一个新的季风指数和全球季风的地理分布(英)   总被引：55，自引：2，他引：55  

LI Jianping  ZENG Qingcun 《大气科学进展》2003,20(2):299-302

一个新的季风指数即动态标准化季节变率被提出用来研究有关季风的问题。这个动态标准化季节变率指数能够很好地描述不同季风区的季节变化和年际变率,而且它还可以用来划分全球季风系统的地理分布。进一步,本文指出它对于深入理解季风来研究经典季风、庸季风和类季风系统的区别、联系及相互作用是非常有用的。  相似文献   

一个新的季风指数和全球季风的地理分布     

李建平  曾庆存 《大气科学进展》2003,20(2):299-302

一个新的季风指数即动态标准化季节变率被提出用来研究有关季风的问题。这个动态标准化季节变率指数能够很好地描述不同季风区的季节变化和年际变率，而且它还可以用来划分全球季风系统的地理分布。进一步，本指出它对于深入理解季风来研究经典季风、庸季风和类季风系统的区别、联系及相互作用是非常有用的。  相似文献   

南京市呼吸道疾病时间序列模型的建立与分析   总被引：1，自引：1，他引：1  

米娜谈建国  姚克敏关宏强 《气象科技》2005,33(6):554-558

利用1990～2000年南京市支气管哮喘与感冒逐月就诊人数病例资料和同期国家气象中心资料室的月平均压、温、湿等资料，讨论了2种疾病发病人数的月际和年际变化规律，分别建立了包含气象因子的预报2种疾病逐月就诊人数的条件异方差和动态回归模型。南京地区支气管哮喘就诊人数高峰期出现在春末与秋季，逐年的就诊人数呈现上升趋势，其发病与当月月平均气压、上一个月月平均温度有关。感冒就诊人数高峰期出现在夏秋季，其发病与月平均最低温度和月极端最低温度有关。将模型应用于2种疾病逐月就诊人数的等级预报中，其预报等级准确率分别达75．0％和66．7％，表明此建模方案是可行的，此类模型有一定的使用价值。  相似文献   

广州禽流感流行的气象条件分析   总被引：3，自引：3，他引：3  

范伶俐 《气象科技》2005,33(6):580-582

2003年底到2004年初在中国及其周边国家和地区爆发了高致病性禽流感，它使得这些地区几百万的家禽生病，甚至出现了人体感染死亡的现象，其危害巨大。运用对比分析的方法，对广州地区禽流感流行期间的天气形势和气温、空气湿度、风速等气象要素变化情况进行了分析，发现在2004年1月中旬至2月上旬禽流感高发期，广州地区呈现出低温高湿的气候特点，得出低温高湿的气象条件对该地区禽流感的发生和传播非常有利的结论，而2004年2月中旬以后该地区气温回升、光照充足的气象条件则抑制了禽流感的传播。  相似文献   

Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA     

DAVID B. FINKELSTEIN  LISA M. PRATT  TARA M. CURTIN†  SIMON C. BRASSELL 《Sedimentology》2005,52(3):587-599

Lithostratigraphic and organic chemostratigraphic studies of fluvial/lacustrine sediments in the Late Cretaceous Fort Crittenden Formation in south-eastern Arizona USA, reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level. The lower Fort Crittenden is dominated by marginal wetland to deep-water lake deposits, whereas the upper Fort Crittenden is characterized by wetland to deltaic deposits. Abundance of polycyclic aromatic hydrocarbons (PAH) and reflectance of fusinite substantiate the impact of wildfires within the watershed. Organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences. Sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones. Distinct variations in PAH assemblages, characterized by the number of aromatic rings, indicate that there were variations in the intensities of wildfires, assuming no variations in the types of fuel. Fusinite reflectance values are consistent with combustion temperatures from 470 to 550 °C observed in modern wildfires.  相似文献   

Assessing changes in the rainfall regime in Nigeria between 1961 and 2004     

Theophilus Odeyemi Odekunle  Samuel A. Adejuwon 《GeoJournal》2007,70(2-3):145-159

The study assessed changes in the rainfall regime in Nigeria between 1961 and 2004 in terms of (a) absolute seasonality—the length of dry and wet season; (b) relative seasonality—rainfall contrast during the year; (c) number of rainfall maxima and minima; and (d) timing of rainfall maxima and minima. Trends in the mean monthly surface locations of the Inter-tropical Discontinuity (ITD) were also examined as a prominent factor of the rainfall regime. Changes in the regime were examined over four time slices: 1961–1971, 1972–1982, 1983–1993 and 1994–2004. The results show that, in the area of single rainfall maximum regime, the length of the wet season has increased from 4 months (in 1961–1971) to 5 months (since 1972–1982). The rainfall relative seasonality has consistently been ‘most rain in 3 months or less’. The rainfall maxima still indicate single rainfall maximum but shift in the peak from August to July. Rainfall during the months of June to September appears to have witnessed declining trends over the first three time slices. The last time slice however indicates trends towards a wetter condition. For the area of double maxima rainfall regime, the length of the wet season has consistently been 8 months. The rainfall relative seasonality has consistently been ‘rather seasonal with a short drier season’. The rainfall maxima and minima still indicate double rainfall maxima with August as the month of the minimum but shift in the primary peak from July to September. The northward latitudinal distance of the surface location of the ITD from the equator indicates significant upward trends during the months of May to September only and for a period of 1983–2000. The trend results of the ITD appears to account for most of the observed changes in the rainfall regime in Nigeria.  相似文献   

基于Internet与GIS的全球禽流感时空动态分析   总被引：3，自引：0，他引：3  

孙根年  杨欢欢 《地理与地理信息科学》2006,22(6):24-29

全球禽流感的爆发具有年际尺度的周期性,且周期缩短、频率加快、危害增强,这种趋势与生态环境恶化有关;2003年以来全球禽流感的年内活动具有明显的季节性,多集中在秋末冬初和冬末春初,季节交替、气温变化剧烈是禽流感的诱发因素;通过对2000年以前和2003年以来禽流感发生地的制图研究,发现全球禽流感集中分布在从西欧、地中海、经西亚到东南亚再到拉丁美洲的弧形环带上,这里海陆交互作用强烈、飞禽和水禽活动集中,人类活动排放的某些化学毒物是病毒变异的诱因;将近年来全球禽流感时空分布与候鸟迁徙路线相比较,发现在亚欧非“世界岛”上的8条路线具有良好的对应关系,候鸟迁徙应是禽流感全球传播的重要途径。  相似文献   

Seasonal controls on DOC dynamics in nested upland catchments in NE Scotland   总被引：1，自引：0，他引：1  

Julian J. C. Dawson  Doerthe Tetzlaff  Mark Speed  Markus Hrachowitz  Chris Soulsby 《水文研究》2011,25(10):1647-1658

Spatial and temporal variability of hydrological responses affecting surface water dissolved organic carbon (DOC) concentrations are important for determining upscaling patterns of DOC export within larger catchments. Annual and intra‐annual variations in DOC concentrations and fluxes were assessed over 2 years at 12 sites (3·40–1837 km²) within the River Dee basin in NE Scotland. Mean annual DOC fluxes, primarily correlated with catchment soil coverage, ranged from 3·41 to 9·48 g m^?2 yr^?1. Periods of seasonal (summer–autumn and winter–spring) DOC concentrations (production) were delineated and related to discharge. Although antecedent temperature mainly determined the timing of switchover between periods of high DOC in the summer‐autumn and low DOC in winter‐spring, inter‐annual variability of export within the same season was largely dependent on its associated water flux. DOC fluxes ranged from 1·39 to 4·80 g m^?2 season^?1 during summer–autumn and 1·43 to 4·15 g m^?2 season^?1 in winter–spring.Relationships between DOC areal fluxes and catchment scale indicated that mainstem fluxes reflect the averaging of highly heterogeneous inputs from contrasting headwater catchments, leading to convergent DOC fluxes at catchment sizes of ca 100 km². However, during summer–autumn periods, in contrast to winter–spring, longitudinal mainstem DOC fluxes continue to decrease, most likely because of increasing biological processes. This highlights the importance of considering seasonal as well as annual changes in DOC fluxes with catchment scale. This study increases our understanding of the temporal variability of DOC upscaling patterns reflecting cumulative changes across different catchment scales and aids modelling of carbon budgets at different stages of riverine systems. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Seasonal differences in the physiology of Carcinus maenas (Crustacea: Decapoda) from estuaries with varying levels of anthropogenic contamination     

Awantha Dissanayake  Tamara S. Galloway  Malcolm B. Jones 《Estuarine, Coastal and Shelf Science》2011

This study reports the seasonal variability in aspects of the physiology of the shore crab Carcinus maenas from three estuaries in South-west England, each with varying anthropogenic inputs: Avon Estuary (‘relatively low’ impact), Yealm Estuary (‘intermediate’ impact) and Plym Estuary (‘relatively high’ impact). Crabs collected over 12 months from the Avon had a significantly ‘lower’ physiological condition in winter and spring compared to summer and autumn; in particular, haemocyte phagocytic capability (a general indicator of immune function) was significantly higher in winter and spring compared to summer and autumn, and total haemolymph antioxidant status (an indicator of oxidative stress) was significantly lower in winter compared to the remainder of the year. Potentially, shore crabs may be more susceptible to the effects of contaminant exposure, such as increased immunotoxicity (thus, reduction of immune function) and/or oxyradicals (or reactive oxygen species) exposure) especially in seasons of increased susceptibility i.e. summer/autumn (lower phagocytic capability) and winter (lowest antioxidant function). As the Avon was taken to represent the ‘reference’ site, this pattern is considered to reflect the ‘normal’ seasonal variability in shore crab physiology. Shore crab physiological condition from the ‘relatively high’ impact estuary (Plym) revealed increased cellular viability and antioxidant status in autumn and winter compared with that of the ‘standard’ pattern (Avon) However, crabs from the intermediate impact estuary (Yealm) only demonstrated significant physiological differences in summer as shown by a lower cellular viability. All crabs had been exposed to PAHs (confirmed by the presence of PAH metabolites in their urine) which may account for the observed differences in shore crab physiology. In conclusion, to aid understanding of the potential contaminant impacts on biota it is imperative that the ’normal’ seasonal variability of physiological condition be established. Biological effects-based monitoring studies should therefore be employed seasonally to potentially highlight ‘windows of sensitivity’ to contaminant impact.  相似文献   

Impact of climate variability on ichthyoplankton communities: An example of a small temperate estuary     

Ana Lígia Primo  Ulisses Miranda Azeiteiro  Sónia Cotrim Marques  Miguel Ângelo Pardal 《Estuarine, Coastal and Shelf Science》2011

Recent variations in the precipitation regime across southern Europe have led to changes in river fluxes and salinity gradients affecting biological communities in most rivers and estuaries. A sampling programme was developed in the Mondego estuary, Portugal, from January 2003 to December 2008 at five distinct sampling stations to evaluate spatial, seasonal and inter-annual distributions of fish larvae. Gobiidae was the most abundant family representing 80% of total catch and Pomatoschistus spp. was the most important taxon. The fish larval community presented a clear seasonality with higher abundances and diversities during spring and summer seasons. Multivariate analysis reinforced differences among seasons but not between years or sampling stations. The taxa Atherina presbyter, Solea solea, Syngnathus abaster, Crystallogobius linearis and Platichthys flesus were more abundant during spring/summer period while Ammodytes tobianus, Callionymus sp., Echiichthys vipera and Liza ramada were more abundant in autumn/winter. Temperature, chlorophyll a and river flow were the main variation drivers observed although extreme drought events (year 2005) seemed not to affect ichthyoplankton community structure. Main changes were related to a spatial displacement of salinity gradient along the estuarine system which produced changes in marine species distribution.  相似文献