共查询到20条相似文献，搜索用时 15 毫秒
1.
Greeley R Schubert G Limonadi D Bender KC Newman WI Thomas PE Weitz CM Wall SD 《Science (New York, N.Y.)》1994,263(5145):358-361
Magellan images reveal surface features on Venus attributed to wind processes. Sand dunes, wind-sculpted hills, and more than 5830 wind streaks have been identified. The streaks serve as local "wind vanes," representing wind direction at the time of streak formation and allowing the first global mapping of near-surface wind patterns on Venus. Wind streaks are oriented both toward the equator and toward the west. When streaks associated with local transient events, such as impact cratering, are deleted, the westward component is mostly lost but the equatorward component remains. This pattern is consistent with a Hadley circulation of the lower atmosphere. 相似文献
2.
Alexandrov YN Crymov AA Kotelnikov VA Petrov GM Rzhiga ON Sidorenko AI Sinilo VP Zakharov AI Akim EL Basilevski AT Kadnichanski SA Tjuflin YS 《Science (New York, N.Y.)》1986,231(4743):1271-1273
From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled. 相似文献
3.
Seiff A Kirk DB Sommer SC Young RE Blanchard RC Juergens DW Lepetich JE Intrieri PF Findlay JT Derr JS 《Science (New York, N.Y.)》1979,203(4382):787-790
The four Pioneer Venus entry probes transmitted data of good quality on the structure of the atmosphere below the clouds. Contrast of the structure below an altitude of 50 kilometers at four widely separated locations was found to be no more than a few degrees Kelvin, with slightly warmer temperatures at 30 degrees south latitude than at 5 degrees or 60 degrees north. The atmosphere was stably stratified above 15 or 20 kilometers, indicating that the near-adiabatic state is maintained by the general circulation. The profiles move from near-adiabatic toward radiative equilibrium at altitudes above 40 kilometers. There appears to be a region of vertical convection above the dense cloud deck, which lies at 47.5 to 49 kilometers and at temperature levels near 360 K. The atmosphere is nearly isothermal around 100 kilometers (175 to 180 K) and appears to exhibit a sizable temperature wave between 60 and 70 kilometers. This is where the 4-day wind is believed to occur. The temperature wave may be related to some of the wavelike phenomena seen in Mariner 10 ultraviolet photographs. 相似文献
4.
Corbet PS 《Science (New York, N.Y.)》1969,166(3907):865-866
At latitudes north of the Arctic Circle the diel range of sun altitude declines progressively, reducing the frequency of temperature inversions over level, unshaded ground in summer and extending the frost-free season. North of about 70 degrees north, the potential number of inversion-free days increases rapidly with latitude; this ameliorates the microclimate close to the ground-the zone to which terrestrial organisms are increasingly restricted in higher latitudes. The relation between screen and ground-surface temperatures differs north and south of about 70 degrees north; north of that latitude there are progressively more frost-free days than would be inferred from screen temperatures, were no allowance made for this latitude-dependent change. 相似文献
5.
Zwally HJ Bindschadler RA Brenner AC Major JA Marsh JG 《Science (New York, N.Y.)》1989,246(4937):1587-1589
Measurements of ice-sheet elevation change by satellite altimetry show that the Greenland surface elevation south of 72 degrees north latitude is increasing. The vertical velocity of the surface is 0.20 +/- 0.06 meters per year from measured changes in surface elevations at 5906 intersections between Geosat paths in 1985 and Seasat in 1978, and 0.28 +/- 0.02 meters per year from 256,694 intersections of Geosat paths during a 548-day period of 1985 to 1986. 相似文献
6.
Radar observations of a narrow belt of the surface of Mars, centered at 16 degrees south latitude, show a very rugged terrain, with elevation differences greater than 13 kilometers from peak to valley. For nearby points, the relative altitude is measured to 40 meters at best; the precision is worse for points at different latitudes, or widely separated in longitude, because of orbital uncertainties. Some of the larger craters have been resolved, and their depth and, in some cases, the height of the raised rim have been measured. Where high resolution photographs, are available, the correlation is excellent. 相似文献
7.
基于1961~2010年山西62个测站逐日最低地温资料,分析了山西初霜冻变化特征,结果表明:(1)山西1961~2010年平均初霜冻日为10月7日;其分布总体表现为北早南晚,平均初霜冻日与海拔高度和纬度呈显著的负相关,相关系数分别为-0.85和-0.82。(2)M-K突变检验表明,山西近50年大部分站点的初霜日都有突变发生,主要集中在20世纪80~90年代,其分布表现为中部偏晚、北部和南部偏早的特征;突变年份与海拔高度和纬度均为负相关,相关系数分别为-0.45和-0.51。(3)大部分站点初霜冻日为推后趋势,推后幅度较大的地区集中在北部及中东部地区,提前较多的地区主要位于南部及中南部的部分地区;趋势变化与海拔高度和纬度均为负相关,相关系数分别为-0.30和-0.37。(4)轻微、中度和重度初霜冻出现的概率分别为:62%~82%、6%~26%和4%~22%,出现最大的区域分别为:中南部和东北部、中部和北中部、西部和北中部;海拔高度与不同等级初霜冻发生概率的相关都不大,纬度对初霜冻发生概率的影响都大于海拔高度。 相似文献
8.
Brune WH Toohey DW Anderson JG Starr WL Vedder JF Danielsen EF 《Science (New York, N.Y.)》1988,242(4878):558-562
In order to test photochemical theories linking chlorofluorocarbon derivatives to ozone(O(3)) depletion at high latitudes in the springtime, several related atmospheric species, including O(3), chlorine monoxide(ClO), and bromine monoxide (BrO) were measured in the lower stratosphere with instruments mounted on the NASA ER-2 aircraft on 13 February 1988. The flight path from Moffett Field, California (37 degrees N, 121 degrees W), to Great Slave Lake, Canada (61 degrees N, 115 degrees W), extended to the center of the polar jet associated with but outside of the Arctic vortex, in which the abundance of O(3) was twice its mid-latitude value, whereas BrO levels were 5 parts per trillion by volume (pptv) between 18 and 21 kilometers, and 2.4 pptv below that altitude. The ClO mixing ratio was as much as 65 pptv at 60 degrees N latitude at an altitude of 20 kilometers, and was enhanced over mid-latitude values by a factor of 3 to 5 at altitudes above 18 kilometers and by as much as a factor of 40 at altitudes below 17 kilometers. Levels of ClO and O(3) were highly correlated on all measured distance scales, and both showed an abrupt change in character at 54 degrees N latitude. The enhancement of ClO abundance north of 54 degrees N was most likely caused by low nitrogen dioxide levels in the flight path. 相似文献
9.
Campbell DB Jurgens RF Dyce RB Harris FS Pettengill GH 《Science (New York, N.Y.)》1970,170(3962):1090-1092
A radar interferometer was used to map unambiguously the surface reflectivity of Venus in the polarized mode at a wavelength of 70 centimeters. The observed region extended from 260 degrees to 30 degrees in longitude and from -60 degrees to 50 degrees in latitude with a surface resolution of approximately 3 degrees by 3 degrees . The result agrees well in most respects with earlier maps made elsewhere at shorter wavelengths and, in addition, discloses a number of new "features." 相似文献
10.
Knudsen WC Spenner K Whitten RC Spreiter JR Miller KL Novak V 《Science (New York, N.Y.)》1979,205(4401):105-107
Pioneer Venus in situ measurements made with the retarding potential analyzer reveal strong variations in the nightside ionospheric plasma density from location to location in some orbits and from orbit to orbit. The ionopause is evident at night as a relatively abrupt decrease in the thermal plasma concentration from a few hundred to ten or fewer ions per cubic centimeter. The nightside ion and electron temperatures above an altitude of 250 kilometers, within the ionosphere and away from the terminator, are comparable in magnitude and have a value at the ionopause of approximately 8000 K. The electron temperature increases from a few tens of thousands of degrees Kelvin just outside the ionopause to several hundreds of thoussands of degrees Kelvin further into the shocked solar wind. The coldest ion temperatures measured at an altitude of about 145 kilometers are 140 to 150 K and are still evidently above the neutral temperature. Preliminary day-and nightside model ion and electron temperature height profiles are compared with measured profiles. To raise the model ion temperature to the measured ion temperature on both day-and nightsides, it was necessary to include an ion energy source of the order of 4 x 10(-3) erg per square centimeter per second, presumably Joule heating. The heat flux through the electron gas from the solar wind into the neutral atmosphere averaged over day and night may be as large as 0.05 erg per square centimeter per second. Integrated over the planet surface, this heat flux represents one-tenth of the solar wind energy expended in drag on the sunward ionopause hemisphere. 相似文献
11.
Pioneer Venus orbiter dual-frequency radio occultation measurements have produced many electron density profiles of the nightside ionosphere of Venus. Thirty-six of these profiles, measured at solar zenith angles (chi) from 90.60 degrees to 163.5 degrees , are discussed here. In the "deep" nightside ionosphere (chi > 110 degrees ), the structure and magnitude of the ionization peak are highly variable; the mean peak electron density is 16,700 +/- 7,200 (standard deviation) per cubic centimeter. In contrast, the altitude of the peak remains fairly constant with a mean of 142.2 +/- 4.1 kilometers, virtually identical to the altitude of the main peak of the dayside terminator ionosphere. The variations in the peak ionization are not directly related to contemporal variations in the solar wind speed. It is shown that electron density distributions similar to those observed in both magnitude and structure can be produced by the precipitation on the nightside of Venus of electron fluxes of about 108 per square centimeter per second with energies less than 100 electron volts. This mechanism could very likely be responsible for the maintenance of the persistent nightside ionosphere of Venus, although transport processes may also be important. 相似文献
12.
Seiff A Kirk DB Young RE Sommer SC Blanchard RC Findlay JT Kelly GM 《Science (New York, N.Y.)》1979,205(4401):46-49
The altitude profiles of temperature and pressure measured during the descent of the four Pioneer Venus probes show small contrast below the clouds but significant differences within the clouds at altitudes from 45 to 61 kilometers. At 60 kilometers, the probe which entered at 59.3 degrees north latitude sensed temperatures 25 K below those of the lower latitude probes, and a sizable difference persisted down to and slightly below the cloud base. It also sensed pressure below those of the other probes by as much as 49 millibars at a mean pressure of 200 millibars. The measured pressure differences are consistent with cyclostrophic balance of zonal winds ranging from 130 +/- 20 meters per second at 60 kilometers to 60 +/- 17 meters per second at 40 kilometers, with evidence in addition of a nonaxisymmetric component of the winds. The clouds were found to be 10 to 20 K warmer than the extended profiles of the lower atmosphere, and the middle cloud is convectively unstable. Both phenomena are attributed to the absorption of thermal radiation from below. Above the clouds, in the lower stratosphere, the lapse rate decreases abruptly to 3.5 K per kilometer, and a superimposed wave is evident. At 100 kilometers, the temperature is minimum, with a mean value of about 170 K. 相似文献
13.
本文根据长白落叶松不同种源种子性状、苗期性状、7年生幼林性状共24个因子的观测数据,采用生物统计分析方法,系统研究了长白落叶松的地理变异规律及其引起变异的气候生态基础。结果表明:长白落叶松不同种源具有显著的遺传分化;幼林生长性状主要受纬度和海拔双重控制,表现为南部和低海拔种源较北部和高海拔种源生长快。同一地点不同海拔种源幼林生长性状变异显著,中、低海拔种源显著大于高海拔种源。落叶病感病性状主要受经度控制,至西向东病情加重。种子发芽率主要受经度和纬度双重控制,至西向东从高海拔向低海拔种子发芽率降低,长白落叶松性状地理变异具有明显的气候生态基础,影响幼林生长性状的主要气候因子是温度,影响种子性状的主要气候因子是光照和水分。 相似文献
14.
Jones WL Black PG Boggs DM Bracalente EM Brown RA Dome G Ernst JA Halberstam IM Overland JE Peteherych S Pierson WJ Wentz FJ Woiceshyn PM Wurtele MG 《Science (New York, N.Y.)》1979,204(4400):1413-1415
The Seasat microwave scatterometer was designed to measure, globally and in nearly all weather, wind speed to an accuracy of +/- 2 meters per second and wind direction to +/- 20 degrees in two swaths 500 kilometers wide on either side of the spacecraft. For two operating modes in rain-free conditions, a limited number of comparisons to high-quality surface truth indicates that these specifications may have been met. 相似文献
15.
Venus: mapping the surface reflectivity by radar interferometry 总被引：2，自引：0，他引：2
The surface reflectivity of Venus obtained by radar interferometry at a wavelength of 3.8 centimeters has been mapped for a region extending approximately from -80 degrees to 0 degrees in longitude (Carpenter's definition) and from -50 degrees to +40 degrees in latitude. The map is free from the twofold range-Doppler ambiguity because the interferometer fringe pattern makes possible the separation of two points of equal range and Doppler shift. The map presents many new features and clearly delineates features already observed. Most notably, the map shows large circular regions of significantly lower reflectivity than their surroundinigs. 相似文献
16.
17.
Ground-based observations of two conspicuous features near the north pole of Saturn, the polar vortex and the hexagonal wave structure, were made from July 1990 to October 1991, 10 years after their discovery. During this period the polar spot drifted in longitude, relative to system III, by -0.0353 degrees per day on average. Superimposed on this mean motion, the spot also underwent short-term rapid excursions in longitude of up to approximately 14 degrees at rates of up to approximately 1 degrees per day. The spot also exhibited irregular variations in its latitude location. A combination of these data together with those obtained by Voyager 1 and 2 in 1980 and 1981 shows that the spot drifted -0.0577 degrees per day for the 11-year interval from 1980 to 1991. The large lifetime of both features indicates that they are insensitive to the strong variations in the seasonal heating of the cloud layers in the upper polar atmosphere. 相似文献
18.
小崎齿瓢虫属 Afidentula Kapur 1955自建立以来,迄今该属共有14个种,其中包括我国云南省记载的一新种。本文在概括小崎齿瓢虫属的分类地位、种类及分布的基础上,讨论了小崎齿瓢虫属的区系,色斑类型等问题。列出了已知种的检索表,文后并附种的特征图。 相似文献
19.
《Science (New York, N.Y.)》1992,255(5043):383
Table 3 in the report "Latitudinal and longitudinal oscillations of cloud features on Neptune" by Lawrence A. Sromovsky (1 Nov., p. 684) contained errors. In column 4, the two values for inferred shear should have been -0.8 and -13.8 m/(s-deg), respectively. The corresponding text in column 1 on page 686 should have read, "the advection model is quantitatively upheld for the DS2 motions, but not for the short-period component of the GDS motions. They both agree on phase lags, although the GDS is not in good quantitative agreement on amplitudes. Relative to a smooth shear profile obtained from a simple polynomial fit to the observed wind speeds as a function of latitude (11), the shear derived from the advective model amplitude ratio is almost the same for DS2, but a ninth as large for the GDS." 相似文献
20.
2011年10月9日15时,于吉林市环志站6号网44°00’31.1″N,126°33’32.0″E,海拔221 m处捕获1只黄腹山雀(Parus venustulus)的离巢雏,其雏羽尚未换完,但已经显露出雄鸟的特征,其形态特征与《东北鸟类图鉴》中描述的基本一致。气候变暖、随机因素和鸟类调查研究的深入是吉林省鸟类新纪录增加的主要原因。 相似文献