Climate variability significantly impacts agricultural water resources,particularly in regions like Vietnam's Plain of Reeds that heavily utilize rain-fed conditions.This study employs the FAO-AquaCrop model to es...Climate variability significantly impacts agricultural water resources,particularly in regions like Vietnam's Plain of Reeds that heavily utilize rain-fed conditions.This study employs the FAO-AquaCrop model to estimate current and future irrigation water needs for rice cultivation in this critical subregion,aiming to identify optimal sowing schedules(OSS)that enhance rainwater utilization and reduce irrigation dependency.The model was driven by current climate data and future projections(2041-2070 and 2071-2099)derived from downscaled Global Circulation Models under RCP4.5 and RCP8.5 scenarios.The AquaCrop model demonstrated robust performance during validation and calibration,with d-values(0.82-0.93)and R²values(0.85-0.92)indicating strong predictive accuracy for rice yield.Simulation results for efficient irrigation water potential(IWP)under RCP4.5 revealed that strategic shifts in sowing dates can substantially alter water requirements;for instance,advancing the winter-spring sowing to December 5th decreased IWP by 15.6%in the 2041-2070 period,while delaying summer-autumn crop sowing to April 20th increased IWP by 48.6%due to greater reliance on irrigation as rainfall patterns shift.Similar dynamic responses were observed for the 2071-2099 period and for autumn-winter crops.These findings underscore that AquaCrop modeling can effectively predict future irrigation needs and that adjusting cultivation calendars presents a viable,low-cost adaptation strategy.This approach allows farmers in the Plain of Reeds to optimize rainwater use,thereby reducing dependency on supplementary irrigation and mitigating the adverse impacts of climate variability,contributing to more sustainable agricultural water management.展开更多
Climate in China's Mainland can be divided into the monsoon region in the southeast and the westerly region in the northwest as well as the intercross zone, i.e., the monsoon northernmost marginal active zone that...Climate in China's Mainland can be divided into the monsoon region in the southeast and the westerly region in the northwest as well as the intercross zone, i.e., the monsoon northernmost marginal active zone that is oriented from Southwest China to the upper Yellow River, North China, and Northeast China. In the three regions, dry-wet climate changes are directly linked to the interaction of the southerly monsoon flow on the east side of the Tibetan Plateau and the westerly flow on the north side of the Plateau from the inter-annual to inter-decadal timescales. Some basic features of climate variability in the three regions for the last half century and the historical hundreds of years are reviewed in this paper. In the last half century, an increasing trend of summer precipitation associated with the enhancing westerly flow is found in the westerly region from Xinjiang to northern parts of North China and Northeast China. On the other hand, an increasing trend of summer precipitation along the Yangtze River and a decreasing trend of summer precipitation along the monsoon northernmost marginal active zone are associated with the weakening monsoon flow in East Asia. Historical documents are widely distributed in the monsoon region for hundreds of years and natural climate proxies are constructed in the non-monsoon region, while two types of climate proxies can be commonly found over the monsoon northernmost marginal active zone. In the monsoon region, dry-wet variation centers are altered among North China, the lower Yangtze River, and South China from one century to another. Dry or wet anomalies are firstly observed along the monsoon northernmost marginal active zone and shifted southward or southeastward to the Yangtze River valley and South China in about a 70-year timescale. Severe drought events are experienced along the monsoon northernmost marginal active zone during the last 5 centuries. Inter-decadal dry-wet variations are depicted by natural proxies for the last 4-5 centuries in several areas over the non-monsoon region. Some questions, such as the impact of global warming on dry-wet regime changes in China, complex interactions between the monsoon and westerly flows in Northeast China, and the integrated multi-proxy analysis throughout all of China, are proposed.展开更多
A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-base...A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-based terrestrial ecosystem model （DLEM, Dynamic Land Ecosystem Model）, we provide an estimate of global terrestrial NPP induced by multiple environmental factors and examine the response of terrestrial NPP to climate variability at biome and global levels and along latitudes throughout the first decade of the 21st century. The model simulation estimates an average global terrestrial NPP of 54.6 Pg C yr-1 during 2000-2009, varying from 52.8 Pg C yr-1 in the dry year of 2002 to 56.4 Pg C yr-1 in the wet year of 2008. In wet years, a large increase in terrestrial NPP compared to the decadal mean was prevalent in Amazonia, Africa and Australia. In dry years, however, we found a 3.2% reduction in global terrestrial NPP compared to the decadal mean, primarily due to limited moisture supply in tropical regions. At a global level, precipitation explained approximately 63% of the variation in terrestrial NPP, while the rest was attributed to changes in temperature and other environmental factors. Precipitation was the major factor determining inter-annual variation in terrestrial NPP in low-latitude regions. However, in midand high-latitude regions, temperature variability largely controlled the magnitude of terrestrial NPP. Our results imply that pro- jected climate warming and increasing climate extreme events would alter the magnitude and spatiotemporal patterns of global terrestrial NPP.展开更多
As the largest wetland in the North China Plain （NCP）, the Baiyangdian Lake plays an important role in maintaining water balance and ecological health of NCP. Ir the past few decades, the decreasing streamflow in th...As the largest wetland in the North China Plain （NCP）, the Baiyangdian Lake plays an important role in maintaining water balance and ecological health of NCP. Ir the past few decades, the decreasing streamflow in the Baiyangdian Basin associated with climate vari- ability and human activities has caused a series of water and eco-environmer,tal issues. In this study, we quantified the impacts of climate variability and human activities on streamflow in the water source area of the Baiyangdian Lake, based on analyses of hydrologic changes of the upper Tanghe river catchment （a sub-basin of the Baiyangdian Basin） from 1960 to 2008. Climate elasticity method and hydrological modeling method were used to distinguish the effects of climate variability and human activities. The results showed that the annual streamflow decreased significantly （P〉0.05） by 1.7 mm/a and an abrupt change was identi- fied around the year 1980. The quantification results indicated that climate variations ac- counted for 38%-40% of decreased streamflow, while human activities accounted for 60%--62%. Therefore, the effect of human activities played a dominant role on the decline of the streamflow in the water source area of the Baiyangdian Lake. To keep the ecosystem health of the Baiyangdian Lake, we suggest that minimum ecological water demand and in- tegrated watershed management should be guaranteed in the future.展开更多
A coupled earth system model（ESM） has been developed at the Nanjing University of Information Science and Technology（NUIST） by using version 5.3 of the European Centre Hamburg Model（ECHAM）, version 3.4 of the Nu...A coupled earth system model（ESM） has been developed at the Nanjing University of Information Science and Technology（NUIST） by using version 5.3 of the European Centre Hamburg Model（ECHAM）, version 3.4 of the Nucleus for European Modelling of the Ocean（NEMO）, and version 4.1 of the Los Alamos sea ice model（CICE）. The model is referred to as NUIST ESM1（NESM1）. Comprehensive and quantitative metrics are used to assess the model＇s major modes of climate variability most relevant to subseasonal-to-interannual climate prediction. The model＇s assessment is placed in a multi-model framework. The model yields a realistic annual mean and annual cycle of equatorial SST, and a reasonably realistic precipitation climatology, but has difficulty in capturing the spring–fall asymmetry and monsoon precipitation domains. The ENSO mode is reproduced well with respect to its spatial structure, power spectrum, phase locking to the annual cycle, and spatial structures of the central Pacific（CP）-ENSO and eastern Pacific（EP）-ENSO; however, the equatorial SST variability,biennial component of ENSO, and the amplitude of CP-ENSO are overestimated. The model captures realistic intraseasonal variability patterns, the vertical-zonal structures of the first two leading predictable modes of Madden–Julian Oscillation（MJO）, and its eastward propagation; but the simulated MJO speed is significantly slower than observed. Compared with the T42 version, the high resolution version（T159） demonstrates improved simulation with respect to the climatology, interannual variance, monsoon–ENSO lead–lag correlation, spatial structures of the leading mode of the Asian–Australian monsoon rainfall variability, and the eastward propagation of the MJO.展开更多
Time-variable gravity data from the Gravity Recovery and Climate Experiment （GRACE） satellite mission are used to study terrestrial water storage （TWS） changes over the Pearl River Basin （PRB） for the period 200...Time-variable gravity data from the Gravity Recovery and Climate Experiment （GRACE） satellite mission are used to study terrestrial water storage （TWS） changes over the Pearl River Basin （PRB） for the period 2003-Nov. 2014. TWS estimates from GRACE generally show good agreement with those from two hydrological models GLDAS and WGHM. But they show different capability of detecting significant TWS changes over the PRB. Among them, WGHM is likely to underestimate the seasonal variability of TWS, while GRACE detects long- term water depletions over the upper PRB as was done by hydrological models, and observes significant water increases around the Longtan Reservoir （LTR） due to water impoundment. The heavy drought in 2011 caused by the persistent precipitation deficit has resulted in extreme low surface runoff and water level of the LTR. Moreover, large variability of summer and autumn precipitation may easily trigger floods and droughts in the rainy season in the PRB, especially for summer, as a high correlation of 0.89 was found between precipitation and surface runoff. Generally, the PRB TWS was negatively correlated with El Nifio-Southern Oscillation （ENSO） events. However, the modulation of the Pacific Decadal Oscillation （PDO） may impact this relationship, and the significant TWS anomaly was likely to occur in the peak of PDO phase as they agree well in both of the magnitude and timing of peaks. This indicates that GRACE-based TWS could be a valuable parameter for studying climatic in- fluences in the PRB.展开更多
Studies of the multi-scale climate variability of the Asian monsoon are essential to an advanced understanding of the physical processes of the global climate system.In this paper,the progress achieved in this field i...Studies of the multi-scale climate variability of the Asian monsoon are essential to an advanced understanding of the physical processes of the global climate system.In this paper,the progress achieved in this field is systematically reviewed,with a focus on the past several years.The achievements are summarized into the following topics:(1)the onset of the South China Sea summer monsoon;(2)the East Asian summer monsoon;(3)the East Asian winter monsoon;and(4)the Indian summer monsoon.Specifically,new results are highlighted,including the advanced or delayed local monsoon onset tending to be synchronized over the Arabian Sea,Bay of Bengal,Indochina Peninsula,and South China Sea;the basic features of the record-breaking mei-yu in 2020,which have been extensively investigated with an emphasis on the role of multi-scale processes;the recovery of the East Asian winter monsoon intensity after the early 2000s in the presence of continuing greenhouse gas emissions,which is believed to have been dominated by internal climate variability(mostly the Arctic Oscillation);and the accelerated warming over South Asia,which exceeded the tropical Indian Ocean warming,is considered to be the main driver of the Indian summer monsoon rainfall recovery since 1999.A brief summary is provided in the final section along with some further discussion on future research directions regarding our understanding of the Asian monsoon variability.展开更多
Much attention has recently been focused on the effects of climate variability and human activities on the runoff. In this study, we analyzed 56-yr(1957–2012) runoff change and patterns in the Jinghe River Basin(JRB)...Much attention has recently been focused on the effects of climate variability and human activities on the runoff. In this study, we analyzed 56-yr(1957–2012) runoff change and patterns in the Jinghe River Basin(JRB) in the arid region of northwest China. The nonparametric Mann–Kendall test and the precipitation-runoff double cumulative curve(PRDCC) were used to identify change trend and abrupt change points in the annual runoff. It was found that the runoff in the JRB has periodically fluctuated in the past 56 yr. Abrupt change point in annual runoff was identified in the JRB, which occurred in the years around 1964 and 1996 dividing the long-term hydrologic series into a natural period(1957 – 1964) and a climate and man-induced period(1965 – 1996 and 1997 – 2012). In the 1965 – 1996 period, human activities were the main factor that decreased runoff with contribution of 88.9%, while climate variability only accounted for 11.1%. However,the impact of climate variability has been increased from 11.1% to 47.5% during 1997 – 2012, showing that runoff in JRB is more sensitive to climate variability during global warming. This study distinguishes theeffect of climate variability from human activities on runoff, which can do duty for a reference for regional water resources assessment and management.展开更多
Taoer River Basin, which is located in the west of Northeast China, is an agropastoral ecotone. In recent years, the hydrological cycle and water resources have changed significantly with the deterioration of the envi...Taoer River Basin, which is located in the west of Northeast China, is an agropastoral ecotone. In recent years, the hydrological cycle and water resources have changed significantly with the deterioration of the environment. Many water problems such as river blanking, wetland shrinking and salinization have occurred in this region. All of these phenomena were directly caused by changes in stream flow under climate variability and human actiities. In light of the situation, the impact of climate variability and human activities on stream flow should be identified immediately to identify the primary driving factors of basin hydrological processes. To achieve this, statistical tests were applied to identify trends in variation and catastrophe points in mean annual stream flow from 1961 to 2011. A runoff sensitive coefficients method and a SIMHYD model were applied to assess the impacts of stream flow variation. The following conclusions were found： 1 ） The years 1985 and 2000 were confirmed to be catastrophe points in the stream flow series. Thus, the study period could be divided into three periods, from 1961 to 1985 （Period I）, 1986 to 2000 （Period II） and 2001 to 2011 （Period III）. 2） Mean annual observed stream flow was 31.54 mm in Period I, then increased to 65.60 mm in Period II and decreased to 2.92 mm in Period III. 3） Using runoff sensitive coefficients, the contribution of climate variability was 41.93% and 43.14% of the increase in stream flow during Periods II and III, suggesting that the contribution of human activities to the increase was 58.07% and 56.86%, respectively. 4） Climate variability accounted for 42.57% and 44.30% of the decrease in stream flow, while human activities accounted for 57.43% and 55.70% of the decrease, according to the SIMHYD model. 5） In comparison of these two methods, the primary driving factors of stream flow variation could be considered to be human activities, which contributed about 15% more than climate variability. It is hoped that these conclusions will .benefit future regional planning and sustainable development.展开更多
A new modeling concept, referred to as Modeling Surgery, has been recently developed at University of Wisconsin-Madison. It is specifically designed to diagnose coupled feedbacks between different climate components a...A new modeling concept, referred to as Modeling Surgery, has been recently developed at University of Wisconsin-Madison. It is specifically designed to diagnose coupled feedbacks between different climate components as well as climatic teleconnections within a specific component through systematically modifying the coupling configurations and teleconnective pathways. It thus provides a powerful means for identifying the causes and mechanisms of low-frequency variability in the Earth's climate system. In this paper, we will give a short review of our recent progress in this new area.展开更多
The climate variability in global land precipitation is important for the global hydrological cycle.Based on the Coupled Model Intercomparison Project Phase 6(CMIP6)historical experiments and the Global Monsoons Model...The climate variability in global land precipitation is important for the global hydrological cycle.Based on the Coupled Model Intercomparison Project Phase 6(CMIP6)historical experiments and the Global Monsoons Model Intercomparison Project(GMMIP)Tier-1 experiments,the spatialtemporal characteristics of global and regional land precipitation long-term climate changes in CAS FGOALS-f3-L are evaluated in this study.By comparing these two kinds of experiments,the precipitation biases related to the SSTs are also discussed.The results show that the two experiments could capture the precipitation trend and amplitude to a certain degree compared with observations.The GMMIP simulations show a higher skill than the historical runs verified by correlation coefficients partly because the observed monthly mean SST was prescribed.For the Northern Hemisphere,GMMIP can reproduce the trend and variability in global precipitation,while historical simulations cannot reproduce the trend and variability.However,both experiments fail to simulate the amplitude of the southern hemisphere summer precipitation anomalies.Ensemble empirical mode decomposition(EEMD)was applied to compare the simulated precipitation on different time scales.The sea surface temperature anomaly(SSTA)bias,especially the La Ni?a-type SSTA,is the dominant source of the model bias for simulating interannual precipitation anomalies.The authors also emphasize that the response of precipitation anomalies to the ENSO effect varies regionally.This study highlights the importance of the multiannual variability in SSTAs in global and hemispheric precipitation simulations.The ways to improve the simulation of global precipitation for CAS FGOALS-f3-L are also discussed.展开更多
This study aims to characterize the climatic variability in the South-East of Ivory Coast and to show its impact on the supply of water resources. To do this, statistical and hydrological methods were applied to clima...This study aims to characterize the climatic variability in the South-East of Ivory Coast and to show its impact on the supply of water resources. To do this, statistical and hydrological methods were applied to climatic data collected at the Marc DELORME Research Station of the CNRA. The statistical trend tests on this data revealed a significant decrease in precipitation and an increase in temperature, insolation and evaporation. Statistical break methods indicate a rainfall break in 1982 which marks a modification of the rainfall regime thus translating a drop in rainfall of 15%, a recession in the frequency of rainy days in general and in particular in rainfall heights between 10 and 30 mm and greater than 50 mm. This break is accompanied by a shortening of the rainy seasons, with average rainfall durations ranging from 54 days (short rainy season) to 104 days (great rainy season). Despite the disturbances in the different seasons of the year, the monthly rainfall regimes in the area have not changed. The assessment of the effects of drought on water resources using the Standardized Precipitation and Evapotranspiration Index (SPEI) for three-time scales (1 month, 3 months and 12 months) indicates a severe drought ranging from 3% to 7% over the period 1961 to 2018. However, despite the presence of this severe drought, the intensity of the drought was found to be moderate on all time scales. The Thorrnthwaite method was used to highlight the impacts of this climatic variability on the region’s water resources. The average annual recharge estimated at 402 mm, has been reduced to 153 mm during a deficit period, a decrease of about 62%. The average annual runoff, which was 294 mm, fells to 257 mm, a decrease of about 13%. This recorded decrease in the water infiltrated after the rainfall break (1983-2018), explains the heterogeneous decrease in the depth of the water table.展开更多
An Giang province in the Mekong Delta is the most vulnerable province the impact of flooding and climate variability. Thousand of households are at risk due to severe annual floods. This study applied the LVI （liveli...An Giang province in the Mekong Delta is the most vulnerable province the impact of flooding and climate variability. Thousand of households are at risk due to severe annual floods. This study applied the LVI （livelihood vulnerability index） to estimate flood vulnerability of Phu Huu and Ta Danh villages in An Giang province. Data on socio-demographics, livelihoods, health, social networks, physical, financial and natural resources, natural disasters and climate variability were collected from a survey of 120 households in each village. From these data the LVI of each village was calculated. Results show that the overall LV1 of Phu Huu village, located in the early flooded zone, is higher than that of Ta Danh village, located in the late flooded zone. The analysis also indicated that this practical method can be applied for other purposes such as to monitor vulnerability, evaluate development programs or policy effectiveness by incorporating with scenario comparison.展开更多
<p align="justify"> <span style="font-family:Verdana;"></span><span style="font-family:Verdana;">Climate change and variability are a reality and have had marked e...<p align="justify"> <span style="font-family:Verdana;"></span><span style="font-family:Verdana;">Climate change and variability are a reality and have had marked effects on both human and ecological systems. Adaptation to such effects either directly or indirectly is viewed as a novel way of reducing the spread of the associated risks. The study was conducted in Rubanda District with a general aim of evaluating the effectiveness of adaptation measures to climate variability used </span><span style="font-family:Verdana;">by smallholder Irish potatoes farmers. Specifically, we sought to appraise</span><span style="font-family:Verdana;"> small</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">holder Irish potato farmers’ perceptions about the effectiveness of climate variability adaptation measures and implications on Irish potato productivity. We undertook a cross-sectional study to collect data from total of 197 farmers using a structured questionnaire. Other participatory methods such as focus group discussions and key informant interview were also used to complement the household survey. Data w</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ere</span></span></span><span><span><span style="font-family:'Minion Pro Capt','serif';"><span style="font-family:Verdana;"> analyzed using SPSS Version 23 to generate descriptive statistics as well as relationships between the adaptation measures and the productivity of the Irish potatoes using a Cobb-Douglas production function. The Cobb-Douglas model revealed that the use of fertilizers was significantly and positively associated with productivity of Irish potato (</span><i><span style="font-family:Verdana;">P </span></i><span style="font-family:Verdana;">< 0.001). Furthermore, Smallholder Irish potato farmers perceived the use of technology, terracing, early planting and application of fertilizers as the most effective climate variability adaptation measures. The study recommends that measures that are cost-effective, efficient and coherent should be promoted to offset the impacts of climate variability which would include the adoption of improved potato varieties and use of fertilizers with proper management of erosion. Off-season planting of Irish potatoes in the wetlands should be discouraged by the local administration and the National Environment Management Authority. This calls for a collective action involving the agricultural practitioners and inline civil society organizations to ensure that farmers have access to such inputs.</span></span></span></span> </p>展开更多
Rainfall and Temperature are important factors in agriculture especially in Nigeria where rain-fed agriculture is practiced extensively and agriculture contributes to food security and provides employment for urban an...Rainfall and Temperature are important factors in agriculture especially in Nigeria where rain-fed agriculture is practiced extensively and agriculture contributes to food security and provides employment for urban and rural dwellers.Therefore,climate variability represents a major danger to agriculture by modifying the rainfall and temperature pattern,thereby resulting to a big peril in the sustainability of agriculture.This is the reason all countries of the world are concerned about the effects of climate variability on agriculture.This work therefore,examined the impact of climate variability on rainfall and temperature in Imo State,South Eastern Nigeria.The rainfall and temperature data were gotten from Nigerian Meteorological Agency(NIMET)for a period of 30 years which was analyzed by using descriptive statistics,decadal distribution,trend graph anomalies and 5 year moving average.The analysis showed increasing trend pattern in yearly maximum,minimum temperature and decrease in annual rainfall,The third order polynomial trend shows a decrease in the anomaly of annual mean rainfall(y=-0.0002x4)and a persistent increase in the mean temperature anomaly especially in the second decade(1996-2007).The discoveries show that there is a notable variability in temperature and rainfall pattern which revealed an increase in temperature and decrease in annual rainfall.This calls for serious attention as people in this part of Nigeria critically depend on rainfall for agricultural practices.It is recommended that government should support the agricultural sector by providing mechanized farming systems such as irrigation and drilling of water borehole in farm sites for agriculture,especially for the rural farmers and create awareness to the farmers on recent trends in climate issues to achieve sustainable agriculture.展开更多
Kigezi highlands currently experiences changes in precipitation and temperature which modify the evaporation and soil moisture storage leading to alterations in runoff and other components of hydrological systems. Ext...Kigezi highlands currently experiences changes in precipitation and temperature which modify the evaporation and soil moisture storage leading to alterations in runoff and other components of hydrological systems. Extreme events, like floods and droughts, are more intense and frequent. Furthermore heavy unpredictable rainfall has become frequent in the area, causing soil erosion and floods that destroy crops. Soil erosion is particularly a pressing challenge due to steep-sided hills leading to deterioration of soil nutrients including soil fertility. The unpredictable rains and droughts are attributed to climate change and variability. Consequently, climate change and variability have caused a significant impact on soil nutrients which have affected the agricultural productivity in the area. This paper presents findings of empirical study which explored the climate variability and soil nutrient status along altitudinal gradient. The paper particularly addresses key questions of: land management practices in the study area, nutrient availability and their effects on productivity of selected crops along altitudinal gradient in changing climate and variability. Independent variables such as topographic sequence along altitudinal gradient were evaluated against dependent variables such as yield harvests of selected grown crops and soil nutrients. Samples for crop yields were collected along transect of 0.5 kilometer using a quadrant of 4 × 4 m<sup>2</sup> along attitudinal gradient. Soil samples were taken from selected plots at 0-20cm soil depth for nutrient analysis. Analysis of physical and chemical soil parameters was carried out on soil samples and these include: soil pH, soil organic content, total nitrogen, available soil phosphorous and exchangeable bases (Ca, Mg, K and Na). The study showed that middle parts of the transects had the highest concentration of most soil nutrients, probably because the middle parts could have been a deposition centre for some organic matter from the upper parts of the hills, and lower lying areas were being affected by floods that affects the decomposition of organic matter which is the main source of nutrients. Similarly, the middle parts of the study were the most fertile due to the high concentration of soil nutrient compositions. This indicates that crop yields were significantly affected by availability of soil nutrients along same gradient, attributable to the severity in soil erosion, nutrients leaching and farming practices.展开更多
Introduction The agriculture sector contributes approximately 14%of India’s total gross domestic productivity(source:Indian Ministry of Agriculture,2013-2014).The variability in the monsoonal precipitation has a crit...Introduction The agriculture sector contributes approximately 14%of India’s total gross domestic productivity(source:Indian Ministry of Agriculture,2013-2014).The variability in the monsoonal precipitation has a critical impact on agricultural productivity and thus the economy of the country(Krishna Kumar et al.,2004).展开更多
This study evaluated the annual rainfall for the Tabuk region obtained from observed datasets for the period 1978-2013. The objective of this study was to determine Tabuk catchment climate characteristics in terms of ...This study evaluated the annual rainfall for the Tabuk region obtained from observed datasets for the period 1978-2013. The objective of this study was to determine Tabuk catchment climate characteristics in terms of precipitation. The annual average precipitation in the Tabuk region is 33.5 mm which is below the global average precipitation receiving in arid regions set as less than 250 mm. There is a drop in the annual rainfall from (25 - 30) mm to (5 - 10) mm (1978-2004). The lowest annual rainfall (0 - 6.0 mm) occurred in the year 2004, which is the driest year in a 35-year period.展开更多
Main problem of modern climatology is to assess the present as well as future climate change, For this aim two approaches are used: physic-mathematic modeling on the basis of GCMs and palaeoclimatic analogues. The thi...Main problem of modern climatology is to assess the present as well as future climate change, For this aim two approaches are used: physic-mathematic modeling on the basis of GCMs and palaeoclimatic analogues. The third approach is based on the empirical-statistical methodology and is developed in this paper. This approach allows to decide two main problems: to give a real assessment of climate changes by observed data for climate monitoring and extrapolation of obtained climate tendencies to the nearest future (10-15 years) and give the empirical basis for further development of physic-mathematical models. The basic theory and methodology of empirical-statistic approach have been developed as well as a common model for description of space-time climate variations taking into account the processes of different time scales. The way of decreasing of the present and future uncertainty is suggested as the extraction of long-term climate changes components in the particular time series and spatial generalization of the same climate tendencies in the obtained homogeneous regions. Algorithm and methods for realization of empirical-statistic methodology have been developed along with methods for generalization of intraannual fluctuations, methods for extraction of homogeneous components of different time scales (interannual, decadal, century), methodology and methods for spatial generalization and modeling, methods for extrapolation on the basis of two main kinds of time models: stochastic and deterministic-stochastic. Some applications of developed methodology and methods are given for the longest time series of temperature and precipitation over the world and for spatial generalization over the European area.展开更多
As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and ch...As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and changes significantly within 5–10years,provides a new way to study the response to regional climate variability.This study explored the distribution and vertical displacement patterns of the low treeline in the Upper Minjiang River of China,using SPOT remote sensing images in 1999 and 2013and long-term positional observations.Using the Geodetector model,the study investigated the dominant climatic factors influencing the low treeline displacement.The results showed that the low treeline was located at 1700–3200 m elevation on sunny slopes(southeast,south,southwest,and west slopes)with slopes over 25°.From 1999 to 2013,the low treeline moved downward by 6 m from 2561±264m to 2555±265 m,along with a warm–humid climate tendency.The downward displacement was greater on slopes over 25°and shady slopes(-20 m and-10 m,respectively)than on slopes≤25°and sunny slopes.Additionally,the downward was greater in the warm and humid Zagunao River Basin(-15 m)compared to the arid valley center(-7 m)and the cold Heishui River Basin(-3 m).Meanwhile,the low treeline displacement correlated negatively with precipitation and relative humidity variations at the significance level of 0.05,with correlation coefficients of-0.572and-0.551,respectively.Variations in relative humidity and temperature significantly affected the spatial differentiation of low treeline displacement with influencing power of 0.246(p=0.036<0.05)and 0.183(p=0.032<0.05),respectively.Thus,the low treeline is a moisture-limited line,and its formation and variation are closely related to regional water–heat balance.The study clarifies the indicative value of the low treeline for climate variability in mountain areas and can provide references for ecological restoration in arid valleys.展开更多
文摘Climate variability significantly impacts agricultural water resources,particularly in regions like Vietnam's Plain of Reeds that heavily utilize rain-fed conditions.This study employs the FAO-AquaCrop model to estimate current and future irrigation water needs for rice cultivation in this critical subregion,aiming to identify optimal sowing schedules(OSS)that enhance rainwater utilization and reduce irrigation dependency.The model was driven by current climate data and future projections(2041-2070 and 2071-2099)derived from downscaled Global Circulation Models under RCP4.5 and RCP8.5 scenarios.The AquaCrop model demonstrated robust performance during validation and calibration,with d-values(0.82-0.93)and R²values(0.85-0.92)indicating strong predictive accuracy for rice yield.Simulation results for efficient irrigation water potential(IWP)under RCP4.5 revealed that strategic shifts in sowing dates can substantially alter water requirements;for instance,advancing the winter-spring sowing to December 5th decreased IWP by 15.6%in the 2041-2070 period,while delaying summer-autumn crop sowing to April 20th increased IWP by 48.6%due to greater reliance on irrigation as rainfall patterns shift.Similar dynamic responses were observed for the 2071-2099 period and for autumn-winter crops.These findings underscore that AquaCrop modeling can effectively predict future irrigation needs and that adjusting cultivation calendars presents a viable,low-cost adaptation strategy.This approach allows farmers in the Plain of Reeds to optimize rainwater use,thereby reducing dependency on supplementary irrigation and mitigating the adverse impacts of climate variability,contributing to more sustainable agricultural water management.
基金supported by the National Natural Science Foundation of China(Nos40890053,90502001,and 90711003)
文摘Climate in China's Mainland can be divided into the monsoon region in the southeast and the westerly region in the northwest as well as the intercross zone, i.e., the monsoon northernmost marginal active zone that is oriented from Southwest China to the upper Yellow River, North China, and Northeast China. In the three regions, dry-wet climate changes are directly linked to the interaction of the southerly monsoon flow on the east side of the Tibetan Plateau and the westerly flow on the north side of the Plateau from the inter-annual to inter-decadal timescales. Some basic features of climate variability in the three regions for the last half century and the historical hundreds of years are reviewed in this paper. In the last half century, an increasing trend of summer precipitation associated with the enhancing westerly flow is found in the westerly region from Xinjiang to northern parts of North China and Northeast China. On the other hand, an increasing trend of summer precipitation along the Yangtze River and a decreasing trend of summer precipitation along the monsoon northernmost marginal active zone are associated with the weakening monsoon flow in East Asia. Historical documents are widely distributed in the monsoon region for hundreds of years and natural climate proxies are constructed in the non-monsoon region, while two types of climate proxies can be commonly found over the monsoon northernmost marginal active zone. In the monsoon region, dry-wet variation centers are altered among North China, the lower Yangtze River, and South China from one century to another. Dry or wet anomalies are firstly observed along the monsoon northernmost marginal active zone and shifted southward or southeastward to the Yangtze River valley and South China in about a 70-year timescale. Severe drought events are experienced along the monsoon northernmost marginal active zone during the last 5 centuries. Inter-decadal dry-wet variations are depicted by natural proxies for the last 4-5 centuries in several areas over the non-monsoon region. Some questions, such as the impact of global warming on dry-wet regime changes in China, complex interactions between the monsoon and westerly flows in Northeast China, and the integrated multi-proxy analysis throughout all of China, are proposed.
基金NSF Decadal and Regional Climate Prediction using Earth System Models,No.AGS-1243220NSF Dynamics of Coupled Natural and Human Systems,No.1210360+2 种基金NSF Computer and Network Systems,No.CNS-1059376NASA Land Cover/Land Use Change Program,No.NNX08AL73G S01NASA Interdisciplinary Science Program,No.NNX10AU06G,No.NNX11AD47G
文摘A wide variety of studies have estimated the magnitude of global terrestrial net primary production （NPP）, but its variations, both spatially and temporally, still remain uncertain. By using an improved process-based terrestrial ecosystem model （DLEM, Dynamic Land Ecosystem Model）, we provide an estimate of global terrestrial NPP induced by multiple environmental factors and examine the response of terrestrial NPP to climate variability at biome and global levels and along latitudes throughout the first decade of the 21st century. The model simulation estimates an average global terrestrial NPP of 54.6 Pg C yr-1 during 2000-2009, varying from 52.8 Pg C yr-1 in the dry year of 2002 to 56.4 Pg C yr-1 in the wet year of 2008. In wet years, a large increase in terrestrial NPP compared to the decadal mean was prevalent in Amazonia, Africa and Australia. In dry years, however, we found a 3.2% reduction in global terrestrial NPP compared to the decadal mean, primarily due to limited moisture supply in tropical regions. At a global level, precipitation explained approximately 63% of the variation in terrestrial NPP, while the rest was attributed to changes in temperature and other environmental factors. Precipitation was the major factor determining inter-annual variation in terrestrial NPP in low-latitude regions. However, in midand high-latitude regions, temperature variability largely controlled the magnitude of terrestrial NPP. Our results imply that pro- jected climate warming and increasing climate extreme events would alter the magnitude and spatiotemporal patterns of global terrestrial NPP.
基金National Basic Research Program of China,No.2010CB428406National Natural Science Foundation of China,No.40830636No.40971023
文摘As the largest wetland in the North China Plain （NCP）, the Baiyangdian Lake plays an important role in maintaining water balance and ecological health of NCP. Ir the past few decades, the decreasing streamflow in the Baiyangdian Basin associated with climate vari- ability and human activities has caused a series of water and eco-environmer,tal issues. In this study, we quantified the impacts of climate variability and human activities on streamflow in the water source area of the Baiyangdian Lake, based on analyses of hydrologic changes of the upper Tanghe river catchment （a sub-basin of the Baiyangdian Basin） from 1960 to 2008. Climate elasticity method and hydrological modeling method were used to distinguish the effects of climate variability and human activities. The results showed that the annual streamflow decreased significantly （P〉0.05） by 1.7 mm/a and an abrupt change was identi- fied around the year 1980. The quantification results indicated that climate variations ac- counted for 38%-40% of decreased streamflow, while human activities accounted for 60%--62%. Therefore, the effect of human activities played a dominant role on the decline of the streamflow in the water source area of the Baiyangdian Lake. To keep the ecosystem health of the Baiyangdian Lake, we suggest that minimum ecological water demand and in- tegrated watershed management should be guaranteed in the future.
基金supported by the Research Innovation Program for college graduates of Jiangsu Province (CXLX13 487)
文摘A coupled earth system model（ESM） has been developed at the Nanjing University of Information Science and Technology（NUIST） by using version 5.3 of the European Centre Hamburg Model（ECHAM）, version 3.4 of the Nucleus for European Modelling of the Ocean（NEMO）, and version 4.1 of the Los Alamos sea ice model（CICE）. The model is referred to as NUIST ESM1（NESM1）. Comprehensive and quantitative metrics are used to assess the model＇s major modes of climate variability most relevant to subseasonal-to-interannual climate prediction. The model＇s assessment is placed in a multi-model framework. The model yields a realistic annual mean and annual cycle of equatorial SST, and a reasonably realistic precipitation climatology, but has difficulty in capturing the spring–fall asymmetry and monsoon precipitation domains. The ENSO mode is reproduced well with respect to its spatial structure, power spectrum, phase locking to the annual cycle, and spatial structures of the central Pacific（CP）-ENSO and eastern Pacific（EP）-ENSO; however, the equatorial SST variability,biennial component of ENSO, and the amplitude of CP-ENSO are overestimated. The model captures realistic intraseasonal variability patterns, the vertical-zonal structures of the first two leading predictable modes of Madden–Julian Oscillation（MJO）, and its eastward propagation; but the simulated MJO speed is significantly slower than observed. Compared with the T42 version, the high resolution version（T159） demonstrates improved simulation with respect to the climatology, interannual variance, monsoon–ENSO lead–lag correlation, spatial structures of the leading mode of the Asian–Australian monsoon rainfall variability, and the eastward propagation of the MJO.
基金supported by the National Natural Science Foundation of China (41174020, 41131067)the Fundamental Research Funds for the Central Universities (2014214020203)+1 种基金the open fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education (14-02-011)the open fund of Guangxi Key Laboratory of Spatial Information and Geomatics (14-045-24-17)
文摘Time-variable gravity data from the Gravity Recovery and Climate Experiment （GRACE） satellite mission are used to study terrestrial water storage （TWS） changes over the Pearl River Basin （PRB） for the period 2003-Nov. 2014. TWS estimates from GRACE generally show good agreement with those from two hydrological models GLDAS and WGHM. But they show different capability of detecting significant TWS changes over the PRB. Among them, WGHM is likely to underestimate the seasonal variability of TWS, while GRACE detects long- term water depletions over the upper PRB as was done by hydrological models, and observes significant water increases around the Longtan Reservoir （LTR） due to water impoundment. The heavy drought in 2011 caused by the persistent precipitation deficit has resulted in extreme low surface runoff and water level of the LTR. Moreover, large variability of summer and autumn precipitation may easily trigger floods and droughts in the rainy season in the PRB, especially for summer, as a high correlation of 0.89 was found between precipitation and surface runoff. Generally, the PRB TWS was negatively correlated with El Nifio-Southern Oscillation （ENSO） events. However, the modulation of the Pacific Decadal Oscillation （PDO） may impact this relationship, and the significant TWS anomaly was likely to occur in the peak of PDO phase as they agree well in both of the magnitude and timing of peaks. This indicates that GRACE-based TWS could be a valuable parameter for studying climatic in- fluences in the PRB.
基金study was supported by the National Natural Science Foundation of China(Grant Nos.42230605 and 41721004).
文摘Studies of the multi-scale climate variability of the Asian monsoon are essential to an advanced understanding of the physical processes of the global climate system.In this paper,the progress achieved in this field is systematically reviewed,with a focus on the past several years.The achievements are summarized into the following topics:(1)the onset of the South China Sea summer monsoon;(2)the East Asian summer monsoon;(3)the East Asian winter monsoon;and(4)the Indian summer monsoon.Specifically,new results are highlighted,including the advanced or delayed local monsoon onset tending to be synchronized over the Arabian Sea,Bay of Bengal,Indochina Peninsula,and South China Sea;the basic features of the record-breaking mei-yu in 2020,which have been extensively investigated with an emphasis on the role of multi-scale processes;the recovery of the East Asian winter monsoon intensity after the early 2000s in the presence of continuing greenhouse gas emissions,which is believed to have been dominated by internal climate variability(mostly the Arctic Oscillation);and the accelerated warming over South Asia,which exceeded the tropical Indian Ocean warming,is considered to be the main driver of the Indian summer monsoon rainfall recovery since 1999.A brief summary is provided in the final section along with some further discussion on future research directions regarding our understanding of the Asian monsoon variability.
基金supported by the International S&T Cooperation Program of China (Grant No. 2010DFA92720-12)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-GJ04)+2 种基金the Natural Science Foundation of China (Grant Nos. 41130531, 41375101)the Ministry of Water Resources Special Funds for Scientific Research on Public Causes (Grant No. 201301103)the Program for Innovative Research Team in University (Grant No. IRT1180)
文摘Much attention has recently been focused on the effects of climate variability and human activities on the runoff. In this study, we analyzed 56-yr(1957–2012) runoff change and patterns in the Jinghe River Basin(JRB) in the arid region of northwest China. The nonparametric Mann–Kendall test and the precipitation-runoff double cumulative curve(PRDCC) were used to identify change trend and abrupt change points in the annual runoff. It was found that the runoff in the JRB has periodically fluctuated in the past 56 yr. Abrupt change point in annual runoff was identified in the JRB, which occurred in the years around 1964 and 1996 dividing the long-term hydrologic series into a natural period(1957 – 1964) and a climate and man-induced period(1965 – 1996 and 1997 – 2012). In the 1965 – 1996 period, human activities were the main factor that decreased runoff with contribution of 88.9%, while climate variability only accounted for 11.1%. However,the impact of climate variability has been increased from 11.1% to 47.5% during 1997 – 2012, showing that runoff in JRB is more sensitive to climate variability during global warming. This study distinguishes theeffect of climate variability from human activities on runoff, which can do duty for a reference for regional water resources assessment and management.
基金National Natural Science Foundation of China,No.91547114,No.41201568,No.41201572
文摘Taoer River Basin, which is located in the west of Northeast China, is an agropastoral ecotone. In recent years, the hydrological cycle and water resources have changed significantly with the deterioration of the environment. Many water problems such as river blanking, wetland shrinking and salinization have occurred in this region. All of these phenomena were directly caused by changes in stream flow under climate variability and human actiities. In light of the situation, the impact of climate variability and human activities on stream flow should be identified immediately to identify the primary driving factors of basin hydrological processes. To achieve this, statistical tests were applied to identify trends in variation and catastrophe points in mean annual stream flow from 1961 to 2011. A runoff sensitive coefficients method and a SIMHYD model were applied to assess the impacts of stream flow variation. The following conclusions were found： 1 ） The years 1985 and 2000 were confirmed to be catastrophe points in the stream flow series. Thus, the study period could be divided into three periods, from 1961 to 1985 （Period I）, 1986 to 2000 （Period II） and 2001 to 2011 （Period III）. 2） Mean annual observed stream flow was 31.54 mm in Period I, then increased to 65.60 mm in Period II and decreased to 2.92 mm in Period III. 3） Using runoff sensitive coefficients, the contribution of climate variability was 41.93% and 43.14% of the increase in stream flow during Periods II and III, suggesting that the contribution of human activities to the increase was 58.07% and 56.86%, respectively. 4） Climate variability accounted for 42.57% and 44.30% of the decrease in stream flow, while human activities accounted for 57.43% and 55.70% of the decrease, according to the SIMHYD model. 5） In comparison of these two methods, the primary driving factors of stream flow variation could be considered to be human activities, which contributed about 15% more than climate variability. It is hoped that these conclusions will .benefit future regional planning and sustainable development.
文摘A new modeling concept, referred to as Modeling Surgery, has been recently developed at University of Wisconsin-Madison. It is specifically designed to diagnose coupled feedbacks between different climate components as well as climatic teleconnections within a specific component through systematically modifying the coupling configurations and teleconnective pathways. It thus provides a powerful means for identifying the causes and mechanisms of low-frequency variability in the Earth's climate system. In this paper, we will give a short review of our recent progress in this new area.
基金jointly funded by the National Key Research and Development Program of ChinaGrant No. 2017YFA0604004the National Natural Science Foundation of China Grant Nos. 91737306,41530426,91837101,91937302,and 41606032。
文摘The climate variability in global land precipitation is important for the global hydrological cycle.Based on the Coupled Model Intercomparison Project Phase 6(CMIP6)historical experiments and the Global Monsoons Model Intercomparison Project(GMMIP)Tier-1 experiments,the spatialtemporal characteristics of global and regional land precipitation long-term climate changes in CAS FGOALS-f3-L are evaluated in this study.By comparing these two kinds of experiments,the precipitation biases related to the SSTs are also discussed.The results show that the two experiments could capture the precipitation trend and amplitude to a certain degree compared with observations.The GMMIP simulations show a higher skill than the historical runs verified by correlation coefficients partly because the observed monthly mean SST was prescribed.For the Northern Hemisphere,GMMIP can reproduce the trend and variability in global precipitation,while historical simulations cannot reproduce the trend and variability.However,both experiments fail to simulate the amplitude of the southern hemisphere summer precipitation anomalies.Ensemble empirical mode decomposition(EEMD)was applied to compare the simulated precipitation on different time scales.The sea surface temperature anomaly(SSTA)bias,especially the La Ni?a-type SSTA,is the dominant source of the model bias for simulating interannual precipitation anomalies.The authors also emphasize that the response of precipitation anomalies to the ENSO effect varies regionally.This study highlights the importance of the multiannual variability in SSTAs in global and hemispheric precipitation simulations.The ways to improve the simulation of global precipitation for CAS FGOALS-f3-L are also discussed.
文摘This study aims to characterize the climatic variability in the South-East of Ivory Coast and to show its impact on the supply of water resources. To do this, statistical and hydrological methods were applied to climatic data collected at the Marc DELORME Research Station of the CNRA. The statistical trend tests on this data revealed a significant decrease in precipitation and an increase in temperature, insolation and evaporation. Statistical break methods indicate a rainfall break in 1982 which marks a modification of the rainfall regime thus translating a drop in rainfall of 15%, a recession in the frequency of rainy days in general and in particular in rainfall heights between 10 and 30 mm and greater than 50 mm. This break is accompanied by a shortening of the rainy seasons, with average rainfall durations ranging from 54 days (short rainy season) to 104 days (great rainy season). Despite the disturbances in the different seasons of the year, the monthly rainfall regimes in the area have not changed. The assessment of the effects of drought on water resources using the Standardized Precipitation and Evapotranspiration Index (SPEI) for three-time scales (1 month, 3 months and 12 months) indicates a severe drought ranging from 3% to 7% over the period 1961 to 2018. However, despite the presence of this severe drought, the intensity of the drought was found to be moderate on all time scales. The Thorrnthwaite method was used to highlight the impacts of this climatic variability on the region’s water resources. The average annual recharge estimated at 402 mm, has been reduced to 153 mm during a deficit period, a decrease of about 62%. The average annual runoff, which was 294 mm, fells to 257 mm, a decrease of about 13%. This recorded decrease in the water infiltrated after the rainfall break (1983-2018), explains the heterogeneous decrease in the depth of the water table.
文摘An Giang province in the Mekong Delta is the most vulnerable province the impact of flooding and climate variability. Thousand of households are at risk due to severe annual floods. This study applied the LVI （livelihood vulnerability index） to estimate flood vulnerability of Phu Huu and Ta Danh villages in An Giang province. Data on socio-demographics, livelihoods, health, social networks, physical, financial and natural resources, natural disasters and climate variability were collected from a survey of 120 households in each village. From these data the LVI of each village was calculated. Results show that the overall LV1 of Phu Huu village, located in the early flooded zone, is higher than that of Ta Danh village, located in the late flooded zone. The analysis also indicated that this practical method can be applied for other purposes such as to monitor vulnerability, evaluate development programs or policy effectiveness by incorporating with scenario comparison.
文摘<p align="justify"> <span style="font-family:Verdana;"></span><span style="font-family:Verdana;">Climate change and variability are a reality and have had marked effects on both human and ecological systems. Adaptation to such effects either directly or indirectly is viewed as a novel way of reducing the spread of the associated risks. The study was conducted in Rubanda District with a general aim of evaluating the effectiveness of adaptation measures to climate variability used </span><span style="font-family:Verdana;">by smallholder Irish potatoes farmers. Specifically, we sought to appraise</span><span style="font-family:Verdana;"> small</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">holder Irish potato farmers’ perceptions about the effectiveness of climate variability adaptation measures and implications on Irish potato productivity. We undertook a cross-sectional study to collect data from total of 197 farmers using a structured questionnaire. Other participatory methods such as focus group discussions and key informant interview were also used to complement the household survey. Data w</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">ere</span></span></span><span><span><span style="font-family:'Minion Pro Capt','serif';"><span style="font-family:Verdana;"> analyzed using SPSS Version 23 to generate descriptive statistics as well as relationships between the adaptation measures and the productivity of the Irish potatoes using a Cobb-Douglas production function. The Cobb-Douglas model revealed that the use of fertilizers was significantly and positively associated with productivity of Irish potato (</span><i><span style="font-family:Verdana;">P </span></i><span style="font-family:Verdana;">< 0.001). Furthermore, Smallholder Irish potato farmers perceived the use of technology, terracing, early planting and application of fertilizers as the most effective climate variability adaptation measures. The study recommends that measures that are cost-effective, efficient and coherent should be promoted to offset the impacts of climate variability which would include the adoption of improved potato varieties and use of fertilizers with proper management of erosion. Off-season planting of Irish potatoes in the wetlands should be discouraged by the local administration and the National Environment Management Authority. This calls for a collective action involving the agricultural practitioners and inline civil society organizations to ensure that farmers have access to such inputs.</span></span></span></span> </p>
文摘Rainfall and Temperature are important factors in agriculture especially in Nigeria where rain-fed agriculture is practiced extensively and agriculture contributes to food security and provides employment for urban and rural dwellers.Therefore,climate variability represents a major danger to agriculture by modifying the rainfall and temperature pattern,thereby resulting to a big peril in the sustainability of agriculture.This is the reason all countries of the world are concerned about the effects of climate variability on agriculture.This work therefore,examined the impact of climate variability on rainfall and temperature in Imo State,South Eastern Nigeria.The rainfall and temperature data were gotten from Nigerian Meteorological Agency(NIMET)for a period of 30 years which was analyzed by using descriptive statistics,decadal distribution,trend graph anomalies and 5 year moving average.The analysis showed increasing trend pattern in yearly maximum,minimum temperature and decrease in annual rainfall,The third order polynomial trend shows a decrease in the anomaly of annual mean rainfall(y=-0.0002x4)and a persistent increase in the mean temperature anomaly especially in the second decade(1996-2007).The discoveries show that there is a notable variability in temperature and rainfall pattern which revealed an increase in temperature and decrease in annual rainfall.This calls for serious attention as people in this part of Nigeria critically depend on rainfall for agricultural practices.It is recommended that government should support the agricultural sector by providing mechanized farming systems such as irrigation and drilling of water borehole in farm sites for agriculture,especially for the rural farmers and create awareness to the farmers on recent trends in climate issues to achieve sustainable agriculture.
文摘Kigezi highlands currently experiences changes in precipitation and temperature which modify the evaporation and soil moisture storage leading to alterations in runoff and other components of hydrological systems. Extreme events, like floods and droughts, are more intense and frequent. Furthermore heavy unpredictable rainfall has become frequent in the area, causing soil erosion and floods that destroy crops. Soil erosion is particularly a pressing challenge due to steep-sided hills leading to deterioration of soil nutrients including soil fertility. The unpredictable rains and droughts are attributed to climate change and variability. Consequently, climate change and variability have caused a significant impact on soil nutrients which have affected the agricultural productivity in the area. This paper presents findings of empirical study which explored the climate variability and soil nutrient status along altitudinal gradient. The paper particularly addresses key questions of: land management practices in the study area, nutrient availability and their effects on productivity of selected crops along altitudinal gradient in changing climate and variability. Independent variables such as topographic sequence along altitudinal gradient were evaluated against dependent variables such as yield harvests of selected grown crops and soil nutrients. Samples for crop yields were collected along transect of 0.5 kilometer using a quadrant of 4 × 4 m<sup>2</sup> along attitudinal gradient. Soil samples were taken from selected plots at 0-20cm soil depth for nutrient analysis. Analysis of physical and chemical soil parameters was carried out on soil samples and these include: soil pH, soil organic content, total nitrogen, available soil phosphorous and exchangeable bases (Ca, Mg, K and Na). The study showed that middle parts of the transects had the highest concentration of most soil nutrients, probably because the middle parts could have been a deposition centre for some organic matter from the upper parts of the hills, and lower lying areas were being affected by floods that affects the decomposition of organic matter which is the main source of nutrients. Similarly, the middle parts of the study were the most fertile due to the high concentration of soil nutrient compositions. This indicates that crop yields were significantly affected by availability of soil nutrients along same gradient, attributable to the severity in soil erosion, nutrients leaching and farming practices.
文摘Introduction The agriculture sector contributes approximately 14%of India’s total gross domestic productivity(source:Indian Ministry of Agriculture,2013-2014).The variability in the monsoonal precipitation has a critical impact on agricultural productivity and thus the economy of the country(Krishna Kumar et al.,2004).
文摘This study evaluated the annual rainfall for the Tabuk region obtained from observed datasets for the period 1978-2013. The objective of this study was to determine Tabuk catchment climate characteristics in terms of precipitation. The annual average precipitation in the Tabuk region is 33.5 mm which is below the global average precipitation receiving in arid regions set as less than 250 mm. There is a drop in the annual rainfall from (25 - 30) mm to (5 - 10) mm (1978-2004). The lowest annual rainfall (0 - 6.0 mm) occurred in the year 2004, which is the driest year in a 35-year period.
文摘Main problem of modern climatology is to assess the present as well as future climate change, For this aim two approaches are used: physic-mathematic modeling on the basis of GCMs and palaeoclimatic analogues. The third approach is based on the empirical-statistical methodology and is developed in this paper. This approach allows to decide two main problems: to give a real assessment of climate changes by observed data for climate monitoring and extrapolation of obtained climate tendencies to the nearest future (10-15 years) and give the empirical basis for further development of physic-mathematical models. The basic theory and methodology of empirical-statistic approach have been developed as well as a common model for description of space-time climate variations taking into account the processes of different time scales. The way of decreasing of the present and future uncertainty is suggested as the extraction of long-term climate changes components in the particular time series and spatial generalization of the same climate tendencies in the obtained homogeneous regions. Algorithm and methods for realization of empirical-statistic methodology have been developed along with methods for generalization of intraannual fluctuations, methods for extraction of homogeneous components of different time scales (interannual, decadal, century), methodology and methods for spatial generalization and modeling, methods for extrapolation on the basis of two main kinds of time models: stochastic and deterministic-stochastic. Some applications of developed methodology and methods are given for the longest time series of temperature and precipitation over the world and for spatial generalization over the European area.
基金the Natural Science Foundation of Southwest University of Science and Technology(18zx7117)the National Science and Technology Support Program of China(2015BAC05B05-01)。
文摘As climate change intensifies,finding an ecological indicator to quickly and accurately reflect the impact on mountain ecosystems is necessary.The low treeline/timberline,highly sensitive to climate variability and changes significantly within 5–10years,provides a new way to study the response to regional climate variability.This study explored the distribution and vertical displacement patterns of the low treeline in the Upper Minjiang River of China,using SPOT remote sensing images in 1999 and 2013and long-term positional observations.Using the Geodetector model,the study investigated the dominant climatic factors influencing the low treeline displacement.The results showed that the low treeline was located at 1700–3200 m elevation on sunny slopes(southeast,south,southwest,and west slopes)with slopes over 25°.From 1999 to 2013,the low treeline moved downward by 6 m from 2561±264m to 2555±265 m,along with a warm–humid climate tendency.The downward displacement was greater on slopes over 25°and shady slopes(-20 m and-10 m,respectively)than on slopes≤25°and sunny slopes.Additionally,the downward was greater in the warm and humid Zagunao River Basin(-15 m)compared to the arid valley center(-7 m)and the cold Heishui River Basin(-3 m).Meanwhile,the low treeline displacement correlated negatively with precipitation and relative humidity variations at the significance level of 0.05,with correlation coefficients of-0.572and-0.551,respectively.Variations in relative humidity and temperature significantly affected the spatial differentiation of low treeline displacement with influencing power of 0.246(p=0.036<0.05)and 0.183(p=0.032<0.05),respectively.Thus,the low treeline is a moisture-limited line,and its formation and variation are closely related to regional water–heat balance.The study clarifies the indicative value of the low treeline for climate variability in mountain areas and can provide references for ecological restoration in arid valleys.
