El Niño-Southern Oscillation(ENSO)affects the changes in ocean physical elements in Taiwan Strait(TWS)primarily by regulating the strength of the East Asian Winter Monsoon(EAWM)and the intrusion of the Kuroshio.A...El Niño-Southern Oscillation(ENSO)affects the changes in ocean physical elements in Taiwan Strait(TWS)primarily by regulating the strength of the East Asian Winter Monsoon(EAWM)and the intrusion of the Kuroshio.Additionally,the fluctuating impact between nutrient-poor seawater with high dissolved inorganic carbon(DIC)that infiltrates owing to the Kuroshio during El Niño phases and nutrient-rich seawater with low DIC from the South China Sea(SCS)carried by the EAWM during La Niña phases determines the nutrient content in TWS,thereby sculpting appropriate or unsuitable biochemical environment.In this study,based on high-resolution sea-surface partial pressure of carbon dioxide(pCO_(2))data,we investigate the relationship between pCO_(2)level of TWS and ENSO events in winter.The physical mechanisms affecting the anomalous distribution of pCO_(2)level during ENSO are also explored.Stepwise regression was employed to identify the optimal influencing factors for modeling pCO_(2).Results indicate a significant positive correlation between Niño3.4 index and pCO_(2),which is significantly influenced by factors such as sea-surface temperature(SST),chlorophyll-a(Chl a),and DIC.These are related to the anomalously strong Kuroshio intrusion and weaker EAWM during El Niño years.It brings a large amount of high SST water with low nutrient concentration and high DIC,which is detrimental to CO_(2)dissolution and phytoplankton growth over the TWS,leading to an increase in pCO_(2).Conversely,pCO_(2)level is significantly low under the influence of SCS seawater during La Niña years.Based on the characterization of the pCO_(2)level response to ENSO,the carbon balance at TWS can be explored.展开更多
There is a need for more focus in understanding the economic benefits of Climate-Smart Agriculture(CSA)interventions,particularly in sub-Saharan Africa,where extreme climate events are significantly affecting agricult...There is a need for more focus in understanding the economic benefits of Climate-Smart Agriculture(CSA)interventions,particularly in sub-Saharan Africa,where extreme climate events are significantly affecting agriculture and rural livelihoods.This study used the Net Present Value(NPV),Internal Rate of Return(IRR),Benefit-Cost Ratio(BCR),and payback period to evaluate the economic viability of the adopted CSA interventions in the three villages(Doggoh,Jeffiri,and Wulling)of the dryland farming systems of northern Ghana,where CSA interventions were mostly practiced.Data were collected from 161 farm households by the questionnaire survey.The results showed that CSA interventions including livestock-crop integration,mixed cropping,crop rotation,nutrient integration,and tie ridging enhanced crop yield and the household income of smallholder farmers.The five CSA interventions selected by smallholders were in the following order of priority:livestock-crop integration(BCR=2.87),mixed cropping(BCR=2.54),crop rotation(BCR=2.24),nutrient integration(BCR=1.98),and tie ridging(BCR=1.42).Results further showed that livestock-crop integration was the most profitable CSA intervention even under a pessimistic assumption with a long payback period of 5.00 a.Moreover,this study indicated that the implementation of CSA interventions,on average,was relatively profitable and had a nominal financial risk for smallholder farmers.Understanding the economic viability of CSA interventions will help in decision-making process toward selecting the right CSA interventions for resilience development.展开更多
The sediment content of the Yellow River is resulted from the interactions of natural, economic, and social factors, so it includes some evolutive information of the Yellow River Basin system. Sediment contents from 1...The sediment content of the Yellow River is resulted from the interactions of natural, economic, and social factors, so it includes some evolutive information of the Yellow River Basin system. Sediment contents from 1952 to 2007 on Toudaoguai, Tongguan, Huayuankou and Lijin sections along the river are chosen as the study time series, and correlation dimensions （D2）, Kolmogorov entropies （K2）, and Hurst indexes （H） of the time series were calculated. Correlation dimensions on Toudaoguai, Tongguan, Huayuankou, and Lijin sections are 3.24, 5.69, 6.57 and 7.34 respectively, and the Kolmogorov entropies are 0.13, 0.37, 0.40 and 0.38 respectively, which indicates that the systems controlled by different sections along the Yellow River are chaotic systems and the chaotic degrees increase gradually from the upper to lower section. The average predictable period of the sediment contents is 8 years on Toudaoguai section and 3 years on the other sections with the reciprocals of the Kolmogorov entropies. The more obvious the chaotic degree is, the shorter the average predictable period is. Hurst indexes on the sections are above 0.5, with the maximum of 0.86 on Tongguan section and the minimum of 0.68 on Toudaoguai section, which indicates that the time series have persistent trends in the average predictable period. Eight state variables and two control parameters are necessary to construct the dynamic model of the Yellow River Basin system.展开更多
The improvement of agriculture through irrigation farming is now of great need in the country Nigeria and Delta State. The country is going through a phase of famine and food insecurity caused by climate change and ra...The improvement of agriculture through irrigation farming is now of great need in the country Nigeria and Delta State. The country is going through a phase of famine and food insecurity caused by climate change and rain dependent agricultural practices. The aim of the study therefore, was to evaluate the quality of water from River Ethiope in Southern Nigeria for irrigation agriculture purposes using the percentage sodium (%Na), sodium-adsorption ratio (SAR) and irrigation-water quality index (IWQ1) techniques. The study deployed the experimental design and water samples were collected from different segments of the Ethiope River. A total of 144 water samples were collected and analysed for physicochemical parameters quality (EC, HCO3, Cl−, Na+, Mg2+, Ca2+ and K+) from January to December, 2022. The results showed that all the calculated values for %Na were within the classified rating of 20 < N ≤ 40 and 60 < Na ≤ 80;while SAR were within the range of 0 < SAR ≤ 10. The recorded values of IWQI were within the range of 70 - 55 and 55 - 40. This implies that the water is good to doubtful for %Na, excellent for SAR and of moderate and high restrictions for IWQI. Water was adjudged to be good for irrigation activities, and should be applicable in areas with moderate and high soil permeability. The routine testing of the water to ascertain physicochemical parameters quality regularly, in order not to affect its use for irrigation was among the recommendations. This finding herein shall be of use to Water Resources and Agriculture ministries in Nigeria.展开更多
Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The str...Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The stratigraphy is arranged as LF1,PDC1,LF2,LF3,LF4,LF5,LF6,LF7,LD1,and LD2;furthermore,these rocks were divided into two types.TypeⅠ,observed in the oldest(LF1)sample,has poor MgO and high Ba/Nb,Th/Yb and Sr.The remaining samples(PDC1–LD2)represent typeⅡ,characterized by high MgO and low Ba/Nb,Th/Yb and Sr values.We suggest that type I is derived from AOC(altered oceanic crust)-rich melts that underwent significant crustal assimilation,while typeⅡoriginates from mantle-rich melts with less significant crustal assimilation.The early stage of typeⅡmagma(PDC1–LF3)was considered a closed system,evolving basaltic andesite into andesite(55.0–60.2 wt%SiO_(2))with a progressively increasing phenocryst(0.30–0.48φ_(PC))and decreasing crystal size distribution(CSD)slope(from-3.9 to-2.9).The evidence of fluctuating silica and phenocryst contents(between 55.9–59.7 wt%and 0.25–0.41φ_(PC),respectively),coupled with the kinked and steep(from-5.0 to-3.3)CSD curves imply the interchanging condition between open(i.e.,magma mixing)and closed magmatic systems during the middle stage(LF4–LF6).Finally,it underwent to closed system again during the final stage(LF7–LD2)because the magma reached dacitic composition(at most 68.9 wt%SiO_(2))with abundant phenocryst(0.38–0.45φ_(PC))and gentle CSD slope(from-4.1 to-1.2).展开更多
The Alborz Mountains are some of the highest in Iran,and they play an important role in controlling the climate of the country’s northern regions.The land surface temperature(LST)is an important variable that affects...The Alborz Mountains are some of the highest in Iran,and they play an important role in controlling the climate of the country’s northern regions.The land surface temperature(LST)is an important variable that affects the ecosystem of this area.This study investigated the spatiotemporal changes and trends of the nighttime LST in the western region of the Central Alborz Mountains at elevations of 1500-4000 m above sea level.MODIS data were extracted for the period of 2000-2021,and the Mann-Kendall nonparametric test was applied to evaluating the changes in the LST.The results indicated a significant increasing trend for the monthly average LST in May-August along the southern aspect.Both the northern and southern aspects showed decreasing trends for the monthly average LST in October,November,and March and an increasing trend in other months.At all elevations,the average decadal change in the monthly average LST was more severe along the southern aspect(0.60°C)than along the northern aspect(0.37°C).The LST difference between the northern and southern aspects decreased in the cold months but increased in the hot months.At the same elevation,the difference in the lapse rate between the northern and southern aspects was greater in the hot months than in the cold months.With increasing elevation,the lapse rate between the northern and southern aspects disappeared.Climate change was concluded to greatly decrease the difference in LST at different elevations for April-July.展开更多
Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the me...Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the melt source and emplacement age of the leucogranites from Sikkim in order to decipher the deep geodynamic processes of the eastern Himalayas.Zircon U-Pb analysis of the Higher Himalayan Sequence(HHS)metamorphic core reveals a prolonged period of crustal melting between>33 Ma and ca.14 Ma.Major and trace element abundances are presented for 27 leucogranites from North Sikkim that are classified into two-mica and tourmaline leucogranite types.They are peraluminous in composition,characterized by high SiO2(70.91-74.9 wt.%),Al2O3(13.69-15.82 wt.%),and low MgO(0.13-0.74 wt.%).Elemental abundances suggest that Sikkim Himalayan leucogranites are derived from crustal melts.The two-mica leucogranites are derived from a metagreywacke source,whereas the tourmaline leucogranites are sourced from metapelitic sources,with inherited zircons indicating an HHS origin for both types.U-Pb zircon geochronology of the two mica leucogranites indicates ages of ca.19-15 Ma,consistent with crustal melting recorded in HHS gneisses from Darjeeling.Monazites from both the two-mica and tourmaline leucogranites yield a crystallization age of ca.15-14 Ma,coeval with movement on the Main Central Thrust and South Tibetan Detachment System which further provides constraints on the timing and mechanism of petrogenesis of leucogranites in the Sikkim Himalayas.展开更多
Machine learning(ML)algorithms are frequently used in landslide susceptibility modeling.Different data handling strategies may generate variations in landslide susceptibility modeling,even when using the same ML algor...Machine learning(ML)algorithms are frequently used in landslide susceptibility modeling.Different data handling strategies may generate variations in landslide susceptibility modeling,even when using the same ML algorithm.This research aims to compare the combinations of inventory data handling,cross validation(CV),and hyperparameter tuning strategies to generate landslide susceptibility maps.The results are expected to provide a general strategy for landslide susceptibility modeling using ML techniques.The authors employed eight landslide inventory data handling scenarios to convert a landslide polygon into a landslide point,i.e.,the landslide point is located on the toe(minimum height),on the scarp(maximum height),at the center of the landslide,randomly inside the polygon(1 point),randomly inside the polygon(3 points),randomly inside the polygon(5 points),randomly inside the polygon(10 points),and 15 m grid sampling.Random forest models using CV-nonspatial hyperparameter tuning,spatial CV-spatial hyperparameter tuning,and spatial CV-forward feature selection-no hyperparameter tuning were applied for each data handling strategy.The combination generated 24 random forest ML workflows,which are applied using a complete inventory of 743 landslides triggered by Tropical Cyclone Cempaka(2017)in Pacitan Regency,Indonesia,and 11 landslide controlling factors.The results show that grid sampling with spatial CV and spatial hyperparameter tuning is favorable because the strategy can minimize overfitting,generate a relatively high-performance predictive model,and reduce the appearance of susceptibility artifacts in the landslide area.Careful data inventory handling,CV,and hyperparameter tuning strategies should be considered in landslide susceptibility modeling to increase the applicability of landslide susceptibility maps in practical application.展开更多
基金The Key R&D Project of Zhejiang Province under contract No.2023C03120the General Scientific Research Project of Zhejiang Province under contract No.Y202353957the National Natural Science Foundation of China under contract No.42106017.
文摘El Niño-Southern Oscillation(ENSO)affects the changes in ocean physical elements in Taiwan Strait(TWS)primarily by regulating the strength of the East Asian Winter Monsoon(EAWM)and the intrusion of the Kuroshio.Additionally,the fluctuating impact between nutrient-poor seawater with high dissolved inorganic carbon(DIC)that infiltrates owing to the Kuroshio during El Niño phases and nutrient-rich seawater with low DIC from the South China Sea(SCS)carried by the EAWM during La Niña phases determines the nutrient content in TWS,thereby sculpting appropriate or unsuitable biochemical environment.In this study,based on high-resolution sea-surface partial pressure of carbon dioxide(pCO_(2))data,we investigate the relationship between pCO_(2)level of TWS and ENSO events in winter.The physical mechanisms affecting the anomalous distribution of pCO_(2)level during ENSO are also explored.Stepwise regression was employed to identify the optimal influencing factors for modeling pCO_(2).Results indicate a significant positive correlation between Niño3.4 index and pCO_(2),which is significantly influenced by factors such as sea-surface temperature(SST),chlorophyll-a(Chl a),and DIC.These are related to the anomalously strong Kuroshio intrusion and weaker EAWM during El Niño years.It brings a large amount of high SST water with low nutrient concentration and high DIC,which is detrimental to CO_(2)dissolution and phytoplankton growth over the TWS,leading to an increase in pCO_(2).Conversely,pCO_(2)level is significantly low under the influence of SCS seawater during La Niña years.Based on the characterization of the pCO_(2)level response to ENSO,the carbon balance at TWS can be explored.
文摘There is a need for more focus in understanding the economic benefits of Climate-Smart Agriculture(CSA)interventions,particularly in sub-Saharan Africa,where extreme climate events are significantly affecting agriculture and rural livelihoods.This study used the Net Present Value(NPV),Internal Rate of Return(IRR),Benefit-Cost Ratio(BCR),and payback period to evaluate the economic viability of the adopted CSA interventions in the three villages(Doggoh,Jeffiri,and Wulling)of the dryland farming systems of northern Ghana,where CSA interventions were mostly practiced.Data were collected from 161 farm households by the questionnaire survey.The results showed that CSA interventions including livestock-crop integration,mixed cropping,crop rotation,nutrient integration,and tie ridging enhanced crop yield and the household income of smallholder farmers.The five CSA interventions selected by smallholders were in the following order of priority:livestock-crop integration(BCR=2.87),mixed cropping(BCR=2.54),crop rotation(BCR=2.24),nutrient integration(BCR=1.98),and tie ridging(BCR=1.42).Results further showed that livestock-crop integration was the most profitable CSA intervention even under a pessimistic assumption with a long payback period of 5.00 a.Moreover,this study indicated that the implementation of CSA interventions,on average,was relatively profitable and had a nominal financial risk for smallholder farmers.Understanding the economic viability of CSA interventions will help in decision-making process toward selecting the right CSA interventions for resilience development.
基金National Natural Science Foundation of China, No.40601105 Key Project of Science and Technology of Henan Province, No.0721021500
文摘The sediment content of the Yellow River is resulted from the interactions of natural, economic, and social factors, so it includes some evolutive information of the Yellow River Basin system. Sediment contents from 1952 to 2007 on Toudaoguai, Tongguan, Huayuankou and Lijin sections along the river are chosen as the study time series, and correlation dimensions （D2）, Kolmogorov entropies （K2）, and Hurst indexes （H） of the time series were calculated. Correlation dimensions on Toudaoguai, Tongguan, Huayuankou, and Lijin sections are 3.24, 5.69, 6.57 and 7.34 respectively, and the Kolmogorov entropies are 0.13, 0.37, 0.40 and 0.38 respectively, which indicates that the systems controlled by different sections along the Yellow River are chaotic systems and the chaotic degrees increase gradually from the upper to lower section. The average predictable period of the sediment contents is 8 years on Toudaoguai section and 3 years on the other sections with the reciprocals of the Kolmogorov entropies. The more obvious the chaotic degree is, the shorter the average predictable period is. Hurst indexes on the sections are above 0.5, with the maximum of 0.86 on Tongguan section and the minimum of 0.68 on Toudaoguai section, which indicates that the time series have persistent trends in the average predictable period. Eight state variables and two control parameters are necessary to construct the dynamic model of the Yellow River Basin system.
文摘The improvement of agriculture through irrigation farming is now of great need in the country Nigeria and Delta State. The country is going through a phase of famine and food insecurity caused by climate change and rain dependent agricultural practices. The aim of the study therefore, was to evaluate the quality of water from River Ethiope in Southern Nigeria for irrigation agriculture purposes using the percentage sodium (%Na), sodium-adsorption ratio (SAR) and irrigation-water quality index (IWQ1) techniques. The study deployed the experimental design and water samples were collected from different segments of the Ethiope River. A total of 144 water samples were collected and analysed for physicochemical parameters quality (EC, HCO3, Cl−, Na+, Mg2+, Ca2+ and K+) from January to December, 2022. The results showed that all the calculated values for %Na were within the classified rating of 20 < N ≤ 40 and 60 < Na ≤ 80;while SAR were within the range of 0 < SAR ≤ 10. The recorded values of IWQI were within the range of 70 - 55 and 55 - 40. This implies that the water is good to doubtful for %Na, excellent for SAR and of moderate and high restrictions for IWQI. Water was adjudged to be good for irrigation activities, and should be applicable in areas with moderate and high soil permeability. The routine testing of the water to ascertain physicochemical parameters quality regularly, in order not to affect its use for irrigation was among the recommendations. This finding herein shall be of use to Water Resources and Agriculture ministries in Nigeria.
基金funded by the Faculty of Geography under the scheme of“Dana Hibah Penelitian Mandiri Dosen Tahun 2023 Tahap 1”。
文摘Ten rock samples consisting of one pyroclastic density current(PDC1)deposit,seven lava flows(LF1–7),and two summit lava domes(LD1,2)were studied to understand the petrogenesis and magma dynamics at Mt.Sumbing.The stratigraphy is arranged as LF1,PDC1,LF2,LF3,LF4,LF5,LF6,LF7,LD1,and LD2;furthermore,these rocks were divided into two types.TypeⅠ,observed in the oldest(LF1)sample,has poor MgO and high Ba/Nb,Th/Yb and Sr.The remaining samples(PDC1–LD2)represent typeⅡ,characterized by high MgO and low Ba/Nb,Th/Yb and Sr values.We suggest that type I is derived from AOC(altered oceanic crust)-rich melts that underwent significant crustal assimilation,while typeⅡoriginates from mantle-rich melts with less significant crustal assimilation.The early stage of typeⅡmagma(PDC1–LF3)was considered a closed system,evolving basaltic andesite into andesite(55.0–60.2 wt%SiO_(2))with a progressively increasing phenocryst(0.30–0.48φ_(PC))and decreasing crystal size distribution(CSD)slope(from-3.9 to-2.9).The evidence of fluctuating silica and phenocryst contents(between 55.9–59.7 wt%and 0.25–0.41φ_(PC),respectively),coupled with the kinked and steep(from-5.0 to-3.3)CSD curves imply the interchanging condition between open(i.e.,magma mixing)and closed magmatic systems during the middle stage(LF4–LF6).Finally,it underwent to closed system again during the final stage(LF7–LD2)because the magma reached dacitic composition(at most 68.9 wt%SiO_(2))with abundant phenocryst(0.38–0.45φ_(PC))and gentle CSD slope(from-4.1 to-1.2).
文摘The Alborz Mountains are some of the highest in Iran,and they play an important role in controlling the climate of the country’s northern regions.The land surface temperature(LST)is an important variable that affects the ecosystem of this area.This study investigated the spatiotemporal changes and trends of the nighttime LST in the western region of the Central Alborz Mountains at elevations of 1500-4000 m above sea level.MODIS data were extracted for the period of 2000-2021,and the Mann-Kendall nonparametric test was applied to evaluating the changes in the LST.The results indicated a significant increasing trend for the monthly average LST in May-August along the southern aspect.Both the northern and southern aspects showed decreasing trends for the monthly average LST in October,November,and March and an increasing trend in other months.At all elevations,the average decadal change in the monthly average LST was more severe along the southern aspect(0.60°C)than along the northern aspect(0.37°C).The LST difference between the northern and southern aspects decreased in the cold months but increased in the hot months.At the same elevation,the difference in the lapse rate between the northern and southern aspects was greater in the hot months than in the cold months.With increasing elevation,the lapse rate between the northern and southern aspects disappeared.Climate change was concluded to greatly decrease the difference in LST at different elevations for April-July.
基金supported by Innovation in Science Pursuit for Inspired Research(INSPIRE)No.DST/INSPIRE Fellowship/2016/IF160729,。
文摘Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the melt source and emplacement age of the leucogranites from Sikkim in order to decipher the deep geodynamic processes of the eastern Himalayas.Zircon U-Pb analysis of the Higher Himalayan Sequence(HHS)metamorphic core reveals a prolonged period of crustal melting between>33 Ma and ca.14 Ma.Major and trace element abundances are presented for 27 leucogranites from North Sikkim that are classified into two-mica and tourmaline leucogranite types.They are peraluminous in composition,characterized by high SiO2(70.91-74.9 wt.%),Al2O3(13.69-15.82 wt.%),and low MgO(0.13-0.74 wt.%).Elemental abundances suggest that Sikkim Himalayan leucogranites are derived from crustal melts.The two-mica leucogranites are derived from a metagreywacke source,whereas the tourmaline leucogranites are sourced from metapelitic sources,with inherited zircons indicating an HHS origin for both types.U-Pb zircon geochronology of the two mica leucogranites indicates ages of ca.19-15 Ma,consistent with crustal melting recorded in HHS gneisses from Darjeeling.Monazites from both the two-mica and tourmaline leucogranites yield a crystallization age of ca.15-14 Ma,coeval with movement on the Main Central Thrust and South Tibetan Detachment System which further provides constraints on the timing and mechanism of petrogenesis of leucogranites in the Sikkim Himalayas.
文摘Machine learning(ML)algorithms are frequently used in landslide susceptibility modeling.Different data handling strategies may generate variations in landslide susceptibility modeling,even when using the same ML algorithm.This research aims to compare the combinations of inventory data handling,cross validation(CV),and hyperparameter tuning strategies to generate landslide susceptibility maps.The results are expected to provide a general strategy for landslide susceptibility modeling using ML techniques.The authors employed eight landslide inventory data handling scenarios to convert a landslide polygon into a landslide point,i.e.,the landslide point is located on the toe(minimum height),on the scarp(maximum height),at the center of the landslide,randomly inside the polygon(1 point),randomly inside the polygon(3 points),randomly inside the polygon(5 points),randomly inside the polygon(10 points),and 15 m grid sampling.Random forest models using CV-nonspatial hyperparameter tuning,spatial CV-spatial hyperparameter tuning,and spatial CV-forward feature selection-no hyperparameter tuning were applied for each data handling strategy.The combination generated 24 random forest ML workflows,which are applied using a complete inventory of 743 landslides triggered by Tropical Cyclone Cempaka(2017)in Pacitan Regency,Indonesia,and 11 landslide controlling factors.The results show that grid sampling with spatial CV and spatial hyperparameter tuning is favorable because the strategy can minimize overfitting,generate a relatively high-performance predictive model,and reduce the appearance of susceptibility artifacts in the landslide area.Careful data inventory handling,CV,and hyperparameter tuning strategies should be considered in landslide susceptibility modeling to increase the applicability of landslide susceptibility maps in practical application.
