviation angle is 20°..,40° left to the wind direction, as IS expected from EcKMANN's law, and the wind coefficient 0. 02..,0.03. The only exception is the case on 14th January, when the wind direction was WSW reverse to the ocean current. But it is corrected to a possible value if the effect of the ocean current is considered as is seen in Fig. 16. Here the ocean current is estimated from the preceeding two day's average wind vector. As a whole it resulted that the deviation angle is calculated to be 16° and the wind coefficient 0.023. 13. The rate of recession of ice edge in midsummer Throughout of this expedition, the north edge line of the closed pack-ice was ascertained 3 times at the almost same longitude; 1. e. on 8 th, 18th and 24th February as is seen in Fig. 17. The rate of recession of the ice edge line is calculated to be 1. 2 km/ day; had not retired so far from the ice edge but waited for a chance near the ice edge, the relief flight would have been successful and the Base would have been able to be manned for one year ahead. 10. On the Antarctic front in the vicinity of Liitzow-Holm Bay Through the . remarkable and a coat of new ice was observed ·. to be forming over the lead;autumn was get.
