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671.
The Southern Annular Mode(SAM)plays an important role in regulating Southern Hemisphere extratropical circulation.State-of-the-art models exhibit intermodel spread in simulating long-term changes in the SAM.Results from Atmospheric Model Intercomparison Project(AMIP)experiments from 28 models archived in CMIP5 show that the intermodel spread in the linear trend in the austral winter(June?July?August)SAM is significant,with an intermodel standard deviation of 0.28(10 yr)?1,larger than the multimodel ensemble mean of 0.18(10 yr)?1.This study explores potential factors underlying the model difference from the aspect of extratropical sea surface temperature(SST).Extratropical SST anomalies related to the SAM exhibit a dipole-like structure between middle and high latitudes,referred to as the Southern Ocean Dipole(SOD).The role of SOD-like SST anomalies in influencing the SAM is found in the AMIP simulations.Model performance in simulating the SAM trend is linked with model skill in reflecting the SOD?SAM relationship.Models with stronger linkage between the SOD and the SAM tend to simulate a stronger SAM trend.The explained variance is about 40%in the AMIP runs.These results suggest improved simulation of the SOD?SAM relationship may help reproduce long-term changes in the SAM. 相似文献
672.
利用17年(1979~1995)的NMC全球格点分析资料及从NOAA极轨卫星观测的地球向外长波辐射(OLR)资料,研究了南海夏季风暴发的年际变化特征。用本文的定义标准,南海季风从1979年到1995年间暴发的平均日期是5月第4候。南海夏季风暴发前后,南海周围地区对夏季风暴发的直接影响来自南海上游70°~90°E的赤道西风的加强和北抬东伸,同时索马里越赤道气流的加强和阿拉伯海高压在海上消失通过影响赤道西风也间接影响到南海。其中阿拉伯海反气旋的消失可能是南海夏季风暴发的一个重要信号。南海夏季风暴发的年际变化较 相似文献
673.
垂测电离图反演对研究电离层结构及运动、电离层波传播、空间气象应用等具有重要意义,一直以来受到十分广泛的重视.F_1层未充分发展的回波描迹是垂测电离图中观测到的最多的一种情况,此时垂测描迹上表现为F_1层到F_2层的平滑过渡,而不是F_1层充分发展时出现的尖点,然而现有电离层模型以及反演算法更多的是针对F_1层充分发展情况,即模型剖面在F_1层峰高处近似为抛物形状,此处电子浓度剖面梯度为无穷大,这不符合F_1层未充分发展时的剖面形态,即F_1层剖面未到达抛物顶点处就已经达到该层电子浓度的最大值然后到达F_2层,剖面梯度为一个有限的数值.因此,本文针对垂直探测中经常出现的F_1层未充分发展情况,引入F_1层模型设定临频这一参数,建立了F_1层未充分发展时的基于移位切比雪夫多项式的电离层模型,并从电离层剖面的光滑性考虑,在所建模型的基础上,提出了约束优化F_1层参数、F_2层参数的垂测电离图反演方法.然后,通过仿真分析,从理论上验证了所建电离层模型和反演算法的合理性,并通过反演电子浓度剖面合成的垂测、斜测描迹与实测数据的对比,对反演算法的有效性进行了进一步的试验验证. 相似文献
674.
从变质作用演化、构造变形作用演化方面探讨了处于冀东与密云之间的兴隆地区太古宙变质岩系的变形变质构造演化史 相似文献
675.
676.
The seasonal variability and spatial distribution of precipitation are the main cause of flood and drought events.The study of spatial distribution and temporal trend of precipitation in river basins has been paid more and more attention.However,in China,the precipita- tion data are measured by weather stations(WS)of China Meteorological Administration and hydrological rain gauges(RG)of national and local hydrology bureau.The WS data usually have long record with fewer stations,while the RG data usually hav... 相似文献
677.
S.M. Andrievsky N.I. Gorlova V.G. Klochkova V.V. Kovtyukh V.E. Panchuk 《Astronomische Nachrichten》1999,320(1):35-41
The F‐type supergiant HD172365 was discovered by Luck (1982) to be a high Li abundance star. We find that the lithium abundance in this star is log A(Li) = 2.9 from a careful spectroscopic study. This value is larger than the abundance derived by Luck. We discuss the properties of this supergiant and tentatively conclude that HD172365 may, in fact, be a post‐blue straggler star with a mass ∼2 times greater than the “turn‐off point” mass for the open cluster IC 4756, of which HD172365 is a member. The star is formed by a merger of a close binary system. This conclusion is supported by, for example, its large projected rotational velocity, solar carbon abundance and high lithium content. 相似文献
678.
679.
《New Astronomy》2022
In this research article, we have investigated resonant curves due to the rate of change of earth’s equatorial ellipticity parameter , steady-state value of the angular velocity of the moon , and angular velocity of barycenter in the Earth-Moon system. Equations of motion of the moon are determined in a spherical coordinate system with the help of the gravitational potential of the earth. By using the unperturbed solution, equations of motion of the moon reduced into the second-order differential equation. From the solution it is observed that resonance occurs due to the frequencies , , and at the resonant points , , , . Finally, we have analyzed the phase portrait and phase space by method of Poincaré section when the system is free from forces. 相似文献
680.
P. Rafanelli S. Roi A. Tegon H. Schulz S. Di Serego-Alighieri S. Komossa G. Richter J. Vennik 《Astronomische Nachrichten》1997,318(6):319-327
[OIII] images and blue spectra of the emission-line dwarf galaxy F348 are presented. In [OIII] light, the object contains two knots about 9” NE of the nucleus and one large extended knot 11” to the SW. The nuclear region is hundred times less luminous in emission-line light than the knots. Despite the presence of line intensity ratios [OIII]λ5007/Hβ > 3 the prior classification as a Seyfert-2 object cannot be upheld. This clinches an earlier suggestion by Veron-Cetty & Veron (1986). In particular, we show that the line spectra can be modeled with photoionization models employing stellar input continua. Also, the line luminosities of the extranuclear knots are typical for giant HII regions. There is neither evidence for tidal tails nor for high velocity differences between the knots. In addition, the linear arrangement of the knots does not support interaction. It rather suggests self-propagating star formation In this picture, the faintness of the nuclear region can be understood by an edge-on view. In addition, the nuclear starburst appears to be fading in contrast to the young extranuclear star formation regions. Within the scheme of Melnick (1987), F348 has to be classified as a multiple-system HII galaxy. 相似文献