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1.
Precipitation variation in the northeastern Tibetan Plateau recorded by the tree rings since 850 AD and its relevance to the Northern Hemisphere temperature 总被引：17，自引：2，他引：17
John K. Kutzbach 《中国科学D辑(英文版)》2006,49(4):408-420
With their high resolution and reliability, tree rings play a very important role in global climate change study. The long tree-ring chronology is considered as one of the most important information sources to study the climatic change in the past several thousands years. In recent years, the tree-ring researches in China have made great progress, and the temperature and precipita- tion in some areas were reconstructed[1-20] which on- tributed to the global change studies in China. Due to the… 相似文献
2.
E. L. Afraimovich E. I. Astafyeva I. V. Zhivetiev A. V. Oinats Yu. V. Yasyukevich 《Geomagnetism and Aeronomy》2008,48(2):187-200
Global electron content (GEC) as a new ionospheric parameter was first proposed by Afraimovich et al. [2006]. GEC is equal to the total number of electrons in the near-Earth space. GEC better than local parameters reflects the global response to a change in solar activity. It has been indicated that, during solar cycle 23, the GEC dynamics followed similar variations in the solar UV irradiance and F 10.7 index, including the 11-year cycle and 27-day variations. The dynamics of the regional electron content (REC) has been considered for three belts: the equatorial belt and two midlatitude belts in the Northern and Southern hemispheres (±30° and 30°–65° geomagnetic latitudes, respectively). In contrast to GEC, the annual REC component is clearly defined for the northern and southern midlatitude belts; the REC amplitude is comparable with the amplitude of the seasonal variations in the Northern Hemisphere and exceeds this amplitude in the Southern Hemisphere by a factor of ～1.7. The dayside to nightside REC ratio, R(t), at the equator is a factor of 1.5 as low as such a GEC ratio, which indicates that the degree of nighttime ionization is higher, especially during the solar activity maximum. The pronounced annual cycle with the maximal R(t) value near 8.0 for the winter Southern Hemisphere and summer Northern Hemisphere is typical of midlatitudes. 相似文献
3.
A. D. Kostyuk N. A. Sycheva S. L. Yunga L. M. Bogomolov Y. Yagi 《Izvestiya Physics of the Solid Earth》2010,46(3):230-243
For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the
seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms
of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006.
In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This
approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well
as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS
measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust
were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal
data is carried out. 相似文献
4.
Because atmosphere itself is a nonlinear system and there exist some problems using the linearized equations to study the initial error growth, in this paper we try to use the error nonlinear growth theory to discuss its evolution, based on which we first put forward a new concept: nonlinear local Lyapunov exponent. It is quite different from the classic Lyapunov exponent because it may characterize the finite time error local average growth and its value depends on the initial condition, initial error, variables, evolution time, temporal and spatial scales. Based on its definition and the at-mospheric features, we provide a reasonable algorithm to the exponent for the experimental data, obtain the atmospheric initial error growth in finite time and gain the maximal prediction time. Lastly, taking 500 hPa height field as example, we discuss the application of the nonlinear local Lyapunov exponent in the study of atmospheric predictability and get some reliable results: atmospheric predictability has a distinct spatial structure. Overall, predictability shows a zonal distribution. Prediction time achieves the maximum over tropics, the second near the regions of Antarctic, it is also longer next to the Arctic and in subtropics and the mid-latitude the predictability is lowest. Particularly speaking, the average prediction time near the equation is 12 days and the maximum is located in the tropical Indian, Indonesia and the neighborhood, tropical eastern Pacific Ocean, on these regions the prediction time is about two weeks. Antarctic has a higher predictability than the neighboring latitudes and the prediction time is about 9 days. This feature is more obvious on Southern Hemispheric summer. In Arctic, the predictability is also higher than the one over mid-high latitudes but it is not pronounced as in Antarctic. Mid-high latitude of both Hemispheres (30°S―60°S, 30°―60°N) have the lowest predictability and the mean prediction time is just 3―4 d. In addition, predictability varies with the seasons. Most regions in the Northern Hemisphere, the predictability in winter is higher than that in summer, especially in the mid-high latitude: North Atlantic, North Pacific and Greenland Island. However in the Southern Hemisphere, near the Antarctic regions (60°S―90°S), the corresponding summer has higher predictability than its winter, while in other areas especially in the latitudes of 30°S―60°S, the prediction does not change obviously with the seasons and the average time is 3―5 d. Both the theoretical and data computation results show that nonlinear local Lyapunov exponent and the nonlinear local error growth really may measure the predictability of the atmospheric variables in different temporal and spatial scales. 相似文献
5.
Summary The wavenumber-frequency spectra of the meridional transport of sensible heat at 20°, 30°, 40°, 50°, 60°, and 70°S, at 500 mb in the Southern Hemisphere, show a definite spectral domain for the transport at various latitudes, which is dominated by the wave motion of the meridional component of the velocity. In middle latitudes, the spectral band of the meridional flux of sensible heat is oriented from a region of low wavenumbers and low frequencies to a region of high wavenumbers and negative frequencies assigned for waves moving from west to east. In low latitudes, the spectral band is confined to a narrow band centered near the zero frequency. It is found that most of the meridional transport of sensible heat at 500 mb in the Southern Hemisphere is accomplished by waves of medium wavelengths moving from west to east in middle and high latitudes. The meridional flux of sensible heat at 500 mb in the summer of the Southern Hemisphere is about three times that in the summer of the Northern Hemisphere. However, the meridional flux of sensible heat at 500 mb is about the same in the winter of both hemispheres. In the Southern Hemisphere practically all the meridional flux of sensible heat is associated with the moving waves in all seasons, whereas in the Northern Hemisphere the stationary waves contribute about 40% of the transport in winter.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
6.
陆地水储量的季节性变化是导致地表周期性负荷形变位移的主要因素,有效地剔除地表位移中的陆地水储量影响,是获取地壳构造垂向运动的必要过程.四川地处青藏高原东边缘,地形分区明显,境内以长江水系为主,水资源丰富,研究四川地区地表负荷形变位移,有助于分析陆地水储量的时空分布特性及地壳构造形变信息.本文利用研究区域内59个CORS站的GPS观测数据,计算了CORS站点的垂向位移,并将其与GRACE所得相应结果进行对比分析.结果显示,GPS和GRACE所得垂向位移时间序列的振幅大小整体相符,但存在明显的相位差.GPS站点振幅最大值为12.7 mm,对应HANY站,最小值为1.5 mm,对应SCMX站.GRACE所得的地表垂向位移振幅大小均为3~4 mm,且最大位移集中出现在7-9月份;而GPS站点出现最大位移的月份和地形相关,东部盆地、西北部高原和南部山地分别出现在7-8月份、10-11月份和10月份.GPS站点时间序列中的周年项与陆地水的季节性变化强相关,为了讨论陆地水储量对GPS站点位移的影响,本文利用改进的总体经验模态分解方法（MEEMD：Modified Ensemble Empirical Mode Decomposition）,从GPS垂向位移时间序列中提取出周年项及约2年的年际变化项.发现利用MEEMD获取的周年项改正原始GPS时间序列时可使其WRMS（Weight Root Mean Square）减少量减小约26%,结果优于最小二乘拟合方法提取的GPS周年项改正效果,验证了MEEMD方法在GPS坐标时间序列处理中的可行性及有效性. 相似文献
7.
S. A. Yazev 《Geomagnetism and Aeronomy》2011,51(7):879-887
Results of the study of activity complexes of (AC) on the Sun that evolved during the 23rd solar cycle (SC) are presented.
Based on ananalysis of synoptic charts of sunspot activity, 69 AC cores have been detected in the Northern Hemisphere, and
77 AC cores, in the Southern Hemisphere during the 23rd SC. An AC core catalogue has been composed. We have found an increase
in the number of AC cores with lifetime (maximum 14 rotations); their nonuniform longitudinal distribution; and a local drop
in the number of AC cores during the 23rd SC maximum (1967th–1979th rotations, October 2000–August 2001). The quasiperiodic
character of variations in the total rotation-to-rotation power of AC cores during the cycle has been ascertained; the quasi-has
12–14 rotations. A feature of the 23rd SC is a prolonged period of AC generation in comparison with the 22nd SC. Last AC cores
in the Southern Hemisphere were observed until the 144th rotation after the previous minimum according to the Wolf numbers
(to the 110th rotation in the 22nd SC). The total number of AC cores in the 23rd SC (146) far exceeds that in the 22nd SC
(104). Ninety-four percent of high-power proton flares with an energy higher than 10 MeV and a flux of more than 10/(s sm2 sr) at the Earth’s orbit occurred near the AC cores. The total number of proton flares related to AC cores of the above class
increased: 48 in the 22nd SC versus 62 in the 23rd SC. We have also revealed a strong north-south asymmetry in the AC evolution
manifesting itself in different indices describing AC on the Sun. 相似文献
8.
9.
Variations of the total electron content according to the index IONEX IGS in the period of preparation of the earthquake in
Haiti (M7.9) on January 12, 2010, are considered. The situation is exceptional owing to the unique position of the island
of Haiti relative to the structure of the ionosphere over the Caribbean Sea: the ionospheric region over Haiti is in the trough
formed by the northern slope of the equatorial anomaly and additional maximum formed at latitudes of approximately 30° N within
this longitudinal interval. Distortion of the shape of the equatorial anomaly, total decrease in the electron content in the
equatorial anomaly a few days prior to the earthquake, increase in the electron concentration directly over the earthquake
epicenter a few days prior to the earthquake, increase in the additional maximum at latitudes of ∼30° N, and formation of
an additional maximum in the Southern Hemisphere in the region conjugated to the additional maximum in the Northern Hemisphere
in the periods of its intensification are observed. The configuration of the equatorial anomaly is restored after the earthquake. 相似文献
10.
Ogurtsov M. G. Jungner H. Lindholm M. Helama S. Dergachev V. A. 《Geomagnetism and Aeronomy》2009,49(7):1056-1062
Paleoclimatological reconstructions of temperature of the Earth’s Northern Hemisphere for the last thousand years have been
studied using the up-to-date methods of statistical analysis. It has bee indicated that the quasisecular (a period of 60–130
years) cyclicity, which is observed in the climate of the Earth’s Northern Hemisphere, has a bimodal structure, i.e., being
composed of the 60–85 and 85–130 year periodicities. The possible relation of the quasisecular climatic rhythm to the corresponding
Gleissberg solar cycle has been studied using the solar activity reconstructions performed with the help of the solar paleoastrophysics
methods. 相似文献
11.
John Ball Robinson Jr. 《Pure and Applied Geophysics》1970,80(1):319-334
Summary From meteorological IGY data for the calendar year 1958, the mean meridional eddy transport of enthalpy was evaluated for the Southern Hemisphere. Levels chosen for the study were 1000, 850, 700, 500, 400, 300, 200, 150 and 100 mb. Data from 84 Southern Hemisphere and 25 equatorial Northern Hemisphere stations were used. Yearly mean quantities related to meridional eddy enthalpy flux were computed and analyzed.It was found that around 40° S there is a double-maximum zone of poleward, meridional, transient eddy enthalpy flux, the stronger transport occurring at 850 mb, and the weaker near 200 mb. The countergradient transient eddy flux regions in the low latitude mid-troposphere and in the middle and upper latitude lower stratosphere, found in previous Northern Hemisphere investigations, were observed to exist in the Southern Hemisphere also. The standing eddy heat transport, as expected, was very weak except at high latitudes where Antarctic continentality effected a large double-maximum poleward flux centered near the surface and in the lower stratosphere. The total vertically integrated enthalpy transport by the eddies was found to be poleward everywhere, reaching a maximum between 35° and 40° S. 相似文献
12.
The specific features of the spatial structure and time dynamics of the main geomagnetic field during the 20th century, proceeding
from the present-day concepts of geomagnetic jerks have been studied. The variations, caused by global dissipation of the
geomagnetic field dipole part, have been separated from the regional variations, described by nondipole spatial harmonics
of the spherical harmonic expansion series. It has been indicated that the geomagnetic field westward drift manifests itself
in a limited region of the Earth’s surface, forming the known Brazil anomaly. However, the drift component in the variations
in the geomagnetic field morphological structures is globally found out during the considered almost 100-year period along
the narrow belt around the geomagnetic axis. However, this drift is northwestward in the Northern Hemisphere, and the structures
drift southeastward in the Southern Hemisphere. The detected variations of the drift nature are reflected in the variations
in the integral geomagnetic characteristic, when changes in the position of the Earth’s magnetic center are considered. The
direct correlation between the global geomagnetic variations of the drift nature and the trend variations in the orientation
of the vector of the Earth daily rotation velocity has been detected. 相似文献
13.
Summary The wavenumber-frequency spectra of the meridional flux of angular momentum at 20°, 30°, 40°, 50°, 60° and 70°S, at 500 mb, show a definite domain of wave interactions between the zonal and meridional components of the velocity at various latitudes. In middle latitudes, the spectral band of the meridional flux of angular momentum is oriented from a region of low wavenumbers and low frequencies to a region of high wavenumbers and negative frequencies assigned for waves moving from west to east. In low latitudes, however, the spectral domain is confined to a narrow band centered near the zero frquency.In contrast to the meridional flux of angular momentum in the Northern Hemisphere in which the intensity in winter is about twice that in Summer, in the Southern Hemisphere the meridional flux shows same intensity for all seasons.In the Southern Hemisphere, most of the meridional flux of angular momentum is directed toward the south pole and is accomplished by the eastward moving waves. In the Northern Hemisphere, however, most of the meridional flux is directed toward the north pole and is contributed by the stationary waves.The National Center for Atmospheric Research, Boulder, Colorado 80302, (USA). 相似文献
14.
Some comparisons between the middle atmosphere dynamics of the Southern and Northern Hemispheres 总被引：1，自引：0，他引：1
David G. Andrews 《Pure and Applied Geophysics》1989,130(2-3):213-232
Comparisons are drawn between certain middle atmosphere dynamical processes in the Southern Hemisphere and the Northern Hemisphere. Attention is focused on the zonal-mean climatological state, stationary waves, transient waves of various types, stratospheric sudden warmings and polar ozone minima. Observations of the similarities and differences between the hemispheres are mentioned, and ways in which these comparisons may be used to enhance our dynamical knowledge of the whole middle atmosphere are discussed. 相似文献
15.
Fangli Qiao Yeli Yuan Tal Ezer Changshui Xia Yongzeng Yang Xingang Lü Zhenya Song 《Ocean Dynamics》2010,60(5):1339-1355
A theoretical framework to include the influences of nonbreaking surface waves in ocean general circulation models is established
based on Reynolds stresses and fluxes terms derived from surface wave-induced fluctuation. An expression for the wave-induced
viscosity and diffusivity as a function of the wave number spectrum is derived for infinite and finite water depths; this
derivation allows the coupling of ocean circulation models with a wave number spectrum numerical model. In the case of monochromatic
surface wave, the wave-induced viscosity and diffusivity are functions of the Stokes drift. The influence of the wave-induced
mixing scheme on global ocean circulation models was tested with the Princeton Ocean Model, indicating significant improvement
in upper ocean thermal structure and mixed layer depth compared with mixing obtained by the Mellor–Yamada scheme without the
wave influence. For example, the model–observation correlation coefficient of the upper 100-m temperature along 35° N increases
from 0.68 without wave influence to 0.93 with wave influence. The wave-induced Reynolds stress can reach up to about 5% of
the wind stress in high latitudes, and drive 2–3 Sv transport in the global ocean in the form of mesoscale eddies with diameter
of 500–1,000 km. The surface wave-induced mixing is more pronounced in middle and high latitudes during the summer in the
Northern Hemisphere and in middle latitudes in the Southern Hemisphere. 相似文献
16.
Vladimir Schenk Zdeňka Schenkova Zuzana Jechumtálová 《Studia Geophysica et Geodaetica》2009,53(3):329-341
In West Bohemia in the period of 2003–2005 five permanent GPS stations were established to detect local movement trends. Their
mutual position changes were determined from time series of GPS observations and were associated with seismic, gravity, and
geo-scientific data related to the geodynamics of the West Bohemian region. Knowledge of local physical processes based on
spatial and time earthquake occurrences, focal mechanisms of main events, stress and strain fields set up a tool for recent
seismotectonic analyses. The permanent GPS measurements bring independent effective phenomenon, direct monitoring of site
movements. The movements detected by our GPS stations evidenced WSW-ENE extension with subsiding trends in the western part
of the Cheb Basin and the Smrčiny Mts. Besides, there were monitored dextral movements along the Mariánské Lázně tectonic
fault zone (MLF). A comparison of results with previous data formed a presumption that an antithetic stress pattern has to
exist inside the inner part of the MLF tectonic zone. This antithetic stress can explain the coexistence of dextral and sinistral
movements on individual tectonic elements in the West Bohemian area. 相似文献
17.
Antecedent anomalies of sea surface temperature and atmospheric circulation are important signals for making long-term streamflow forecasts. In this study, four groups of ocean-atmospheric indices, i.e, El Niño Southern Oscillation (ENSO), the Northern Hemisphere atmospheric circulation, the Southern Hemisphere atmospheric circulation (SAC), and the Western Pacific and Indian Ocean SST (WPI), are evaluated for forecasting summer streamflow of the Yangtze River. The gradient boosting regression tree (GBRT) is used to forecast streamflow based on each group of indices. The score based on receiver operating characteristics (ROC) curves, i.e., area under the ROC curve (AUC), is used to evaluate skills of models for identifying the high category and the low category of summer streamflow. It is found that the ENSO group and the SAC group show higher AUC values. Furthermore, both AUC values of GBRT models and individual indices show that the low flow years are easier to be identified than the high flow years. The result of this study highlights the skill from the Southern Hemisphere circulation systems for forecasting summer streamflow of the Yangtze River. Results of relative influences of predictors in GBRT models and AUC of individual indices indicate some key ocean-atmospheric indices, such as the Multivariate ENSO Index and the 500-hPa height of the east of Australia. 相似文献
18.
Most GPS coordinate time series, surface displacements derived from the Gravity Recovery and Climate Experiment (GRACE), and loading models display significant annual signals at many regions. This paper compares the annual signals of the GPS position time series from the Crustal Dynamics Data Information System (CDDIS), estimates of loading from GRACE monthly gravity field models calculated by three processing centers (Center of Spatial Research, CSR; Jet Propulsion Laboratory, JPL; GeoForschungsZentrum, GFZ) and three geophysical fluids models (National Center for Environmental Prediction, NCEP; Estimating the Circulation and Climate of the Ocean, ECCO; Global Land Data Assimilation System, GLDAS) for 270 globally distributed stations for the period 2003-2011. The results show that annual variations derived from the level-2 products from the three GRACE product centers are very similar. The absolute difference in annual amplitude between any two centers is never larger than 1.25 mm in the vertical and 0.11 mm in horizontal displacement. The mean phase differences of the GRACE results are less than ten days for all three components. When we correct the GPS vertical coordinate time series using the GRACE annual amplitudes using the products from three GRACE analysis centers, we find that we are able to reduce the GPS annual signal in the vertical at about 80% stations and the average reduction is about 47%. In the north and the east, the annual amplitude is reduced on 77% and 72% of the stations with the average reduction 32% and 33%. We also compare the annual surface displacement signal derived from two environmental models; the two models use the same atmospheric and non-tidal ocean loading and differ only in the continental water storage model that we use, either NCEP or GLDAS. We find that the model containing the GLDAS continental water storage is able to better reduce the annual signal in the GPS coordinate time series. 相似文献
19.
QiuMing Yang 《中国科学D辑(英文版)》2009,52(10):1485-1501
Based on the observational data in summer, the variations of intraseasonal oscillation (ISO) of the daily rainfall over the
lower reaches of the Yangtze River valley (LYRV) were studied by using the non-integer spectrum analysis. The NCEP/NCAR reanalysis
data for the period of 1979–2005 were analyzed by principal oscillation pattern analysis (POP) to investigate the spatial
and temporal characteristics of principal ISO patterns of the global circulation. The relationships of these ISO patterns
to the rainfall ISO and the heavy precipitation process over LYRV were also discussed. It is found that the rainfall over
LYRV in May–August is mainly of periodic oscillations of 10–20, 20–30 and 60–70 days, and the interannual variation of the
intensity of its 20–30-day oscillation has a strongly positive correlation with the number of the heavy precipitation process.
Two modes (POP1, POP2) are revealed by POP for the 20–30-day oscillation of the global 850 hPa geopotential height. One is
a circumglobal teleconnection wave train in the middle latitude of the Southern Hemisphere (SCGT) with an eastward propagation,
and the other is the southward propagation pattern in the tropical western Pacific (TWP). The POP modes explain 7.72% and
7.66% of the variance, respectively. These two principal ISO patterns are closely linked to the low frequency rainfall and
heavy precipitation process over LYRV, in which the probability for the heavy precipitation process over LYRV is 54.9% and
60.4% for the positive phase of the imaginary part of POP1 and real part of POP2, respectively. Furthermore, the models of
the global atmospheric circulation for the 20–30-day oscillation in association with or without the heavy precipitation process
over LYRV during the Northern Hemisphere summer are set up by means of the composite analysis method. Most of the heavy precipitation
processes over LYRV appear in Phase 4 of SCGT or Phase 6 of TWP. When the positive phases of 20–30-day oscillations for the
rainfall over LYRV are associated with (without) the heavy precipitation process, a strong westerly stream appears (disappears)
from the Arabian Sea via India and Bay of Bengal (BOB) to southern China and LYRV for the global 850 hPa filtered wind field
during Phase 4 of SCGT. This situation is favorable (unfavorable) for the forming of the heavy precipitation process over
LYRV. Similarly, a strong (weak) western wind belt forms from India through BOB to southern China and LYRV and the subtropical
northwestern Pacific and central and eastern equatorial Pacific during Phase 6 of TWP for the cases with (without) the heavy
precipitation process. The evolutions of these ISO patterns related to the 20–30-day oscillation are excited by either the
interaction of extratropical circulation in both hemispheres or the heat source forcing in Asia monsoon domain and internal
interaction of circulation in East Asia. These two global circulation models might therefore provide valuable information
for the extended-range forecastof the heavy precipitation process over LYRV during the 10–30 days. 相似文献
20.
Relationship between phases of quasi-decadal oscillations of total ozone and the 11-year solar cycle
K. N. Visheratin 《Geomagnetism and Aeronomy》2012,52(1):94-102
Temporal variability of the relationship between the phases of quasi-decadal oscillations (QDOs) of total ozone (TO), measured
at the Arosa station, and the Ri international sunspot number have been analyzed for the period of 1932–2009. Before the 1970s, the maximum phase of ozone
QDOs lagged behind solar activity variations by about 2.5–2.8 years and later outstripped by about 1.5 years. We assumed that
the TO QDOs in midlatitudes of the Northern Hemisphere were close to being in resonance with solar activity oscillations in
the period from the mid-1960s to the mid-1970s and assessed the characteristic delay period of TO QDOs. The global distribution
of phases and amplitudes of TO QDOs have been studied for the period from 1979 to 2008 based on satellite data. The maximum
phase of TO QDOs first onsets in northern middle and high latitudes and coincides with the end of the growth phase of the
11-year solar cycle. In the tropics, the maximum oscillation phase lags behind by 0.5–1 year. The maximum phase lag near 40–50°
S is about two years. The latitudinal variations of the phase of TO QDOs have been approximated. 相似文献