共查询到20条相似文献，搜索用时 46 毫秒
1.
Christopher Uche Ezeh Michael Chukwuma Obeta Raymond N. C. Anyadike 《Arabian Journal of Geosciences》2016,9(16):681
The study compared the sequences of daily rainfall over coastal southern and semi-arid northern Nigeria. Daily rainfall occurrences for 41 years (1971–2011) over four meteorological stations in Lagos, Rivers, Borno, and Katsina were analyzed using frequency analysis and Markov chain model. Findings indicate that the coastal area had a predominance of 2–4-day wet spells while the semi-arid area showed a wet spell distribution that is geometric in nature with 1-day spell predominance. The dry spell behavior was nearly the opposite of the wet spell occurrence. The coastal region showed a dry spell of 1–4-day spell predominance while the semi-arid region showed a predominance of higher dry spells of 2–6 days. Accumulation of the amount of rainfall in each spell also showed that much rainfall from the coastal area was obtained from rains of spells of 3 days and above while the semi-arid had more of its rain from spells of 1–3 days. The mean annual rainfall was 1423.75 mm (Lagos), 2173.56 mm (Rivers), 517.50 mm (Katsina), and 578.34 mm (Borno). The wettest month was June (274.08 mm) in Lagos, September (378.18 mm) in Rivers, and August in Katsina and Borno (172.98 and 184.81 mm, respectively). The driest months were January for Lagos and Rivers (15.77 and 18.96 mm, respectively) and November–February for Katsina and Borno (0–0.06 mm). This showed that the coastal areas had nearly three times the volume of rain in the semi-arid area. The study further showed that onset of rain for the coastal area was March/April while the cessation of rainy season was October/November. On the other hand, the onset of rainy season in the semi-arid area was May/June and cessation of rainy season was September. Findings portend drier days for the semi-arid area due to dry spell persistence and hence, the consequent challenges of providing artificial water supply for agriculture and other purposes especially from October to May. 相似文献
2.
太湖流域梅雨时空演变规律研究 总被引：3，自引：1，他引：2
了解和掌握太湖流域梅雨特性,对预测未来流域水文水资源情势变化,制订流域水资源利用和防洪决策等具有重要意义。本文根据1954~2009年共56年的梅雨特征量资料,采用经验正交函数分解(EOF)、非参数统计方法和Morlet连续小波等方法全面分析了太湖流域梅雨空间分布、长期变化趋势、丰枯变异和周期振荡等时空演变特征。研究结果表明:56年来,太湖流域梅雨主要有两种分布型态,梅雨特征量中,梅期长度与梅雨空间差异度具有显著增长的趋势,出梅日期、梅雨期长度、梅雨量、梅雨强度和梅雨集中度均在20世纪60年代末期具有明显的突变特征,太湖流域梅雨量在经历了5个阶段的丰枯变化之后,预计在2010年之后将进入偏丰期。 相似文献
3.
Weili Duan Bin He Kaoru Takara Pingping Luo Daniel Nover Yosuke Yamashiki Wenrui Huang 《Natural Hazards》2014,73(3):1255-1267
During July 11–14, 2012, deadly floods and landslides triggered by a series of unprecedented heavy rains hit Kyushu, Japan, causing at least 32 deaths and around 400,000 evacuations. We focus on synoptic anomalies identified after inspecting rainfall patterns and documenting the conditions associated with this tragic event using data combined from the Global Rainfall Map in Near Real Time data, the NCEP/NCAR Reanalysis dataset, and the global forecast system. Rainfall maps indicated that there were many heavy rains in Kyushu in these days and this disaster was associated with the pattern of forecasts and standardized anomalies. A weather trough with positive height anomalies appeared, the center of which moved to the north of Japan over this period, which might cause wind anomalies and whereby lots of water vapor were transported to Kyushu area with up to 90 m s?1, and high values of precipitable water formed with up to 60 mm. These results suggest that a larger-scale pattern is conducive for heavy rainfall and the anomalies put the pattern in context as to the potential for an extreme rainfall event, which can provide insights and methods for predicting extreme events’ or something similar. 相似文献
4.
近实时卫星降水反演数据具有覆盖范围广、空间连续性和时效性较强以及开放获取等优势, 是重要的全球性降水资料。针对2021年河南省“7·20”极端暴雨, 基于116个地面气象站观测资料及其空间插值数据, 综合解析了4种GPM近实时卫星降水数据(IMERG early、IMERG late、GSMaP NOW和GSMaP Gauge NOW)对极端强降水事件的表征能力。结果发现:①IMERG early、IMERG late对站网累积雨量的低估程度在20%左右, GSMaP NOW和GSMaP Gauge NOW的高估程度分别达到了约35%和70%, 但2种GSMaP数据更易探测到500 mm以上的累积雨量。②在雨量过程方面, 4种GPM数据对小时降水事件均具有较强的分类辨识能力, 但未捕捉到主要雨峰过程, 定量误差较突出, 与地面降水量之间表现出显著的负相关关系。GPM降水数据对小时雨量低于10 mm的降水事件以高估为主;对于小时雨量超过30mm的降水事件以低估为主, 甚至存在普遍低估。③在空间格局方面, 4种GPM数据的精度指标均具有较强的时间波动性, IMERG数据的空间相关系数和体积临界成功指数等指标总体上优于GSMaP数据, 但后者对较高量级的降水事件更敏感。④2种IMERG数据中, IMERG late相对IMERG early的精度具有较明显改善;2种GSMaP数据中, GSMaP Gauge NOW相对GSMaP NOW提高了对较高量级雨量的探测能力, 但也明显增大了较低量级雨量的定量估计误差。本文研究深化了对GPM近实时卫星降水数据性能的认识, 为完善GPM降水反演算法、提升其对极端降水的监测能力提供了重要反馈信息。 相似文献
5.
全球大气季节内振荡对长江流域持续暴雨影响的研究进展 总被引：4，自引：0，他引：4
在引证论述大气季节内振荡(ISO)对暴雨(强降水)重要作用的基础上,概括性地回顾影响长江流域持续暴雨的大气ISO基本特征及其形成机制的主要成果。重点针对全球热带内外不同时间尺度的大气ISO的空间变化和年际变化与长江流域持续暴雨之间联系的研究工作进行总结评述,较为完整地总结长江流域夏季降水季节内变化的气候特征和全球不同空间和时间尺度的ISO对东亚副热带地区持续暴雨影响的已有认识,并结合2个半球的ISO与长江流域持续暴雨关系的研究现状,对未来暴雨(强降水)与不同时尺度ISO相互作用及其在10～30 d延伸期预报中的应用中有价值的科学问题和研究热点进行探讨,以期强调南半球ISO变化在全球和东亚副热带气候系统中的重要地位,提高夏季长江流域持续暴雨10～30 d延伸期预报和旱涝气候预测准确率。 相似文献
6.
Impact of extreme rainfall in the central Sudan during 1999 as a partial analogue for reconstructing early Holocene prehistoric environments 总被引：1，自引：0，他引：1
The year 1999 was an exceptionally wet year, with severe floods in China, India and Australia and very high flow in the Nile. In Sudan, the July rainfall was unusually early and heavy, and persistent rains throughout August and early September caused severe floods in much of central Sudan, including Khartoum.The synoptic conditions historically associated with extreme rainfall events in central Sudan include a warm equatorial Indian Ocean, a strong summer monsoon over both Africa and India, a northward shift of the Inter-tropical Convergence Zone earlier and further north than usual, and the presence of deep, well-developed westerly air masses accompanied by a strong Tropical Easterly Jet that allowed more moisture transport into Africa from the South Atlantic via the Congo basin, leading to very heavy precipitation in the Ethiopian uplands and the central Sudan.The intense late wet season rains in 1999 caused a major canal in the Gezira Irrigation Area to break its banks and filled normally dry depressions between dunes with water, providing a partial analogue of early Holocene environments in this region when small groups of Later Stone Age peoples occupied the sandy ridges seasonally. Global Circulation Models cannot provide such detailed local information. 相似文献
7.
Climatological drought in Nigeria 总被引：1，自引：0，他引：1
Peter Kwabenah Acheampong 《GeoJournal》1990,20(3):209-219
In this paper, the definitions of drought are reviewed and evaluated for Nigeria. Drought in Nigeria is thought of as a purely climatological or meteorological phenomenon, that is, a temporary abnormal rainfall deficiency over the country, the result of some unfavourable meteorological conditions such as persistent widespread subsistence and the absence or weakness in the atmospheric rain-generating systems during the rainfall season. 相似文献
8.
Justice Kufour Owusu-Ansah 《GeoJournal》2016,81(4):555-570
Each year during the rainy seasons, the Ghanaian media is dominated by banner headlines of flooded urban landscapes along with emergency response teams doling out relief items to the victims. However, when the rains subside and the floods are no longer newsworthy, the key stakeholders return to their normal duties only to await the next cycle of rains with bated breath. Based on the analyses of secondary and fieldwork data, the paper found no significant change in recent rainfall patterns that could account for the city’s flood problems. Rather, the impervious surfaces created through the removal of wetlands, riparian lands and urban vegetation, along with deposits of sediments and domestic wastes into streams and drains, have combined to slow down the velocity of stormwater flows and allowing it to disperse into the surrounding built up areas in lower terrains. The paper recommends the construction of modern city-wide sewerage systems to cope up with the current and predicted rainfall patterns, complemented by non-structural approaches including the protection of wetlands and urban vegetation to reduce the amount of storm water flows. Planners should anticipate and project future land use demands to cater emerging activities such as LPG stations which currently take sites in open space or flood ways and manage and direct physical development into low risk locations. Other measures would include the consideration of free domestic waste collection systems, mandatory flood insurance schemes on properties, with premiums assessed based on site risks, the development of early warning systems to minimize the effects of floods. 相似文献
9.
Meso-scale characteristics of disturbances that bring about atmospheric disasters in pre- and mature monsoon seasons in Bangladesh
are analyzed. Several types of meteorological instruments capable of observations with high temporal and spatial resolutions
were introduced for the first time in this area to capture the meso-scale structure of rainfall systems. We installed an automatic
weather station (AWS) and several automatic raingauges (ARGs) and utilized the weather radar of Bangladesh Meteorological
Department (BMD). From the radar image in the summer of 2001 (16–18 July), a striking feature of the systematic diurnal variation
in this area was elucidated. In these 3 days, the diurnal evolutions of convective activity were remarkably similar to each
other, implying that this pattern can be understood as a typical response of local cloud systems to the diurnal variation
of insolation under some summer monsoon situations. The ARG data show the difference in characteristics of rainfall between
pre- and mature monsoon seasons. The short intense downpour tends to occur more frequently in the pre-monsoon season than
in the mature monsoon season. The pre-monsoon rainfall also has clear diurnal variation with a peak that is more strongly
concentrated in time. In the northern part the rainfall peak is found in between midnight and early morning, while it is observed
in the daytime in central to western parts of the country. Two disaster cases caused by meso-scale disturbances are analyzed.
Although they occurred in the same season, the structures of the cloud systems were largely different from each other. The
disturbance brought about tornadoes on 14 April 2004, consisting of many spherical cloud systems of approximately 20 km size.
On the other hand, another one that caused the tragic river water transport accident on 23 May 2004 had meso-scale rain band
structure. The latter case was captured by the AWS located at Dhaka. Sudden changes in temperature, wind and pressure were
observed clearly, showing the typical structure of convective rain bands. 相似文献
10.
E. Olukayode Oladipo 《Natural Hazards》1993,8(2):171-188
A long-period instrumental data set (1916–1987) of monthly growing season (April–October) rainfall totals for 34 stations in northern Nigeria is used to quantify drought following the method of H. N. Bhalme and D. A. Mooley. It is established that there are remarkable seasonal changes in the patterns of wetness and dryness over the region with no consistent recurrent spatial patterns in the moisture anomalies. In general, large-scale droughts only rarely cover the region as a whole, and there are distinct spatial differences dominating the wet and dry years. The length and severity of drought varies from sub-area to sub-area with very low interannual persistence. Although discrete areas do catch the brunt of drought on a year-by-year basis, drought occurrence in the region is largely sporadic in its spatial distribution. The rather noisy spatial characteristics of drought in northern Nigeria suggests that the seasonal shift in the Intertropical Discontinuity (ITD) is not likely the most important causal mechanism of drought in the region. 相似文献
11.
Afolayan AA 《GeoJournal》1985,11(2):183-193
The paper sets out to test whether or not the movement pattern of people in Nigeria is step-wise. It examines the spatial order in the country and the movement pattern of people. It then analysizes the survey data and tests for the validity of step-wise migration in the country. The findings show that step-wise migration cannot adequately describe all the patterns observed. The multistep moves of the people is an indication of the complexity of factors influencing human mobility behaviour. Moreover, the preponderance of circuitory movement pattern is an indication of the socio-cultural life of the people. The urban-urban movement pattern that was observed is used as a basis for advocating for the development of intermediate urban centres, in addition to the rural areas. This is seen as a way of alleviating the increasing convergence of people on Lagos. 相似文献
12.
Kenya experienced extraordinarily heavy rainfall between May 1997 and February 1998 due to the El-Nino weather phenomenon.
This period of about 10 months heavy rainfall caused widespread landslides and floods which were experienced in various parts
of the country. Normally mid-December to late March is the driest and hottest season in Kenya. However, during this period,
the season turned out to be the wettest with one of the heaviest precipitation events recorded in the country in the past
several decades. Research investigations have revealed that the landslides were a result of four major factors. The factors
included, geology and soils of the landslide prone areas, high relief, steep slopes with poor anchorage for slope stability,
continuous heavy precipitation which resulted into oversaturation of rocks and soils. The effects of the El-Nino-triggered
landslides in Kenya were enormous. Although statistical data about landslide destruction are not presently quantified, human
and animal fatalities and plant destruction were enormous. Fertile farmlands, roads, railway lines, bridges, telephone and
power lines were relocated and destroyed. Soil erosion which increased from higher surface runoff and surface exposure filled
rivers with sediments. The sediments were transported to the hydro-electricity producing dams which eventually became clogged
and power generation stopped. The national economic loss to the country is estimated at about US $ 1 billion and will take
a long time to recover.
Received: 7 April 1998 · Accepted: 2 March 1999 相似文献
13.
Tyson P. D. 《GeoJournal》1981,2(2):3-10
Short-term changes in the general circulation of the atmosphere, which may lead to prolonged periods of drought, are catalysts for producing accelerated desertification. In southern Africa the northeastward thrust of desertification from the western and central arid and semi-arid areas (the Karoo) has long been recognised, but up til 1970 research failed to demonstrate a clear-cut relationship between the process of desertification and long term rainfall data. The application of sophisticated analytical techniques to regional rainfall data showed, however, that spatial and temporal variations in the Southern African rainfall pattern have a striking degree of organization. The summer rainfall region of the northeastern part of the subcontinent experiences 16–20 year fluctuations, in contrast with 10–12 year fluctuations in the all-season rainfall region along the southern Cape coast. Concentrating on regionally averaged data for the summer rainfall region, the author used Fourier analysis to confirm the persistence of the quasi 20-year fluctuations since 1840. The wet spell of the late 1970s is expected to die out by 1982 and may be followed by a dry spell running from 1983 to 1992. Policy and management practices should be geared to prevent further desertification during this period. 相似文献
14.
Simulation of a flood producing rainfall event of 29 July 2010 over north-west Pakistan has been carried out using the Weather Research and Forecasting (WRF) model. This extraordinary rainfall event was localized over north-west Pakistan and recorded 274 mm of rainfall at Peshawar (34.02°N, 71.58°E), within a span of 24 h on that eventful day where monthly July normal rainfall is only 46.1 mm. The WRF model was run with the triple-nested domains of 27, 9, and 3 km horizontal resolution using Kain–Fritsch cumulus parameterization scheme having YSU planetary boundary layer. The model performance was evaluated by examining the different simulated parameters. The model-derived rainfall was compared with Pakistan Meteorological Department–observed rainfall. The model suggested that this flood producing heavy rainfall event over north-west region of Pakistan might be the result of an interaction of active monsoon flow with upper air westerly trough (mid-latitude). The north-west Pakistan was the meeting point of the southeasterly flow from the Bay of Bengal following monsoon trough and southwesterly flow from the Arabian Sea which helped to transport high magnitude of moisture. The vertical profile of the humidity showed that moisture content was reached up to upper troposphere during their mature stage (monsoon system usually did not extent up to that level) like a narrow vertical column where high amounts of rainfall were recorded. The other favourable conditions were strong vertical wind shear, low-level convergence and upper level divergence, and strong vorticity field which demarked the area of heavy rainfall. The WRF model might be able to simulate the flood producing rainfall event over north-west Pakistan and associated dynamical features reasonably well, though there were some spatial and temporal biases in the simulated rainfall pattern. 相似文献
15.
阜新萤石成矿区稀土元素地球化学特征及指示意义 总被引：1，自引：0，他引：1
为了研究阜新萤石成矿机制,对其稀土元素地球化学特征进行了分析。阜新地区萤石矿赋存于早二叠世、晚三叠世和晚侏罗世花岗岩中。地球化学分析结果显示,所有萤石均具有弱的Ce负异常,其稀土配分模式存在3种类型:Eu明显亏损型、Eu弱亏损型和Eu富集型。萤石中稀土元素的含量并不随围岩中的稀土元素含量的增加而增加,晚期侵入的花岗岩富集轻稀土元素。从成矿早期到成矿晚期,萤石的稀土元素配分型式从Eu明显亏损型向富集型演化,稀土元素总量逐渐降低。赋存于早二叠世和晚三叠世花岗岩中萤石矿流体包裹体中SO42-含量及液相成分还原参数指标指示,成矿流体由还原条件向氧化条件转变,成矿物质主要来源于赋矿花岗岩。 相似文献
16.
研究了柑桔林下穿透雨的分布特征,结果表明:在测定期间,穿透雨量占总降雨量的68.3%,5月的穿透雨量最大(245.1 mm),而穿透雨率最大值(73.3%)出现在8月。穿透雨量与降雨量具有显著相关性(p<0.01),而穿透雨率与降雨量和降雨强度的相关性均达到显著水平(p<0.05)。柑桔林下穿透雨显示出明显的空间变化,各观测点间穿透雨率具有显著性的差异,而且穿透雨的空间异质性(穿透雨率的变异系数CV)随着降雨量或降雨强度的增加而降低,聚类分析也显示出穿透雨在不同观测点间具有差异性。柑桔林下穿透雨呈现明显的聚集效应。 相似文献
17.
陕南地区滑坡灾害气象预报预警及其防范对策探析 总被引：10，自引：0，他引：10
王雁林 《地质灾害与环境保护》2005,16(4):345-349
选择典型研究区．采用统计方法研究了陕南地区2001～2003年区域性滑坡灾害与降雨量及降雨强度的相关性，确定了滑坡灾害的降雨临界值以及相应的预报预警分级．为实时时间预警提供了定量依据；在此基础上，提出了滑坡灾害预警防范的对策措施。 相似文献
18.
Praveen B. Gawali Sainath P. Aher B. V. Lakshmi Ravindra D. Gaikwad K. Deendayalan Pramod T. Hanamgond J. L. V. Mahesh Babu Sandeep A. Arote Shashikant I. Bairage 《Journal of the Geological Society of India》2017,90(3):301-311
Heavy rainfall triggered landslides are on the rise along the Western Ghats making it a matter of priority to identify landslide-prone areas well in advance. The present effort is aimed at identifying landslide susceptible villages (LSV) around the Kalsubai region of Deccan volcanic province (DVP), Maharashtra, India from 8 weighted landslide parameters- rainfall, slope, lithology, land use and land cover (LULC), soil properties, relative relief, aspect and lineament. These parameters were combined with advanced remote sensing (RS) data and processed in geographical information system (GIS) as well as in image processing software, which are an integral part of geospatial techniques. Out of the total 59 villages, the study identified 9 villages are situated in very high, 13 in high, 12 in moderate, 11 in low and 14 in very low risk zones. Our data reveals incessant heavy rains and steep slopes are the dominant factors in triggering landslides, exacerbated by anthropogenic activity prevalent in the study area. The spatial and non-spatial database created will help to take effective steps in preventing and/or mitigating landslide disasters in the study area. The methodology can be applied to identify other landslide prone areas in a cost effective way. 相似文献
19.
广东省1960～2007年降雨侵蚀力变化趋势分析 总被引：3，自引：0，他引：3
降雨侵蚀力反映由降雨引起的土壤侵蚀的潜在能力.本文利用广东省25个站点48年(1960～2007)的日雨量资料计算了各站的降雨侵蚀力,并用Mann-Kendall(M-K)非参数检验和克里格空间插值法分析了降雨侵蚀力的时空变化规律.结果表明:广东省降雨侵蚀力的空间分布呈沿海向内陆逐渐递减的趋势.全省大部分地区的年降雨侵蚀力呈现不明显上升趋势,且存在较明显的年代际和年际变化.降雨侵蚀力的年内分布特征和降雨量分布类似,呈"双峰型",主要集中在4～9月的雨季.对于季节序列,冬季、春季和夏季大部分地区的降雨侵蚀力有不同程度的上升,秋季全省几乎所有地区呈下降趋势.汛期的降雨侵蚀力变化特征与年降雨侵蚀力相似. 相似文献
20.
Giovanni Dolif Andre Engelbrecht Alessandro Jatobá Antônio José Dias da Silva José Orlando Gomes Marcos R. S. Borges Carlos A. Nobre Paulo Victor R. de Carvalho 《Natural Hazards》2013,65(3):1831-1847
Natural disasters, particularly those triggered by heavy rainfall, may cause major damage and death. However, if an accurate early warning is issued, the damage can be mitigated. In Latin America and Brazil, characteristics of socioeconomic development often lead to a disorderly growth of cities and, consequently, occupation and irregular construction in risk areas. Therefore, forecasts of heavy rainfall, as well as preventative and mitigatory actions based on meteorological data/alerts, are essential to saving lives and minimizing material loss. An event that would have benefited from such actions is that which occurred in the mountainous region of Rio de Janeiro in January 2011, when over 800 people lost their lives. This work describes the first research initiative on resilience engineering domain in systems to forecast heavy rains in Rio de Janeiro. The results indicate important sources of brittleness in the system that supports the work of meteorologists, mainly related to the technical and organizational framework, and suggests that the main source of resilience in dealing with critical situations is the tacit knowledge of experts. 相似文献