Summertime stratospheric wind measurements above the South Pole

Observations of the mean wind flow and wave motions in the stratosphere at the South Pole are presented. The atmospheric motions are determined from the tracking of a high altitude, zero-pressure balloon launched from Amundsen-Scott Station during the austral summer of 1985–1986. The balloon position was precisely monitored by an optical theodolite for a large portion of the flight so that small scale motions could be resolved. The mean flow above the pole was approximately 3ms⁻¹. Atmospheric motions characteristic of internal gravity waves were observed with an intrinsic period of approximately 4.5 h and vertical and horizontal wavelengths of approximately 2.5km and 125km, respectively. The horizontal perturbation velocity of the observed waves was large compared to the mean horizontal flow velocity. The implication is that wave motions play a dominant role in the transport of stratospheric constituents in regions where the mean winds are light, such as over the South Pole during austral summer.     

极北之地

<正>北极,地球最后的边疆。在人们的想象中,北极地区天寒地冻,万物萧条,其实,早在一万多年前,人类就已经踏上这片极寒之地,与冰雪为伴,繁衍生息,在环境恶劣的北极地区,人类渺小而卑微,每一次狩猎都是冒着生命危险去和大自然讨生活。北极有着非常独特而美丽的自然景观,还有古老的生物圈,他们从远古走来,绽放着美丽、野性和智慧。美丽的极光,从天际划过,婀娜多姿,吸引着无数人到北极赴一场极光之约。     

Interannual fluctuations of the stratospheric temperature over the north polar region

The monthly means for the years 1964–1991 of 30 hPa temperatures over the North Pole and averaged over the 70–90°N region are analyzed. A multiple regression model is used to find long-term monthly trends and possible linear associations between these temperatures and the QBO, ENSO, and the 11-yr solar cycle. The model's residuals are examined for detection of other periodic interannual fluctuations in Arctic temperatures.It is found that the interannual variations of temperature at 30 hPa over the Arctic are a superposition of the oscillations due to the QBO, ENSO, the 11-yr solar cycle, and approximate 6-yr periodic fluctuations of unknown origin. The QBO, ENSO, and the solar cycle effects in the Arctic temperature explain about 35% of the total variance of the temperature monthly anomalies. In winter, the QBO, ENSO, and the 11-yr solar cycle signals in the temperature data depend on the phase of the equatorial QBO. The polar vortex seems to be warmer (colder) than normal when the West (East) phase of the equatorial QBO in a period of high solar activity. The monthly temperature trends over the Arctic show seasonal variations with positive trends in February and March. The year-round trends (sum of the monthly trends) are about −0.5 K per decade.     

Long-term tropospheric and lower stratospheric ozone variations from ozonesonde observations

An analysis is presented of the long-term mean pressure latitude seasonal distribution of tropospheric and lower stratospheric ozone for the four seasons covering, in part, over 20 years of ozonesonde data. The observed patterns show minimum ozone mixing ratios in the equatorial and tropical troposphere except in regions where net photochemical production is dominant. In the middle and upper troposphere, and low stratosphere to 50 mb, ozone increases from the tropics to subpolar latitudes of both hemispheres. In mid stratosphere, the ozone mixing ratio is a maximum over the tropics. The observed vertical ozone gradient is small in the troposphere but increases rapidly above the tropopause. The seasonal variation at a typical mid latitude station (Hohenpeissenberg) shows a summer maximum in the low to middle troposphere, shifting to a winter-spring maximum in the upper troposphere and lower stratosphere and spring -summer maximum at 10 mb. The amplitude of the annual variation increases from a minimum in the tropics to a maximum in polar regions. Also, the amplitude increases with height at all latitudes up to about 30 mb where the phase of the annual variation changes abruptly. The phase of the annual variation is during spring in the boundary layer, summer in mid troposphere, and spring in the upper troposphere and lower stratosphere. The annual long-term ozone trends are significantly positive at about + 1.2% yr in mid troposphere (500 mb) and significantly negative at about − 0.6% yr¹ in the lower stratosphere(50mb)     

Large scale coherence of the mesospheric and upper stratospheric temperature fluctuations

A large set of temperature profiles has been obtained in the upper stratosphere and the mesosphere over Europe during the MAP/WINE compaign by the use of different techniques: datasondes and falling spheres launched by metrockets, ground-based OH spectrometers and a Rayleigh lidar. These data have been used to study the large scale variability of the middle atmosphere during the winter 1983–1984. The temperature variations with periods longer than 25 days are clearly related to the succession of minor upper stratospheric warmings observed during this winter. The variations in the period range 10–20 days are at least partially due to westward propagating Rossby waves, of which one mode, with a 12.5 days period, is tentatively identified as the second symmetric mode of the wave number 2.     

Balloon observations of stratospheric electricity above the South Pole: vertical electric field,conductivity, and conduction current

This paper summarizes the results of measurements of the electrical conductivity σ and vertical component of the vector electric field E_z acquired from eight stratospheric balloon flights launched from Amundsen-Scott Station, South Pole, in the austral summer of 1985–1986. The major findings of this research are as follows

• 1.(1) The data contribute to the set of global atmospheric electricity measurements and extend the work of COBB [(1977), Atmospheric electric measurements at the South Pole. In Electrical Processes in Atmospheres, Dolezalek H. and Reiter R. (eds), pp. 161–167. Steinkopf, Darmstadt, F.R.G.] to determine the electrical environment of the south polar region
• 2.(2) The average vertical profile of the conductivity at the South Pole, when compared with profiles obtained at other Antarctic locations, suggests that the conductivity scale height may increase with increasing geomagnetic latitude across the polar cap.
• 3.(3) The conductivity profiles measured at the South Pole and other Antarctic locations differ significantly from polar cap model profiles. On the basis of these measurements, the model profiles appear to require modification
• 4.(4) The magnitudes of the E_z profiles were observed to vary from day-to-day by a factor of > 2
• 5.(5) In all of the flights the air-Earth conduction current J_z, calculated as the product of E_z and σ, decreased with altitude in agreement with previous direct measurements of the air-Earth current by Cobb [( 1977), Atmospheric electric measurements at the South Pole. In Electrical Processes in Atmospheres, Dolezalek H. and Reiter R. (eds), pp. 161–167. Steinkopf, Darmstadt, F.R.G.]
• 6.(6) The magnitude of J_z was 2–3 times larger than the global average, which can be attributed to the lower columnar resistance of the atmosphere above the high-elevation Antarctic plateau. The magnitude of J_z agrees with that observed by Cobb, if the Cobb measurements are multiplied by the Few and Weinheimer [(1986), Factor of 2 error in balloon-borne atmospheric conduction current measurements. J. geophys. Res.91, 10937] correction factor of 2
• 7.(7) E_z from all of the flights during times of balloon float demonstrates characteristics of the classical ‘Carnegie’ diurnal variation, which is indicative of global influences on the ionospheric potential
• 8.(8) The influence of geomagnetic activity was observed as a decrease in the amplitude of the diurnal variation of E_z with increasing geomagnetic activity index K_p, which is the predicted effect at the South Pole of the magnetospheric polar-cap potential superimposed on the ‘Carnegie’ potential variation.

     

Pole to Pole. Archaeology and Adaptation in the Middle Pleistocene at Opposite Ends of the Acheulean World

The concept of cultural evolution in the Acheulean is linked to a number of important anatomical, phylogenetic, adaptive, cultural and cognitive research questions. Yet there are very few studies which are able to demonstrate advancements in material culture (technological and/or conceptual) supported by large bodies of empirical data. Derek Roe's work at Olduvai Gorge is one of the few exceptions and here, in my opinion, raw material considerations affect the evidence of increasing diachronic sophistication (Leakey and Roe 1994). Otherwise, evidence for such material culture evolution is largely anecdotal. This study takes large bodies of handaxe data from South Africa and Britain, and using dated assemblages, wherever possible, explores the idea of hominins paying increasing attention to shape and morphological regularity (not symmetry) over time. The results give no reason to believe such a diachronic trend exists. These data are set against the latest research in chronostratigraphic studies and hominin taxonomy.     

Temperature dependences of stratospheric aerosol extinction at a tropical station

Characteristics of aerosol extinction in lower stratospheric altitudes over a tropical station are studied using the ruby lidar data at Trivandrum (8°55′N, 77°E) for the period 1986–1987. The integrated stratospheric aerosol extinction as well as the aerosol extinction at fixed altitudes in this region showed a significant negative correlation with tropopause temperature. This is attributed to tropospheric convective activity. Though the direct correlation between ambient temperature and aerosol extinction is insignificant at these altitudes, the partial correlation eliminating the influence of tropopause temperature becomes increasingly significant at altitudes far from the tropopause. This indicates the increasing influence of stratospheric microphysical processes at higher altitudes, that is, near the altitude of stratospheric aerosol peak.     

Upper stratospheric and mesospheric temperatures derived from lidar observations at Aberystwyth

From lidar observations of relative atmospheric density above Aberystwyth (52.4°N, 4.1°W) upper stratospheric and mesospheric temperatures have been derived for a total of 93 nights between December 1982 and February 1985. Excellent agreement was found between radiances synthesised from these temperatures and those measured by satellite-borne instruments. Summer temperatures showed a smooth and regular variation with altitude and reasonably good agreement with the CIRA (1972) model atmosphere. By contrast, winter temperatures showed a much greater variability with altitude and greater changes from night to night, with the frequent occurrence of a large amplitude wave-like perturbation in the mesosphere with about 15 km vertical wavelength and amplitude about 20K between 60 and 80 km.Pronounced warmings of the stratosphere were observed during the three winters of observation. During the warming event occurring in early February 1983 the stratopause temperature increased to 303K at 43 km, while the major warming event of late December 1984/early January 1985 produced a stratospheric temperature gradient of 16K km⁻¹ between 34 and 36 km. During the latter event a distinct local temperature minimum at 32.6 km was observed on New Year's Eve, this descending to 29 km by the following night and being accompanied by a lowering of the stratopause from 43 to 38.5 km in the same period. These results demonstrate the ability of the present technique to resolve the high stratopause temperatures and steep stratospheric temperature gradients which occur during stratospheric warmings, in marked contrast to the limited resolution achieved by satellite experiments.     

"南方丝绸之路"上发现的"立杆测影"文物

"立杆测影"是最古老的天文观测仪器之一,古代"南方丝绸之路"地区诸多遗址中出土了若干可能是"立杆测影"文物的遗物。其中包括三星堆遗址出土的青铜神树、羊首龙柱、公鸡杖首、太阳神鸟、牙璋等;盐源县出土的青铜树、羊首虎杖、青铜鸡杖等;云南石寨山出土贮贝器上的"表柱"、贵州汉墓出土的青铜树连枝灯、伏羲女娲石刻、广西苗族的"盘龙表柱等。这些"立杆测影"文物都与"树、龙、鸟、虎、羊"等动物标志性图像有密切关系。     

First low-power VHF radar observations of tropospheric,stratospheric and mesospheric winds and turbulence at the Arecibo Observatory

First VHF radar measurements with height resolution of 300 m and angular resolution of 1.7° were carried out in low latitudes at the Arecibo Observatory, Puerto Rico. A short outline is given of the experimental set-up which consisted of a 160W average power radar-transceiver and a self-contained digital radar control and data acquisition unit. The new VHF feed system of the Arecibo dish is described shortly. Reliable radar echoes were detected from the troposphere, lower stratosphere and from some heights in the mesosphere, indicating that the described VHF radar is capable of proper investigations of dynamical processes in the low latitude middle atmosphere. The angular dependence of aspect sensitive tropospheric and stratospheric turbulence structures was measured to be 1.5–2.5 dB degree⁻¹. Echoes from the mesosphere indicate a patchy structure of turbulence. The analysis of the signal-to-noise ratio shows considerably high reflectivity in the upper troposphere, which can be caused by high-reaching tropical cumulus convection. Wind profiles measured with the VHF radar between 7.5 and 19.5 km with a height resolution of 300m are very similar to radiosonde wind profiles. Mesospheric VHF radar winds are roughly consistent in amplitude with tidal winds.     

行止第三极

“西藏,一块孤独的石头坐满整个天空,没有任何夜晚能使我沉睡。”每次读海子的《西藏》,总能感受到西藏遗世独立的纯净,却充满让人热血沸腾的力量。在众多热爱户外的人心中,西藏正是这样一个魂牵梦萦之地。他们说,“西藏是最好的户外天堂”,不单单因为它的高远纯净,还因为它能够唤起本能的热情。     

Balloon measurements of stratospheric ion conductivities over the tropics

Conductivity measurements of negative and positive ions were made from about 20 to 35 km by two identical balloon-borne spherical probes at Hyderabad (17.5°N, 78.6°E), India on 22 April 1989 and 22 December 1990. One balloon was launched at 0158 h IST (Indian Standard Time) which reached its ceiling around 0330 h IST. After that time, it floated for about 3 h, 1.5 h before sunrise and 1.5 h after sunrise. Thus it gave data for both day- and night-time conditions at float altitude. The other balloon was launched at 0535 h IST. It gave data for daytime only. Several interesting results have been obtained at the float altitudes. During the night, in the flight of 22 April 1989 the conductivity values of positive ions were found to be about 1.5 times those of negative ions at the float altitude. During the day, in the flight of 22 April 1989, the positive ion conductivity values were found to increase with the increase of solar elevation angle at around 37.5 km altitude. The negative ion conductivity values, however, did not show any day-night variation. In the flight of 22 December 1990, these features were not seen. Instead, a pocket was found where conductivity values were very high (of the order of 10⁻¹¹ mho m⁻¹) at an altitude of about 32.5 km. Also in this flight, the positive ion conductivity was always found to be approximately equal to that of the negative ion conductivity.     

珠穆朗玛峰——世界巅峰第三极

正在漫长的岁月中,人类对自己生存的空间产生过各种遐想。大地有尽头吗?它是方的还是圆的?为什么日、月、星辰总是东升西落?为什么会有四季变化等等。从1492年,哥伦布首航发现美洲大陆开始,人类进入了地球地理发现的时代,这个阶段持续了400年。到20世纪初期,地球上的所有地方都被绘制在地图上,其中有3个地点虽然被人所知,但没有人去过。它们就是被称为极地的"北极""南极"和地球上的最高点——珠穆朗玛峰(以下简称珠峰)。     

Long-term developments in complex hunter-gatherer societies: Recent perspectives from the pacific coast of North America

The Pacific coast of North America is ideally suited to the study of long-term developments in complex hunter-gatherer societies. This paper synthesizes current research in California and the Northwest Coast on three related research problems. The first concerns the timing, spatial distribution, and economies of the earliest coastal peoples in the region. The second problem involves the growth and florescence of complex Pacific hunter-gatherer societies. What constitutes archaeological evidence of hunter-gatherer complexity, when and where it occurs, and the interpretations proposed to account for it are reviewed. The final problem addresses how complex hunter-gatherer peoples responded to European exploration and colonization, and how these early encounters affected the Pacific coast societies recorded in early ethnohistoric accounts and later studied by ethnographers.     

Modelling of ozone reduction by stratospheric aircraft

Using a two-dimensional model of the atmospheric circulation and composition, different scenarios of the effects of stratospheric aircraft on ozone layer destruction were calculated. It is shown that the ozone loss depends strongly on the altitude and composition of engine emissions from high-speed civil transport aircraft. The inclusion in the two-dimensional model of the effects of chemical eddies results in significantly reduced ozone losses in the high latitudes of the northern hemisphere during wintertime, when the dynamics of the stratosphere are strongly disturbed by planetary waves. This result can be connected with the increase of stratosphere/troposphere exchange.