A preliminary estimate of inertia effects in a bulk model of katabatic wind

Observed sastrugi orientations showed considerable deviation from a bulk theory of katabatic wind in lee sides of troughs in ice sheet undulations of which the wavelength is about 400km on the Mizuho Plateau, East Antarctica. The effect of the inertia term which may account for the deviations but is often neglected in the equation of motion for katabatic wind is estimated with the perturbation method. A sinusoidally undulating slope with ridges and troughs is assumed for the model calculation instead of an infinite flat slope for the inertiafree model. The calculated results, in a typical inversion, suggest that the inertia term is significant if the wavelength of the undulations is smaller than about 200km while the effect of the undulations can be neglected if the wavelength is smaller than about 50km. Observed variability in the wind direction in the lee of the troughs may be accounted for by the effect of the inversion height which enhances the inertia effect

ナンキョク ノ シャメン カコウフウ イキ ニオケル サスツルギ ヤ ドリフト ノ ショウモウ ニ ツイテ ニホン ナンキョク チイキ カンソクタイ ノ ホウコク

The observations were made on net ablation of some of sastrugi and drifts (like barchanoids) in the area subjected to strong katabatic winds between 100 and 200 km inland from the Antarctic coast near Syowa Station in September and November, 1969 and in January, 1970 by means of the stake measurements. The net ablation of hard sastrugi during the period from November to January (mean 2.8 cm/month) was larger than that from September to November (mean 0.7 cm/month). The large amount of ablation from November to January may be attributed to the increase of solar radiation which accelerates sublimation-deflation on the surface of sastrugi. On the other hand, net ablation of soft sastrugi and drifts from September to November was larger than that from November to January. The large amount of ablation from September to November may be attributed to the strong erosion by the wind, since sastrugi and drifts were soft. Since they were hardened or flattened after erosion by the wind from September to November, the ablation from November to January was not larger than that from September to November. Since the rate of ablation at the top of sastrugi and drifts was higher than that at the surrounding surface in late spring and summer, and the bulk of yearly accumulation is deposited in autumn and winter, it can be said that surface irregularities are supposed to be built up in winter, then smoothed in summer. The best season for yearly stake measurements is considered to be the end of summer when the more accurate value of mean net accumulation may be expected since surface irregularities are less than any other season. Gow (1965) and WELLER (1969) gave some explanation for the higher rate of net ablation of sastrugi than the surrounding surface at the South Pole and Plateau Station. However, since the area of this report is located where the katabatic winds are strong as mentioned above, the situation is different from their case. According to the logarithmic increase of wind velocity, the top of sastrugi is expected to be subjected to stronger winds, hence greater wind erosion, than the surrounding surface

ダイ 36ジ ナンキョク チイキ カンソクタイ ナツタイ ホウコク 1994-1995

第36次南極地域観測隊夏隊16名(上田観測隊長), ドイツの交換科学者1名および越冬隊40名(召田隊長, 石沢副隊長)は, 1994年11月14日「しらせ」にて東京港を出発し, フリーマントル寄港後, 12月24日昭和基地に接岸した。翌年1月12日までに, 約1070トンの物資輸送を終え, 2月14日まで昭和基地施設更新建設工事, 大型短波レーダー設置ほかの作業を行った。氷床ドーム深層掘削計画では, ドーム往復内陸旅行を実施し, ドームふじ観測拠点で第35次拠点建設班と合流, 完成した新拠点で1月29日から9名による初越冬を開始した。昭和基地とその近辺では潮汐・海潮流, 生物, 測地, 気球回収予備実験, リュツォ・ホルム湾周辺露岸域とリーセルラルセン山域では地殼形成過程に関する地質調査, 測地, 生物などの観測を実施した。また往路に引き続き帰路の船上で, 海洋物理・化学・生物, 地磁気ほかの観測をしつつシドニーに到着した。第36次夏隊は順調な成果をあげ, 第35次越冬隊とともに3月28日空路帰国した。The 36th Japanese Antarctic Research Expedition (JARE-36) consisted of 40 wintering members and 16 summer members with one atmospheric chemist from Germany. The icebreaker SHIRASE left Tokyo on November 14,1994,and arrived at Syowa Station on December 24 via Fremantle. All cargo of about 1070t was unloaded by January 12,1995. Constructions to replace old buildings and facilities at Syowa Station and for a large HF radar system and others were carried out by February 14. For the Deep Ice Coring Project at Dome Fuji, an oversnow traverse to/from the Dome Fuji Station (77°19′S, 39°42′E, 3810m a.s.l.) was performed; the first wintering at the new station was started by 9 members from January 29. Observations on geology, geodesy, biology and others were carried out around Syowa Station, Lutzow-Holm Bay and Riiser-Larsen Massif. Observations on physical, chemical and biological oceanography, geomagnetism and others were made through the voyage of the SHIRASE from Tokyo via Antarctica to Sydney. The summer party of JARE-36 returned together with the JARE-35 wintering party to Tokyo from Sydney by air on March 28 with satisfactory results