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1.
云南南部与东南部热带地区在地理上接近,具有类似的热带季风气候和热带雨林植被,它们的植物区系均以热带成分占优势,在现代植物区系分区上都属于热带亚洲或印度—马来西亚植物区系。研究发现在云南东南部植物区系中具有丰富的东亚植物区系的代表成分,如木兰科、山茱萸科、菝葜科、茶科、安息香科、山矾科、忍冬科、冬青科、卫矛科等,意味着它... 相似文献
2.
利用美国NCAR CAM3大气环流模式,分析了末次盛冰期（LGM）两个不同的热带海表温度重建方案中,北半球冬季热带中、西太平洋对流活动及大气环流对暖池外（赤道东太平洋和热带大西洋）热带SST异常的敏感性。结果表明： 1）SST异常首先引起大气环流的改变。 赤道东太平洋对流层下沉增强,而作为经向补偿,副热带东太平洋上升运动增强,其中南半球尤为明显,同时南半球热带中、西太平洋上升运动增强,加剧了该区纬向逆时针环流,说明冰期热带海气耦合过程受气候背景场（如SST）影响很大; 2）大气环流格局改变引起热带中西太平洋的大气加热、对流活动、表层风场及降雨的巨大变化。 140°E以西的婆罗洲和菲律宾区域,总的大气加热减少是由于对流与辐射加热减少所致,对应于该区风场辐散和降雨减少; 而140°E以东的南半球热带中、西太平洋,大气吸收热量增加,对流与辐射加热均增强,总降雨量也随之增加,反映该区赤道辐合带南移并增强。该项研究为探索热带太平洋在冰期/间冰期旋回中的古海洋学变化提供了新的数据支撑。此外,不同重建SST对赤道辐合带的影响比较大,因此利用重建SST进行数值模拟或者利用耦合模式研究LGM热带海气相互作用时,应该十分重视全球热带SST分布特征。 相似文献
3.
热带平流层准两年振荡对热带对流层顶和深对流活动的影响 总被引：1，自引：0，他引：1
利用NCEP/NCAR再分析资料通过合成分析的方法研究了热带平流层准两年振荡(QBO)影响热带对流层顶及深对流活动的基本特征及可能的物理机制。研究发现,QBO对对流层顶和大气射出长波辐射(OLR)的影响存在明显的季节和空间上的差异。QBO对对流层顶和OLR的影响在冬、秋季最大,春、夏季相对较弱。与QBO造成的对流层顶高度和温度异常所不同是,QBO造成的OLR异常并没有呈现出一样的沿热带的带状分布特征,OLR异常沿赤道区域有正有负。另外,QBO对OLR的影响主要在热带对流活跃区域,尤其是在印度尼西亚和西太平洋区域,QBO东风位相下的对流活动要强于QBO西风位相下的对流活动。QBO造成的OLR异常和对流层顶异常在水平分布上有显著的差异,表明QBO对对流层顶的影响主要是与QBO风切变的异常有关,QBO影响热带深对流活动进而影响对流层顶温度的作用是次要的。进一步研究QBO影响对流活动可能的机制发现,QBO造成的浮力频率异常和对流层有效位能(CAPE)异常与OLR异常在水平分布上有较一致的变化,说明QBO不仅通过调节对流层顶高度和温度影响热带的深对流活动,还可以通过调节对流层的静力稳定度、CAPE来影响热带地区深对流活动。 相似文献
4.
塔里木及邻区晚古生代早期古气候与构造 总被引：2，自引：0，他引：2
影响塔里木及邻区晚古生代早期气候的地球内部因素为古昆仑和南天山两个古洋盆封闭及有关的两条缝合构造带演化，从而形成上述时空段内热带海洋气候、热（亚热）带季风气候、热带沙漠气候以及热带滨岸干湿气候区域的更替，古气候特征的判断主要依据古地磁数据、古生态气候学、沉积环境诸方面。 相似文献
5.
The classification and influencing factors of modern marine productivity were reviewed at the beginning. We discussed the pros and cons of different paleoproductivity proxies. Based on these discussions, we collected paleoproductivity reconstructions in tropical marine from previous studies and focus on the glacial-interglacial features, periodicity and forcing mechanisms of tropical marine productivity. We found that the productivity in most tropical sites decreased from MIS 2 to MIS 1. The productivity was not always higher in glacial: The glacial-interglacial pattern of productivity turned at MIS 22 in western Pacific. There were remarkable differences between tropical productivity and high latitude productivity. The precession and obliquity bands were more significant in tropical productivity and ~30 ka cycles caused by the superimposing of different orbital cycles were common in tropical. The coccolith based productivity seemed to have a quasiperiod of 400 ka and more researches are needed to discover the relationship between productivity and global 13C in this band. 相似文献
6.
Fine assessment of tropical cyclone disasters based on GIS and SVM in Zhejiang Province, China 总被引：1，自引：1，他引：0
Tropical cyclones represent major natural disasters in low- and mid-latitude coastal areas. Effective assessment of tropical cyclone disasters provides a scientific reference for the formulation of tropical cyclone prevention and disaster-relief measures. Tropical cyclone disasters in Zhejiang Province are mainly studied based on GIS technology, by considering disaster-causing factors, disaster-affected bodies, the disaster-formative environment, and spatial distribution of disaster prevention and relief capacity. In light of an uncertain nonlinear relationship between assessment factors and disaster factors, we used support vector machines to establish a fine, quantitative assessment model. This model evaluates the following disaster indices: Disaster-affected population, direct economic loss, affected crop area, and number of damaged houses resulting from a tropical cyclone disaster in Zhejiang, with the county as basic assessment unit. Assessment of tropical cyclone No. 0908 shows that the developed assessment model is able to accurately evaluate the geographical distribution of losses caused by a tropical cyclone. 相似文献
7.
In recent years, tropical cyclones on the Pacific Northwest have decreased. We cannot infer that tropical cyclones impact China have reduced, because the Pacific Northwest is not homogeneous, and the variation characteristics of tropical cyclones in different sea areas are not clear. This paper uses gray relational density clustering algorithm to cluster tropical cyclone data sets between 1949 and 2008, according to the generated position of tropical cyclones, generated density and the possibility of landing. The Pacific Northwest is divided into different sea areas. Then, we analyze the risk of tropical cyclones generated in these sea areas. The results show that the probability of tropical cyclones landing generated in some sea areas is very high, reached 74 %, but the probability of tropical cyclones landing generated in other sea areas is only 2 %. Tropical cyclones generated in some sea areas are more likely to develop into typhoons, strong typhoons and so on, but the intensity of tropical cyclones generated in other sea areas is lower, there is little risk for China. Finally, according to the climate change stage trends, we divide the period 1949–2008 into three stages and analyze the tropical cyclone risk of each sea areas. 相似文献
8.
Since the launch of the first satellite in 1972, ecologists have been equipped with new tools to address the degradation of
tropical forests, previously limited by field-based methods. This article is a review of the state of remote sensing technology
in characterizing the degradation of tropical forest. The factors responsible for the structural and functional degradation
of the tropical forest and its likely impacts are described in view of generating remote sensing based inputs. In order to
assess the degradation and utility of geo-informatics tools, 32 parameters are identified. The research developments at different
levels of information extraction from the historic to recent periods are elaborated, and future challenges are predicted.
The article concludes that an additional momentum of research is required to answer many unresolved questions of tropical
forest degradation. 相似文献
9.
Dominik Brill Katharina Seeger Anna Pint Felix Reize Kay Thwe Hlaing Martin Seeliger Stephan Opitz Khin Mi Mi Win Win Thuzar Nyunt Nilar Aye Aung Aung Kyaw Kyaw Frauke Kraas Helmut Brückner 《Sedimentology》2020,67(3):1431-1459
The catastrophic storm surge of tropical cyclone Nargis in May 2008 demonstrated Myanmar's exposure to coastal flooding. The investigation of sediments left by tropical cyclone Nargis and its predecessors is an important contribution to prepare for the impact of future tropical cyclones and tsunamis in the region, because they may extend the database for long-term hazard assessment beyond the relatively short instrumental and historical record. This study, for the first time, presents deposits of modern and historical tropical cyclones and tsunamis from the coast of Myanmar. The aim is to establish regional sedimentary characteristics that may help to identify and discriminate cyclones and tsunamis in the geological record, and to document post-depositional changes due to tropical weathering in the first years after deposition. These findings if used to interpret older deposits will extend the existing instrumental record of flooding events in Myanmar. Evaluating deposits that can be related to specific events, such as the 2006 tropical cyclone Mala and the 2004 Indian Ocean tsunami, indicates similar sedimentary characteristics for both types of sediments. Landward thinning and fining trends, littoral sediment sources and sharp lower contacts allow for the differentiation from underlying deposits, while discrimination between tropical cyclone and tsunami origin is challenging based on the applied methods. The modern analogues also demonstrate a rather low preservation potential of the sand sheets due to carbonate dissolution, formation of organic top soils, and coastal erosion. However, in coastal depressions sand sheets of sufficient thickness (>10 cm) may be preserved where the shoreline is prograding or stable. In the most seaward swale of a beach-ridge plain at the Rakhine coast, two sand sheets have been identified in addition to the deposits of 2006 tropical cyclone Mala. Based on a combination of optically stimulated luminescence, radiocarbon and 137Cs dating, the younger sand layer is related to 1982 tropical cyclone Gwa, while the older sand layer is most probably the result of an event that took place prior to 1950. Comparison with historical records indicates that the archive is only sensitive to tropical cyclones of category 4 (or higher) with landfall directly in or a few tens of kilometres north of the study area. While the presented tropical cyclone records are restricted to the last 100 years, optically stimulated luminescence ages of the beach ridges indicate that the swales landward of the one investigated in this study might provide tropical cyclone information for at least the past 700 years. 相似文献
10.
The interannual variability of near-coastal eastern North Pacific tropical cyclones is described using a data set of cyclone tracks constructed from U.S. and Mexican oceanic and atmospheric reports for the period 1951-2006. Near-coastal cyclone counts are enumerated monthly, allowing us to distinguish interannual variability during different phases of the May-November tropical cyclone season. In these data more tropical cyclones affect the Pacific coast in May-July, the early months of the tropical cyclone season, during La Niña years, when equatorial Pacific sea surface temperatures are anomalously cool, than during El Niño years. The difference in early season cyclone counts between La Niña and El Niño years was particularly pronounced during the mid-twentieth century epoch when cool equatorial temperatures were enhanced as described by an index of the Pacific Decadal Oscillation. Composite maps from years with high and low near-coastal cyclone counts show that the atmospheric circulation anomalies associated with cool sea surface temperatures in the eastern equatorial Pacific are consistent with preferential steering of tropical cyclones northeastward toward the west coast of Mexico. 相似文献
11.
Since tropical rainfall is important in the global energy and hydrologic cycle, the tropical rainfall changes under global warming have attracted extensive attention around the world in recent decades. The advances in the observational studies and model projection for the tropical rainfall changes under global warming were reviewed here. The frontiers in the mechanism of regional tropical rainfall changes and the approaches of rainfall change research are summarized. The large intermodel spread in the multi-model projections, the sources of uncertainty and the methods to reduce the uncertainty were also introduced. Finally, the challenges about the tropical rainfall changes were discussed. 相似文献
12.
The differences and similarities between near-pristine estuaries of different latitudinal regions were examined by selecting three tropical systems from North Queensland, Australia (Jardine, Annan, Daintree) and three temperate systems from Scotland, United Kingdom (Inverness, Cromarty, Dornoch Firths) for comparison. Although estuaries from the different regions have a number of unifying features, such as salinity gradients, tidal variations and terrestrial inputs they also have a number of important differences. The most distinct of these is the timing and variability of the major physical forcings on the estuary (e.g., river flow, insolation). The three tropical estuaries were much more episodic than their temperate counterparts, with a much more dynamic salinity structure and more variable riverwater concentrations, so that delivery of material to the estuary is dominated by short-lived flood events. In contrast, seawater concentrations were more stable in the tropical estuaries due to a more constant input of insolation, resulting in year round biological activity. There was biological removal of dissolved inorganic phosphorus in the low salinity region of the tropical Jardine and Daintree estuaries and a low salinity input of nitrate in the tropical Annan estuary most likely due to nitrification in the bottom sediments, and the biological reaction zone in the tropical Annan Estuary was flushed out of the estuarine basin to the edge of the offshore plume during a flood. Similar effects were not seen in the temperate Inverness, Cromarty, and Dornoch Firths. Similarities between estuaries include mid-estuary inputs of ammonium which were seen in both the temperate and tropical estuaries, although they occur under vastly contrasting conditions of low river discharge and periods of flood, respectively. Five of the estuaries show a general increase in dissolved inorganic phosphorus concentrations towards the sea during low flows, reflecting their pristine condition, and all six estuaries had low salinity silicate maxima probably sourced from the dissolution of freshwater biogenic silicate that has been carried seaward, except in the tropical estuaries during the dry season when a benthic source is proposed. 相似文献
13.
Tropical forests play a crucial role in the function of our planet and in the maintenance of life. Tropical forest vegetation maps are very important for managing tropical forests. Mapping tropical forest vegetation only by spectral-based remote sensing techniques has proven to be problematic. The objective of the study is to develop a rule-based model to identify different forest types using Landsat TM images and GIS. In this paper, we developed the rule-based model to identify different forest types in Xishuangbanna, P.R. of China, using two temporal Landsat TM images and geo-data such as DEM, rainfall and temperature. The results show that the method put forward is useful and effective in tropical forest vegetation mapping, which can effectively integrate multi-knowledge and multi-resource data to identify the tropical forest vegetation types with higher accuracy. 相似文献
14.
本文回顾了近年来有关热带内外地区相互作用的研究进展。它主要包括三个方面：（１）热带外扰动对热地区的影响；（２）热带地区大气了研究；（３）热带对热带外地区的影响。本文内容涉及了有关观测资料分析、理论研究以及数值试验三个方面的研究成果。 相似文献
15.
16.
Stephen Vermette 《Natural Hazards》2007,42(1):91-103
The tropical storm database used in this study was obtained from the National Oceanic and Atmospheric Administration’s (NOAA)
Coastal Service Center, using the Historical Hurricane Tracks tool. Queries were used to determine the number of storms of
tropical origin that have impacted the State and each of its counties. A total of 76 storms of tropical origin passed over
New York State between 1851 and 2005. Of these storms, 14 were classified as hurricanes. The remaining hurricanes passed over
New York State as weaker or modified systems—27 tropical storms, 7 tropical depressions, and 28 extratropical storms (ET).
Long Island experiences a disproportionate number of hurricanes and tropical storms. The average frequency of hurricanes and
storms of tropical origin (all types) is one in every 11 years and one in every 2 years, respectively. September is the month
of greatest frequency for storms of tropical origin, although the storms of greatest intensity tend to arrive later in the
hurricane season and follow different poleward tracks. While El Nino Southern Oscillation (ENSO) cycles appear to show some
influence, the frequency and intensity of storms of tropical origin appear to follow a multidecadal cycle. Storm activity
was greatest in both the late 19th and 20th centuries. During periods of increased storm frequency and intensity storms reached
New York State at progressively later dates. While the number and timing of storms of tropical origin is likely to increase,
this increase appears to be attributed to a multidecadal cycle, as opposed to a trend in global warming. 相似文献
17.
The present work is concerned with the study of intensification of tropical disturbances with a view to improve prediction
and early warning. The tropical disturbances are known to come in sizes (radii) ranging from 100–400 kms. Since the vortices
of different sizes give rise to different initial convergence fields and since the subsequent development of the tropical
depressions is very sensitive to the initial convergence fields, we argue that the size of the incipient vortex is likely
to be an important factor in determining the subsequent development of a tropical disturbance.
We have examined the above hypothesis using an axisymmetric model of tropical cyclone. The incipient vortex is introduced
by prescribing an initial temperature perturbation with wind in gradient balance. The results show a fairly sharp selection
of scale at about 250 km radius. This implies that out of a number of initial disturbances of varying sizes and embedded in
the same large scale environment, it is the vortex with about 250 km radius size that will develop to the most severe system.
The sensitivity of this selective intensification at this incipient vortex radius to initial perturbation field and the mean
thermodynamic state is investigated. Finally, the importance of such a selective scale of intensification for prediction,
tracking and early warning of tropical cyclones is emphasized. 相似文献
18.
Benthic carbonate factories of the Phanerozoic 总被引：3，自引：0，他引：3
Wolfgang Schlager 《International Journal of Earth Sciences》2003,92(4):445-464
Marine carbonate precipitation occurs in three basic modes: abiotic (or quasi-abiotic), biotically induced, and biotically controlled. On a geologic scale, these precipitation modes combine to form three carbonate production systems, or "factories" in the benthic environment: (1) tropical shallow-water factory, dominated by biotically controlled (mainly photo-autotrophic) and abiotic precipitates; (2) cool-water factory, dominated by biotically controlled (mainly heterotrophic) precipitates; and (3) mud-mound factory, dominated by biotically induced (mainly microbial) and abiotic precipitates. Sediment accumulations of the factories differ in composition, geometry, and facies patterns, and some of these differences appear prominently in seismic data, thus facilitating subsurface prediction. The characteristic accumulation of the tropical factory is the flat-topped, often reef-rimmed platform. In cool-water systems, reefs in high-energy settings are scarce and hydrodynamic influence dominates, producing seaward-sloping shelves and deep-water sediment drifts often armored by skeletal framework. The typical accumulation of the mud-mound factory is groups of mounds in deeper water. Where the mud-mound factory expands into shallow water, it forms rimmed platforms similar to the tropical factory. The tropical factory is most productive; the mud-mound factory reaches 80–90%, and the cool-water factory 20–30% of the tropical growth rate. The three factories represent end members connected by transitions in space. Transitions in time are linked to biotic evolution. 相似文献
19.
Michael E Brookfield 《Sedimentary Geology》1988,60(1-4):137-153
Mid-Ordovician limestones of southern Ontario are usually considered to be tropical shelf limestones and interpreted using facies models derived from Recent tropical carbonate environments. Nevertheless, depositional rates, grain types, faunas, erosion surfaces, mineralogy and geochemistry are more compatible with a temperate or even cold shelf environment. In view of the low latitudes (20°S) indicated by paleomagnetism, this suggests deposition in relatively cold seas, deposition below a tropical thermocline, or that the paleomagnetic data are wrong. Similar features in other Caradocian limestones of eastern North America show that these inferred cooler conditions were widespread. If deposition occurred below a tropical thermocline, most shallow-water Caradocian limestones must be re-interpreted as deeper-water deposits. More likely, in view of the evidence for temperate conditions in shallow water, is that the whole eastern seaboard of North America was affected by cold currents arising from southern polar ice caps, and thus was a temperate shelf environment. 相似文献
20.
利用Scripps海温再分析资料,对赤道印度洋0～400m深度范围内海温变化和偶极子异常变化特征进行了初步分析。结果显示,赤道印度洋上层海温呈现西低东高,而次表层以下海温则为西高东低。同时发现,温跃层是赤道印度洋上、下层很好的分界面。温跃层之上海温变化受海气相互作用明显,之下海温变化主要受海洋自身的运动影响。赤道印度洋偶极子现象存在于各个深度,其偶极子指数变化存在半年周期,季节变化表现为双峰双谷型,并从深层（400m）向表层传递。分析发现,海气相互作用不是表层赤道印度洋偶极子变化的决定因素。较深层偶极子变化决定于海洋自身的运动变化特征（如洋流）,并向上层传输,进而影响上层偶极子的异常变化。赤道印度洋偶极子指数由西印度洋和东印度洋海温变化共同制约,但西印度洋海温变化起主导作用,东印度洋仅起到加强或减弱偶极子强度变化的作用。 相似文献