The Indonesian Throughflow(ITF), which connects the tropical Pacific and Indian oceans, plays important roles in the inter-ocean water exchange and regional or even global climate variability. The Makassar Strait is t...The Indonesian Throughflow(ITF), which connects the tropical Pacific and Indian oceans, plays important roles in the inter-ocean water exchange and regional or even global climate variability. The Makassar Strait is the main inflow passage of the ITF, carrying about 77% of the total ITF volume transport. In this study, we analyze the simulated ITF in the Makassar Strait in the Simple Ocean Data Assimilation version 3(SODA3) datasets. A total of nine ensemble members of the SODA3 datasets, of which are driven by different surface forcings and bulk formulas, and with or without data assimilation, are used in this study. The annual mean water transports(i.e.,volume, heat and freshwater) are related to the combination of surface forcing and bulk formula, as well as whether data assimilation is employed. The phases of the seasonal and interannual variability in water transports cross the Makassar Strait, are basically consistent with each other among the SODA3 ensemble members. The interannual variability in Makassar Strait volume and heat transports are significantly correlated with El Ni?oSouthern Oscillation(ENSO) at time lags of-6 to 7 months. There is no statistically significant correlation between the freshwater transport and the ENSO. The Makassar Strait water transports are not significantly correlated with the Indian Ocean Dipole(IOD), which may attribute to model deficiency in simulating the propagation of semiannual Kelvin waves from the Indian Ocean to the Makassar Strait.展开更多
Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in...Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in summer than La Niña-related nIOD.However,the characteristics and triggering mechanisms of early nIOD are unclear.Our results based on reanalysis datasets indicate that the early nIOD and La Niña-related nIOD are the two major types of nIOD,and the former accounts for over one third of all the nIOD events in the past six decades.These two types of nIODs are similar in their intensities,but are different in their spatial patterns and seasonal cycles.The early nIOD,which develops in spring and peaks in summer,is one season earlier than the La Niña-related nIOD.The spatial pattern of the wind anomaly associated with early nIOD exhibits a winter monsoon-like pattern,with strong westerly anomalies in the equatorial Indian Ocean and eastly anomalies in the northern Indian Ocean.Opposite to the triggering mechanism of early positve IOD,the early nIOD is induced by delayed Indian summer monsoon onset.The results of this study are helpful for improving the prediction skill of IOD and its climate impacts.展开更多
Recently,Internet of Drones(IoD)has garnered significant attention due to its widespread applications.However,deploying IoD for area coverage poses numerous limitations and challenges.These include interference betwee...Recently,Internet of Drones(IoD)has garnered significant attention due to its widespread applications.However,deploying IoD for area coverage poses numerous limitations and challenges.These include interference between neighboring drones,the need for directional antennas,and altitude restrictions for drones.These challenges necessitate the development of efficient solutions.This research paper presents a cooperative decision-making approach for an efficient IoDdeployment to address these challenges effectively.The primary objective of this study is to achieve an efficient IoDdeployment strategy thatmaximizes the coverage regionwhile minimizing interference between neighboring drones.In deployment problem,the interference increases as the number of deployed drones increases,resulting in bad quality of communication.On the other hand,deploying a few drones cannot satisfy the coverage demand.To accomplish this,an enhanced version of a concise population-based meta-heuristic algorithm,namely Improved Particle SwarmOptimization(IPSO),is applied.The objective function of IPSO is defined based on the coverage probability,which is primarily influenced by the characteristics of the antennas and drone altitude.A radio frequency(RF)model is derived to evaluate the coverage quality,considering both Line of Sight(LOS)and Non-Line of Sight(NLOS)down-link coverage probabilities for ground communication.It is assumed that each drone is equipped with a directional antenna to optimize coverage in a given region.Extensive simulations are conducted to assess the effectiveness of the proposed approach.Results demonstrate that the proposed method achieves maximum coverage with minimum transmission power.Furthermore,a comparison is made against Collaborative Visual Area Coverage Approach(CVACA),and a game-based approach in terms of coverage quality and convergence speed.The simulation results reveal that our approach outperforms both CVACA and the gamebased schemes in terms of coverage and convergence speed.Comparisons validate the superiority of our approach over existing methods.To assess the robustness of the proposed RFmodel,we have considered two distinct ranges of noise:range1 spanning from−120 to−90 dBm,and range2 spanning from−90 to−70 dBmfor different numbers of UAVs.In summary,this research presents a cooperative decision-making approach for efficient IoD deployment to address the challenges associatedwith area coverage and achieves an optimal coveragewithminimal interference.展开更多
The East African short rainy season (October-November-December) is one of the major flood seasons in the East African region. The amount of rainfall during the short rainy season is closely related to the lives of the...The East African short rainy season (October-November-December) is one of the major flood seasons in the East African region. The amount of rainfall during the short rainy season is closely related to the lives of the people and the socio-economic development of the area. By using precipitation data and sea surface temperature data, this study reveals the spatial and temporal variation patterns of extreme precipitation during the East African short rainy season. Key findings include significant rainfall variability, with Tanzania experiencing the highest amounts in December due to the southward shift of the Intertropical Convergence Zone (ITCZ), while other regions receive less than 100 mm. Extreme rainfall events (90th percentiles) are evenly distributed, averaging 2 to 10 days annually. Historical data shows maximum seasonal rainfall often peaks at 15 mm, with frequent occurrences of daily rainfall exceeding 10 mm during OND. Additionally, a positive correlation (0.48) between OND precipitation extremes and Indian Ocean Dipole (IOD) anomalies is statistically significant. These findings highlight the climatic variability and potential trends in extreme rainfall events in East Africa, providing valuable insights for regional climate adaptation strategies.展开更多
Net heat flux,sea surface temperature(SST),and sea surface wind in the northern Indian Ocean were investigated using the TropFlux,ERA5,and J-OFURO3 datasets and correlation analysis,power spectrum analysis,and singula...Net heat flux,sea surface temperature(SST),and sea surface wind in the northern Indian Ocean were investigated using the TropFlux,ERA5,and J-OFURO3 datasets and correlation analysis,power spectrum analysis,and singular value decomposition(SVD)methods,respectively.The relationships between net heat flux,SST,and sea surface winds were determined.The coupled modes of net heat flux and wind have been found to explain the SST variations in the Indian Ocean basin and the generation mechanism of the Indian Ocean Dipole(IOD).The correlation between net heat flux and wind is strongly negative.The SST lags the net heat flux and wind by approximately one month and has strong positive and negative correlations,respectively.The correlation between net heat flux and wind in the northern Indian Ocean is not only seasonal but also regionally dependent on seasonal variations.Using the SVD method,the important role of net heat flux in local sea-air interactions is discussed and identified as the initial perturbation that triggers the SST anomalies in the Southeast Indian Ocean,and the areas with key sea-air interactions and the generation mechanisms of the local sea-air interactions that form the IOD are determined.展开更多
Climate anomalies can cause natural disasters such as severe fires and floods on peatlands in South Sumatra.Factors that affect the natural disasters on peatlands include rainfall,groundwater level,and soil moisture.T...Climate anomalies can cause natural disasters such as severe fires and floods on peatlands in South Sumatra.Factors that affect the natural disasters on peatlands include rainfall,groundwater level,and soil moisture.This paper aims to study the effect of the climate anomalies in 2019 and 2020 and effects of these influencing factors on peatlands in South Sumatra.The data used in this study was derived from insitu measurement at two SESAME’s measurement stations in the study area.The results indicate that in the 2019 dry season,the rainfall was minimal,the lowest groundwater table depth was-1.14 m and the lowest soil moisture was 3.4%.In the 2020 dry season,rainfall was above the monthly average of 100 mm,the lowest groundwater level was-0.44 m,and the lowest soil moisture was 26.64%.There is also a strong correlation between soil moisture and groundwater table depth.The correlation between the two is stronger when there is less rainfall.展开更多
There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have d...There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have different understandings on the extent to which climate events control upwelling in this area,which leads to a lack of basis for studies on the evaluation and mechanisms of the variability of fishery resources in the region.The correlation between environmental parameters,including surface temperature(SST),chlorophyll-a(Chl-a)concentration,and climate event indices in South Java from 2003 to 2020 was analyzed.Results show that the Indian Ocean Dipole(IOD)has a greater influence on the interannual variability of upwelling intensity than ENSO.During the IOD,variations in equatorial latitudinal winds excite different types of Kelvin waves that anomalously deepen or shallow the thermocline,which is the main cause of anomalous variations in upwelling,independent of variations in the local wind field.A correlation between the interannual variability in upwelling and the annual catches was revealed,showing that climatic events indirectly affect fishery resources through upwelling effects.During positive IOD/El Niño periods,strong upwelling delivers more nutrients to the surface layer,which favors fish growth and reproduction,resulting in higher annual catches.A negative IOD/La Niña,on the other hand,leads to weaker upwelling and fewer nutrients into the surface waters.Fish tend to move in deeper waters,making traditional fishing methods less efficient and consequently lower annual catches.展开更多
基金The Fund of Laoshan Laboratory under contract No. LSKJ202202700the National Natural Science Foundation of China under contract Nos 42076023, 42076024 and 41876027the Global Change and Air-Sea Interaction Ⅱ Project under contract No.GASI-01-AIP-STwin。
文摘The Indonesian Throughflow(ITF), which connects the tropical Pacific and Indian oceans, plays important roles in the inter-ocean water exchange and regional or even global climate variability. The Makassar Strait is the main inflow passage of the ITF, carrying about 77% of the total ITF volume transport. In this study, we analyze the simulated ITF in the Makassar Strait in the Simple Ocean Data Assimilation version 3(SODA3) datasets. A total of nine ensemble members of the SODA3 datasets, of which are driven by different surface forcings and bulk formulas, and with or without data assimilation, are used in this study. The annual mean water transports(i.e.,volume, heat and freshwater) are related to the combination of surface forcing and bulk formula, as well as whether data assimilation is employed. The phases of the seasonal and interannual variability in water transports cross the Makassar Strait, are basically consistent with each other among the SODA3 ensemble members. The interannual variability in Makassar Strait volume and heat transports are significantly correlated with El Ni?oSouthern Oscillation(ENSO) at time lags of-6 to 7 months. There is no statistically significant correlation between the freshwater transport and the ENSO. The Makassar Strait water transports are not significantly correlated with the Indian Ocean Dipole(IOD), which may attribute to model deficiency in simulating the propagation of semiannual Kelvin waves from the Indian Ocean to the Makassar Strait.
基金The Basic Scientific Fund for National Public Research Institutes of China under contract No.2022S02the National Natural Science Foundation of China under contract No.41976021.
文摘Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in summer than La Niña-related nIOD.However,the characteristics and triggering mechanisms of early nIOD are unclear.Our results based on reanalysis datasets indicate that the early nIOD and La Niña-related nIOD are the two major types of nIOD,and the former accounts for over one third of all the nIOD events in the past six decades.These two types of nIODs are similar in their intensities,but are different in their spatial patterns and seasonal cycles.The early nIOD,which develops in spring and peaks in summer,is one season earlier than the La Niña-related nIOD.The spatial pattern of the wind anomaly associated with early nIOD exhibits a winter monsoon-like pattern,with strong westerly anomalies in the equatorial Indian Ocean and eastly anomalies in the northern Indian Ocean.Opposite to the triggering mechanism of early positve IOD,the early nIOD is induced by delayed Indian summer monsoon onset.The results of this study are helpful for improving the prediction skill of IOD and its climate impacts.
基金funded by Project Number INML2104 under the Interdisciplinary Center of Smart Mobility and Logistics at King Fahd University of Petroleum and Minerals.This study also was supported by the Special Research Fund BOF23KV17.
文摘Recently,Internet of Drones(IoD)has garnered significant attention due to its widespread applications.However,deploying IoD for area coverage poses numerous limitations and challenges.These include interference between neighboring drones,the need for directional antennas,and altitude restrictions for drones.These challenges necessitate the development of efficient solutions.This research paper presents a cooperative decision-making approach for an efficient IoDdeployment to address these challenges effectively.The primary objective of this study is to achieve an efficient IoDdeployment strategy thatmaximizes the coverage regionwhile minimizing interference between neighboring drones.In deployment problem,the interference increases as the number of deployed drones increases,resulting in bad quality of communication.On the other hand,deploying a few drones cannot satisfy the coverage demand.To accomplish this,an enhanced version of a concise population-based meta-heuristic algorithm,namely Improved Particle SwarmOptimization(IPSO),is applied.The objective function of IPSO is defined based on the coverage probability,which is primarily influenced by the characteristics of the antennas and drone altitude.A radio frequency(RF)model is derived to evaluate the coverage quality,considering both Line of Sight(LOS)and Non-Line of Sight(NLOS)down-link coverage probabilities for ground communication.It is assumed that each drone is equipped with a directional antenna to optimize coverage in a given region.Extensive simulations are conducted to assess the effectiveness of the proposed approach.Results demonstrate that the proposed method achieves maximum coverage with minimum transmission power.Furthermore,a comparison is made against Collaborative Visual Area Coverage Approach(CVACA),and a game-based approach in terms of coverage quality and convergence speed.The simulation results reveal that our approach outperforms both CVACA and the gamebased schemes in terms of coverage and convergence speed.Comparisons validate the superiority of our approach over existing methods.To assess the robustness of the proposed RFmodel,we have considered two distinct ranges of noise:range1 spanning from−120 to−90 dBm,and range2 spanning from−90 to−70 dBmfor different numbers of UAVs.In summary,this research presents a cooperative decision-making approach for efficient IoD deployment to address the challenges associatedwith area coverage and achieves an optimal coveragewithminimal interference.
文摘The East African short rainy season (October-November-December) is one of the major flood seasons in the East African region. The amount of rainfall during the short rainy season is closely related to the lives of the people and the socio-economic development of the area. By using precipitation data and sea surface temperature data, this study reveals the spatial and temporal variation patterns of extreme precipitation during the East African short rainy season. Key findings include significant rainfall variability, with Tanzania experiencing the highest amounts in December due to the southward shift of the Intertropical Convergence Zone (ITCZ), while other regions receive less than 100 mm. Extreme rainfall events (90th percentiles) are evenly distributed, averaging 2 to 10 days annually. Historical data shows maximum seasonal rainfall often peaks at 15 mm, with frequent occurrences of daily rainfall exceeding 10 mm during OND. Additionally, a positive correlation (0.48) between OND precipitation extremes and Indian Ocean Dipole (IOD) anomalies is statistically significant. These findings highlight the climatic variability and potential trends in extreme rainfall events in East Africa, providing valuable insights for regional climate adaptation strategies.
基金supported by Institut de Recherche pour le Développement(IRD,France)(ESSO-INCOIS-Indian National Centre for Ocean Information Services)funded by the Specialized in Global Change and Sea-Air Interactions and Special Projects-Study on the Mechanism of the Influence of Ocean Mixing on Leapfrog and the Tianjin Key Laboratory of Marine Meteorology 2020 Open Fund Project(No.2020TKLOMZD01)Large-Scale Wave Glider Platform Development
文摘Net heat flux,sea surface temperature(SST),and sea surface wind in the northern Indian Ocean were investigated using the TropFlux,ERA5,and J-OFURO3 datasets and correlation analysis,power spectrum analysis,and singular value decomposition(SVD)methods,respectively.The relationships between net heat flux,SST,and sea surface winds were determined.The coupled modes of net heat flux and wind have been found to explain the SST variations in the Indian Ocean basin and the generation mechanism of the Indian Ocean Dipole(IOD).The correlation between net heat flux and wind is strongly negative.The SST lags the net heat flux and wind by approximately one month and has strong positive and negative correlations,respectively.The correlation between net heat flux and wind in the northern Indian Ocean is not only seasonal but also regionally dependent on seasonal variations.Using the SVD method,the important role of net heat flux in local sea-air interactions is discussed and identified as the initial perturbation that triggers the SST anomalies in the Southeast Indian Ocean,and the areas with key sea-air interactions and the generation mechanisms of the local sea-air interactions that form the IOD are determined.
文摘Climate anomalies can cause natural disasters such as severe fires and floods on peatlands in South Sumatra.Factors that affect the natural disasters on peatlands include rainfall,groundwater level,and soil moisture.This paper aims to study the effect of the climate anomalies in 2019 and 2020 and effects of these influencing factors on peatlands in South Sumatra.The data used in this study was derived from insitu measurement at two SESAME’s measurement stations in the study area.The results indicate that in the 2019 dry season,the rainfall was minimal,the lowest groundwater table depth was-1.14 m and the lowest soil moisture was 3.4%.In the 2020 dry season,rainfall was above the monthly average of 100 mm,the lowest groundwater level was-0.44 m,and the lowest soil moisture was 26.64%.There is also a strong correlation between soil moisture and groundwater table depth.The correlation between the two is stronger when there is less rainfall.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB42010203,XDA19060401)the National Natural Science Foundation of China(Nos.42176090,41776011)。
文摘There is a vast upwelling area induced by the southeast monsoon in the waters off South Java,making the region an important fishing ground.Climate events can affect the variation of upwelling,but oceanographers have different understandings on the extent to which climate events control upwelling in this area,which leads to a lack of basis for studies on the evaluation and mechanisms of the variability of fishery resources in the region.The correlation between environmental parameters,including surface temperature(SST),chlorophyll-a(Chl-a)concentration,and climate event indices in South Java from 2003 to 2020 was analyzed.Results show that the Indian Ocean Dipole(IOD)has a greater influence on the interannual variability of upwelling intensity than ENSO.During the IOD,variations in equatorial latitudinal winds excite different types of Kelvin waves that anomalously deepen or shallow the thermocline,which is the main cause of anomalous variations in upwelling,independent of variations in the local wind field.A correlation between the interannual variability in upwelling and the annual catches was revealed,showing that climatic events indirectly affect fishery resources through upwelling effects.During positive IOD/El Niño periods,strong upwelling delivers more nutrients to the surface layer,which favors fish growth and reproduction,resulting in higher annual catches.A negative IOD/La Niña,on the other hand,leads to weaker upwelling and fewer nutrients into the surface waters.Fish tend to move in deeper waters,making traditional fishing methods less efficient and consequently lower annual catches.
