首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Changes in rainfall pattern have been suggested as a mechanism for the landward incursion of mangrove into salt marsh. The aim of the research was to assess the relationship between rainfall patterns and the spatial distribution of mangrove forests at study sites in Moreton Bay, Southeast Queensland, Australia, over a 32-year period from 1972 to 2004. To identify periods of relatively consistent rainfall patterns points at which rainfall patterns changed (change-points) were identified using the non-parametric Pettitt–Mann–Whitney-Statistic and the cumulative sum technique. The change-points were then used to define the temporal periods over which changes to mangrove area were assessed. Both mangrove and salt marsh area were measured by digitizing aerial photographs acquired in 1972, 1990 (the year with the most significant change-point), and 2004. The rates of change in mangrove area pre-1990 (a wetter period) and post-1990 (a drier period) were estimated. A significant positive relationship was demonstrated between rainfall variables and landward mangrove expansion, but not for seaward expansion. We concluded that rainfall variability is one of the principal factors influencing the rate of upslope encroachment of mangrove. However, the rate of expansion may vary from site to site due to site-specific geomorphological and hydrological characteristics and the level of disturbance in the catchment.  相似文献   

2.
Lake Manapouri in the South Island of New Zealand has a significant hydroelectric generation facility, which potentially has a negative impact on the successful emigration of longfin eels (Anguilla dieffenbachii) from the upper Waiau catchment. Consequently, a trap-and-transfer programme has been implemented to allow silver (migratory) eels access to the sea. The present study analysed data on the timing of captures and numbers of silver eels over four seasons, including the influence of possible migration cues. Silver eels were captured over an extended season of seven months (November–May), with peak numbers during December and January. Flow at the lake outflow was found to have a weak relationship with the number of eels caught, as did lake level, but moon phase and rainfall had no significant effect. These results highlight the variability in silver longfin eel behaviour both in terms of timing and response to potential environmental cues.  相似文献   

3.
ABSTRACT

The planting of degraded land with tree plantations may be effective at improving land use sustainability and profitability but it can also have significant effects on stream hydrology. In this paired catchment study, we report the stream hydrological response to partial (62%) afforestation of a steep pastoral catchment in the western Waikato Region, North Island, New Zealand. We comprehensively analyse the hydrological regime changes over a 23-year period (including eight years before pine planting) with reference to a native-forested ‘control’ catchment. Our results show that afforestation has markedly affected stream hydrology. Seven years after planting, the total annual runoff was 380?mm lower than predicted for the catchment in pasture. Two phases of plantation thinning resulted in the difference between measured and predicted runoff reducing to only 129?mm. Peak flows reduced by ～50% while total stormflow reduced by ～30% – which we attribute to canopy interception attenuating and delaying water yield. The impact of plantation establishment on low flows is not so clear, although afforestation appears to have reduced low flows by ～25%. This study provides information on the hydrological impact of afforestation within a hitherto poorly-represented New Zealand environment (i.e. high rainfall, sedimentary lithology-based, North Island hill country).  相似文献   

4.
对赣北黄茅潭近代湖泊沉积岩芯进行了~(137)Cs、~(210)Pb测试和SCP(球状碳粒)计数分析,阐述了~(137)Cs蓄积特征,结合SCP计数、粒度指标及降水记录厘定了一些事件性沉积层位。研究表明,1986年前后是沉积环境中~(137)Cs行为的转折点;在这之前,~(137)Cs以大气散落为主,其蓄积行为大致与降水存在正相关关系,在这之后,~(137)Cs以流域侵蚀为主,其蓄积行为与降水呈负相关关系。1953—1954年、1974—1975年、1998—1999年,流域降水丰沛,相应沉积层位~(137)Cs比活度低,这与流域强烈侵蚀稀释了进入湖泊的~(137)Cs有关。1963—1964年沉积层位~(137)Cs蓄积峰稳定而显著,与高通量的大气散落有关,也与当时降水量低,大雨、暴雨次数少,流域侵蚀强度低造成较低的沉积速率等密切相关,是可靠的定年时标。1986年存在同样的气候环境特点,其蓄积峰可能也是存在的,但需要进一步确认。基于~(210)Pb方法,利用多种计年模式计算了沉积岩芯的年代,发现与这些事件性沉积层位具有较大差异。研究认为,在长江中游这种降水高、流域侵蚀强度高的较为复杂的沉积环境中,~(210)Pb计年存在较大误差。复杂沉积环境中近代沉积的定年,有必要深度挖掘~(137)Cs环境行为,在全面阐述其蓄积特点的基础上,辅以SCP计数、粒度指标及降水等识别事件性沉积层位,矫正~(210)Pb计年,是精确建立近代沉积时标的必要方法。  相似文献   

5.
We compared fish community structure in Guaratiba Mangrove, SE Brazil, among three seasons of the hydrological cycle [(i) spring, increasing temperature and rainfall, decreasing salinity; (ii) summer/early fall, high temperature and rainfall, intermediate salinity; (iii) late fall/winter, low temperature and rainfall, high salinity] and between the years 2002–2003 and 2008–2009. The aim was to test the hypothesis that the fish community structure changes seasonally, associated with seasonal changes in environmental conditions, and that changes occurred between the two yearly periods because of increased anthropogenic activities. The sampling protocol for the two surveys was identical. A total of 63 species was recorded, with 38 species occurring in 2002–2003, and 53 species in 2008–2009. The main changes in the mangrove's fish assemblage between 2002–2003 and 2008–2009 were (i) an increase in species richness, fish density and total biomass; and (ii) an increase in the zoobenthivorous species of gerreids Eucinostomus argenteus, Diapterus rhombeus and Ulaema lefroyi, and a decrease in the planktivorous clupeid Harengula clupeola. Other abundant species, such as the opportunistic atherinopsid. Atherinella brasiliensis, the detritivorous mullet Mugil liza and the zoobenthivorous pufferfish Sphoeroides testudineus did not differ in abundance between the two yearly periods. Ten species occurred only in 2002–2003, and 23 species only in 2008–2009, indicating significant changes in community structure over the 6‐year period. Seasonal changes in community structure were more conspicuous in 2008–2009, when species abundance and richness were greatest. The highest fish abundance was recorded in spring and in summer/early fall, and the lowest in late fall/winter. The increased abundance and richness over time may be at least partially attributable to protection policies because of the effective implementation of a biological reserve in the area.  相似文献   

6.
2011年夏季胶州湾表层溶解有机物荧光特征的时空变化   总被引：2，自引：0，他引：2  
利用三维荧光光谱技术(EEMs)结合平行因子分析(PARAFAC)的方法,对2011年8月至9月胶州湾表层海水溶解有机物荧光特征的时间与空间变化进行了研究。PARAFAC模型共鉴别出四个荧光组分:类蛋白质荧光组分(C1),陆源类腐殖质荧光组分(C2,C4)和海源类腐殖质荧光组分(C3)。类蛋白组分在调查期间的荧光强度最强(0.14±0.06),其余三个组分荧光强度相近(0.07±0.02,0.09±0.02,0.05±0.02)。这四种组分在8月下旬多雨期和9月上旬受径流影响的时期荧光强度较高,在9月下旬雨季影响消退后荧光强度显著降低。研究表明各组分荧光强度总体上与叶绿素a浓度显著正相关,与盐度负相关,说明胶州湾夏季FDOM浓度主要受降雨引发的生物活动影响。  相似文献   

7.
山东省东接太平洋，西连欧亚大陆，受海洋和大陆的影响，季风气候特点相当显著，常导致严重旱、涝灾害。山东全年降水主要集中在夏季，6~8月降水占全年降水的60%以上。其原因主要是受西太平洋副热带高压和夏季风活动的影响。副热带高压的增强和北伸与梅雨锋的位置和强度变化对山东夏季降水有直接作用，其夏季降水的年际变率较大，是旱、涝频发的省份。 我国旱涝变化与太平洋海洋热状况有着极为密切关系(翁学传等，1994)。El Nino现象对气候的影响更加引起了海洋气象学家对海洋变化的高度重视。他们分析了El Nino现象和太平洋海表温度(SST)与山东夏季降水的关系(如:奚秀芬，1988；卢金墀，1982；张苏平等1999)，但对比降水分布发现无论是 El Nino发生的当年还是次年，降水距平百分率的零线均从山东中部通过。我国夏季降水主要受三种类型雨带控制。由于山东处于一类雨带(华北多雨)和二类雨带(江淮多雨)的转换地带，近40年的降水资料分析表明，三种类型雨带在山东夏季降水正、负距平年出现率几乎均等。因此，山东夏季降水的变化有其特殊性，需要从多方面进行研究。 西太平洋暖池是全球海温最高的海域，也是全球海气能量交换总量最大的区域。它的存在和变化对北半球夏季气候异常有着重要作用。西太平洋副热带高压的变化与西太平洋暖池面积大小有密切关系(李万彪等，1998)，20世纪70年代末以来的西太平洋副高增强也与这一时期暖池的跃变有关(赵永平等，2002)，暖池及其上空的对流活动的异常影响着西太平洋副高的变化和我国雨带的位置(黄荣辉等，1992，1994)，由此所激发的大气遥相关波列可波及西欧和北美。最近的研究也表明，冬、春季暖池区热含量的变化对南海夏季风爆发早、晚有重要影响(Chen et al.，2001)。当西太平洋暖池区海洋热含量高时，南海夏季风爆发早，反之则爆发晚。这对我国夏季季风雨的变化研究有重要意义，而且也必将对山东夏季旱涝产生重要影响。 本文作者通过对山东夏季降水资料的分析，对山东夏季降水时空变化及其与西太平洋暖池区域海洋热状态及副热带环流和夏季风变化的关系和影响的可能过程进行了探讨。  相似文献   

8.
Abstract

In the present study, mean rainfall for the months of June-July-August-September (JJAS) during summer monsoon is simulated over India and its adjoining regions for a period between 1982 and 2006. The study was carried out using Regional Climate Model (RegCM) version 4.6 at a resolution of 25?km. The simulated mean JJAS monsoon rainfall was validated against the observational IMD data. Comparison of JJAS seasonal mean summer rainfall for the first decade 1982–1991, with the later decade 1997–2006 indicate that the intensity of rainfall increases over Indian land-mass during the later decade under the forced conditions of Era-Interim. The observed JJAS mean rainfall indicates two maximum rainfall areas i.e. the Western Ghats and the Himalayan region. A significant bias is observed in the central and Jammu and Kashmir (J&K) region. The JJAS mean seasonal surface air temperature distribution at 0.25?×?0.25-degree grids resolution shows a decreasing trend of temperature over the Indian landmass.  相似文献   

9.
采用EOF（Emprical Orthogonal Function）、小波分析和交叉小波分析等方法研究了福建省汛期降水的不同空间分布型在不同的时间尺度下与西北太平洋夏季风、印度洋夏季风的关系.结果表明：福建汛期降水空间分布以全省一致型和东南—西北反相型两种模态为主;西北太平洋夏季风主要影响福建整个汛期降水总量的多寡,当西太平洋夏季风较强（弱）时,福建整个汛期全省降水偏多（少）;而印度洋夏季风则主要影响福建汛期降水量东南-西北向差异,即ISM强（弱）,福建东南-西北部降水差异增大（减小）.  相似文献   

10.
To date, coral proxy studies have proved largely unsuccessful in reconstructing temporal variability of the Indian monsoon system in the NW Indian Ocean. In a recent publication in this journal, Storz and Gischler demonstrated that extension rates in corals can be used to fill this gap. Those authors found a link between decadal and interannual variations of the SW monsoon current velocities and Porites lutea extension rates in the lagoon of Rasdhoo Atoll (4°N/73°W) in the central Maldives for the period 1917–2007. This sister paper shows that this extension-rate record can be used to reconstruct decadal variations of summer monsoon rainfall over peninsular India and adjacent areas. The amount of monsoon rainfall and current velocities during summer are both affected by the strength of the Indian monsoon system. Assessments of coral extension rates and the mean May–September All India Monsoon Rainfall index, a measure of monsoon strength over the Indian subcontinent, revealed a significant spectral coherence within periods of 18–19 and 6–7 years. Almost 92% of variance is shared between both time series in the former band, and 85% in the latter. A correlation between the 5-year running mean extension rate and rainfall records from the Western Ghats (grid of 73–76°E/13–15°N) is significant especially for 1958–2006 (r = −0.82, p < 0.05). These findings imply that coral growth characteristics can serve as a new marine archive to reconstruct past variations of the Indian monsoon system on interannual to decadal timescales.  相似文献   

11.
From 12 rainbow trout (Salmo gairdneri Richardson) taken from each of three lakes (Rerewhakaaitu, Opouri and Okataina) in the Rotorua district, N.Z., samples of liver, skeletal muscle and, from mature fish, the gonads were examined for organochlorine insecticides.

Lindane, heptachlor and heptachlor epoxide were not detected in any of the samples. Traces of dieldrin were detected only in trout taken from Rerewhakaaitu Lake. In all fish examined, pp'‐DDT, pp’DDD and pp’‐DDE were detected in all three tissues. The highest concentrations were found in some of the ovaries of fish from Rerewhakaaitu Lake, the catchment area of which had been extensively topdressed with DDT. Although most of the catchment area of Lake Okataina had never been topdressed with DDT, fish from this lake contained small amounts of DDT and its metabolites.  相似文献   

12.
Abstract

Nitrate runoff from pastoral fanning is of concern because it contributes to lake eutrophication. Surface flow in wetlands is a measure of the runoff likely to experience nitrate attenuation. This study assessed the potential of small headwater wetlands to reduce catchment nitrate loads by quantifying the proportion of total runoff that occurred as surface flow at the outlet of wetlands. Surface flow can be measured from wetlands in side valleys (valley wetlands) with well defined flow channels, but not in those parallel to the stream (riparian wetlands) with distributed flow. This study, from November 2004 to June 2008: (1) measured the mean specific flow yield (mm yr?1) at the outlet of 6 wetlands; (2) classified wetlands into 3 types based on hydrology; (3) mapped and classified all wetlands in the catchment; and (4) calculated the area‐weighted mean specific yield of wetlands for the whole catchment. The 6.6 km2 study catchment at Taupo, North Island, New Zealand, was predominantly pasture on volcanic soils where flows were baseflow dominated. Riparian and valley wetlands occupied 5% of catchment area. Type 1 wetlands flowed continuously, were dominated by baseflow (81–83%), and had a mean annual yield (± SE) of 167 ± 46 mm (34% of stream yield). Type 2 wetlands dried up during droughts and type 3 wetlands dried up each summer. Both latter types had a low baseflow component (20%) and a yield of 66±18 mm (13% of stream yield). In one tributary, gaugings over 4 days in summer during a wet year indicated that 27% of streamflow originated from wetlands. For the catchment as a whole, wetland baseflow accounted for 11± 4% of mean annual streamflow and wetland quickflow another 8 ± 2%, although these percentages are likely underestimates because seepages occurred downslope from measurement points. Although riparian and valley wetlands occupied only 5% of the catchment area, they could potentially have attenuated nitrogen in 11–19% of runoff. Other catchments may have different hydrology and wetland nitrate attenuation, and the methods outlined here could be used to quantify these differences.  相似文献   

13.
Three estuaries with differing catchment use and freshwater input were investigated in terms of their nutrient status, phytoplankton biomass, freshwater inflow and salinity between 1993 and 1995. The nutrients analysed include phosphate, nitrate, nitrite, ammonia and total particulate nitrogen. All the parameters were investigated for their relationship with land-use and freshwater abstraction. The Kromme River catchment area is relatively pristine, the river is impounded for ca. 133% of its mean annual runoff, and consequently, freshwater input into the estuary is only episodic. Nutrient and chlorophyll-a concentrations are low, but become elevated when freshwater does reach the estuary. The Geelhoutboom tributary contributes nutrients to the Kromme estuary during high freshwater inflow conditions, but is not a viable nutrient contributor during low flow conditions. Freshwater abstraction from the Swartkops River catchment is limited, and it is characterised by urbanisation and industrial development. The Swartkops River was the main source of phosphate in the estuary, whereas other small tributaries along the estuary were additional point sources for nitrate, ammonia and nitrite. The third system, the Sundays estuary, has no tributaries or other point sources except the Sundays River, where the catchment is extensively used for agriculture and freshwater input relatively high. The phytoplankton biomass (in terms of chlorophyll-a) was highest in the Sundays estuary, although phosphate concentrations were as low as in the Kromme estuary. Trends over time indicated a decrease in phosphate concentrations and showed variations for inorganic dissolved nitrogen concentrations since the previous 15 years in all the three estuaries. Nutrient stochiometry had changed in favour of inorganic dissolved nitrogen.  相似文献   

14.
This study documents long-term changes of a Zostera noltii landscape induced by a natural cyclic event in a coastal lagoon. The barrier-islands forming this system are very dynamic with drifting movements controlling ecological patterns and processes occurring in this area. Changes in the areal extent of the Z. noltii meadows were assessed using historical aerial photographs from 1940, 1980, 1989, 1996 and 1998. Landscape indices such as total patch area (TA), mean patch size (MPS), number of patches (NP), mean shape coefficient of variation (CV) and landscape fractal dimension (D) were calculated for each year and related to an index of disturbance intensity. The spatial distribution of the Z. noltii meadows varied greatly during the studied period and changes observed were related to the disturbance created by the barrier-islands' spatial dynamics. After an artificial inlet relocation the Z. noltii area, number of patches, patch mean size and coefficient of variation decreased. The fractal dimension of the Z. noltii landscape increased by 50% showing that besides a decrease in total area, number of patches, and patch mean area, patch fragmentation was an important consequence of this anthropogenic disturbance.Seagrass natural distribution patterns changed in response to natural and human-induced activities. This study emphasizes the importance of the landscape approach and the historical perspective when studying seagrass changes and the importance of taking into consideration long-term changes in seagrass landscapes to avoid confusion between man-induced effects with natural cyclic events.  相似文献   

15.
Abstract. The feeding and resting patterns of Littorina angulifera, the southern periwinkle, were observed in mangrove habitats of Belize (Central America). The snails feed predominantly on the surface of prop roots of Rhizophora mangle in a narrow zone at and above the mean high water mark. This area contains large numbers of hyphae and chlamydospores of an unidentified marine fungus (Deuteromycetes) and filaments of a chlorophyte (Chlorochytrium sp.). Both organisms are ingested by snails whose digestive tracts and fecal pellets contain ground-up cork cells, tricho-sclereids, tracheids, calcium oxalate crystals, fungal hyphae and chlamydospores, as well as undigested cyanobacteria. Most fungal particles pass through the gut unchanged. During dry periods, L. angulifera is in a dormant state, usually attached with dried mucus to leaves high in the tree, causing necrotic, crescent-shaped marks. The leaf tissue under the area of shell attachment becomes meristematic, separating dead tissues from healthy mesophyll. The snails detach during rainfall and move downward to the feeding sites on the prop roots.  相似文献   

16.
山东夏季旱涝指数的振荡特征   总被引：8，自引：1，他引：8  
针对山东旱涝变化规律的特殊性 ,利用 Z指数对山东单站旱涝等级进行了评定 ,在 Z指数的基础上构造了新的区域旱涝指标 ,对山东 1 95 1～ 2 0 0 3年区域旱涝指数进行计算和分类 ,利用Morlet和 Mexican hat小波变换对山东和邻近地区的夏季旱涝指数的振荡规律进行对比分析。结果表明 ,山东夏季旱涝与华北、黄淮地区相差较大 ,山东夏季旱涝具有明显的阶段性和群发性的特征和2～ 5年的振荡周期。  相似文献   

17.
On October 1, 2009, a small area along the Sicilian coast between the villages of Scaletta Zanclea and Giampilieri was struck by intense and concentrated rainfall causing countless small landslides widespread over the catchment area of steep subaerial creeks, locally known as Fiumara. Dense and quick debris flows were channelized within the Fiumara and destructively hit the villages and entered the sea, where they likely transformed into hyperpycnal flows. The availability of pre- and post-flood high-resolution bathymetry allows us to recognize the main features and the most significant morphological variations related to the impact of the flows on the seafloor. The passage of hyperpycnal flows on the seafloor possibly produced a suite of mass-wasting events, encompassing sheet landslides (i.e. erosive scours), retrogressive slope failure on loose sediment at the canyon headwall and rock-falls on the conglomeratic bedrock along canyon sidewall. The possible causes of these events are discussed on the basis of available morphological evidence and geotechnical considerations. Finally, the widespread occurrence of mass-wasting features (i.e. submarine landslide scars) morphologically similar to those generated by the 2009 flash flood allows us to hypothesize, from one side, a strong correlation between this catastrophic event and the evolution of submarine canyons, and from the other side, the possible use of these features for the assessment of flash-flood occurrence.  相似文献   

18.
赤道印度洋海温偶极子的气候影响及数值模拟研究   总被引：5，自引：0，他引：5  
在分析研究印度洋海温变化的基本特征,尤其是在分析赤道印度洋海温偶极子及其影响的基础上,利用IAP9L大气环流模式模拟研究了赤道印度洋海温偶极子异常对亚洲季风区气候变化的影响.其结果表明,印度洋、亚洲南部和东部地区的流场和降水都对印度洋海温异常的强迫作用比较敏感.正位相印度洋偶极子的作用使得赤道东印度洋-印度次大陆南部-阿拉伯海一带出现距平东风,孟加拉湾-中南半岛出现异常反气旋性环流,从而对减少印度南部和中南半岛南部、印度尼西亚地区的夏季降水,以及增加中国南部和东非的夏季降水有十分重要的作用.与此相反,负位相印度洋偶极子的作用将使赤道东印度洋附近出现西风异常,孟加拉湾-中南半岛存在异常气旋性环流,从而使印度次大陆和中南半岛南部、印度尼西亚地区的降水增加,使中国西部和孟加拉湾的降水减少.数值模拟结果与资料分析相互映证,切实地揭示了印度洋海温偶极子对亚洲季风区的气候变化有重要影响.  相似文献   

19.
Nutrient (C, N and P) fluxes were monitored in a microtidal semi-arid mangrove system, which links a semi-enclosed shallow coastal lagoon with the Gulf of California. We assessed the role of the mangrove ecosystem as a nutrient sink/source and determined how mangrove litterfall rates, tidal regime and climate factors influence these fluxes. Despite high seasonal differences in DOC, POC, N-NO3− and TP levels, nutrient concentrations were only marginally influenced by either hydrological variables or the concentration of these fractions in the adjacent lagoon. The carbon budget appeared to be balanced throughout the study. Retention rates in the mangrove system were related to litterfall rates. Export of DIN was observed mainly in the wet season due to the low nitrogen assimilation efficiency of the system. Import of organic nitrogen was related to the high retention efficiency of particulate organic nitrogen. Phosphorus fractions were imported and retained in the mangrove supporting previous findings that mangroves are phosphorus sinks. Finally, through a simple meta-analysis we tested the quantitative importance of main variables (tidal flow, tidal elevation, tidal range, rainfall, mangrove catchment area, litterfall) controlling mangrove nutrient dynamics. Although results suggest that generalizations can be made about factors regulating nutrient export from mangroves, the lack of statistical significance highlights the relative importance of the local environment for the magnitude of nutrient exchange in mangroves. Future research should focus on finding mechanistic models to explain these general patterns, taking into account the main biogeochemical processes and their roles in coastal ecosystem ecology.  相似文献   

20.
东亚夏季气候主要模态的年际变化及其机理   总被引：3，自引：0，他引：3  
胡增臻 《海洋学报》1999,21(6):26-39
主要研究了东亚(中国和日本)夏季气候(降水和气温)主要模态的年际变化及其机理。研究发现,中国区域夏季降水和气温的大尺度年际变化间有很强的耦合:大范围多(少)雨对应大范围低(高)温。奇异值分解的第一个模态的长期变化主要反映了长江中下游地区降水逐年增加(变湿)的趋势而气温逐年降低(变冷)的趋势。在70年代中期以后,长江中下游地区降水和气温耦合变化的准两年分量明显增强。研究表明,影响长江中下游地区夏季降水和气温年际变化的大尺度环流背景异常十分相似,即主要是两个遥相关型:太平洋-日本(PJ)型和欧亚型遥相关型。与夏季东亚梅雨异常相联系的长江中下游地区降水和气温异常是中高纬度干冷空气和低纬度暖湿空气相互作用的结果。热带西太平洋海表温度异常和相关的对流活动的年际变化通过PJ型对东亚地区夏季降水和气温的年际变化产生十分显着的影响。西太平洋对流活动与北半球大气环流遥相关的相互作用有明显的季节性。PJ型不仅是夏季西太平洋对流活动与北半球夏季热带外地区500hPa高度场年际变化耦合相互作用的最重要模态,而且也是两者各自变化的一个十分重要的模态。1984年夏季北半球500hPa位势高度主振荡型分析表明存在着能量从热带西太平洋向东亚北部的PJ型的振荡传播。低纬度的影响可传播到70°N,同时也存在能量从高纬度向低纬度的传播.即从极地传播到70°N。高纬度和低纬度的影响在70°N附近汇合。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号