中间层顶区域大气平均风场年和半年振荡的全球结构   总被引：1，自引：0，他引：1  

凌超  陈泽宇  陈洪滨 《气候与环境研究》2014,19(3):383-392

利用2003~2011年TIDI(TIMED Doppler Interferometer)风场观测数据研究了中间层顶区域80~105 km纬向平均风场年振荡和半年振荡振幅和相位的全球分布结构,并给出了它们的年际变化。在热带地区,纬向风半年振荡最显著。振幅峰值中心位于南半球10°S~20°S范围,出现与平流层半年振荡类似的相对于赤道不对称的分布,并且振幅峰值与以前在该区域的研究结果存在较大差别。在中高纬度地区,纬向风和经向风被年振荡所控制。纬向风在高度100 km以下中高纬度都存在振幅大值中心;经向风年振荡只出现在两半球中纬度高度95 km以下,并且南北半球振幅峰值中心分布不一致。分析结果还显示年振荡和半年振荡振幅存在显著地年际变化,相位的年际变化则较小,但北半球热带地区经向风年振荡振幅和相位表现出2年周期的变化。  相似文献   

Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall     

Fan Ping  Zhexian Luo 《Atmospheric Research》2009,93(4):862-873

Microphysical and radiative effects of ice clouds on diurnal variations of tropical convective and stratiform rainfall are examined with the equilibrium simulation data from three experiments conducted with a two-dimensional cloud resolving model with imposed temporally and zonally invariant winds and sea surface temperature and zero mean vertical velocity. The experiment without ice radiative effects is compared with the control experiment with ice microphysics (both the ice radiative and microphysical effects) to study effects of ice radiative effects on diurnal rainfall variations whereas it is compared with the experiment without ice microphysics to examine ice microphysical effects on the diurnal rainfall variations. The ice radiative processes mainly affect diurnal cycle of convective rainfall whereas the ice microphysical processes have important impacts on the diurnal cycles of both convective and stratiform rainfall. Turning off the ice radiative effects generally enhances convective rainfall during the morning and evening and suppresses convective rainfall in the afternoon whereas turning off the ice microphysical effects generally suppresses convective and stratiform rainfall during the morning and enhances convective and stratiform rainfall in the afternoon and evening. The ice radiative and microphysical effects on the diurnal cycle of surface rainfall are mainly associated with that of vapor condensation and deposition, which is controlled by air temperature through saturation specific humidity. The ice effects on the diurnal cycle of local temperature tendency are largely explained by that of latent heating since the diurnal cycle of radiation is insensitive to the ice effects.  相似文献   

Spatial and Temporal Variations of Tropical Cyclones at Different Intensity Scales over the Western North Pacific from 1945 to 2005          下载免费PDF全文

YUAN Jinnan  LIN Ailan  LIU Chunxia 《Acta Meteorologica Sinica》2009,23(5):550-561

The tropical cyclone （TC） track data provided by the Joint Typhoon Warning Center （JTWC） of the U.S. Navy over the western North Pacific （including the South China Sea） from 1945 to 2005 are employed to analyze the temporal and spatial variations of TCs of different intensity scales. Most of the TCs occurred between 15° and 25°N, from the northern part of the South China Sea to the eastern part of the Bashi Channel until near 140°E. Most of the severe and super typhoons occurred over waters from the eastern part of the Bashi Channel to about 140°E. The TCs in a weakening or steady state take up a weak majority in the area west of 123°E and north of 20°N; those in an intensifying or steady state are mostly found in the area east of 123°E and south of 20°N. For severe tropical storms, typhoons, severe typhoons, and super typhoons, their average decaying rates are all greater than the respective average growing rates; for tropical storms, however, the average decaying rate is smaller than the average growing rate. Generally speaking, the stronger the TC, the faster the intensification （weakening） is. The percentage of weak TCs is higher in June to August while that of strong TCs is higher in September to November. There are annual, interannual, and interdecadal variations in the observed number （every 6 h） and frequency of TCs at different intensity scales. As far as the long-term trend is concerned, the frequency and observed number of tropical storms have a significant linear increase, but the averaged intensity and number of TCs of other intensity categories do not exhibit such a significant linear trend. In E1 Nifio years, the number and percentage of super typhoons are significantly higher, while the total number of tropical storms, severe tropical storms, typhoons, and severe typhoons is significantly lower, and the mean intensity of TCs is prominently stronger; in La Nifia years, however, the opposite comes true.  相似文献   

Population biology of the portunid crab Callinectes arcuatus Ordway in the Gulf of Nicoya,Costa Rica,Central America     

Ana I. Dittel  C.E. Epifanio  Juan Bautista Chavarria 《Estuarine, Coastal and Shelf Science》1985,20(5):593-602

Tropical blue crabs Callinectes arcuatus were collected by trawling in the Gulf of Nicoya on the Pacific coast of Costa Rica, Central America. The gulf population was generally dominated by females. Adult females were common in the upper, more estuarine regions of the gulf during rainy season, but appeared to migrate to the lower gulf during dry season for spawning. Biomass varied with seasonal changes in abundance, but was generally similar to biomass of C. sapidus in Chesapeake Bay. Analysis of size frequency indicated that the population is numerically dominated by adults during January and February and that juveniles are common during the remainder of the year. Extrapolation of available data suggests that female crabs reach maturity in approximately one year after hatching.  相似文献   

The Würmian Late-glacial in Iowland Switzerland     

B. Ammann  A. F. Lotter  U. Eicher  M.-J. Gaillard  B. Wohlfarth  W. Haeberli  G. Lister  M. Maisch  F. Niessen  Ch. Schlüchter 《第四纪科学杂志》1994,9(2):119-125

A synthesis is provided of Late-glacial (14-9 ka BP) environmental changes in lowland Switzerland (the ‘Swiss Plateau’). The chronology of deglaciation and subsequent developments in vegetation cover in the area are summarised. The sequence of climatic variations experienced in the region during the Late-glacial is then described and a curve representing the main palaeotemperature variations is presented.  相似文献   

Seismic rays in media with slight lateral variation in velocity     

Beverley J. Moore 《Geophysical Journal International》1991,105(1):213-227

  相似文献   

Variations in mangrove forest productivity in northern Australia and Papua New Guinea     

K.G. Boto  J.S. Bunt  J.T. Wellington 《Estuarine, Coastal and Shelf Science》1984,19(3):321-329

A survey method previously developed for estimating potential net primary production (P_N) of mangrove forests was applied at 19 widely separated sites in tropical northern Australia and six sites in the Gulf of Papua. These estimates are compared with previous results for mangrove forests at Hinchinbrook Island, north Queensland. Surveys of soil properties in these areas indicate that low availability of soil phosphorus is a major contributing factor to the consistently in P_N estimates of Cape York and North-western Australian forests (range in P_N=11–26; mean P_N= 19kg C ha^?1 day^?1) compared with the Hinchin-brook Island and Gulf of Papua forests (range in P_N=3–38; mean P_N=26 kg C ha^?1 day^?1). The regional variation and possible effects of other soil properties, such as redox potential and salinity, are discussed briefly. It is suggested that the generally low salinities and moderate soil redox status may partially offset the effects of low soil P in the Cape York region.  相似文献   

The eclipsing binary V 836 Cygni: Photometric evidence for an early evolutionary status     

R. A. Breinhorst  H. W. Duerbeck 《Journal of Astrophysics and Astronomy》1982,3(3):219-231

ThreeUBV light curves of the short-period EB-type eclipsing binary V 836 Cyg, observed in 1971, 1976 and 1980, are presented. The instability of the light curve found by previous authors is confirmed. However, the activity was not very strong between 1971 and 1980. From the observed period variation, previous light-curve analysis data and spectroscopic data it is concluded that V 836 Cyg consists of two main-sequence stars, and will undergo rapid mass exchange before terminating the main sequence (case A evolution). Visiting astronomer, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation  相似文献   

Role of lateral thickness variations on the development of oblique structures at the Western end of the South Pyrenean Central Unit     

R. Soto  A. M. Casas  F. Storti  C. Faccenna 《Tectonophysics》2002,350(3)

The Montsec unit is one of the most important detached South-verging nappes within the South Pyrenean Central Unit (SPCU, Southern Pyrenees). A N–S cross-section of its Western sector, based on seismic reflection profiles, shows a hangingwall ramp geometry in Mesozoic strata, overlain by a syntectonic series of Lower Eocene sediments with growth geometry. The geometry of growth strata constrains the age of its movement between the Paleocene and the Middle Eocene. The geometry of the Western, oblique ramp of the South Pyrenean Central Unit is defined by a series of N–S folds, in some cases associated with underlying West-verging thrusts, as indicated by seismic reflection profiles and field data. In this paper, we propose that the geometry of the thrust wedge of Mesozoic units, progressively thinning from East to West, strongly contributed to constrain the location and geometry of the Western termination of the Montsec thrust. The hypothesis proposed is checked by a series of experimental wedges developed in a sandpack with lateral and three-dimensional thickness variations. Oblique structures form as thrusting progresses at the tip of the sand wedge.  相似文献   

Preliminary study on the source field mode of geomagnetic six-month-period variations     

P. F. Chen  P. C. W. Fung 《中国科学D辑(英文版)》1997,40(2):183-188

The monthly means of north component X of geomagnetic field from 16 observatories during 1984–1988 were analyzed using the Sompi spectral analysis technique Most of these observatories are located in China. The analysis of the semiannual variations indicates that the latitude has no apparent effect on the X component. This clearly implies that the source field mode of semiannual variations cannot simply be described by using the p ₁ ⁰ mode. Using the p ₁ ⁰ mode to estimate the inductive scale lengthC in the semiannual period, the value ofC at each observatory would be biased significantly. The purpose of this study is to find which kind of modes is optimal for estimating the values ofC corresponding to the semiannual variations. The results show that a composite mode, involving five terms P _n ⁰ (n = 1,, 5), might be a reasonable and acceptable one  相似文献