共查询到20条相似文献，搜索用时 31 毫秒
1.
为定量评估我国北方地区苹果不同干旱等级灾害时空分布特征,以我国苹果主产地为研究区域,对前人提出的干旱指数进行等级划分,结合历史灾情资料,对划分的等级进行验证;利用验证后的干旱指数,明确1981—2016年苹果不同干旱等级时空变化特征。结果表明:划分的干旱指数等级能够较好地反映我国北方地区苹果实际干旱特征;各生育阶段甘肃省中北部、宁夏回族自治区各年代以重旱发生为主,山西省、陕西省、山东省以及河南省干旱等级随年代变化较大;重旱发生面积在果树萌动-花芽萌动和成熟-落叶生育阶段1981—2000年随年代变化逐渐增加;各生育阶段无旱和重旱高频区频率高于50%,轻旱和中旱高频区频率高于30%;1981—2016年轻旱发生范围最大,果树萌动-花芽萌动生育阶段的重旱和盛花-成熟生育阶段的中旱站次比呈显著上升趋势。研究区域西北地区干旱严重,且发生频率较高。 相似文献
2.
Drought over the Greek region is characterized by a strong seasonal cycle and large spatial variability. Dry spells longer than 10 consecutive days mainly characterize the duration and the intensity of Greek drought. Moreover, an increasing trend of the frequency of drought episodes has been observed, especially during the last 20 years of the 20th century. Moreover, the most recent regional circulation models (RCMs) present discrepancies compared to observed precipitation, while they are able to reproduce the main patterns of atmospheric circulation. In this study, both a statistical and a dynamical downscaling approach are used to quantify drought episodes over Greece by simulating the Standardized Precipitation Index (SPI) for different time steps (3, 6, and 12 months). A statistical downscaling technique based on artificial neural network is employed for the estimation of SPI over Greece, while this drought index is also estimated using the RCM precipitation for the time period of 1961–1990. Overall, it was found that the drought characteristics (intensity, duration, and spatial extent) were well reproduced by the regional climate models for long term drought indices (SPI12) while ANN simulations are better for the short-term drought indices (SPI3).
相似文献3.
Estimation of drought in a certain temporal and spatial scale is crucial in climate change studies. The current study targets on three agricultural areas widespread in Greece, Ardas River Basin in Northeastern Greece, Sperchios River Basin in Central Greece, and Geropotamos River Basin in Crete Island in South Greece that are characterized by diverse climates as they are located in various regions. The objective is to assess the spatiotemporal variation of drought conditions prevailing in these areas. The Standardized Precipitation Index (SPI) was used to identify and assess the present and future drought conditions. Future simulated data were derived from a number of Regional Climatic Models (RCMs) from the ENSEMBLES European Project. The analysis was performed for the future periods of 2021–2050 and 2071–2100, implementing A1B and B1 scenarios. The spatial analysis of the drought conditions was performed using a combined downscaling technique and the Ordinary Kriging. The Mann-Kendall test was implemented for trend investigation. During both periods and scenarios, drought conditions will tend to be more severe in the upcoming years. The decrease of the SPI values in the Sperchios River Basin is expected to be the strongest, as it is the only study area that will show a negative balance (in SPI values), regarding the drought conditions. For the Ardas and the Geropotamos River Basins, a great increase of the drought conditions will occur during the 2021–2050 period, while for 2071–2100 period, the decrease will continue but it will be tempered. Nevertheless, the situation in all study areas according to the SPI classification is characterized as “Near-normal”, in terms of drought conditions. 相似文献
4.
I. Tselepidaki B. Zarifis D. N. Asimakopoulos 《Theoretical and Applied Climatology》1992,46(2-3):115-121
Summary The unusual low precipitation observed during 1989–1990 in Greece is the subject of the present study. Statistical comparisons of this drought period with other dry periods in the historical records, possible statistical cycles, (periodicities), or general trends, together with the behaviour of the long time series are investigated. Power spectra of the annual rainfall series are also plotted considering the 95 years of data for the most reliable station in Greece. Furthermore, the drought persistence between successive months is also analysed using standard methods. The analysis identified periodicities of 2.1 and 3.6 years while no significant trends were observed in almost all cases. Finally the persistency of successive dry days was found to be insignificant after the fourth day.With 5 Figures 相似文献
5.
6.
Severe droughts have affected much of Europe over the last 40 years. A limitation to current understanding of droughts is based around drought characteristics (e.g. frequency, severity and duration) as there are limited long series (>100 years) with well documented severe droughts. This is further complicated with future climate projections, and the potential implications that these will have on drought characteristics. This paper presents reconstructed drought series from 1697, 1726 and 1767 to 2011 for three sites in southeast England. Precipitation and temperature series are reconstructed to generate long drought series using the self-calibrated Palmer Drought Severity Index, enabling determination of drought characteristics. The reconstructions identify multiple drought-rich periods, 1730–1760 and 1890-present, with an increasing tendency towards more severe droughts during the latter period. Prolonged rainfall deficiencies are found to be the primary cause of severe droughts, with rising temperatures increasing soil moisture deficit, therefore intensifying drought conditions. Cycles at the 6–10 year period identify a sub-decadal to decadal signal during drought-rich periods. Analysis of the spatial variability of droughts finds that whilst severe events are predominantly regionally coherent, there are notable variations in severity and duration between sites, which are attributed to localised rainfall variability. This study extends the temporal range of previous drought studies and places recent drought events in a longer context improving upon existing ‘benchmark’ drought analyses in southeast England; with far-reaching implications for local, national and continental scale reduction of drought vulnerability and risk. 相似文献
7.
Alexandros P. Dimitrakopoulos M. Vlahou Ch. G. Anagnostopoulou I. D. Mitsopoulos 《Climatic change》2011,109(3-4):331-347
An increasing trend and a statistically significant positive correlation between wildfire occurrence, area burned and drought (as expressed by the Standardized Precipitation Index, SPI) have been observed all over Greece, during the period 1961?C1997. In the more humid and colder regions (Northern and Western Greece) the number of fires and area burned were positively correlated to both summer (SPI6_October) and annual drought (SPI12_September), whereas in the relatively more dry and hot regions (Southern and Central Greece) the number of fires and area burned were correlated only to summer drought. In 1978, Greece entered a period of prolonged drought, possibly as a result of the global climatic change. Data analysis of the period 1978?C1997 revealed a statistically significant increase in the mean annual number of fires, the area burned and the summer and annual drought episodes in the relatively more humid and colder regions (Northern and Western) of Greece (which in the past were characterized by less fires and area burned) compared to the more dry and hot regions (Southern and Eastern Greece), which always presented high fire activity. Additionally, analyzing the two sub-periods (1961?C1977, 1978?C1997) separately, drought was significantly correlated only to fire occurrence during the years 1961?C1977, whereas during 1978?C1997 drought was significantly correlated mainly to area burned. It became obvious that drought episodes, although they are not solely responsible for fire occurrence and area burned, they exert an increasingly significant impact on wildfire activity in Greece. 相似文献
8.
佛山市前汛期旱涝及其环流异常特征 总被引：18，自引：18，他引：0
基于佛山市降水量和NCEP/NCAR再分析资料,采用二维风场差异的显著性检验方法等,分析了佛山市前汛期降水异常特征及旱、涝年水平风场和垂直经圈环流的差异。结果表明,佛山市前汛期降水量存在多时间尺度振荡,降水量的气候变化趋势不明显。旱、涝年热带低纬度的南海中北部及西太平洋地区的850 hPa风场存在显著差异,影响前汛期旱涝的关键区是副高的西北侧和南侧。分析还表明,旱、涝年经圈环流差异显著,北半球风场显著区位于南海区域和华南地区,层次集中在大气低层和中层。 相似文献
9.
以西北地区东部的17个代表站1470—2008年的旱涝等级资料和1958—2015年5—9月气象站降水量数据为基础，建立了546年中国西北地区东部旱涝等级序列，采用经验正交函数分解、滑动t检验等统计方法，对其干湿演变规律进行分析，详细讨论了546年极端干旱事件及干旱持续性特征。结果表明:旱涝等级资料能够较好地反映西北地区东部干旱变化的时、空特征；在百年尺度上，20世纪发生旱、偏旱最为频繁，且高值区位于宁夏及陕北；干旱尺度因子的空间分布表明宁夏东部及陕北地区的干旱持续性相对较强，陇南及陕西南部地区的干旱持续性较差；空间范围较大且强度较大的重大干旱事件对干旱的持续发生起重要作用，历史上发生在1470—1500年和1910—1940年的两次西北地区东部百年甚至两百年一遇的极端干旱事件，对该地区干旱持续性的影响较为显著。 相似文献
10.
Within Canada, the Canadian Prairies are particularly drought-prone mainly due to their location in the lee of the western cordillera and distance from large moisture sources. Although previous studies examined the occurrence of Canadian Prairie droughts during instrumental, pre-instrumental and to a lesser extent, future periods, none have specifically focused on all time three scales. Using two different drought indicators, namely the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI), this investigation assesses the variability of summer drought duration and intensity over a core region of the Prairies during (a) the pre-instrumental record extending back several centuries (inferred from tree rings), (b) the instrumental record (1901–2005), and (c) the twenty-first century using statistically downscaled climate variables from several Atmosphere–Ocean Global climate models with multiple emission scenarios. Results reveal that observed twentieth century droughts were relatively mild when compared to pre-settlement on the Prairies, but these periods are likely to return (and even worsen) in the future due to the anticipated warming during the course of the twenty-first century. However, future drought projections are distinctly different between the two indices. All PDSI-related model runs show greater drought frequency and severity mainly due to increasing temperatures. Conversely, the precipitation-based SPI indicates no significant changes to future summer drought frequency although there tends to be a higher persistence of multi-year droughts in central and southern portions of Canadian Prairies. These findings therefore stress the importance of considering anticipated warming trends when assessing future regional-scale drought, especially given the uncertainties and lack of consistency in future precipitation signals among climate models. This study can be considered an initial step toward quantifying and understanding Canadian Prairie drought occurrence and severity over several centuries as determined from paleo, instrumental, and climate model data sources. 相似文献
11.
我国北方地区冬小麦干旱灾害风险评估 总被引：7，自引：0，他引：7
选取我国粮食重要生产区——北方冬麦区作为研究区,基于干旱灾害对作物产量的影响开展冬小麦干旱灾害风险评估和区划。在确定干旱灾害危险性指标过程中,通过对比分析MCI、CWDIa、CI、Pa及Ma干旱指数的适应性,确定了干旱灾害风险危险性指数;在分析北方冬麦区干旱背景和脆弱性时,考虑了冬麦区的地形、土壤类型、土壤有效持水量、河网水系、灌溉条件、降水量及干燥度等环境因素,以及冬小麦的耕地面积、播种面积、主要生育期的水分敏感系数、历史产量等。与以往致灾因子危险性分析方法不同,本文首先建立了干旱指标与冬小麦减产率之间的关系,通过减产率等级来确定干旱致灾临界阈值,在此基础上计算分析了冬小麦全生育期和6个关键生育期不同等级干旱发生的频率。综合考虑干旱发生的危险性、不同地区干旱背景和脆弱性,建立了我国北方冬麦区全生育期和6个关键生育期的干旱灾害风险评估模型和区划方法,实现了我国北方冬麦区干旱灾害的风险评估和区划。结果表明,MCI更能反映北方冬麦区干旱的特征,故以MCI指数作为干旱灾害风险危险性指数;我国北方冬麦区中北部的干旱灾害风险较高,应该加强防旱抗旱能力建设,南部地区包括苏皖和河南东南部的干旱灾害风险较小。本文建立的北方冬麦区不同生育期干旱灾害风险评估模型可应用于干旱灾害风险动态评估实时业务中。 相似文献
12.
基于CRU逐月降水和NCEP/NCAR再分析等资料,利用集合经验模态分解(Ensemble Empirical Mode Decomposition,EEMD)方法,分析1948—2016年中国中部地区夏季降水变化的多时间尺度特征及其对应的环流、海温异常,进而解释不同时期影响干旱发生的背景场有何不同。结果表明,中部地区夏季降水以年际变化为主,周期长度为3.8 a和6.9 a,年代际和多年代际变化的方差贡献不足20%。然而,各时间尺度降水变化对不同时期干旱事件的贡献存在较大差异,1960s、1970s,降水年际变化偏弱,相反地,多年代际变化正处于负位相的极小值期;1980s、1990s,多年代际变化位相转正;2000s初,年际变化明显增强。此外,通过分析不同时间尺度降水变化对应的环流、海温背景场,发现热带印度洋海温异常及其引起的西北太平洋副热带高压的变化、大西洋北部海温异常激发的纬向波列以及贝加尔湖地区的阻塞活动、1970s末PDO位相转变伴随的东亚夏季风突变是分别解释降水年际、年代际和多年代际变化的主要原因,进而揭示影响中部地区夏季干旱发生的关键因子及其相对重要性。 相似文献
13.
Recent tree-growth reduction in north central China as a combined result of a weakened monsoon and atmospheric oscillations 总被引：1，自引：0，他引：1
Tree-ring records are a valuable source of information for understanding long-term, regional-scale drought changes. In this study, a tree ring width chronology spanning the last 330?years (A.D. 1681–2010) is developed for the northern fringe of the Asian summer monsoon in north central China based on tree ring widths of the Chinese pine (Pinus tabulaeformis) at three sites in the Hasi Mountain (HSM). An annual (running from the previous August to the present July) Palmer Drought Severity Index (PDSI) series is reconstructed for the period A.D. 1698 to 2010 using a linear regression model. This reconstruction accounts for 49?% of the actual PDSI variance during the calibration period (A.D.1951–2005). During the last past 330?years, the year 1759 drought was the most severe and the 1926–1932 drought was the most long-lasting. These drought episodes resulted in huge economic losses and severe famine. Similar periods of drought are also found in the Great Bend of the Yellow River region, northeastern Tibetan Plateau and northern China. Our drought reconstruction is consistent with the dry-wet index derived from historical documents for the Great Bend of the Yellow River region for the last three centuries, revealing that our annual PDSI reconstruction reflects broad-scale climate anomalies and represents drought variations in the northern fringe of the Asian summer monsoon. The PDSI reconstruction correlates significantly with sea surface temperature (SST) in the eastern equatorial Pacific Ocean and northern Indian Ocean at an annual timescale, implying that El Ni?o-Southern Oscillation and the Indian monsoon might be influencing drought variability in the study area. Some extremely dry years of 1707, 1764, 1837, 1854, 1878, 1884, 1926 and 1932 coincided with major El Ni?o events in historical times. The decadal-scale variability is linked to Pacific Decadal Oscillation (PDO) and SST variations in the Atlantic Ocean. The observed recent tree growth reduction is unusual when viewed from a long-term perspective. 相似文献
14.
Drought analysis in Jordan under current and future climates 总被引：2，自引：0，他引：2
Mohammed I. Al-Qinna Nezar A. Hammouri Mutewekil M. Obeidat Fayez Y. Ahmad 《Climatic change》2011,106(3):421-440
Droughts have adverse socioeconomic, agricultural, and environmental impacts that can be reduced by assessing and forecasting
drought behavior. The paper presents detailed analyses of both meteorological and vegetative droughts over the period from
1970 to 2005. Standardized Precipitation Index (SPI) and Normalized Difference Vegetation Index (NDVI) have been used to quantify
drought according to severity, magnitude and spatial distribution at the Hashemite Kingdom of Jordan. Results suggest that
the country faced during the past 35 years frequent non-uniform drought periods in an irregular repetitive manner. Drought
severity, magnitudes and life span increased with time from normal to extreme levels especially at last decade reaching magnitudes
of more than 4. Generated NDVI maps spatial analyses estimate crop-area percentage damage due to severe and extremely severe
drought events occurred during October, December, and February of 2000 to be about 10%, 45%, and 30%, respectively. In response
to drought spatial extent, the paper suggest the presence of two drought types, local drought acting on one or more geographical
climatic parts and national drought, of less common but more severe, that extend over the whole country. Droughts in Jordan
act intensively during January, February and March and tend to shift position with time by alternative migrations from southern
desert parts to northern desert parts and from the eastern desert parts to highlands and Jordan Rift Valley (JRV) at the west.
The paper also investigates the potential use of Global Climate Model’s (GCM) to forecast future drought events from 2010
till 2040. Tukey HSD test indicates that ECHAM5OM GCM is capable to predicted rainfall variation at the country and suggests
future droughts to become more intensive at the northern and southern desserts with 15% rainfall reduction factor, followed
by 10% reduction at the JRV, and 5% at the highlands. 相似文献
15.
A Comparative Analysis of Primary and Extreme Characteristics of Dry or Wet Status between Asia and North America 总被引：1，自引：0，他引：1
In this study, the Palmer Drought Severity Index (PDSI) was used to analyze the average and extreme dry/wet states of Asia and North America from 1953 to 2003. The results indicate that the two continents underwent drying trends during this period. Compared with North America, Asia showed more severe drought trends. However, more significant and regular seasonal variation for drought was found in North America. The driest regions in Asia were located in the northern region of China, Mongolia, and eastern mid-Siberian plateau. Most regions in central North America were relatively wetter than other regions. The northern and southwestern regions of North America, as well as the Atlantic and Pacific coastal areas, experienced the most drought during this period. A sharp increase of the drought area and the number of extreme drought events took place from 1997 to 2003 in both Asia and North America. Severe drought events were more likely to occur during the summer on both continents. Asia had the most extreme drought events during July, but North America reached its highest drought frequency from June to September. In Asia, a persistent increasing trend of extreme drought emerged throughout the studied period. However, a more complex evolution of drought emerged in North America: a decreasing trend appeared before the mid-1960s and an increasing trend appeared after the late 1970s. A relatively steady dry/wet status was observed between the mid-1960s and the late 1970s. The role of exceptional, extreme drought events with respect to the La Nin?a event was considered during 1997–2003. 相似文献
16.
17.
基于辽宁省1114个国家级和区域级地面台站1961年以来的逐日气温和降水观测资料,利用距离平方反比法差值生成了1717个乡镇的气象资料序列,采用气象干旱综合监测指数统计分析了辽宁省2017年4—8月精细化到乡镇的气象干旱特征。结果表明:2017年辽宁省春夏季异常高温,同时降水异常偏少,致使气象干旱不断发展;干旱在4月5日前从中部和北部开始,4月末扩展到西部,5—6月再向东南发展,波及88%的乡镇,7月以来气象干旱程度开始减轻;气象干旱持续时间长的乡镇主要集中在中部和北部,最长持续时间153d;受气温偏高和降水过程的影响,中度以上气象干旱面积呈阶段性变化,且极端干旱的发展伴随高温时段。由于气象干旱不同于农业干旱,在开展为农服务时要因地制宜采取应对措施。 相似文献
18.
Flash drought is a rapidly intensifying drought with abnormally high temperature, which has greatly threatened crop yields and water supply, and aroused wide public concern in a warming climate. However, the preferable hydrometeorological conditions for flash drought and its association with conventional drought at longer time scales remain unclear. Here, we investigate two types of flash drought over China: one is high-temperature driven (Type I), while the other is water-deficit driven (Type II). Results show that the frequencies of the two types of flash drought averaged over China during the growing season are comparable. Type I flash drought tends to occur over southern China, where moisture supply is sufficient, while Type II is more likely to occur over semi-arid regions such as northern China. Both types of flash drought increase significantly (p0.01) during 1979-2010, with a doubled rise in Type I as compared with Type II. Composite analysis shows that high temperature quickly increases evapotranspiration (ET) and reduces soil moisture from two pentads before the onset of Type I flash drought. In contrast, there are larger soil moisture deficits two pentads before the onset of Type II flash drought, leading to a decrease in ET and increase in temperature. For flash drought associated with seasonal drought, there is a greater likelihood of occurrence during the onset and recovery phases of seasonal drought, suggesting perfect conditions for flash drought during transition periods. This study provides a basis for the early warning of flash drought by connecting multiscale drought phenomena. 相似文献
19.
20.
Qiang Zhang Mingzhong Xiao Vijay P. Singh Xiaohong Chen 《Theoretical and Applied Climatology》2013,111(1-2):119-131
Daily precipitation data for the period of 1960–2005 from 42 precipitation gauging stations in the Pearl River basin were analyzed using the Mann–Kendall trend test and copula functions. The standardized precipitation index method was used to define drought episodes. Primary and secondary return periods were also analyzed to evaluate drought risks in the Pearl River basin as a whole. Results indicated that: (1) in general, the drought tendency was not significant at a 95 % confidence level. However, significant drought trends could be found in November, December, and January and significant wetting trends in June and July. The drought severity and drought durations were not significant at most of the precipitation stations across the Pearl River basin; (2) in terms of drought risk, higher drought risk could be observed in the lower Pearl River basin and lower drought risk in the upper Pearl River basin. Higher risk of droughts of longer durations was always corresponding to the higher risk of droughts with higher drought severity, which poses an increasing challenge for drought management and water resources management. When drought episodes with higher drought severity occurred in the Pearl River basin, the regions covered by higher risk of drought events were larger, which may challenge the water supply in the lower Pearl River basin. As for secondary return periods, results of this study indicated that secondary return periods might provide a more robust evaluation of drought risk. This study should be of merit for water resources management in the Pearl River basin, particularly the lower Pearl River basin, and can also act as a case study for determining regional response to drought changes as a result of global climate changes. 相似文献