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1.
Xiaoyan Wang Tao Yang Bin Yong Valentina Krysanova Pengfei Shi Zhenya Li Xudong Zhou 《Environmental Earth Sciences》2018,77(12):465
Climate change is expected to have substantial impacts on flow regime in the Upper Yellow River (UYR) basin that is one of the most important biodiversity hotspots in the world. These impacts will most possibly exert negative effects on the habitat availability for riverine species. Thus, it is necessary to understand the alteration of river flow regime under climate scenarios. In this paper, we use the modified hydrological model HBV in conjunction with three general circulation models under three representative concentration pathways (RCP 2.6, 4.5, and 8.5) to address changes in flow regime under climate change for the UYR basin in the mid-term (2050s) and end-term (2080s) of the twenty-first century. Flow regime is quantified using the Indicators of hydrological alteration approach. Thereafter, the potential threats to riverine ecosystem in the UYR basin are identified based on the projected alterations of various flow characteristics and their ecological influences. The results showed that the magnitude of monthly flow would increase during the dry period. The date of the annual 1-day minimum streamflow will likely shift toward earlier time under different scenarios, and significant increases in magnitude of annual minimum flow of different durations were detected under both RCP 4.5 and 8.5 scenarios in the 2080s. In addition, assessments of the modification degree of the overall flow regime revealed that climate change would remarkably modify (medium level) the overall flow regime in the UYR basin, particularly by the end of the twenty-first century or under the high emission scenarios. Besides, destruction of habitat and reduced availability of food induced by substantially increased hydrological instability in the 2080s would make two endangered fishes more vulnerable in the UYR basin. These findings provide insights into potential adaptive countermeasures for water resource management and environmental system restoration in the Upper Yellow River. 相似文献
2.
Victor Ongoma Haishan Chen Chujie Gao Aston Matwai Nyongesa Francis Polong 《Natural Hazards》2018,90(2):901-920
This study investigates the variability of extreme rainfall (temperature) events in the twenty-first century based on 18 (24)-member multimodel simulations of models participating in phase 5 of the Couple Model Intercomparison Project (CMIP5). The study employed extreme indices defined by the WMO’s Experts Team on Climate Change Detection Indices, under two radiative forcing scenarios: RCP4.5 and RCP8.5. Two 30-year time periods, mid- (2021–2050) and end (2071–2100) of the twenty-first century, are considered for investigation of extremes, relative to the baseline period (1961–1990). Mann–Kendall test statistic and Sen’s slope estimator are used to investigate trend. Temperature shows a remarkable increase with an increase in radiative forcing. A sharp augmentation in temperature is projected towards the end of the twenty-first century. There will be almost zero cool days and cold nights by the end of the century. Very wet and extremely very wet days increase, especially over Uganda and western Kenya. Variation in maximum 1-day precipitation (R × 1 day) and maximum 5-day precipitation amount shows a remarkable increase in variance towards the end of the twenty-first century. Although the results are based on relatively coarse resolution data, they give likely conditions that can be utilized in long-term planning and be relied on in advanced studies. 相似文献
3.
Spatio-temporal distributions of climate disasters and the response of wheat yields in China from 1983 to 2008 总被引：1，自引：0，他引：1
Climate disasters are now on the rise and more likely to increase in frequency and/or severity under climate change in the future. To clearly illustrate spatial–temporal distributions of climate disasters and the response of wheat yields to disasters over the past three decades, several disaster indices including the impact of climate disasters, the sensitivity to climate disasters and the response index of wheat yield losses to climate disasters were defined and calculated. The impact and sensitivity indices were examined by the agricultural production losses due to climate disasters, and the response of wheat yields to climate disasters was assessed by wheat yield loss compared with the 5-year moving average. The results showed that the indices of climate disaster impacts and sensitivities as well as response index of wheat yields to climate disasters could represent the spatial–temporal distributions of climate disasters well in the whole China. Droughts in northern China had higher impacts and sensitivities than those in southern China during the period 1983–2008, but the impacts of floods were opposite. In northern China, although impacted area by drought was larger than that by flood, the flood sensitivities were larger than drought sensitivities when flood happened. Although drought significantly affected wheat yields in most of the regions with drier conditions during 1983–2008 in major wheat-producing regions, better management practices like irrigation and drought-tolerant cultivars applied in the Huang-Huai-Hai Plain can adapt to climate disasters especially droughts. To ensure the stability of agricultural production, future food security will need to be achieved through quantifying the relative effects of climate disasters and effective adaptation to increasingly frequent extreme climate events. 相似文献
4.
21世纪北半球中高纬度净初级生产力(NPP)变化及其与气候因子之间的关系 总被引：1，自引：1，他引：0
基于CMIP5模式模拟的净初级生产力(NPP), 对21世纪初期(2016-2035年), 中期(2046-2065年)和末期(2080-2099年)三种排放情景下(RCP2.6、RCP4.5、RCP8.5)北半球中高纬度陆地NPP的时空变化进行了预估, 并结合气候因子分析了NPP的变化和气温、降水、辐射之间的关系. 结果表明: 相对于1986-2005年, 21世纪北半球中高纬度陆地NPP呈增加趋势, RCP8.5情景下NPP的增加比RCP2.6和RCP4.5情景下更为明显; 在季节变化上, 北半球中高纬度NPP也以增加为主, 且NPP在夏季, 尤其是6月增加最显著. NPP对气候变化的响应存在明显的区域差异性, 在中低排放情景下(RCP2.6、RCP4.5), 相对于1986-2005年, 21世纪北半球中高纬度地区温度显著影响的范围在逐渐缩小, 而辐射和降水显著影响的范围在扩大. 在高排放情景下(RCP8.5), 21世纪北半球中高纬度地区NPP的变化主要与温度有关. 相似文献
5.
区域性暴雨事件由于影响范围大、持续时间长,更易引发严重洪涝灾害,对经济社会可持续发展构成严重威胁。因此,预估区域性暴雨事件的未来变化对于气候变化适应和灾害风险管理意义重大。本文基于区域气候模式RegCM4对4个全球气候模式的动力降尺度模拟,利用“追踪式”客观识别方法,对我国区域性暴雨进行了识别,并从发生频次、持续时间、平均降水量、平均影响范围和综合强度5个方面预估了其在RCP4.5情景下的未来变化。多模式预估结果表明,我国平均区域性暴雨事件的发生频次、持续时间、平均降水量、平均影响范围和综合强度到21世纪末均呈不同程度的上升趋势。与1986—2005年相比,无论在21世纪中期(2046—2065年)还是末期(2080—2099年),位于“低值区”的事件出现频率减少,而位于“高值区”的事件出现频率增加。轻度区域性暴雨事件发生频次将减少,而中度、重度和严重的区域性暴雨事件发生频次将增加。在空间分布上,区域性暴雨事件的发生频次、持续时间和降水量均在我国东部区域大范围增加,并且三者增幅的空间分布型态较为一致。增加最显著的区域主要位于长江中下游、江南和华南地区,而且到21世纪末期的增加幅度大于中期。 相似文献
6.
采用淮河流域内1959—2008年110个气象站的逐日降水资料,结合流域1978—2008年农作物旱涝灾害受灾面积数据,基于降水致灾因子与农作物承灾体受损程度等研究,提出旱、涝致灾气候阈值概念,在此基础上分析旱涝灾害发生的时空特征,确定淮河流域合理的旱涝致灾气候阈值区间并建立致灾气候阈值与农作物受灾面积之间的定量关系。结果表明:① 致灾气候阈值可通过计算发生旱涝事件时间段累积降水量除以1959—2008年相应时段累积降水量的平均值来定义,得到的旱、涝致灾气候阈值在不同尺度下对旱、涝灾害事件均有较好地稳定反映,可满足研究区旱、涝事件分析需求;② 洪涝致灾气候阈值与农作物受灾面积存在一致的变化趋势,而干旱致灾气候阈值与农作物受灾面积相关系数高达0.96,构建了基于干旱致灾气候阈值的农作物受灾面积预测模型。 相似文献
7.
C. S. Murthy J. Singh P. Kumar M. V. R. Sesha Sai 《International Journal of Environmental Science and Technology》2017,14(9):1981-1988
Hazard analysis is the first step in any disaster management activity. Drought is a serious environmental hazard strongly limiting the agricultural production in the tropical countries like India. A comprehensive drought hazard map is useful for multiple perspectives such as agriculture, environment and hydrology. In this study, daily rainfall data of the Climate Prediction Centre during the south-west monsoon season (June–September) of 12 years, over India was analysed. Based on rainfall and rainy days, six indicators of drought were generated which were then synthesized into a composite index of drought hazard for every 10 × 10 km pixel. The weights for the composite index were generated through variance approach. The index has effectively captured the spatial variations in meteorological drought across India by showing a typical pattern with increasing hazardous area from east to west. The drought hazard map also shows considerable agreement with the climate classification map and the drought proneness map reported by other studies. Thus, the current study presents a simple and novel approach for drought hazard analysis, using the routinely available geospatial rainfall data products. The methodology can be extended to other geographies and disasters too. Use of time series data of longer period would improve the reliability of the composite drought hazard index. 相似文献
8.
以北江飞来峡水库上游为研究对象,构建了网格分辨率为0.25°×0.25°的VIC(Variable Infiltration Capacity)水文模型,应用CMIP5多模式输出的降尺度结果与VIC模型耦合,对RCP2.6、RCP4.5和RCP8.5情景下未来时期(2020-2050年)飞来峡水库的入库洪水进行预估,并根据IPCC第5次评估报告处理和表达不确定性的方法来描述预估结论的可信度。结果表明,2020-2050年飞来峡水库年最大洪峰流量和年最大7日、15日洪量在RCP2.6情景下"大约可能"呈增加趋势,在RCP4.5和RCP8.5情景下"较为可能"呈增加趋势,水库防洪安全风险增大。与历史时期(1970-2000年)相比,未来水库极端入库洪水增加的可能性从大到小依次为RCP4.5、RCP2.6和RCP8.5情景,其中设计洪水100年、50年和20年一遇的洪峰流量在3种排放情景下均呈上升趋势,100年、50年和20年一遇的最大7日、15日洪量在RCP4.5情景下以上升为主,而在RCP2.6和RCP8.5情景下则主要呈减少态势。 相似文献
9.
A 22-member ensemble from CMIP6 is used to analyze the projected changes and seasonal behavior in surface air temperature over South America during the twenty-first century. In the future projections, CMIP6 models shown a high dependency to the socioeconomic pathway over each country of South America. The multimodel ensemble projects a continuous increase in the annual mean temperature over South America during the twenty-first century under the three future scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Besides, it was possible to identify consistent positive trends across all the models, with values between 0.45 ± 0.05 and 2.05 ± 0.31 °C cy−1 under the historical experiment, however largest trends occurs for the projection periods (near, mid and far future), with values between − 0.87 ± 0.84 to 2.88 ± 0.60 °C cy−1 (SSP1-2.6), 1.41 ± 0.88 to 5.32 ± 0.81 °C cy−1 (SSP2-4.5) and 4.75 ± 0.58 to 8.76 ± 0.74 °C cy−1 (SSP5-8.5) with maximum values at Bolivia, Brasil, Paraguay and Venezuela whilst minimum values for Argentina and Uruguay, regardless of the SSP scenario used. From the seasonal behavior analysis was possible to identify maximum values between January and March whilst minimum between June and July, except in Brasil, Venezuela and Guyana–Surinam–French Guayana, with annual range decreasing as the latidude decreases. By the end of the twenty-first century the annual mean temperature over South america is projected to increase between 0.92–2.11 °C, 0.97–3.37 °C and 1.27–6.14 °C under SSP1-2.6, SSP2-4.5 and SSP5-8.5 projection scenarios respectively. This projected increase of temperature across the continent will produce negative repercussions in the social, economic and political spheres. The results obtained in this study provide insights about the CMIP6 performance over this region, which can be used to develop adaptation strategies and might be useful for the adaptation to the climate change.
相似文献10.
Extreme weather events present environmental and social challenges across the Eurasian steppe. In Mongolia much attention is given to drought and dzud (severe winter conditions) impact on rural livelihoods, landscapes and governance. A link between the two events, fostered by international and state agencies, speculates that drought leads to dzud; this has become the widely accepted doctrine. However, the relationship between the two events is assumed rather than analysed. Whilst there may be natural links between climate events, causality is more difficult to establish yet often claimed post-event. This paper stresses Mongolia’s destructive dzuds of 1999–2001 and 2009–2010 in examining drought frequency before dzud events. Findings question the hazard connection as just 3 of 32 examined dzud events were preceded by drought. Investigation did not document a relationship between the disasters; linkages between extreme events were implied rather than established. The human role in disaster also needs to be assessed as preparation, and response are key factors for mitigation. Study results identified a lack of causality between the disasters, suggesting more assiduous investigation of hazards is needed in Mongolia. This can clarify causal factors, identify risk and improve disaster mitigation strategies in Mongolia. 相似文献
11.
利用多源气象要素数据估算了1998 - 2016年的藏北高寒牧区植被净初级生产力（Net Primary Productivity, NPP）的变化特征并预估了其在2 ℃全球变暖背景下的变化趋势, 结果表明： 研究区域71.9%的NPP呈上升趋势, 仅中部部分区域有下降趋势; 平均NPP以每年0.54%速率增加, 同期气温和降水均呈增加趋势, NPP和气温在2007前后有显著增加趋势; 总体来说降水是影响NPP的最主要气候因子, 且随着纬度升高其影响越来越大, 气温对于NPP的影响从东南向西北依次递减, 在西北地区出现弱的负相关; 在2 ℃全球变暖大背景下, 分析得出IPCC“典型浓度路径”（Representative Concentration Pathways, 简称RCPs）三种温室气体排放情景下（RCP2.6、 RCP4.5、 RCP8.5）的NPP平均状态几乎没有变化, 其影响仅限于对研究区东南部的较高NPP有较小的改善作用, 其作用依次为
12.
CMIP5多模式集合对南亚印度河流域气候变化的模拟与预估 总被引：1，自引：0，他引：1
利用印度河流域CRU、APHRODITE和CMIP5多模式逐月气温、降水格点数据集, 评估了CMIP5模式集合对印度河流域气候变化的模拟能力; 对多模式集合数据进行了偏差订正, 并对流域2046-2065年和2081-2100年气候变化进行了预估. 结果表明: 气候模式对流域年平均气温时间变化和空间分布特征有着较强的模拟能力, 时间空间相关系数均达到了0.01的显著性水平, 尤其对夏季气温的模拟要优于其他季节; 模式对降水的季节性波动也有着较好的模拟能力. 偏差订正后的预估结果表明, RCP2.6、4.5、8.5情景下, 相对于基准期(1986-2005年), 21世纪中期(2046-2065年)和末期(2081-2100年)整个流域年平均气温都有一定上升, 且流域上游增幅较大; 除RCP4.5情景下21世纪中期流域有弱减少趋势外, 年降水量都将有一定增长. 未来夏季持续升温将引起源区冰川的进一步消融, 春季降水对于中高海拔地区水资源的贡献将减弱; 流域北部高海拔区域冬季降水的增加有助冰川累积和上游水资源的增加, 东部高海拔区域冬季降水的减少会减少上游水资源. 两时期夏季降水都有一定的增长, 洪涝的发生风险加大; 流域暖事件和强降水事件也将可能增多. 相似文献
13.
Food security has drawn great attention from both researchers and practitioners in recent years. Global warming and its resultant extreme drought events have become a great challenge to crop production and food price stability. This study aimed to establish a preliminary theoretical methodology and an operational approach for assessing the physical vulnerability of two wheat varieties (“Yongliang #4” and “Wenmai #6”) to agricultural drought using Environmental Policy Integrated Climate model (EPIC). Drought hazard index was set up based on output variables of the EPIC water stress (WS), including the magnitude and duration of WS during the crop-growing period. The physical vulnerability curves of two wheat varieties to drought were calculated by the simulated drought hazard indexes and loss ratios. And the curve’s effect on drought disaster risk was defined as A, B and C sections, respectively. Our analysis results showed that (a) physical vulnerability curves varied between two wheat varieties, which were determined by genetic parameters of crops; (b) compared with spring wheat “Yongliang 4#” winter wheat “Wenmai 6#” was less vulnerable to drought under the same drought hazard intensity scenario; (c) the wheat physical vulnerability curve to drought hazard displayed a S shape, suggesting a drought intensity–dependent magnifying or reducing effect of the physical vulnerability on drought disasters; (d) the reducing effect was mainly in the low-value area of vulnerability curve, whereas the magnifying effect was in the middle-value area, and the farming-pastoral zone and the Qinling Mountain–Huaihe River zone formed important spatial division belts. 相似文献
14.
The impact of irrigation water supply rate on agricultural drought disaster risk: a case about maize based on EPIC in Baicheng City,China 总被引：2，自引：0，他引：2
This study presents a methodology for risk analysis, assessment, and combination of drought disasters under the different irrigational levels in Baicheng City, which is supported by run theory, copula functions, crop growth model, and technique of natural disaster risk assessment from the viewpoints of climatology, geography, hydrology, agricultural science, disaster science, environmental science, and so on. Along with the global warming, the occurrences of water-related disasters become more frequent and more serious. It is necessary to determine the laws of the relationship between irrigational ability and the loss caused by drought. Drought events were identified by using run theory; the drought frequency was calculated by using copula function; the loss of every drought event was simulated by using EPIC model; and the relationship curves under the different irrigational supply conditions between the drought frequency and the yield reduction rate of the drought event were fitted to assess the impact of irrigational supply rate on the loss caused by drought. The results show that in the range of crop water demand, the loss caused by drought decreases as the result of the increase in irrigational supply rate; however, their variations are not proportional. The loss caused by the certain frequency drought event under the certain irrigational supply condition could be calculated by the curve of drought disaster risk assessment constructed by this study. The results obtained from this study are specifically intended to support local and national governmental agencies on agricultural disaster management. 相似文献
15.
The risk analysis of flood and drought disasters and the study of their influencing factors enhance our understanding of the temporal and spatial variation law of disasters and help identify the main factors affecting disasters. This paper uses the provincial administrative region of China as the research area. The proportion of the disaster area represents the degree of the disaster. The statistical distribution of the proportions was optimized from 10 alternative distributions based on a KS test, and the disaster risk was analyzed. Thirty-five indicators were selected from nature, agriculture and the social economy as alternative factors. The main factors affecting flood and drought disasters were selected by Pearson, Spearman and Kendall correlation coefficient test. The results demonstrated that the distribution of floods and drought is right-skewed, and the gamma distribution is the best statistical distribution for fitting disasters. In terms of time, the risk of flood and drought disasters in all regions showed a downward trend. Economic development and the enhancement of the ability to resist disasters were the main reasons for the change in disasters. Spatially, the areas with high drought risk were mainly distributed in Northeast and North China, and the areas with high flood risk were mainly distributed in the south, especially in Hubei, Hunan, Jiangxi and Anhui. The distribution of floods and drought disasters was consistent with the distribution characteristics of precipitation and water resources in China. Among the natural factors, precipitation was the main factor causing changes in floods and drought disasters. Among the agricultural and socioeconomic factors, the indicators reflecting the disaster resistance ability and regional economic development level were closely related to flood and drought disasters. The research results have reference significance for disaster classification, disaster formation mechanisms and flood and drought resistance.
相似文献16.
Built environment, which includes some major investments in Oman, has been designed based on historical data and do not incorporate the climate change effects. This study estimates potential variations of the hourly annual maximum rainfall (AMR) in the future in Salalah, Oman. Of the five climate models, two were selected based on their ability to simulate local rainfall characteristics. A two-stage downscaling–disaggregation approach was applied. In the first stage, daily rainfall projections in 2040–2059 and 2080–2099 periods from MRI-CGCM3 and CNRM-CM5 models based on two Representative Concentration Pathways (RCP8.5 and RCP4.5) were downscaled to the local daily scale using a stochastic downscaling software (LARS-WG5.5). In the second stage, the stochastically downscaled daily rainfall time series were disaggregated using K-nearest neighbour technique into hourly series. The AMRs, extracted from 20 years of projections for four scenarios and two future periods were then fitted with the generalized extreme value distribution to obtain the rainfall intensity–frequency relationship. These results were compared with a similar relationship developed for the AMRs in baseline period. The results show that the reduction in number of wet days and increases in total rainfall will collectively intensify the future rainfall regime. A marked difference between future and historical intensity–frequency relationships was found with greater changes estimated for higher return periods. Furthermore, intensification of rainfall regime was projected to be stronger towards the end of the twenty-first century. 相似文献
17.
冰川作为固体水库以“削峰填谷”的形式显著调节径流丰枯变化,冰川的水文调节功能对于中国西北干旱区至关重要。使用现有VIC-CAS模型模拟得到中国西部寒区2014—2100年径流预估数据,从趋势和波动变化相结合的视角,基于径流变差系数法,构建了冰川水文调节指数（GlacierR）,分析了9个寒区流域冰川径流变化的稳定性,详细剖析了历史时期（1971—2010年）和未来到21世纪末这些流域冰川水文调节功能的强弱变化。结果表明：历史时期及RCP2.6和RCP4.5情景下,除长江流域外,青藏高原其余流域的冰川径流减小时间节点为2020s,西北内陆河流域则为2010s。历史时期及RCP2.6和RCP4.5情景下至21世纪末,尽管西部寒区大部分流域的冰川径流呈减少趋势,但波动幅度减小或无明显变化,冰川径流稳定性增强或无变化。总体上,西北内陆河流域的冰川水文调节功能较高,青藏高原流域的冰川水文调节功能较低。RCP2.6和RCP4.5情景下,至21世纪末,西部寒区各流域冰川水文调节功能均呈现减弱趋势,西北内陆河流域减弱更加显著,如RCP4.5情景下,木扎提河冰川水文调节功能降幅达25.4%,而青藏高原各流域的冰川水文调节功能一直处于较低水平。从年代际变化来看,1970s—2010s是寒区流域冰川水文调节功能较强的时期,1980s和2000s两个时段冰川水文调节功能尤强;RCP2.6和RCP4.5情景下,未来到21世纪末,冰川调节功能明显减弱。减弱的时间节点不同,最早为1970s,最晚为2020s。 相似文献
18.
Spatial and temporal changes of agro-meteorological disasters affecting maize production in China since 1990 总被引：2，自引：1，他引：1
Agro-meteorological (AM) disasters have been reported to be more frequent with climate change. In this study, the spatial and temporal changes in the frequency of major AM disasters affecting maize production are investigated by analyzing observed records at 224 national AM stations in China from 1991 to 2009. To investigate the temporal changes of the disasters with climate warming, the whole study period was separated into a cool period (1991–2000) and a warmer one (2000–2009). We found drought was the most common disaster with a frequency of 49 %, followed by chilling injures (19.46 %). The frequency of disasters affecting maize increased significantly during the reproductive growth period than the vegetative growth period. Spatial patterns of major disaster frequency were characterized by region-specific, with more cold stress in northeastern China, drought in northern and western China, and rainstorms in southwestern China. Our study highlighted that the frequency and scope both increased significantly, implying a potential increasing risk for maize production. It is critical and important for local farmers and governors to take reasonable and timely adaptation measures based on the latest disasters’ features to mitigate the potential yield loss from AM disasters in order to ensure food security in China. 相似文献
19.
Mahdi Zarghami Mohammad Reza Fotookian Nasim Safari Aydin Aslanzadeh 《Arabian Journal of Geosciences》2016,9(16):678
This paper proposes a decision support system for Yamchi reservoir operation in semi-arid region of Iran. The paper consists of the following steps: Firstly, the potential impacts of climate change on the streamflow are predicted. The study then presents the projections of future changes in temperature and precipitation under A2 scenario using the LARS-WG downscaling model and under RCP2.6, RCP4.5, and RCP8.5 using the statistical downscaling model (SDSM) in the northwestern of Iran. To do so, a general circulation model of HadCM3 is downscaled by using the LARS-WG model. As a result, the average temperature, for the horizon 2030 (2011–2030), will increase by 0.77 °C and precipitation will decrease by 11 mm. Secondly, the downscaled variables are used as input to the artificial neural network to investigate the possible impact of climate change on the runoffs. Thirdly, the system dynamics model is employed to model different scenarios for reservoir operation using the Vensim software. System dynamics is an effective approach for understanding the behavior of complex systems. Simulation results demonstrate that the water shortage in different sectors (including agriculture, domestic, industry, and environmental users) will be enormously increased in the case of business-as-usual strategy. In this research, by providing innovative management strategies, including deficit irrigation, the vulnerability of reservoir operation is reduced. The methodology is evaluated by using different modeling tests which then motivates using the methodology for other arid/semi-arid regions. 相似文献
20.
通过对陕西省延安地区明代（公元1368—1644年）历史资料的搜集和整理,对该时期干旱灾害等级、时间变化及成因进行了分析。结果表明：在明代的277年中,延安地区共发生干旱灾害91次,平均每3年发生1次。轻度干旱灾害发生17次,中等干旱灾害发生30次,大干旱灾害发生29次,特大干旱灾害发生15次,分别占到干旱灾害总数的18.7%、32.9%、31.9%和16.5%。大干旱灾害与特大干旱灾害发生频次高是明代延安地区干旱灾害的突出特点,指示明代总体为干旱气候期。延安明代干旱灾害可分为4个阶段,第一阶段为公元1368—1420年,为干旱灾害少发期;第二阶段为公元1421—1520年,为干旱灾害多发期;第三阶段为公元1521—1617年,为干旱灾害少发期;第四阶段为公元1618—1644年,为干旱灾害多发期。各等级干旱灾害特别是大与特大干旱灾害显著增加,指示第二、四阶段气候显著变干,降雨量明显减少。延安地区明代出现了2个极端干旱气候亚阶段,分别在1480—1499年和1626—1641年之间,当时年均降水量比现今少200 mm左右。 相似文献