Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However...Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However, there is no unified and explicit definition for mountainous areas. The local elevation range(LER) is a crucial structural parameter for delineating mountainous areas. However, current LER products are limited by the subjective selection of an optimum statistical window or coarser spatial resolution of topographical data. In this study, we presented an approach using thresholds for three topographic parameters, elevation, slope, and LER, derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM) to redelineate the vast mountainous areas of mainland Southeast Asia(MSEA). The mean change-point analysis method was applied to determine the optimum statistical window of the 1 arc second(approximately 30 m)-resolution GDEM LER. The results showed that: First, the optimum statistical window is 38 × 38 cell units(width × height) in a rectangular neighborhood, or an area of about 1.30 km^2 for calculating GDEM LER in MSEA. Second, the LER of more than 80% of the area ranges from 30 m to 499 m in MSEA. The LERs in the northern and northwestern MSEA are greater than their counterparts in the south and east. Third, the area of the re-delineated mountainous areas was 83.52 × 10~4 km^2, about 38.71% of the total area. Spatially, the mountainous areas are mainly distributed in the north and northeast of MSEA. The re-delineated 30-m resolution map of the mountainous areas will serve as a topographical dataset for monitoring mountainrelated land surface changes in MSEA. The parameter-modified mountain extraction procedure can be expanded to delineate global mountainous areas.展开更多
Landsat data are the longest available records that consistently document global change.However,the extent and degree of cloud coverage typically determine its usability,especially in the tropics.In this study,scene-b...Landsat data are the longest available records that consistently document global change.However,the extent and degree of cloud coverage typically determine its usability,especially in the tropics.In this study,scene-based metadata from the U.S.Geological Survey Landsat inventories,ten-day,monthly,seasonal,and annual acquisition probabilities(AP)of targeted images at various cloud coverage thresholds(10%to 100%)were statistically analyzed using available Landsat TM,ETM+,and OLI observations over mainland Southeast Asia(MSEA)from 1986 to 2015.Four significant results were found.First,the cumulative average acquisition probability of available Landsat observations over MSEA at the 30%cloud cover(CC)threshold was approximately 41.05%.Second,monthly and ten-day level probability statistics for the 30%CC threshold coincide with the temporal distribution of the dry and rainy seasons.This demonstrates that Landsat images acquired during the dry season satisfy the requirements needed for land cover monitoring.Third,differences in acquisition probabilities at the 30%CC threshold are different between the western and eastern regions of MSEA.Finally,the ability of TM,ETM+,and OLI to acquire high-quality imagery has gradually enhanced over time,especially during the dry season,along with consequently larger probabilities at lower CC thresholds.展开更多
Freshwater plays a vital role in global sustainability by improving human lives and protecting nature.In the Lancang-Mekong River Basin(LMRB),sustainable development is principally dependent upon precipitation that pr...Freshwater plays a vital role in global sustainability by improving human lives and protecting nature.In the Lancang-Mekong River Basin(LMRB),sustainable development is principally dependent upon precipitation that predominantly controls freshwater resources availability required for both life and livelihood of~70 million people.Hence,this study comprehensively analyzed long-term historical precipitation patterns(in terms of trends,variability,and links to climate teleconnections)throughout the LMRB as well as its upper(Lancang River Basin,LRB)and lower(Mekong River Basin,MRB)parts employing six gauge-based gridded climate products:Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE),Climate Prediction Center(CPC),Climate Research Unit(CRU),Global Precipitation Climatology Center(GPCC),Precipitation Reconstruction over Land(PRECL),and University of Delaware(UDEL).Accordingly,annual and seasonal(dry and wet)precipitation time series were calculated for three study periods:century-long outlook(1901-2010),mid-past(1951-2010),and recent decades(1981-2010).However,the role of climate teleconnections in precipitation variability over the LMRB was only identified during their available temporal coverages:mid-past and recent decades.The results generally showed that:(i)both annual and seasonal precipitation increased across all three basins in 1981-2010;(ii)wet and dry seasons got drier and wetter,respectively,in all basins in 1951-2010;(iii)all such changes were fundamentally attributed to increases in precipitation variability on both annual and seasonal scales over time;(iv)these variations were most strongly associated with the Pacific Decadal Oscillation(PDO),Atlantic Multi-decadal Oscillation(AMO)and East Pacific/North Pacific(EP/NP)pattern in the LMRB and the MRB during 1951-2010,but with the North Sea-Caspian Pattern(NCP)and the Southern Annular Mode(SAM)in the LRB;(v)such relationships got stronger in 1981-2010,while the Southern Oscillation Index(SOI)became the most influential teleconnection for dry season precipitation variability across all basins;and(vi)GPCC(APHRODITE)provided the most reliable gauge-based gridded precipitation time series over the LMRB for the years before(after)1951.These findings lay a foundation for further studies focusing on water resources and sustainable development in the LMRB.展开更多
在世界文明的相互交流中,军事技术总是最先被引进,因为若不如此,就会大难临头、国破族亡。Anthony Reid,Europe and Southeast Asia:The Military Balance(Townsville,Queensland:Center for Southeast Asian Studies,James Cook Univer...在世界文明的相互交流中,军事技术总是最先被引进,因为若不如此,就会大难临头、国破族亡。Anthony Reid,Europe and Southeast Asia:The Military Balance(Townsville,Queensland:Center for Southeast Asian Studies,James Cook University of North Queesland,1982),p1.——安东尼·瑞德(Anthony Reid):《欧洲和东南亚》武器和军事组织方面的任何巨变都会使一些民族比以前更容易实现目标,却也让其他民族面临前所未有、难以克服的困难,由此影响政治与社会。火枪的出现正是这样一种巨变。William HMcNeill,The Age of Gunpowder Empires,1450-1800(Washington DC:American Historical Association,1989),p1.——威廉·H麦克尼尔(William HMcNeill):《1450~1800年的火药帝国时代》在亚洲军事史上,有关1511年葡萄牙入侵马六甲之前中国火器技术传入东南亚的历史仍遗留诸多空白。笔者曾撰文讨论过明初(1368~1450)火器技术传入大陆东南亚北部地区(主要包括今中国云南南部、印度东北部和大陆东南亚的北部)的历史及影响。Sun Laichen,“Transfers of Military Technology from Ming China to Northern Mainland Southeast Asia,1390-1527”,Journal of Southeast Asian Studies 34,3(2003),pp495-517.中译文《明代中国军事技术的传播和东南亚北部大陆的崛起(1390~1527年)》,《中国东南亚研究会通讯》2005年第1期,李新平、邱普艳译,第27~39页;另收入范宏贵主编《论说东南亚》,民族出版社,2010,第239~269页。本文则主要探讨中越关系和越南历史中与中国火器传播相关的两个问题。展开更多
该文报道了在泰国北部和中国西南部的菊科一个新归化属——苹果蓟属( Centratherum Cass.)。依据所采集的标本,详细描述了该属在东南亚大陆的唯一代表亚种苹果蓟[ Centratherum punctatum Cass. subsp. fruticosum (S. Vidal) K. Kirkma...该文报道了在泰国北部和中国西南部的菊科一个新归化属——苹果蓟属( Centratherum Cass.)。依据所采集的标本,详细描述了该属在东南亚大陆的唯一代表亚种苹果蓟[ Centratherum punctatum Cass. subsp. fruticosum (S. Vidal) K. Kirkman ex Shih H. Chen, M. J. Wu & S. M. Li],并配以插图。苹果蓟与其所在属的其他种的区别在于该亚种叶片菱形至椭圆形,叶缘具不规则锯齿,先端微尖,总苞片基部硬化,先端无芒。文中还提供了苹果蓟的分布图,并讨论了其可能的传播途径。展开更多
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20010203)
文摘Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However, there is no unified and explicit definition for mountainous areas. The local elevation range(LER) is a crucial structural parameter for delineating mountainous areas. However, current LER products are limited by the subjective selection of an optimum statistical window or coarser spatial resolution of topographical data. In this study, we presented an approach using thresholds for three topographic parameters, elevation, slope, and LER, derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM) to redelineate the vast mountainous areas of mainland Southeast Asia(MSEA). The mean change-point analysis method was applied to determine the optimum statistical window of the 1 arc second(approximately 30 m)-resolution GDEM LER. The results showed that: First, the optimum statistical window is 38 × 38 cell units(width × height) in a rectangular neighborhood, or an area of about 1.30 km^2 for calculating GDEM LER in MSEA. Second, the LER of more than 80% of the area ranges from 30 m to 499 m in MSEA. The LERs in the northern and northwestern MSEA are greater than their counterparts in the south and east. Third, the area of the re-delineated mountainous areas was 83.52 × 10~4 km^2, about 38.71% of the total area. Spatially, the mountainous areas are mainly distributed in the north and northeast of MSEA. The re-delineated 30-m resolution map of the mountainous areas will serve as a topographical dataset for monitoring mountainrelated land surface changes in MSEA. The parameter-modified mountain extraction procedure can be expanded to delineate global mountainous areas.
基金This work was supported by the National Natural Science Foundation of China(NSFC)under grants(41301090 and 41271117).
文摘Landsat data are the longest available records that consistently document global change.However,the extent and degree of cloud coverage typically determine its usability,especially in the tropics.In this study,scene-based metadata from the U.S.Geological Survey Landsat inventories,ten-day,monthly,seasonal,and annual acquisition probabilities(AP)of targeted images at various cloud coverage thresholds(10%to 100%)were statistically analyzed using available Landsat TM,ETM+,and OLI observations over mainland Southeast Asia(MSEA)from 1986 to 2015.Four significant results were found.First,the cumulative average acquisition probability of available Landsat observations over MSEA at the 30%cloud cover(CC)threshold was approximately 41.05%.Second,monthly and ten-day level probability statistics for the 30%CC threshold coincide with the temporal distribution of the dry and rainy seasons.This demonstrates that Landsat images acquired during the dry season satisfy the requirements needed for land cover monitoring.Third,differences in acquisition probabilities at the 30%CC threshold are different between the western and eastern regions of MSEA.Finally,the ability of TM,ETM+,and OLI to acquire high-quality imagery has gradually enhanced over time,especially during the dry season,along with consequently larger probabilities at lower CC thresholds.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA20060401,XDA20060402)the National Natural Science Foundation of China(Grant No.41625001)the High-level Special Funding of the Southern University of Science and Technology(Grant No.G02296302,G02296402).
文摘Freshwater plays a vital role in global sustainability by improving human lives and protecting nature.In the Lancang-Mekong River Basin(LMRB),sustainable development is principally dependent upon precipitation that predominantly controls freshwater resources availability required for both life and livelihood of~70 million people.Hence,this study comprehensively analyzed long-term historical precipitation patterns(in terms of trends,variability,and links to climate teleconnections)throughout the LMRB as well as its upper(Lancang River Basin,LRB)and lower(Mekong River Basin,MRB)parts employing six gauge-based gridded climate products:Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE),Climate Prediction Center(CPC),Climate Research Unit(CRU),Global Precipitation Climatology Center(GPCC),Precipitation Reconstruction over Land(PRECL),and University of Delaware(UDEL).Accordingly,annual and seasonal(dry and wet)precipitation time series were calculated for three study periods:century-long outlook(1901-2010),mid-past(1951-2010),and recent decades(1981-2010).However,the role of climate teleconnections in precipitation variability over the LMRB was only identified during their available temporal coverages:mid-past and recent decades.The results generally showed that:(i)both annual and seasonal precipitation increased across all three basins in 1981-2010;(ii)wet and dry seasons got drier and wetter,respectively,in all basins in 1951-2010;(iii)all such changes were fundamentally attributed to increases in precipitation variability on both annual and seasonal scales over time;(iv)these variations were most strongly associated with the Pacific Decadal Oscillation(PDO),Atlantic Multi-decadal Oscillation(AMO)and East Pacific/North Pacific(EP/NP)pattern in the LMRB and the MRB during 1951-2010,but with the North Sea-Caspian Pattern(NCP)and the Southern Annular Mode(SAM)in the LRB;(v)such relationships got stronger in 1981-2010,while the Southern Oscillation Index(SOI)became the most influential teleconnection for dry season precipitation variability across all basins;and(vi)GPCC(APHRODITE)provided the most reliable gauge-based gridded precipitation time series over the LMRB for the years before(after)1951.These findings lay a foundation for further studies focusing on water resources and sustainable development in the LMRB.
文摘在世界文明的相互交流中,军事技术总是最先被引进,因为若不如此,就会大难临头、国破族亡。Anthony Reid,Europe and Southeast Asia:The Military Balance(Townsville,Queensland:Center for Southeast Asian Studies,James Cook University of North Queesland,1982),p1.——安东尼·瑞德(Anthony Reid):《欧洲和东南亚》武器和军事组织方面的任何巨变都会使一些民族比以前更容易实现目标,却也让其他民族面临前所未有、难以克服的困难,由此影响政治与社会。火枪的出现正是这样一种巨变。William HMcNeill,The Age of Gunpowder Empires,1450-1800(Washington DC:American Historical Association,1989),p1.——威廉·H麦克尼尔(William HMcNeill):《1450~1800年的火药帝国时代》在亚洲军事史上,有关1511年葡萄牙入侵马六甲之前中国火器技术传入东南亚的历史仍遗留诸多空白。笔者曾撰文讨论过明初(1368~1450)火器技术传入大陆东南亚北部地区(主要包括今中国云南南部、印度东北部和大陆东南亚的北部)的历史及影响。Sun Laichen,“Transfers of Military Technology from Ming China to Northern Mainland Southeast Asia,1390-1527”,Journal of Southeast Asian Studies 34,3(2003),pp495-517.中译文《明代中国军事技术的传播和东南亚北部大陆的崛起(1390~1527年)》,《中国东南亚研究会通讯》2005年第1期,李新平、邱普艳译,第27~39页;另收入范宏贵主编《论说东南亚》,民族出版社,2010,第239~269页。本文则主要探讨中越关系和越南历史中与中国火器传播相关的两个问题。
文摘该文报道了在泰国北部和中国西南部的菊科一个新归化属——苹果蓟属( Centratherum Cass.)。依据所采集的标本,详细描述了该属在东南亚大陆的唯一代表亚种苹果蓟[ Centratherum punctatum Cass. subsp. fruticosum (S. Vidal) K. Kirkman ex Shih H. Chen, M. J. Wu & S. M. Li],并配以插图。苹果蓟与其所在属的其他种的区别在于该亚种叶片菱形至椭圆形,叶缘具不规则锯齿,先端微尖,总苞片基部硬化,先端无芒。文中还提供了苹果蓟的分布图,并讨论了其可能的传播途径。
