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81.
Agro-meteorological hazards such as drought, waterlogging and cool summer occur with very high frequency and affect maize production and social-economic development in the maize-growing region of Songliao Plain, China. Moreover, both the frequency of these hazards and loss from them are considered to be increasing with global warming. The purpose of this paper is to quantitatively analyze the relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards in the maize-growing area of Songliao Plain, taking Lishu county as a case study area based on GIS (Geographic Information System). Crop yield-climate analysis and regression analysis were employed to analyze and quantify relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards. The parameters and model of damage evaluation were presented using weighted comprehensive analysis, and the degree of damage of drought, waterlogging and cool summer to maize production was comprehensively evaluated and regionalized. It is shown that from 1949 to 1990, the negative value years of the fluctuation of maize yield due to meteorological hazards accounted for 55% of seasons, of which 14% was caused by drought, 30% by waterlogging, 4% by cool summer and drought, 9% by cool summer and waterlogging, 13% by drought and waterlogging, 30% by drought, waterlogging and cool summer. Studies on the instability and spatial variation of the fluctuations in maize yield in Lishu county showed that the middle plains are stable areas to climatic influence, while southeastern hills and low mountains, the low lands of the plains along the East Liao River and the western plain are unstable areas in terms of areas in maize yield. The synthetic index of the degree of damage to maize of drought, waterlogging and cool summer showed a strong positive correlation with the ratio of the amount damaged to the normal yield of maize. This suggests that this index can be used to evaluate such damage. The degree of damage of drought, waterlogging and cool summer to maize in Lishu county shows the regional characteristics, which increase gradually from the center to the west and east, this being almost identical with the spatial distribution of the fluctuation of maize yield due to these hazards. This study can be expected to provide the basis for developing strategies to mitigate agro-meteorological hazards and reducing the losses from them, and adjust the medium and long-term distribution of agricultural activities so as to adapt to environmental changes. 相似文献
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以山西省祁县依法管理工程抗震设防要求为例,论述了强制性审核、确定一般工业、民用建设工程抗震设防要求的重要性及其深远意义。结合工作实际.总结了部分依法行政、规范管理和落实抗震设防要求的经验。 相似文献
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When sediment grains are transported as bed load in overland flow, there is a net transfer of momentum from the flow to the grains. When these grains collide with other grains, whether on the bed or in the flow, streamwise flow velocity decreases and resistance to flow increases. Resistance to flow generated in this manner is termed bed‐load transport resistance. Resistance to flow f over a plane bed may be partitioned into grain resistance fg and bed‐load transport resistance fbt. We use the symbols fbtf and fbtm to denote fbt for flows over fixed beds and over mobile beds, respectively, and we compute the effect of bed mobility on flow resistance fmob by subtracting fbtf from fbtm. The data for this study come from 54 flume experiments with fixed beds and 38 with mobile beds. On average fmob is approximately equal to half of fbtm, which is about one‐quarter of f. Hence, fmob is about one‐tenth of f. Predictive equations are developed for fbtf, fbtm and fmob using dimensional analysis to identify the relevant independent variables and regression analysis to evaluate the coefficients associated with these variables. Values of fmob are always positive which implies that mobile beds offer greater resistance to flow than do fixed beds. Evidently bed‐load grains colliding with mobile beds lose more momentum to the bed than do grains colliding with fixed beds. In other words, grain collisions with mobile beds are less elastic than those with fixed beds. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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In this study, the climate teleconnections with meteorological droughts are analysed and used to develop ensemble drought prediction models using a support vector machine (SVM)–copula approach over Western Rajasthan (India). The meteorological droughts are identified using the Standardized Precipitation Index (SPI). In the analysis of large‐scale climate forcing represented by climate indices such as El Niño Southern Oscillation, Indian Ocean Dipole Mode and Atlantic Multidecadal Oscillation on regional droughts, it is found that regional droughts exhibits interannual as well as interdecadal variability. On the basis of potential teleconnections between regional droughts and climate indices, SPI‐based drought forecasting models are developed with up to 3 months' lead time. As traditional statistical forecast models are unable to capture nonlinearity and nonstationarity associated with drought forecasts, a machine learning technique, namely, support vector regression (SVR), is adopted to forecast the drought index, and the copula method is used to model the joint distribution of observed and predicted drought index. The copula‐based conditional distribution of an observed drought index conditioned on predicted drought index is utilized to simulate ensembles of drought forecasts. Two variants of drought forecast models are developed, namely a single model for all the periods in a year and separate models for each of the four seasons in a year. The performance of developed models is validated for predicting drought time series for 10 years' data. Improvement in ensemble prediction of drought indices is observed for combined seasonal model over the single model without seasonal partitions. The results show that the proposed SVM–copula approach improves the drought prediction capability and provides estimation of uncertainty associated with drought predictions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Likely effects of climate change on groundwater availability in a Mediterranean region of Southeastern Spain
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Hassane Moutahir Pau Bellot Robert Monjo Juan Bellot Miguel Garcia Issam Touhami 《水文研究》2017,31(1):161-176
Groundwater resources are typically the main fresh water source in arid and semi‐arid regions. Natural recharge of aquifers is mainly based on precipitation; however, only heavy precipitation events (HPEs) are expected to produce appreciable aquifer recharge in these environments. In this work, we used daily precipitation and monthly water level time series from different locations over a Mediterranean region of Southeastern Spain to identify the critical threshold value to define HPEs that lead to appreciable aquifer recharge in this region. Wavelet and trend analyses were used to study the changes in the temporal distribution of the chosen HPEs (≥20 mm day?1) over the observed period 1953–2012 and its projected evolution by using 18 downscaled climate projections over the projected period 2040–2099. The used precipitation time series were grouped in 10 clusters according to similarities between them assessed by using Pearson correlations. Results showed that the critical HPE threshold for the study area is 20 mm day?1. Wavelet analysis showed that observed significant seasonal and annual peaks in global wavelet spectrum in the first sub‐period (1953–1982) are no longer significant in the second sub‐period (1983–2012) in the major part of the ten clusters. This change is because of the reduction of the mean HPEs number, which showed a negative trend over the observed period in nine clusters and was significant in five of them. However, the mean size of HPEs showed a positive trend in six clusters. A similar tendency of change is expected over the projected period. The expected reduction of the mean HPEs number is two times higher under the high climate scenario (RCP8.5) than under the moderate scenario (RCP4.5). The mean size of these events is expected to increase under the two scenarios. The groundwater availability will be affected by the reduction of HPE number which will increase the length of no aquifer recharge periods (NARP) accentuating the groundwater drought in the region. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Accepting the concept of standardization introduced by the standardized precipitation index, similar methodologies have been developed to construct some other standardized drought indices such as the standardized precipitation evapotranspiration index (SPEI). In this study, the authors provided deep insight into the SPEI and recognized potential deficiencies/limitations in relating to the climatic water balance it used. By coupling another well‐known Palmer drought severity index (PDSI), we proposed a new standardized Palmer drought index (SPDI) through a moisture departure probabilistic approach, which allows multi‐scalar calculation for accurate temporal and spatial comparison of the hydro‐meteorological conditions of different locations. Using datasets of monthly precipitation, temperature and soil available water capacity, the moisture deficit/surplus was calculated at multiple temporal scales, and a couple of techniques were adopted to adjust corresponding time series to a generalized extreme value distribution out of several candidates. Results of the historical records (1900–2012) for diverse climates by multiple indices showed that the SPDI was highly consistent and correlated with the SPEI and self‐calibrated PDSI at most analysed time scales. Furthermore, a simple experiment of hypothetical temperature and/or precipitation change scenarios also verified the effectiveness of this newly derived SPDI in response to climate change impacts. Being more robust and preferable in spatial consistency and comparability as well as combining the simplicity of calculation with sufficient accounting of the physical nature of water supply and demand relating to droughts, the SPDI is promising to serve as a competent reference and an alternative for drought assessment and monitoring. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献