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1.
A series of long karst spring discharges have been analysed to determine trends, fluctuations and relationship to rainfall.
Data come from aquifers in southern Italy, and in some cases cover more than one hundred years of records. Based on yearly
discharge data, hydrological series show the drop of the discharge after 1986, which has been interrupted by the recent wet
years of 2009 and 2010. This drop is connected to the decrease in annual rainfall, but other factors also seem to contribute
to this phenomenon. Based on monthly scale data series, the relationship between meteorological and hydrological droughts
has been analyzed, using the standard precipitation index (SPI). As karst systems are large reservoirs, only longer meteorological
droughts induce groundwater droughts, and the start, duration and time-lag of the hydrological droughts have been evaluated. 相似文献
2.
Drought has become a recurrent phenomenon in Turkey in the last few decades. Significant drought conditions were observed during years of late 1980s and the trend continued in the late 1990s. The countrys agricultural sector and water resources have been under severe constraints from the recurrent droughts. In this study, spatial and temporal dimensions of meteorological droughts in Turkey have been investigated from vulnerability concept. The Standardized Precipitation Index (SPI) method was used to detail geographical variations in the drought vulnerability based on frequency and severity of drought events at multiple time steps. Critical (threshold) rainfall values were derived for each station at multiple-time steps in varying drought categories to determine least amount of rainfall required to avoid from drought initiation. The study found that drought vulnerability portrays a very diverse but consistent picture with varying time steps. At regional scale, south-eastern and eastern Anatolia are characterized with moderate droughts at shorter time steps, while the occurrence of severe droughts at shorter time steps is observed at non-coastal parts of the country. A similar picture was observed with very severe droughts. The critical (threshold) values exhibited rising numbers during the growing season at 3-month step in the South-eastern Anatolia, which might have significant consequences considering presence of large irrigation projects under-development in the region. In general, rainfall amounts required for non-drought conditions decrease from the coastal parts toward the interiors with increasing time steps. 相似文献
3.
Drought monitoring is carried out using various drought indices, including SPI, to generate time series of dry and wet periods. Furthermore, the dispersion of dry and wet periods was embossed with different intensities (high, medium, and low) over the data record years. Although these results were very necessary for planning and predicting future droughts, it appeared that the application of any trend over dry and wet periods could provide more accurate and unbiased or safer predictions in terms of analysis process. Generally, most of the researchers believed that the results of a drought trend analysis have been influenced by short-term persistence or significant autocorrelation with different lags on drought event time series and the mentioned impact should be preferably removed. Accordingly, drought monitoring was accomplished using SPI and PNPI drought indices to extract time series of dry and wet periods in terms of 50-year (1965–2014) annual rainfall data of 40 synoptic stations over Iran. Having used the basic and modified Mann–Kendall nonparametric tests, it was attempted to analyze the trend of dry and wet periods extracted from mentioned indices. The results represent the relative advantage of using the modified Mann–Kendall test in drought trend analysis. Furthermore, it was shown that the trend of dry and wet periods was negative in the majority of selected stations and that this trend was significant at 95% confidence level in northwest of Iran. Also, the results indicated the similar performance of SPI and PNPI indices in trend analysis of dry and wet periods. 相似文献
4.
The frequency and severity of occurrence of meteorological droughts in different climatic regions depend on regional climatic factors. This study has made an effort to explore the relationship of range of annual temperature variation at a given place with the frequency of occurrence of drought and the maximum magnitude of seasonal rainfall deficit (i.e., severity). The seasonal rainfall refers to sum of monsoon season (rainy season) rainfall in India. The monthly precipitation data of 113 years (1901–2013) for 256 stations in different parts of India have been used to estimate the return period of meteorological drought at different stations. The daily normal values of observed maximum and minimum temperatures from 40 years of records have been utilized to estimate range of temperature variation (θR) during the year at each stations. In various parts of India, the θR ranges from 10 °C in humid regions to 40 °C in arid regions. The various climatic regions have been experiencing maximum deficiency of annual rainfall ranging from 30% (humid) to 90% (arid). The results reveal that places exhibiting θR values between 40 to 30 °C face more frequent droughts with average frequency of once in 3 to once in 6 years. The occurrence of extreme and severe drought events is more frequent in the regions with higher values of θR compare to that in lesser values of θR. The regions with θR values between 30 to 25 °C mostly face severe and moderate events having the average drought return period of 6–9 years, and the occurrence of extreme droughts in these regions is rare. Furthermore, regions with θR?<?20 °C face moderate droughts only with an average return period of 14 years. This study divulges that the average return period and magnitude of deficiency of drought events have notable relationship with the range of temperature variation during the year at a given place. 相似文献
5.
Drought frequency, duration, and severity and its impact on pasture productivity in the four main vegetation zones of Mongolia were analyzed using meteorological, soil moisture, and vegetation data during the growing season (April–August) of 1965–2010. Meteorological and pasture drought characteristics were explored using the Standardized Precipitation Index (SPI), the soil moisture anomalies percentile index ( W p), and Palmer Drought Severity Index (PDSI) on 1-month timescale. Generally, 35–37 (15–16 %) by SPI for meteorological drought while 27–29 (12–13 %) by W p, and 16–21 (7–9 %) by PDSI for pasture drought with different durations were identified over the four vegetation zones during the study period. Most of these droughts (80 % by SPI and 50–60 % by both W p and PDSI) observed during the entire events occurred on a 1-month duration with moderate intensity. Drought frequencies were not significantly ( p > 0.05) different within the four zones. The frequency of the short-term meteorological droughts was observed relatively greater than pasture droughts; however, pasture droughts were more persistent and severe than meteorological droughts. The three indices show that the frequency and severity of droughts have slightly increased over the 46 years with significant ( p < 0.05) dry conditions during the last decade of 2001–2010 in the four zones (except in the high mountain). The results showed the W p was more highly significantly correlated with the precipitation anomalies ( r = 0.68) and pasture production ( r = 0.55) than PDSI ( r = 0.51, p < 0.05 and r = 0.38, p < 0.10, respectively). A statistical model, based on pasture production and the W p, suggested that the consecutive drought months contribution during the growing season was 30 % ( p < 0.05) and that pasture production was more sensitive to the occurrence of droughts during June–August ( R 2 = 0.32, p < 0.05) as seen in 2000–2002 and 2007. We concluded that a greater severity and frequency of growing-season droughts, during the last decade of 2001–2010, have driven a reduction in pasture production in Mongolia. 相似文献
6.
The amount and distribution of precipitation play crucial roles in the occurrence of drought in the Weihe River Basin (WRB), China. Using the precipitation data (1960–2010) of 21 meteorological stations, the spatial and temporal characteristics of short-, medium-, and long-term droughts on 3-, 6-, and 12-month time scales, respectively, were examined using the theory of runs and the Standardized Precipitation Index (SPI). The trends of the drought characteristics were analyzed by a modified Mann-Kendall (MMK) test method. Furthermore, comparative analysis of the SPI at different time scales was conducted. The results showed that (1) the main drought type was moderate drought, which occurred frequently in July and October; (2) the drought intensity and frequency were highest in the 1990s, and the drought severity and drought duration in the northwest was more serious than that in the east; (3) an increasing trend of short droughts appeared mainly in the spring and fall; an increasing trend of medium droughts mainly occurred in the 1990s and that of long-term droughts were mainly presented in the northwest region of the WRB; (4) SPI-3 can better reflect precipitation in the current month, SPI-6 has an advantage in characterizing drought persistence, and SPI-12 performs well in capturing extraordinary droughts; and (5) it was also observed that there is a strong relation between the precipitation distribution and drought zones in the basin, and the drought conditions changed continuously with the seasons depending upon the amount and spatial distribution of precipitation . 相似文献
7.
Climate change is receiving more attention from researchers as the frequency of occurrence of severe natural disasters is getting higher. Tropical countries like Malaysia have no distinct four seasons; rainfall has become the popular parameter to assess climate change. Conventional ways that determine rainfall trends can only provide a general result in single direction for the whole study period. In this study, rainfall series were modelled using additive Holt–Winters method to examine the rainfall pattern in Langat River Basin, Malaysia. Nine homogeneous series of more than 25 years data and less than 10% missing data were selected. Goodness of fit of the forecasted models was measured. It was found that seasonal rainfall model forecasts are generally better than the monthly rainfall model forecasts. Three stations in the western region exhibited increasing trend. Rainfall in southern region showed fluctuation. Increasing trends were discovered at stations in the south-eastern region except the seasonal analysis at station 45253. Decreasing trend was found at station 2818110 in the east, while increasing trend was shown at station 44320 that represents the north-eastern region. The accuracies of both rainfall model forecasts were tested using the recorded data of years 2010–2012. Most of the forecasts are acceptable. 相似文献
8.
Daily precipitation data for 1957?C2009 from 53 stations in the Xinjiang, China, are analyzed, based on the Standardized Precipitation Index (SPI) with the aim to investigate spatio-temporal patterns of droughts. The Mann?CKendall trend test is used to detect the trends in the SPI values of monthly drought series, drought severity and drought duration. The frequencies of moderate, severe and extreme droughts are higher in the North Xinjiang, while mild droughts occur more often in the South Xinjiang. A decreasing frequency of droughts in the North Xinjiang is found in winter, but a drying tendency is detected in the western parts of the North Xinjiang during spring, summer and autumn, which may be harmful for agriculture. The South Xinjiang seems to be getting wetter in summer, while the south parts of the South Xinjiang seem to be getting drier in spring. The middle of the East Xinjiang is identified to be in a slightly dry tendency. The drought severity is decreasing and drought duration is getting shorter in the North Xinjiang, while both of them increase in the southern parts of the South Xinjiang. In addition, droughts in the middle parts of the East Xinjiang are intensifying. 相似文献
9.
Based on the daily precipitation data of 38 weather stations in the Huai River Basin from 1961 to 2010, this study used SPI index, P-III curve to determine the flood/drought years, under what situations for droughts and floods easily happen, and to analyze the evolution law of flood and drought during inter-annual and intra-annual based on the characteristic of monthly precipitation. The results showed that: (1) annual rainfall of the Huai River Basin presented decreasing trend, maximum rainfall appeared from June to August, and multi-year average precipitation increased gradually from north to south; (2) the variation of monthly precipitation during flood years was more severe than other typical years, and precipitation in drought years showed nearly 50 % decline compared with normal years; (3) high rainfall of flood years was mainly caused by the increase in rainfall in flood season, and the strategy of flood control and drought relief was “short-term flood prevention and long-term drought relief”; (4) while precipitation of most months in drought year was reduced, the relevant strategies “annual basin-wide of long-term drought prevention” should be carried out; (5) combination events of floods and droughts occurred frequently. Persistent drought dominated in spring and summer while droughts and floods that happened alternately were mainly in summer and autumn. 相似文献
10.
应用预置白处理后的Mann—Kendall非参数检验方法及小波分析方法,分析了额尔古纳河流域20个水文气象站点近50年水文气象要素(气温、降水和径流)的变化趋势以及典型站点降雨量、径流量的多时间尺度特征。同时应用聚类分析方法推算了径流量序列的突变点。结果表明,该区域气温呈现明显升高的趋势,其中海拉尔站可能由于城市化进程的影响气温升高幅度最大。流域年降水总量变化趋势不显著,但某些月份降水量存在明显增加或者减小的趋势,其中显著增加的月份为11、12和1月,显著减小的月份为7、8月;降水趋势显著变化的站点主要分布在该流域的呼伦湖水系和海拉尔河水系。流域年径流量有减少趋势但不显著,然而4、5月份大多数站点径流量出现显著减少趋势。小波分析表明,典型站点年降水量存在25a左右的主周期,年径流量存在20~26a的主周期。各个站点径流量序列的显著跳跃点大都发生在1999年,这与通过小波分析得出的有关突变点的结论相一致。 相似文献
11.
全球气候变化影响了气象水文要素的时空分布特性,气象水文干旱事件的转化关系及风险传播特征亟待研究。基于站点、栅格观测资料和CMIP5(Coupled Model Inter-comparison Project Phase5)的19个气候模式输出数据,采用新安江等4个水文模型模拟了中国135个流域历史(1961—2005年)和未来时期(2011—2055年,2056—2100年)的水文过程,计算了SPI(Standard Precipitation Index)和SRI(Standard Runoff Index)干旱指标,通过游程理论识别了气象干旱与水文干旱事件,利用Copula函数与最大可能权函数度量二维干旱风险特征,定量评估了气象干旱至水文干旱的潜在风险传播特性。结果表明:①气象-水文干旱对气候变化响应强烈,华北和东北地区的干旱联合重现期增大,干旱潜在风险减小,华中和华南地区的干旱联合重现期减少60%~80%,干旱潜在风险增加;②气象干旱与水文干旱风险在历史和未来时段均存在显著的正相关关系,相关系数超过0.99;③各流域水文干旱风险变化对气象干旱风险变化的敏感程度不会随气候变暖发生较大变化,但未来北方地区水文干旱同气象干旱同时发生的概率将会小幅度增加。 相似文献
12.
Southwest regions of Iran, due to dry environmental and climatic conditions, have been identified as one of the five major regions in the world. In recent years, large parts of Iran have been affected by suspended particles from the dust storms. The studied area is located in foothills of the Zagros Mountain Range just north of Persian Gulf in southwest of Iran. Dust and other meteorological data were prepared in 3-hour intervals from 12 synoptic weather stations. For tracking dust storms, satellite images of MODIS were used. Atmospheric conditions during the occurrence of dust storms were determined using NCEP reanalysis data. According to the statistical calculations, most storms occurred in the spring and summer. The lowest number of dust events occurred in the fall and winter particularly in December and January, when there are high possibilities of rainfall occurrence and dynamical instability conditions in the north and west of the region. The results illustrated that the highest amounts of hourly dust occurred in the afternoon and the lowest amounts occurred at 00UTC (3.30 am local times). It seems that it is closely related to the heating surface and the occurrence of local dry instabilities. Analyses of data showed that dust amounts (or volumes) in all the stations have two climactic peaks, first between 1982 and 1990 and second between 2005 and 2008 periods. These peaks can be related to a variety of factors including anthropogenic factors such as war, agricultural activities, dam construction, and widespread droughts. 相似文献
13.
Meteorological droughts can affect large areas and may have serious environmental, social and economic impacts. These impacts depend on the severity, duration, and spatial extent of the precipitation deficit and the socioeconomic vulnerability of the affected regions. This paper examines the spatiotemporal variation of meteorological droughts in the Haihe River basin. Meteorological droughts events were diagnosed using daily meteorological data from 44 stations by calculating a comprehensive drought index (CI) for the period 1961–2011. Based on the daily CI values of each station over the past 50 years, the drought processes at each station were confirmed, and the severity, duration and frequency of each meteorological drought event were computed and analyzed. The results suggest the following conclusions: (1) the use of the CI index can effectively trace the development of drought and can also identify the duration and severity of each drought event; (2) the average drought duration was 57–85 days in each region of the Haihe River basin, and the region with the highest average values of drought duration and drought severity was Bohai Bay; (3) drought occurred more than 48 times over the study period, which is more than 0.95 times per year over the 50 years studied. The average frequencies of non-drought days, severe drought days and extreme drought days over the study period were 51.2, 3.2 and 0.4 %, respectively. Severe drought events mainly occurred in the south branch of the Hai River, and extreme drought events mainly occurred in the Shandong Peninsula and Bohai Bay; (4) the annual precipitation and potential evapotranspiration of the Haihe River basin show decreasing trends over the past 50 years. The frequency of severe drought and extreme drought events has increased in the past 20 years than during the period 1961–1990. The results of this study may serve as a reference point for decision regarding basin water resources management, ecological recovery and drought hazard vulnerability analysis. 相似文献
14.
Meteorological droughts can affect large areas and may have serious environmental, social and economic impacts. These impacts depend on the severity, duration, and spatial extent of the precipitation deficit and the socioeconomic vulnerability of the affected regions. This paper examines the spatiotemporal variation of meteorological droughts in the Haihe River basin. Meteorological droughts events were diagnosed using daily meteorological data from 44 stations by calculating a comprehensive drought index (CI) for the period 1961–2011. Based on the daily CI values of each station over the past 50 years, the drought processes at each station were confirmed, and the severity, duration and frequency of each meteorological drought event were computed and analyzed. The results suggest the following conclusions: (1) the use of the CI index can effectively trace the development of drought and can also identify the duration and severity of each drought event; (2) the average drought duration was 57–85 days in each region of the Haihe River basin, and the region with the highest average values of drought duration and drought severity was Bohai Bay; (3) drought occurred more than 48 times over the study period, which is more than 0.95 times per year over the 50 years studied. The average frequencies of non-drought days, severe drought days and extreme drought days over the study period were 51.2, 3.2 and 0.4 %, respectively. Severe drought events mainly occurred in the south branch of the Hai River, and extreme drought events mainly occurred in the Shandong Peninsula and Bohai Bay; (4) the annual precipitation and potential evapotranspiration of the Haihe River basin show decreasing trends over the past 50 years. The frequency of severe drought and extreme drought events has increased in the past 20 years than during the period 1961–1990. The results of this study may serve as a reference point for decision regarding basin water resources management, ecological recovery and drought hazard vulnerability analysis. 相似文献
15.
以鄱阳湖流域为研究区, 基于2011—2020年22个墒情站的逐日地面墒情监测数据、1956—2020年49个雨量站的日降雨数据及2016—2019年墒情站所在灌区的气象数据, 采用考虑植被生理状态的土壤水分亏缺指数(SWDI)表征农业干旱, 分析不同尺度下墒情、包气带缺水量和降水量的时空分布, 评估SWDI在鄱阳湖流域农业干旱监测中的适用性, 揭示该流域农业干旱时空演变特征及其对气象干旱的响应规律, 初步探讨土壤质地与农业干旱强度的相关性。结果表明: ① SWDI对鄱阳湖流域农业干旱诊断具有较好的适用性; ②近10 a该流域农业干旱呈显著加重趋势, 其中2019—2020年发生流域性重度农业干旱, 且夏、秋、冬连旱, 是近10 a的主导季节性农业干旱, 对水稻、油菜等粮食产量影响显著; ③相较于气象干旱, 农业干旱发生、结束时间分别平均约晚2.5周和3周, 历时长10.1周, 频次更低, 干旱等级更小; ④砂土持水性最差, 易发生特大农业干旱, 黏土、黏壤土保水性最好, 轻旱和中旱发生概率较大, 壤土、砂壤土和壤砂土则介于二者之间。 相似文献
16.
This work describes the climate change impact study on rainfall patterns in Macta watershed, located in the northwest of Algeria. The monthly rainfall data collection, verification and validation have built a database with 42 stations, each with 42 years of observations from 1970 to 2011. The study of annual total rainfall has identified a downward trend and quantifies the deficits that are within the observation time series. The division of the annual rainfall series into four periods allowed to highlighting the increase in inter-year temporal variability with the coefficient of variation increases from 17 to 27%. The study shows an annual rainfall deficit increment from 13 to 25%. The standard deviation values decrease significantly for the last two periods showing a spatial variability. Multivariate statistical study by the hierarchical clustering method resulted in the formation of station groups indicating the unification of monthly rainfall patterns. 相似文献
17.
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
18.
Drought is one of the most harmful natural hazards in Gansu Province in Northwest China. The changes of precipitation affect
the severity of drought. In order to recognize the trend of precipitation and understand the effect of rainfall change on
water resources management and drought severity, Mann–Kendall test was used. Standardized Precipitation Index (SPI) was calculated
to reconstruct the drought at different time scales and analyze the frequency of drought occurrence in the recent 50 years.
The results show that the SPI is applicable in Gansu Province. The number of severe droughts differs among regions: it is
more obvious as a 3-month drought in the Yellow River Basin and the Yangtze River Basin than in the Inland River Basin, and
other droughts at 6-, 9-, and 12-month time scales have the same effect in the three regions. Mann–Kendall test results show
that there is an upward trend in the summer periods and a downward trend in the autumn-winter-spring intervals ranging from
10.5 mm/10 years to −37.4 mm/10 years, which affect the local water resources management, droughts mitigation, and agriculture
decision making. This situation poses challenges for future study. 相似文献
19.
This article assesses drought status in the Yarmouk Basin (YB), in northern Jordan, using the Standardized Precipitation Index (SPI), the Standardized Water-Level Index (SWI), and the Percent Departure from Normal rainfall (PDNimd) during the years 1993–2014. The results showed that the YB suffers from frequent and irregular periods of drought as variations in drought intensity and frequency have been observed. The SPI results revealed that the highest drought magnitude of ??2.34 appeared at Nuaimeh rainfall station in 1991. This station has also experienced severe drought particularly in years 1995, 1999, 2005, and 2012 with SPI values ranging from ??1.51 to ??1.59. Some other rainfall stations such as Baqura, Ibbin, Khanasiri, Kharja, Mafraq police, Ramtha, Turra, and Umm Qais have also suffered several periods of drought mostly in 1993. The SWI results show the highest extreme drought events in 2001 in Souf well while other extreme drought periods were observed at Wadi Elyabis well in 1994 and at Mafraq well in 1995. As compared to SPI maps, our SWI maps reflect severe and extreme drought events in most years, negatively impacting the groundwater levels in the study area. 相似文献
20.
Meteorological drought during the southwest monsoon season and for the northeast monsoon season over five meteorological subdivisions of India for the period 1901–2015 has been examined using district and all India standardized precipitation index (SPI). Whenever all India southwest monsoon rainfall was less than ?10% or below normal, for those years all India SPI was found as ?1 or less. Composite analysis of SPI for the below normal years, viz., less than ?15% and ?20% of normal rainfall years indicate that during those years more than 30% of country’s area was under drought condition, whenever all India southwest monsoon rainfall was –15% or less than normal. Trend analysis of monthly SPI for the monsoon months identified the districts experiencing significant increase in drought occurrences. Significant positive correlation has been found with the meteorological drought over most of the districts of central, northern and peninsular India, while negative correlation was seen over the districts of eastern India with NINO 3.4 SST. For the first time, meteorological drought analysis over districts and its association with equatorial pacific SST and probability analysis has been done for the northeast monsoon over the affected regions of south peninsular India. Temporal correlation of all India southwest monsoon SPI and south peninsular India northeast monsoon SPI has been done with the global SST to identify the teleconnection of drought in India with global parameters. 相似文献
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