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1.
Modelling and analysis of the impact of irrigation on local arid climate over northwest China 总被引：1，自引：0，他引：1
This study focuses on how irrigation processes affect local climate over arid areas. The chosen study area is northwest China, a typical arid region where three dominant land‐use types are irrigated cropland, grassland, and desert. Observational analysis indicates that the highest precipitation, the coolest surface temperatures, and the slowest warming trend are seen over irrigated cropland from 1979 to 2005. The single column atmospheric model (SCAM), developed by the National Center for Atmospheric Research (NCAR), was used to investigate and better understand the differences in long‐term climate conditions and change over the above three land‐use types. The results indicate that local climate conditions are predominantly controlled by large‐scale forcing in this arid region and that local land surface forcing related to vegetation cover change and irrigation processes also has a significant impact. This study strongly suggests that a realistic climate forecast for this region can be achieved only with both accurate large‐scale and local climate forcing. The irrigated cropland of the region generates stronger evaporation that cools the surface and slows the warming trend more than does the evaporation from the natural grassland and desert. Stronger evaporation also significantly increases precipitation, potentially alleviating the stress of irrigation demands in arid regions. A series of sensitivity SCAM simulations indicate that a drier and warmer climate occurs with decreasing vegetation cover in the irrigated cropland region. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
The history of natural fire since 37 kaBP and its relationship to climate for the northern part of the South China Sea are
revealed from the statistic study of charcoal particles and associated pollen data from deep sea core 17940 (20° 07’N, 117°
23’E, 1 727 m in water depth). Our study indicates that, during the last glaciation, the concentration of charcoal and the
ratio of con centration between charcoal and terrestrial pollen are much higher than that of the Holocene. This can be explained
as the relatively high strength and frequency of natural fire during glaciation which is probably due to the drier climate;
during the Last Glacial Maximum (LGM), the substantial rising of the concentration of large and medium charcoal particles
probably suggests the local source area of the natural fires, i.e. the exposed continental shelf; moreover, the correlation
between charcoal concentration with different size and pollen percentage may elucidate different transport dynamics. During
the glacial time, almost all the peak concentrations of small particles correspond with the peak pollen percentage ofArtemisia, an indicator of comparatively dry climate, while for large particles, their concentrations always lag behind small particles
and thus change with pollen percentage of montane conifers implying relatively cold and humid climate. So, it is possible
to assume that small particles reflect regional emissions under drier climate and were brought over by strengthened winter
monsoon. When the climate became relatively humid, the increasing precipitation carried the large particles accumulated on
continental shelf before under arid condition to the studied area. 相似文献
3.
Many of the world’s coral reefs suffered high coral mortality during the 1998 ENSO, with the highest mortality in the western Indian Ocean (WIO). A meta-analysis of field data on change in coral cover across the 1998 ENSO event was conducted for 36 major reef areas in the WIO, and relationship of the change with the historical sea-surface temperature (SST) variability investigated. WIO reefs were categorized into three major SST groups of differing coral cover change. Cover change was negatively associated with standard deviation (SD) SST until about SD 2.3, with increasing flatness of the SST frequency distributions. It increased with further increase in SD as the SST distributions became strongly bimodal in the Arabian/Persian Gulf area. The study indicates that environmental resistance/tolerance to extreme anomalous events could be predicted and management priorities directed accordingly for a warmer and more variable future climate. 相似文献
4.
《Water Policy》1998,1(2):159-175
Policy makers and water resources managers should be aware of the evolving information on climate change impacts as an activity that is preparatory, but not central, to sound decision making on current water resources management actions. Policies that ensure effective contemporary water management will form the core of a “no regrets” strategy that will contemporaneously serve adaptation to climate change and uncertainty. Hence, an “adaptive management” approach rather than an “anticipatory strategy” is warranted for most water management actions. An effective water management system depends, to a large extent, on a well-functioning institutional framework and the treatment of water as an economic and social good, both of which are a prerequisite for adaptation to contemporary climate variability. It will also serve as the foundation for responding to uncertain climate change scenarios. 相似文献
5.
The aim of this study is to estimate likely changes in flood indices under a future climate and to assess the uncertainty in these estimates for selected catchments in Poland. Precipitation and temperature time series from climate simulations from the EURO-CORDEX initiative for the periods 1971–2000, 2021–2050 and 2071–2100 following the RCP4.5 and RCP8.5 emission scenarios have been used to produce hydrological simulations based on the HBV hydrological model. As the climate model outputs for Poland are highly biased, post processing in the form of bias correction was first performed so that the climate time series could be applied in hydrological simulations at a catchment-scale. The results indicate that bias correction significantly improves flow simulations and estimated flood indices based on comparisons with simulations from observed climate data for the control period. The estimated changes in the mean annual flood and in flood quantiles under a future climate indicate a large spread in the estimates both within and between the catchments. An ANOVA analysis was used to assess the relative contributions of the 2 emission scenarios, the 7 climate models and the 4 bias correction methods to the total spread in the projected changes in extreme river flow indices for each catchment. The analysis indicates that the differences between climate models generally make the largest contribution to the spread in the ensemble of the three factors considered. The results for bias corrected data show small differences between the four bias correction methods considered, and, in contrast with the results for uncorrected simulations, project increases in flood indices for most catchments under a future climate. 相似文献
6.
Shen Jun Wang Yipeng Song Fangmin Yu Weixian Cao Zhongquan Shen Xuhui Hou Xueying and Li ZhixiangInstitute of Geology SSB Beijing ChinaInstitute of Earthquake Engineering Seismological Bureau of Yunnan Province Kunming China 《中国地震研究》1998,(2)
The data of the strike-slip offset along the Xiaojiang active fault can be obviously grouped.The groups of small orders of magnitude data within 100 m show clear linear characteristics of increments between 8 m and 12 m,which indicates that the segments of the Xiaojiang active fault is of characteristic seismicity and the distribution of the values of each group indicates that there are smaller earthquakes and creep between two large earthquakes along each segment of the Xiaojiang active fault.The interval between two characteristic large earthquakes can be calculated with the increments for two groups of slip data and the slip rate of the fault.Furthermore,the frequency of smaller earthquakes can also be estimated by comparing the distributions of the displacements of the large earthquakes with the distributions of the values of each group of data.The groups of large slip displacements show that there is close relationship between the records of the displacements of the fault and the changes of the cli 相似文献
7.
Yonghong Hao Jing Wu Qingxia Sun Yuen Zhu Yan Liu Zhongtang Li Tian‐Chyi J. Yeh 《水文研究》2013,27(18):2605-2613
Based on the groundwater development process, and regional economic and social developing history, we divided the spring hydrological process of the Liulin Springs Basin into two periods: pre‐1973 and post‐1974. In the first period (i.e. 1957–1973), the spring discharge was affected by climate variation alone, and in the second period (i.e. 1974–2009), the spring discharge charge was influenced by both climate variation and human activities. A piecewise analysis strategy was used to differentiate the contribution of anthropogenic activities from climate variation on karst spring discharge depletion in the second period. Then, the ARIMAX model was applied to spring flow time series of the first period to develop a model for the effects of climate variation only. Using this model, we estimated the spring discharge in the second period solely under the influence of climate variation. Based on the water budget, we subtracted observed spring discharge from the estimated spring discharge and acquired the contribution of human activities on spring discharge depletion for the second period. The results of the analysis indicated that the contribution of climate variation to the spring discharge depletion is?0.20 m3/s from 1970s to 2000s. The contribution of anthropogenic activities to the spring flow depletion was ?2.56 m3/s in 2000s, which was about 13 times more than that of climate variation. Our analysis further indicates that groundwater exploitation only accounts for 29% of the spring flow depletion due to the effects of human activities. The remaining 71% of the depletion is likely to be caused by other human activities, including dam building, dewatering during coal mining, and deforestation. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
Increase in temperature extremes is one of the main expected impacts of climate change, as well as one of the first signs of its occurrence. Nevertheless, results emerging from General Circulation Models, while sufficient for large scales, are not enough for forecasting local trends and, hence, the IPCC has called for local studies based on on-site data. Indeed, it is expected that climate extremes will be detected much earlier than changes in climate averages. Heat waves are among the most important and least studied climate extremes, however its occurrence has been only barely studied and even its very definition remains controversial. This paper discusses the observed changes in temperature trends and heat waves in Northwestern Mexico, one of the most vulnerable regions of the country. The climate records in two locations of the region are analyzed, including one of the cities with extreme climate in Mexico, Mexicali City in the state of Baja California and the Yaqui River basin at Sonora State using three different methodologies. Results showed clear trends on temperature increase and occurrence of heat waves in both of the study zones using the three methodologies proposed. As result, some policy making suggestion are included in order to increase the adaptability of the studied regions to climate change, particularly related with heat wave occurrence. 相似文献
9.
E. Roldán M. Gómez M. R. Pino J. Pórtoles C. Linares Julio Díaz 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(3):831-839
Different epidemiological studies have shown that high temperatures are directly related to mortality, furthermore many studies on the effects of climate change on future mortality are being conducted. The objective of this study is to estimate the effect of extreme hot temperatures on daily mortality in Zaragoza (Spain) from 2014 to 2021, utilising various climate-change scenarios. The relationship between temperature and mortality is defined by the concepts of heat wave, threshold temperature and the relative risk of daily deaths according to extreme temperatures in 1987–2006 period. The effect on future mortality is projected by estimating deaths attributable to extreme temperatures in 2014–2021. This estimation was calculated utilising exposure–response functions for three scenarios (A1B, A2 and B1) from the ECHAM5 general circulation model after applying a statistical downscaling technique. Because this study considers the effect of rising temperatures from a health perspective, minimising uncertainty was added to the numerical values obtained from the projected future relation between temperature and mortality. The results shows that expected mortality in Zaragoza will increase by 0.4 % for the period 2014–2021, an excess that can be directly attributed to extreme temperatures. This effect is expected to increase in the 2040s and 2050s until the end of the twenty first century because of a predicted increase in temperatures over this period, with special emphasis on the need to continue studying this line of inquiry and local studies as which arises. Finally, this study will luckily be used to create prevention plans for minimising the effect on health of the high temperatures. 相似文献
10.
Effect of catchment properties on runoff coefficient in a karst area of southwest China 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Frequent human activities and climate change in the karst region of southwest China since the 1950s have led to the investigation of response of runoff to climate and catchment properties. Runoff coefficient (Rc) as an expression variable of the catchment response to rainfall is important to describe runoff dynamics and to estimate available streamflow for utilization. In this study, the equations of Rc associated with its attributors of climate condition and catchment property were derived using the Budyko framework. The equations were used to estimate relationship between the Rc and the attributors in the karst catchments in Guizhou province of southwest China. Analysis in the selected 23 karst catchments demonstrates that the spatial distribution of Rc is dominated by the catchment properties, such as the catchment properties of geology, slope and land use and land cover, rather than climate condition of drought index. Correlation analysis indicates that the catchment with a large slope usually has a high value of Rc, and a large proportion of carbonate rock in a catchment reduces Rc in the study area. Temporal increasing trend of Rc during 1961–2000 was found for most catchments in the study area. This increasing trend was primarily resulted from changes of catchment properties, e.g. deforestation in large areas of Guizhou province during the 1950s–1980s. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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The most reliable data on a change in the intensity of cosmic rays and geomagnetic field on large time scales have been analyzed, and the relations between changes in these processes and climate during the last 1.5 Myr have been studied. An analysis indicated that the climate of the Earth is affected by changes in the Earth’s orbit parameters and geomagnetic dipole values; however, the climate responds to these changes with a delay of 10 kyr and immediately, respectively. In this case about two thirds of the effect of eccentricity on 18O is implemented via an intermediate chain: virtual axial dipole moment, changes in which can be related to changes in eccentricity. Thus, an analysis of the accumulated data on the processes, proceeding in the Earth’s atmosphere during the interaction with cosmic rays on the scales of several years to several hundreds of thousand years, indicates that the cosmophysical factor of influence on climate cannot be rejected. To make the conclusion more convincing, it is necessary to collect data for the studied time interval in a much wider region, to more accurately date samples, and to study the response of the climatic system to the external influence. 相似文献
13.
Pablo A. Mendoza Martyn P. Clark Naoki Mizukami Ethan D. Gutmann Jeffrey R. Arnold Levi D. Brekke Balaji Rajagopalan 《水文研究》2016,30(7):1071-1095
End users face a range of subjective decisions when evaluating climate change impacts on hydrology, but the importance of these decisions is rarely assessed. In this paper, we evaluate the implications of hydrologic modelling choices on projected changes in the annual water balance, monthly simulated processes, and signature measures (i.e. metrics that quantify characteristics of the hydrologic catchment response) under a future climate scenario. To this end, we compare hydrologic changes computed with four different model structures – whose parameters have been obtained using a common calibration strategy – with hydrologic changes computed with a single model structure and parameter sets from multiple options for different calibration decisions (objective function, local optima, and calibration forcing dataset). Results show that both model structure selection and the parameter estimation strategy affect the direction and magnitude of projected changes in the annual water balance, and that the relative effects of these decisions are basin dependent. The analysis of monthly changes illustrates that parameter estimation strategies can provide similar or larger uncertainties in simulations of some hydrologic processes when compared with uncertainties coming from model choice. We found that the relative effects of modelling decisions on projected changes in catchment behaviour depend on the signature measure analysed. Furthermore, parameter sets with similar performance, but located in different regions of the parameter space, provide very different projections for future catchment behaviour. More generally, the results obtained in this study prompt the need to incorporate parametric uncertainty in multi‐model frameworks to avoid an over‐confident portrayal of climate change impacts. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
The run‐off volume altered by the construction of hydropower plants affects ecohydrological processes in catchments. Although the impacts of large hydropower plants have been well documented in the literature, few studies have been conducted on the impacts of small cascaded hydropower plants (SCHPs). To evaluate the impacts of SCHPs on river flow, we chose a representative basin affected by hydropower projects and, to a lesser degree, by other human activities, that is, the Qiuxiang River basin in Southern China. The observed river discharge and climate data during the period of 1958–2016 were investigated. The datasets were divided into a low‐impact period and a high‐impact period based on the number of SCHPs and the capacities of the reservoirs. The daily river discharge alteration was assessed by applying the Indicators of Hydrologic Alteration. To separate the impact of the SCHPs on the local river discharge from that of climate‐related precipitation, the back‐propagation neural network was used to simulate the monthly average river discharge process. An abnormal result was found: Unlike large reservoirs in large watersheds, the SCHPs regulated the flows during the flood season but were not able to mitigate the droughts during the dry season due to their limited storage and the commonly occurring inappropriate interregulations of the SCHPs. The SCHPs also reduced the annual average river discharge in the research basin. The contribution of the SCHPs to the river discharge changes was 85.37%, much higher than the contributions of climate change (13.43%) and other human activities (1.20%). The results demonstrated that the impacts of the SCHPs were different from those of large dams and reservoirs that regulate floods and relieve droughts. It is necessary to raise the awareness of the impacts of these river barriers. 相似文献
15.
V. A. Dergachev P. B. Dmitriev O. M. Raspopov H. Jungner 《Geomagnetism and Aeronomy》2006,46(1):118-128
Direct and indirect data on variations in cosmic rays, solar activity, geomagnetic dipole moment, and climate from the present to 10–12ka ago (the Holocene Epoch), registered in different natural archives (tree rings, ice layers, etc.), have been analyzed. The concentration of cosmogenic isotopes, generated in the Earth’s atmosphere under the action of cosmic ray fluxes and coming into the Earth archives, makes it possible to obtain valuable information about variations in a number of natural processes. The cosmogenic isotopes 14C in tree rings and 10Be in ice layers, as well as cosmic rays, are modulated by solar activity and geomagnetic field variations, and time variations in these concentrations gives information about past solar and geomagnetic activities. Since the characteristics of natural reservoirs with cosmogenic 14C and 10Be vary with climate changes, the concentrations of these isotopes also inform about climate changes in the past. A performed analysis indicates that cosmic ray flux variations are apparently the most effective natural factor of climate changes on a large time scale. 相似文献
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AbstractThe potential impacts of future climate change on the evolution of groundwater recharge are examined at a local scale for a 546-km2 watershed in eastern Canada. Recharge is estimated using the infiltration model Hydrologic Evaluation of Landfill Performance (HELP), with inputs derived from five climate runs generated by a regional climate model in combination with the A2 greenhouse gas emissions scenario. The model runs project an increase in annual recharge over the 2041–2070 period. On a seasonal basis, however, a marked decrease in recharge during the summer and a marked increase during the winter are observed. The results suggest that increased evapotranspiration resulting from higher temperatures does not offset the large increase in winter infiltration. In terms of individual water budget components, clear differences are obtained for the different climate change scenarios. Monthly recharge values are also found to be quite variable, even for a given climate scenario. These findings are compared with results from two regional-scale studies.
Editor D. Koutsoyiannis; Associate editor M. Besbes 相似文献
18.
Gareth Davies Jingyi Huang Fernando Acacio Monteiro Santos John Triantafilis 《Ground water》2015,53(3):424-431
Rising sea levels, owing to climate change, are a threat to fresh water coastal aquifers. This is because saline intrusions are caused by increases and intensification of medium‐large scale influences including sea level rise, wave climate, tidal cycles, and shifts in beach morphology. Methods are therefore required to understand the dynamics of these interactions. While traditional borehole and galvanic contact resistivity (GCR) techniques have been successful they are time‐consuming. Alternatively, frequency‐domain electromagnetic (FEM) induction is potentially useful as physical contact with the ground is not required. A DUALEM‐421 and EM4Soil inversion software package are used to develop a quasi two‐ (2D) and quasi three‐dimensional (3D) electromagnetic conductivity images (EMCI) across Long Reef Beach located north of Sydney Harbour, New South Wales, Australia. The quasi 2D models discern: the dry sand (<10 mS/m) associated with the incipient dune; sand with fresh water (10 to 20 mS/m); mixing of fresh and saline water (20 to 500 mS/m), and; saline sand of varying moisture (more than 500 mS/m). The quasi 3D EMCIs generated for low and high tides suggest that daily tidal cycles do not have a significant effect on local groundwater salinity. Instead, the saline intrusion is most likely influenced by medium‐large scale drivers including local wave climate and morphology along this wave‐dominated beach. Further research is required to elucidate the influence of spring‐neap tidal cycles, contrasting beach morphological states and sea level rise. 相似文献
19.
Ivane Lilian Pairaud Nathaniel Bensoussan Pierre Garreau Vincent Faure Joaquim Garrabou 《Ocean Dynamics》2014,64(1):103-115
In the framework of climate change, the increase in ocean heat wave frequency is expected to impact marine life. Large-scale positive temperature anomalies already occurred in the northwestern Mediterranean Sea in 1999, 2003 and 2006. These anomalies were associated with mass mortality events of macrobenthic species in coastal areas (0–40 m in depth). The anomalies were particularly severe in 1999 and 2003 when thousands of kilometres of coasts and about 30 species were affected. The aim of this study was to develop a methodology to assess the current risk of mass mortality associated with temperature increase along NW Mediterranean continental coasts. A 3D regional ocean model was used to obtain the temperature conditions for the period 2001–2010, for which the model outputs were validated by comparing them with in situ observations in affected areas. The model was globally satisfactory, although extremes were underestimated and required correction. Combined with information on the thermo-tolerance of a key species (the red gorgonian P. clavata) as well as its spatial distribution, the modelled temperature conditions were then used to assess the risk of mass mortality associated with thermal stress for the first time. Most of the known areas of observed mass mortality were found using the model, although the degree of risk in certain areas was underestimated. Using climatic IPCC scenarios, the methodology could be applied to explore the impacts of expected climate change in the NW Mediterranean. This is a key issue for the development of sound management and conservation plans to protect Mediterranean marine biodiversity in the face of climate change. 相似文献
20.
Projecting climate change impacts on stream flow regimes with tracer‐aided runoff models ‐ preliminary assessment of heterogeneity at the mesoscale 下载免费PDF全文
下载免费PDF全文 The northern mid‐high latitudes form a region that is sensitive to climate change, and many areas already have seen – or are projected to see – marked changes in hydroclimatic drivers on catchment hydrological function. In this paper, we use tracer‐aided conceptual runoff models to investigate such impacts in a mesoscale (749 km2) catchment in northern Scotland. The catchment encompasses both sub‐arctic montane sub‐catchments with high precipitation and significant snow influence and drier, warmer lowland sub‐catchments. We used downscaled HadCM3 General Circulation Model outputs through the UKCP09 stochastic weather generator to project the future climate. This was based on synthetic precipitation and temperature time series generated from three climate change scenarios under low, medium and high greenhouse gas emissions. Within an uncertainty framework, we examined the impact of climate change at the monthly, seasonal and annual scales and projected impacts on flow regimes in upland and lowland sub‐catchments using hydrological models with appropriate process conceptualization for each landscape unit. The results reveal landscape‐specific sensitivity to climate change. In the uplands, higher temperatures result in diminishing snow influence which increases winter flows, with a concomitant decline in spring flows as melt reduces. In the lowlands, increases in air temperatures and re‐distribution of precipitation towards autumn and winter lead to strongly reduced summer flows despite increasing annual precipitation. The integration at the catchment outlet moderates these seasonal extremes expected in the headwaters. This highlights the intimate connection between hydrological dynamics and catchment characteristics which reflect landscape evolution. It also indicates that spatial variability of changes in climatic forcing combined with differential landscape sensitivity in large heterogeneous catchments can lead to higher resilience of the integrated runoff response. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献