Around-the-World Atomic Clocks: Observed Relativistic Time Gains

Four cesium beam clocks flown around the world on commercial jet flights during October 1971, once eastward and once westward, recorded directionally dependent time differences which are in good agreement with predictions of conventional relativity theory. Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59 +/- 10 nanoseconds during the eastward trip and gained 273 +/- 7 nanoseconds during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks.     

种茎种植法及芽向对华南205木薯产量的影响

田间试验结果表明:种茎不同种植法对华南205木薯的产量及经济性状没有显著的影响,但平放种植法略优于斜插种植法;种茎芽眼方向对木薯的产量有显著的影响,鲜薯、薯干和淀粉产量均表现为芽眼向南>向东>向西>向北;当采用平放种植法时,木薯产量表现为种茎芽眼向南>向西>向北>向东;当采用斜插种植法时,产量表现为种茎芽眼向东>向南>向西>向北。因此,建议采用起垄、平放、种茎芽眼向南的木薯机械化种植技术。     

The Drift of Saturn's North Polar Spot Observed by the Hubble Space Telescope

Polar projections of 50 images of Saturn at 889 nanometers and 25 images at 718 nanometers taken by the Hubble Space Telescope in November 1990, as well as 3 images at each wavelength taken in June 1991, have been examined. Among them, 31 show the north polar spot, which is associated with Saturn's polar hexagon, in locations suitable for measurement. In each image, planetocentric coordinates of the polar spot were determined, and the movement of the spot with respect to Saturn's system III rotation rate was studied. During the period of observation, the polar spot had first a short-term westward movement and then a long-term eastward drift. The rate of the long-term drift was -0.060 +/- 0.008 degrees per day with respect to system III, approximately 50 percent greater than previously determined from Voyager. The original 1980 and 1981 Voyager data were combined with the new Hubble images to form an 11-year base line. The eastward drift over the longer period was -0.0569 degrees per day. The long-term drift could be due to uncertainty in the standard value of the internal rotation period, which is 810.7939 +/- 0.148 degrees per 24-hour day. The short-term movement in November 1990 has a rate that is greater in magnitude but opposite in sign and probably represents a real, transient motion of the spot relative to the internal rotation system.     

Erratum

The first two sentences of the report "Asian dust: Seasonal transport to the Hawaiian Islands" by J. R. Parrington et al. (8 Apr., p. 195) should have read as follows: "Transport of vast quantities of Sahara desert dust westward across the Atlantic Ocean to Bermuda has been known since the late 1960's (1, 2). Strong evidence now exists for transport of large quantities of Asian dust eastward across the North Pacific (3-7)."     

Around-the-World Relativistic Sagnac Experiment

In 1971 Hafele and Keating carried portable atomic clocks east and then west around the world and verified the Sagnac effect, a special relativity effect attributable to the earth's rotation. In the study reported here observations of the effect were made by using electromagnetic signals instead of portable clocks to make clock comparisons. Global Positioning System satellites transmit signals that can be viewed simultaneously from remote stations on the earth; thus an around-the-world Sagnac experiment can be performed with electromagnetic signals. The effect is larger than that occurring when portable clocks are used. The average error over a 3-month experiment was only 5 nanoseconds.     

Mode-locked lasers: measurements of very fast radiative decay in fluorescent systems

A mnode-locked laser was used to measure fluorescence decay down to 80 picoseconds. Measurements on the fluorescence of methylene blue quenchled with potassium iodide demonstrate the effectiveness of the method. Fluorescence decay times of chlorophyll b (3.87 +/- 0.05 nianoseconds) and c-phycocyanin (1.14 +/- 0.01 nanoseconds) in vitro and chlorophyll a in the green alga Chlorella pyrenoidosa (1.14 to 1.6 nanoseconds) compare well with some of the existing data.     

河南省高温偏多和偏少年环流特征及其与OLR关系分析

首先,通过对河南省夏季≥35℃的高温天气偏多和偏少年采用合成对比的方法,分析了高温偏多与偏少年份大气环流的差异,结果表明,6月南亚高压强度尚弱,而7月南亚高压强度相对较强;6月份,高温偏少年南亚高压加强东伸,西太平洋副热带高压西伸,而7月则相反,即高温偏少年南亚高压加强东伸,而西太平洋副热带高压则表现为东撤。另外,高度距平场也有不同特征。然后,采用OLR资料对高温偏多和偏少的成因进行了探讨;最后,从预报的角度对河南省夏季高温天气与前期秋、冬、春季中低纬OLR进行了相关分析,结果表明,前期一些月份的OLR分布对河南省夏季的高温具有指示意义。     

保定一次寒潮降雪诊断分析

利用NCEP资料、卫星云图以及国家自动观测站数据,对保定市2018年1月21—23日天气形势进行了诊断分析。结果表明,此次寒潮为“横槽型”寒潮。由于冷空气移动路径偏西且较弱,因而寒潮强度一般。高空槽与冷锋的配合下,产生了降雪天气。低层偏东风以及中层偏南气流提供了降水的水汽条件。     

热带对流活动对川渝地区夏季降水的影响

利用1974～2008年川渝地区22站月平均降水资料、NCEP/NCAR月平均再分析资料、OLR资料,通过SVD方法,分析研究了川渝地区夏季降水与春季、夏季热带OLR场的关系,并通过相关分析方法、合成分析方法从高度场、风场等方面分析了热带对流活动对川渝地区夏季降水的影响。结果表明,热带对流活动与川渝地区夏季降水之间呈显著的正相关,即夏季热带对流活动强（弱）,川渝地区夏季降水偏多（少）;当春季经纬度75°～110°E、25°～10°S区域的OLR偏低（偏高）,表明这一地区对流活动强（弱）,夏季川渝地区降水将偏多（偏少）,南印度洋春季热带对流活动的强弱对川渝地区夏季降水有一定的指示意义。若夏季经纬度85°～120°E、15°～5°N区域OLR偏低（高）,这一地区对流活动强（弱）,夏季川渝地区降水将偏多（少）。热带对流活动异常引起东亚地区大气环流异常,强（弱）热带对流活动年,副热带高压位置偏西（东）,南亚高压位置偏东（西）,自南海进入中国的水汽输送偏强（弱）,经向环流偏强（弱）,有更多的暖湿空气自热带地区输入到川渝地区,川渝地区夏季降水偏多（少）。     

Banded surface flow maintained by convection in a model of the rapidly rotating giant planets

In three-dimensional numerical simulations of a rapidly rotating Boussinesq fluid shell, thermally driven convection in the form of columns parallel to the rotation axis generates an alternately directed mean zonal flow with a cylindrical structure. The mean structure at the outer spherical surface consists of a broad eastward flow at the equator and alternating bands of westward and eastward flows at higher latitudes in both hemispheres. The banded structure persists even though the underlying convective motions are time-dependent. These results, although still far from the actual motions seen on Jupiter and Saturn, provide support for theoretical suggestions that thermal convection can account for the remarkable banded flow structures on these planets.     

异常气候下温跃层及时空因子对中西太平洋黄鳍金枪鱼渔场分布的影响

为研究气候变化对渔业资源的影响,采用2008—2017年全球海洋Argo网格数据集（BOA_Argo）和同期商业渔船渔捞日志数据,分析了拉尼娜和厄尔尼诺年中西太平洋黄鳍金枪鱼围网主要作业渔场温跃层的时空变化特征,结合GAM（generalized additive model）对影响黄鳍金枪鱼渔场的变量进行分析。结果表明,拉尼娜年,单位捕捞努力量渔获量(catch per unit effort, CPUE)随温跃层上界温度的高值区向西收缩而西移,最西至145°E;厄尔尼诺年,东移至165°E以东。拉尼娜年较正常年份,赤道太平洋东、西侧温跃层的上界深度差拉大,80~130 m上界深度值偏西。温跃层强度整体上呈现西弱东强,温跃层厚度以15°N和15°S为轴线,分别存在一个较厚的带状分布结构,CPUE分布在厚度值120~200 m之间。温跃层上界温度为27.5～29.5 ℃、强度为0.08～0.13 ℃·m^-1时,CPUE分布密集,温跃层参数中上界温度对CPUE分布的影响最大。且厄尔尼诺年CPUE的东移和拉尼娜年CPUE的西移随渔场所在温跃层的最适参数值而移动。时间因子中年份对CPUE的影响是波动性的,拉尼娜年对CPUE的影响更密切。资源丰度较高海域在5°N—5°S,150°E—175°E。综上所述,异常气候导致的温跃层变化对于CPUE具有显著影响。     

Frequency ratio of Al+ and Hg+ single-ion optical clocks; metrology at the 17th decimal place

Time has always had a special status in physics because of its fundamental role in specifying the regularities of nature and because of the extraordinary precision with which it can be measured. This precision enables tests of fundamental physics and cosmology, as well as practical applications such as satellite navigation. Recently, a regime of operation for atomic clocks based on optical transitions has become possible, promising even higher performance. We report the frequency ratio of two optical atomic clocks with a fractional uncertainty of 5.2 x 10(-17). The ratio of aluminum and mercury single-ion optical clock frequencies nuAl+/nuHg+ is 1.052871833148990438(55), where the uncertainty comprises a statistical measurement uncertainty of 4.3 x 10(-17), and systematic uncertainties of 1.9 x 10(-17) and 2.3 x 10(-17) in the mercury and aluminum frequency standards, respectively. Repeated measurements during the past year yield a preliminary constraint on the temporal variation of the fine-structure constant alpha of alpha/alpha = (-1.6+/-2.3) x 10(-17)/year.     

灌南县“903”区域性大暴雨过程诊断分析

采用天气学、物理量诊断等方法,从天气形势、物理量变化入手,分析形成灌南县"903"区域性大暴雨过程的主要原因。结果表明,此次发生在灌南地区的大暴雨是在高空槽东移、西太平洋副高西伸、台风倒槽北上和低层切变配合的环流背景下所产生的。暴雨期间水汽辐合一直维持,为暴雨产生提供了有力的条件。低空辐合、高空辐散和层结不稳定导致垂直运动发展并维持,促成了大暴雨天气过程。灌南发生大暴雨天气过程均与副高的变化有关,要加强对副高变化动态监测,提高大暴雨的监测预警水平和服务能力。     

Botanical and geological significance of potassium-argon dates from the juan fernandez islands

Potassium-argon dating of five basalts from the three main islands of the Juan Fernández (or Robinson Crusoe) Islands of Chile in the southeastern Pacific gives ages of 1.01 +/- 0.12 and 2.44 +/- 0.14 million years for Masafuera, 3.79 +/- 0.20 and 4.23 +/- 0.16 for Masatierra, and 5.8 +/- 2.1 for Santa Clara. These ages are much younger than that of the underlying oceanic plate and are consistent with the origin of the island-seamount chain from a mantle hot spot beneath the eastward moving Nazca plate. The young age for the archipelago suggests that speciation within endemic genera has occurred within the past 4 to 5 million years. Endemic genera of apparently more ancient origins, such as Lactoris and Thyrsopteris, have apparently dispersed to the islands and survive refugially.     

Millisecond Pulsar PSR 1937+21: A Highly Stable Clock

The stable rotation and sharp radio pulses of PSR 1937+21 make this pulsar a clock whose long-term frequency stability approaches and may exceed that of the best atomic clocks. Improvements in measurement techniques now permit pulse arrival times to be determined in 1 hour at the Arecibo radio telescope with uncertainties of about 300 nanoseconds relative to atomic time. Measurements taken approximately every 2 weeks since November 1982 yield estimates of fractional frequency stability that continue to improve with increasing averaging time. The pulsar's frequency stability is at least as good as 6 x 10(-14) for averaging times longer than 4 months, and over the longest intervals the measurements appear to be limited by the stability of the reference atomic docks. The data yield a firm upper limit of 7 x 10(-36) gram per cubic centimeter for the energy density of a cosmic background of gravitational radiation at frequencies of about 0.23 cycle per year. This limit corresponds to approximately 4 x 10(-7) of the density required to close the universe.     

Erratum

In the Research News article "New test of variable gravitational constant" (23 Dec., p. 1316), in the third paragraph of column two on page 1317, a minus sign was left out of an exponent. The correct value for the drift of atomic clocks relative to gravitational clocks is (0.1 +/- 0.8) x 10(-11) per year.     

Deuterium content of snow as an index to winter climate in the sierra nevada area

The winter of 1968-69 produced two to three times the amount of precipitation in the Sierra Nevada area, California and Nevada, as the winter of 1969-70. The deuterium content in snow cores collected at the end of each winter at the same sites, which represents the total snowfall of each interval, shows a depletion in 1968-69 of approximately 20 per mil. The higher snowfall in 1968-69 and the depletion of deuterium can be explained by an uncommonly strong westward flow of cold air over and down the western slopes of the Sierras, which interacted with an eastward flow of moist Pacific air that overrode and mixed with the cold air; this resulted in precipitation that occurred in greater than normal amounts and at a lower than normal temperature. Pluvial periods of the Pleistocene may have had the same shift in air-mass trajectory as the wet 1968-69 year. Snow cores collected in the norrmal 1970-71 winter have deuterium concentrations that resemble those of the normal 1969-70 winter. Small and nonsystematic differences in samples from these two normal winters are due to variations in climatic character as well as to factors inherent in the sampling sites.     

Neptune's Wind Speeds Obtained by Tracking Clouds in Voyager Images

Images of Neptune obtained by the narrow-angle camera of the Voyager 2 spacecraft reveal large-scale cloud features that persist for several months or longer. The features' periods of rotation about the planetary axis range from 15.8 to 18.4 hours. The atmosphere equatorward of -53 degrees rotates with periods longer than the 16.05-hour period deduced from Voyager's planetary radio astronomy experiment (presumably the planet's internal rotation period). The wind speeds computed with respect to this radio period range from 20 meters per second eastward to 325 meters per second westward. Thus, the cloud-top wind speeds are roughly the same for all the planets ranging from Venus to Neptune, even though the solar energy inputs to the atmospheres vary by a factor of 1000.     

新疆天山北坡带中部大降水专家预报系统

新疆天山北坡带中部地区3-10月大降水天气频繁发生,对农业生产有弊也有利,具有重要意义。笔者通过对这一期间大降水过程前的西风带系统演变特征、西太副高西伸北抬、伊朗副高东伸北挺对大降水的先兆性及各种尺度系统之间的相互作用的分析,并依据这些特征结合T213产品和卫星云图资料的应用,建立了大降水专家预报系统,在2006年至2008年3-10月期间业务化应用中效果显著,大降水量级预报评分T。为66％,使大降水天气的预报准确率有了显著提高。     

Mesoscale ocean eddies in the north pacific: westward propagation

A set of subsurface temperature measurements in the trade wind region northeast of Hawaii reveals large perturbations about the mean state, with zonal wavelengths of 480 kilometers. The perturbations are identified as mesoscale baroclinic eddies, and they appear to drift westward at a rate of 4.7 +/- 2.0 centimeters per second. The large-scale ( 1000 kilometers) baroclinic flow at a depth of 200 meters is 1.5 +/- 0.7 centimeters per second, also toward the west, and comparable in magnitude with the eddy drift velocity; this finding suggests that the eddy drift is strongly influenced by the large-scale flow. Mesoscale eddies have been discovered in the tropical and subtropical Atlantic Ocean. Their existence in the Pacific Ocean is now confirmed.