外热带大气扰动对ENSO的影响   总被引：4，自引：0，他引：4       下载免费PDF全文

薛峰  何卷雄 《地球物理学报》2007,50(5):1311-1318

合成分析了20世纪80年代以来5次主要的ENSO事件,发现外热带大气扰动通过经向风异常不仅对ENSO的发生起到重要的触发作用,而且影响到ENSO的发展和衰减. 因此,尽管ENSO对外热带大气扰动有影响,但同时外热带大气扰动又与ENSO有相互作用. 在ENSO发生前,南印度洋中纬度为反气旋异常,并通过Rossby波的频散作用加强了澳大利亚附近的反气旋异常;同时,澳大利亚东部沿海的南风异常与菲律宾附近的北风异常在赤道辐合,促进了赤道西太平洋西风异常的爆发和其后ENSO的发生. 在ENSO发生之后,东南太平洋上的气旋异常及相关的南风异常进一步增强了赤道中东太平洋的西风异常和ENSO的发展. 当ENSO达到成熟时,澳大利亚东部的反气旋异常东移,使东南太平洋的气旋异常减弱,南方涛动型环流异常亦随之减弱;同时,阿留申气旋异常加强,尤其是副热带北太平洋的风场异常可加强赤道中东太平洋海水的涌升,使该地区海表温度降低,加速ENSO的消亡.  相似文献   

地震期间电离层扰动现象研究   总被引：9，自引：1，他引：8       下载免费PDF全文

蔡军涛  赵国泽  詹艳  汤吉  陈小斌 《地球物理学进展》2007,22(3):695-701

介绍了大量的关于地震电离层扰动现象研究的最新进展,研究表明地震发生前的几天或者几个小时电离层扰动被观测到,电离层前兆是确实存在.但要将震前的电离层扰动作为地震短临预报的工具,还有许多值得我们去深入研究和解决的问题.应用空间技术开展大区域范围内电离层参数的实时观测,如用地震电磁卫星、GPS台网、并和地面电离层垂测仪观测相结合,建立“电离层地震前兆监测系统”,无疑会加速这项研究的进程.  相似文献   

The impact of extreme turbidity events on the nursery function of a temperate European estuary with regulated freshwater inflow     

E. González-Ortegón  M.D. Subida  J.A. Cuesta  A.M. Arias  C. Fernández-Delgado  P. Drake 《Estuarine, Coastal and Shelf Science》2010

Estuaries are used as nursery grounds by numerous marine species despite being usually subject to strong anthropogenic disturbances. Abundances of marine recruits (fish and crustacean decapods) and their main prey (mysids) were monitored by monthly sampling, from June 1997 to February 2009, in the lower reaches of the Guadalquivir estuary (SW Spain). During that period, unusually high and persistent turbidity events (HPTEs) were observed twice. Both HPTEs started with strong and sudden freshwater discharges after relatively long periods of very low freshwater inflow. Data from this time-series were used to test the hypothesis that HPTEs may negatively impact the nursery function of estuaries either by decreasing prey availability or by decreasing survival/arrival of marine recruits. During HPTEs, the commonest mysid (Mesopodopsis slabberi), a key species in the estuarine food web, showed a significant decrease in abundance. Likewise, some marine recruits that prey on M. slabberi and whose peaks of abundance within the estuary occur in summer–autumn (Engraulis encrasicolus and Pomadasys incisus) were less abundant during HPTEs. It is also suggested that HPTEs might have triggered a shift in the distribution of the most euryhaline prey (Neomysis integer) and predator (Dicentrarchus punctatus and Crangon crangon) species, towards more saline waters. This could have contributed to an increase in the inter-specific competition (for food/habitat) within the estuarine nursery area. The results discussed in this study call attention to the need to reduce as much as possible the anthropogenic pressures that may stimulate the occurrence of high and persistent turbidity events (HPTEs) in order to preserve the nursery function of temperate estuaries.  相似文献   

Isotopic analysis to quantify the role of the Indian monsoon on water resources of selected river basins in the Himalayas     

Ghulam Jeelani  Rouf Ahmad Shah  Rajendrakumar D. Deshpande  Ashok P. Dimri  Suraj Mal  Anupam Sharma 《水文研究》2021,35(11):e14406

Western disturbances (WDs) and Indian summer monsoon (ISM) led precipitation play a central role in the Himalayan water budget. Estimating their contributions to water resource is although a challenging but essential for hydrologic understanding and effective water resource management. In this study, we used stable water isotope data of precipitation and surface waters to estimate the contribution of ISM and WDs to the water resources in three mountainous river basins - Indus, Bhagirathi and Teesta river basins of western, central and Eastern Himalayas. The study reveals distinct seasonality in isotope characteristics of precipitation and surface waters in each river basin is due to changes in moisture source, hydrometeorology and relief. Despite steady spatial variance in the slope and intercept of regression lines from the Teesta to Indus and the Bhagirathi river basins, the slope and intercept are close to the global meteoric water line and reported local meteoric water line of other regions in the Himalayas and the Tibetan Plateau. The two-component end-member mixing method using d-excess as tracer were used to estimate the contribution from ISM and WD led precipitation to surface water in aforementioned river basins. The results suggest that the influence of the ISM on the water resources is high (>72% to annual river flow) in Teesta river basin (eastern Himalayas), while as the WDs led precipitation is dominantly contributing (>70% average annual river flow) to the surface waters in the Indus river basin (western Himalayas). The contribution of ISM and WD led precipitation in Bhagirathi river basin is 60% and 40%, respectively. The findings demonstrate that the unusual changes in the ISM and WD moisture dynamics have the potential to affect the economy and food security of the region, which is dependent on the availability of water resources. The obtained results are of assistance to policy makers/mangers to make use of the information for better understanding hydrologic response amid unusual behaviour of the dual monsoon system over the region.  相似文献   

Ecohydrology-a challenging multidisciplinary research perspective / Ecohydrologie: une perspective stimulante de recherche multidisciplinaire     

AMILCARE PORPORATO  IGNACIO RODRIGUEZ-ITURBE 《水文科学杂志》2013,58(5):811-821

Abstract

Ecohydrology is the science that studies the mutual interaction between the hydrological cycle and ecosystems. Such an interaction is especially intense in water-controlled ecosystems, where water may be a limiting factor, not only because of its scarcity, but also because of its intermittent and unpredictable appearance. Soil moisture is the key variable modulating the complex dynamics of the climate-soil-vegetation system and controlling the spatial and temporal patterns of vegetation. In this note the authors' perspective to the field is discussed and some open questions are outlined.  相似文献   

Polar regionSq     

Wen-Yao Xu 《Pure and Applied Geophysics》1989,131(3):371-393

Geomagnetically quiet day variations in the polar region are reviewed with respect to geomagnetic field variation, ionospheric plasma convection, electric field and current. Persistently existing field-aligned currents are the main source of the polar regionSq. Consequently, the morphology and variability of the polar regionSq largely depend upon both field-aligned currents and ionospheric conductivity. Since field-aligned currents are the major linkage between the ionosphere and the magnetosphere, the latter is controlled by solar wind state, in particular, the interplanetary magnetic field, the polar regionSq exhibits remarkable IMF dependence.  相似文献   

Electron loss and the determination of electron concentrations in theD-region     

W. Swider 《Pure and Applied Geophysics》1988,127(2-3):403-414

The most meaningful way to compare observations of the daytimeD-region under all ionization conditions, for the purpose of improving our understanding of this region, would appear to be through use of the effective electron recombination coefficient, =q/[e]², whereq is the ionization production rate, and where [e] is the electron concentration. This ratio apparently increases monotonically with decreasing altitude, and is much less variable than its componentsq and [e]. This parameter appears eminently suitable as a best first order solution to [e] after determiningq. For nighttime conditions, is more sensitive toq. However, an accurate but simple formula exists for the calculation of electron concentrations.  相似文献   

Some results of night-time scintillations at low latitude     

Sushil Kumar  S K Vijay  A K Gwal 《Journal of Earth System Science》1993,102(2):307-312

Ionospheric scintillation observations of VHF radio signals from FLEETSAT satellite (73°E longitude) at Bhopal from January 1990 to December 1990 have been used to study the characteristic variations of scintillation activity. It is found that scintillation occurrence is essentially a night-time phenomenon and day-time scintillations are very rare. Annual average nocturnal variation of percentage occurrence of scintillations shows maximum at around 2100–2200 hours LT. Seasonally, scintillations are most prominent during equinoxes and least during summer. Geomagnetic disturbances tend to decrease the occurrence of scintillations in the pre-midnight period.  相似文献   

吉林省岩溶洞穴旅游资源及其开发中的问题讨论   总被引：2，自引：0，他引：2  

李方正  李立志 《吉林地质》1994,13(4):50-58

近年来，在吉林省中部和东南部地区，发现了一批岩溶洞穴，尚未开发利用者为多数，它们分布在奥陶系马家沟组灰岩和石炭系磨盘山组石灰岩中，规模多为中小型，个别较大，具有开发意义，建议从速开发，面向旅游事业，为振兴吉林省经济服务。  相似文献   

On induction effects at EISCAT and IMAGE magnetometer stations     

Ari Viljanen  Kirsti Kauristie  Kari Pajunpää 《Geophysical Journal International》1995,121(3):893-906

  相似文献