Latitudinal and longitudinal oscillations of cloud features on neptune

Voyager observations suggest that three of Neptune's major cloud features oscillate in latitude by 2 degrees to 4 degrees and that two of them simultaneously oscillate in longitude by 7.8 degrees and 98 degrees about their mean drift longitudes. The observations define most convincingly the two orthogonal oscillations of the second dark spot (near 53 degrees south). These oscillations have similar periods near 800 hours and approximately satisfy a simple advective model in which a latitudinal oscillation produces a phase-shifted longitudinal oscillation proportional to the local wind shear. The latitudinal motion of the Great Dark Spot can be fit with an oscillation period of about 2550 hours, whereas its dominant longitudinal motion, if oscillatory at all, has such a long period that it is not well constrained by the Voyager data.     

Large-scale variations in the obliquity of Mars

Large-scale variations in the obliquity of the planet Mars are produced by a coupling between the motion of its orbit plane due to the gravitational perturbations of the other planets and the precession of its spin axis which results from the solar torque exerted on the equatorial bulge of the planet. The obliquity oscillates on a time scale of approximately 1.2 x 10(5) years. The amplitude of this oscillation itself varies periodically on a time scale of 1.2 X 10(6) years. The present-day obliquity is approximately 25.1 degrees. The maximum possible variation is from about 14.9 to 35.5 degrees. Signtificant climatic effects must be associated with the phenomenon.     

Twentieth-Century Sea Surface Temperature Trends

An analysis of historical sea surface temperatures provides evidence for global warming since 1900, in line with land-based analyses of global temperature trends, and also shows that over the same period, the eastern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, is not reproduced by the complex ocean-atmosphere circulation models currently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations.     

Venus: topography revealed by radar data

Surface height variations over the entire equatorial region on Venus have been estimated from extended series of measurements of interplanetary radar echo delays. Most notable is a mountainous section of about 3-kilometer peak height located at a longitude of 100 degrees (International Astronomical Union coordinate system). The eastern edge has an average inclination of about 0.5 degrees, which is unusually steep for a large-scale slope on Venus. The resolution of the radar measurements along the surface of Venus varied between about 200 and 400 kilometers with a repeatability in altitude determination generally between 200 and 500 meters. The mean equatorial radius was found to be 6050.0+/-0.5 kilometers.     

Stratospheric Mean Ages and Transport Rates from Observations of Carbon Dioxide and Nitrous Oxide

Measurements of stratospheric carbon dioxide (CO2) and nitrous oxide (N2O) concentrations were analyzed to investigate stratospheric transport rates. Temporal variations in tropospheric CO2 were observed to propagate into the stratosphere, showing that tropospheric air enters the lower tropical stratosphere continuously, ascends, and is transported rapidly (in less than 1 month) to both hemispheres. The mean age A of stratospheric air determined from CO2 data is approximately 5 years in the mid-stratosphere. The mean age is mathematically equivalent to a conserved tracer analogous to exhaust from stratospheric aircraft. Comparison of values for A from models and observations indicates that current model simulations likely underestimate pollutant concentrations from proposed stratospheric aircraft by 25 to 100 percent.     

Length-of-Day Variations Caused by El Nino-Southern Oscillation and Quasi-Biennial Oscillation

Two prominent interannual atmospheric fluctuations, the El Ni?o-Southern Oscillation in the troposphere-ocean system and the Quasi-Biennial Oscillation in the equatorial stratosphere, account for most of the observed interannual length-of-day (LOD) variation from 1964 through 1987, with a relative contribution of about 2 to 1. Thus the atmosphere-LOD connection extends from seasonal and shorter periods to interannual periods up to about 10 years.     

Mariner 9 celestial mechanics experiment: gravity field and pole direction of Mars

Analysis of the Mariner 9 radio-tracking data shows that the Martian gravity field is rougher than that of Earth or the moon, and that the accepted direction of Mars's rotation axis is in error by about 0.5 degrees . The new value for the pole direction for the epoch 1971.9, referred to the mean equatorial system of 1950.0, is right ascension alpha= 317.3 degrees +/- 0.3 degrees , declination delta = 52.6 degrees +/- 0.2 degrees . The values found for the coefficients of the low-order harmonics of Mars's gravity field are as follows: J(2)=(1.96+/-0.01)x10(-3), referred to an equatorial radius of 3394 kilometers; C(22) = -(5 +/- 1) x 10(-5); and S(22) = (3 +/- 1) x 10(-5). The value for J(2) is in excellent agreement with the result from, Wilkins' analysis of the observations of Phobos. The other two coefficients imply a value of (2.5 +/- 0.5) x 10(-4) for the fractional difference in the principal equatorial moments of inertia; the axis of the minimum moment passes near 105 degrees W.     

Temperatures, winds, and composition in the saturnian system

Stratospheric temperatures on Saturn imply a strong decay of the equatorial winds with altitude. If the decrease in winds reported from recent Hubble Space Telescope images is not a temporal change, then the features tracked must have been at least 130 kilometers higher than in earlier studies. Saturn's south polar stratosphere is warmer than predicted from simple radiative models. The C/H ratio on Saturn is seven times solar, twice Jupiter's. Saturn's ring temperatures have radial variations down to the smallest scale resolved (100 kilometers). Diurnal surface temperature variations on Phoebe suggest a more porous regolith than on the jovian satellites.     

Recent volcanism and the stratosphere

In the quiet years after the 1956 eruption of the Bezymianny volcano in central Kamchatka, it is doubtful that any volcano vented into the stratosphere until the 1963 eruptions of Agung (Bali), Trident (Alaska), and Surtsey (Iceland). From 1963 to the Hekla (Iceland) event in May 1970, two latitudinal belts of volcanoes have ejected ash and gases into the stratosphere. One belt is equatorial and the other is just below the Arctic Circle. The latter, where the tropopause is considerably lower, may have been the principal source of replenishment of volcanic dust and gases to the stratosphere. Submarine and phreatic volcanic eruptions may have been the sources of reported increase of water vapor in the stratosphere.     

Deep current measurements suggest long waves in the eastern equatorial pacific

During the 1975 El Ni?o expedition an array of conventional and electric field type near-bottom current recorders was deployed at the equator 300 kilometers west of the Galápagos Islands. While hydrographic observations were indicating El Ni?o activity off the South American coast, the current meters recorded an oscillation with a 25-day period, a wavelength of about 1000 kilometers, and an amplitude of 0.04 meter per second propagating westward at approximately 0.5 meter per second. These characteristics agree with theoretical models of a first-mode baroclinic Rossby wave trapped at the equator.     

Reduced interannual rainfall variability in East Africa during the last ice age

Interannual rainfall variations in equatorial East Africa are tightly linked to the El Ni?o Southern Oscillation (ENSO), with more rain and flooding during El Ni?o and droughts in La Ni?a years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall.     

Spin-polarized resonant tunneling in magnetic tunnel junctions

Insertion of a thin nonmagnetic copper Cu(001) layer between the tunnel barrier and the ferromagnetic electrode of a magnetic tunnel junction is shown to result in the oscillation of the tunnel magnetoresistance as a function of the Cu layer thickness. The effect is interpreted in terms of the formation of spin-polarized resonant tunneling. The amplitude of the oscillation is so large that even the sign of the tunnel magnetoresistance alternates. The oscillation period depends on the applied bias voltage, reflecting the energy band structure of Cu. The results are encouraging for the development of spin-dependent resonant tunneling devices.     

Thermal contrast in the atmosphere of venus: initial appraisal from pioneer venus probe data

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.     

Eleven-year variation in polar ozone and stratospheric-ion chemistry

A mechanism for producing an 11-year oscillation in ozone over the polar caps is the modulation of galactic cosmic rays by the solar wind. This mechanism has been shown to give the observed phase in ozone oscillations and the correct qualitative dependence on latitude. However, the production of nitrogen atoms from cosmic-ray collisions seems inadequate to account for the ozone amplitude. Negative ions are also produced as a result of cosmic-ray ionization, and negative-ion chemistry may be of importance in the stratosphere. Specifically, NO(x)(-) may go through a catalytic cycle in much the same fashion as NO(x), but with the important distinction that it does not depend on oxygen atoms to complete the cycle. Estimates of the relevant rates of reaction suggest that negative ions may be especially important over the winter polar cap.     

Interannual variability of temperature at a depth of 125 meters in the north atlantic ocean

Analyses of historical ocean temperature data at a depth of 125 meters in the North Atlantic Ocean indicate that from 1950 to 1990 the subtropical and subarctic gyres exhibited linear trends that were opposite in phase. In addition, multivariate analyses of yearly mean temperature anomaly fields between 20 degrees N and 70 degrees N in the North Atlantic show a characteristic space-time temperature oscillation from 1947 to 1990. A quasidecadal oscillation, first identified at Ocean Weather Station C, is part of a basin-wide feature. Gyre and basin-scale variations such as these provide the observational basis for climate diagnostic and modeling studies.     

来宾近56年来气温变化特征

[目的]分析1957～2012年来宾气温变化规律。[方法]采用来宾地面气象站的近56年气象观测资料,运用一元线性回归、M-K突变、小波分析等方法,对近56年来宾气温变化特征进行了分析。[结果]近56年来宾气温呈明显升高趋势,2000年以后升温显著;年平均最高气温、平均气温、平均最低气温分别上升0.36、0.68、1.07℃;四季气温上升速率从高到低依次为秋季、冬季、夏季、春季,夏秋季的气温升高趋势相对较明显;气温气候突变的时间发生在2000年左右;年平均最低气温对气候变暖的响应最明显;气温的振荡周期主要为4、13年2个时间尺度;2012年气温振荡周期处于升高末期至降低初期。春、夏、秋季气温振荡周期分别以4、23、8年为主,冬季无明显振荡周期。2012年春夏秋季气温均处于升高期。     

近31年来西安垂直温度变化特征

选取1981～2011年西安地温、气温、高空温度的观测资料,采用气候倾向率估算法、Mann-Kendal突变检验法等方法,分析20世纪90年代的平均温度倾向率垂直变化,计算各层年较差,总结地温320 cm～高空20hPa的年、季节温度变化特征.结果表明,气温的变化直接影响到地温、对流层中下层温度变化,接近地面的浅层地温和对流层下层年、季温度变化趋势与气温一致,随着地温深度和对流层高度的增加影响逐渐变小,平流层下层温度变化与气温相反;近年来,温室效应带来的影响主要表现在对流层中下层,20世纪90年代为近地层温度较为活跃的时期;地温-气温-对流层中下层温度突变时间依次有所提前,对流层顶及平流层下层突变年比较分散;春季、秋季垂直温度的变幅较大,冬季和年垂直温度的变幅较小,夏季垂直温度的变幅最小;地温320 cm～高空250 hPa夏季温度高于冬季,200 ～ 50 hPa等压面夏季温度低于冬季,在50 hPa等压面上没有明显的季节区分.     

Long-Term Mean Vertical Motion over the Tropical Pacific: Wind-Profiling Doppler Radar Measurements

Measurement from Christmas Island (2 degrees N, 157 degrees W) of long-term mean vertical motions in the tropical atmosphere using very-high-frequency wind-profiling Doppler radar show that there is a transition from downward motion in the free troposphere to upward motion in the upper troposphere and lower stratosphere. The observations in the free troposphere are consistent with a balance between adiabatic and diabatic heating and cooling rates in a clear atmosphere. Comparison of the results at Christmas Island during El Ni?o and non-El Ni?o conditions with earlier results obtained for stratiform rain conditions over Pohnpei, Federated States of Micronesia, show that cirrus clouds in the vicinity of the tropopause likely play an important role in determining the sense and magnitude of vertical motions in this region. These results have implications for the exchange of mass between the troposphere and stratosphere over the tropics.     

Early meteorological results from the viking 2 lander

Early results from the meteorological instruments on the Viking 2 lander are presented. As on lander 1, the daily patterns of temperature, wind, and pressure have been highly repetitive during the early summer period. The average daily maximum temperature was 241 degrees K and the diurnal minimum was 191 degrees K. The wind has a vector mean of 0.7 meter per second from the southeast with a diurnal amplitude of 3 meters per second. Pressure exhibits both diurnal and semidiurnal oscillations, although of substantially smaller amplitude than those of lander 1. Departures from the repetitive diurnal patterns begin to appear on sol 37.     

Decadal variation of the surface water PCO2 in the western and central equatorial Pacific

The equatorial Pacific Ocean is one of the most important yet highly variable oceanic source areas for atmospheric carbon dioxide (CO2). Here, we used the partial pressure of CO2 (PCO2), measured in surface waters from 1979 through early 2001, to examine the effect on the equatorial Pacific CO2 chemistry of the Pacific Decadal Oscillation phase shift, which occurred around 1988 to 1992. During the decade before the shift, the surface water PCO2 (corrected for temperature changes and atmospheric CO2 uptake) in the central and western equatorial Pacific decreased at a mean rate of about -20 microatm per decade, whereas after the shift, it increased at about +15 microatm per decade. These changes altered the CO2 sink and source flux of the equatorial Pacific significantly.