Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to...Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to climate change.Using remote sensing and meteorological data,this study revealed the spatiotemporal characteristics of leaf area index(LAI)in the north of China during 1982–2022,clarified the response of LAI change to different meteorological factors,quantified the impacts of climate change and human activities on LAI change,and predicted the future trends in LAI change.From 1982 to 2022,the vegetation in the north of China generally showed a greening trend with a change rate of 0.0071 m2/(m2•a).Temperature was strongly positively correlated with LAI and was the main climate factor driving LAI change.Residual analysis revealed that vegetation improvement occurred in across 74.53%of the study area,and vegetation improvement in about 96.83%of the improved zone was attributed to a combination of climate change and human activities.The regions where anthropogenic contribution exceeded 60.00%covered 36.83%of human-affected areas,while the regions where climatic contribution exceeded 60.00%covered 19.77%of climate-affected areas,demonstrating that human activities influenced the intensity of LAI change more deeply despite the broad spatial impact of climate change.Human activities such as afforestation and the Three-North Protective Forest Program played the dominant role in vegetation greening compared to climate change.Hurst index analysis indicated that 80.30%of vegetation in the north of China is expected to experience a non-sustained improvement in the future.These findings will provide a scientific basis for optimizing the protection strategies of the national ecological barrier areas and evaluating the effectiveness of major ecological projects.展开更多
The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in thi...The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.展开更多
The seasonal and inter-annual variations of Arctic cyclone are investigated. An automatic cyclone tracking algorithm developed by University of Reading was applied on the basis of European Center for Medium-range Weat...The seasonal and inter-annual variations of Arctic cyclone are investigated. An automatic cyclone tracking algorithm developed by University of Reading was applied on the basis of European Center for Medium-range Weather Forecasts（ECMWF） ERA-interim mean sea level pressure field with 6 h interval for 34 a period. The maximum number of the Arctic cyclones is counted in winter, and the minimum is in spring not in summer.About 50% of Arctic cyclones in summer generated from south of 70°N, moving into the Arctic. The number of Arctic cyclones has large inter-annual and seasonal variabilities, but no significant linear trend is detected for the period 1979–2012. The spatial distribution and linear trends of the Arctic cyclones track density show that the cyclone activity extent is the widest in summer with significant increasing trend in CRU（central Russia）subregion, and the largest track density is in winter with decreasing trend in the same subregion. The linear regressions between the cyclone track density and large-scale indices for the same period and pre-period sea ice area indices show that Arctic cyclone activities are closely linked to large-scale atmospheric circulations, such as Arctic Oscillation（AO）, North Atlantic Oscillation（NAO） and Pacific-North American Pattern（PNA）. Moreover,the pre-period sea ice area is significantly associated with the cyclone activities in some regions.展开更多
自然对人类的贡献(nature’s contributions to people,NCP)是指大自然对人类生活质量的一切积极贡献和消极影响,分为10个调节型NCP、4个物质型NCP和4个非物质型NCP.但目前这些NCP的全球时空分布及其相互作用规律尚不清楚,直接制约了加...自然对人类的贡献(nature’s contributions to people,NCP)是指大自然对人类生活质量的一切积极贡献和消极影响,分为10个调节型NCP、4个物质型NCP和4个非物质型NCP.但目前这些NCP的全球时空分布及其相互作用规律尚不清楚,直接制约了加强自然界多种有益贡献的生态系统管理实践.本研究构建基于指标体系的评价方法,结合生态系统演变、气候变化与人类活动全球尺度多源空间数据集,在全球范围内对1990~2018年所有18个NCPs进行空间制图,在15,204个流域单元上识别主导了NCP组合,并基于NCPs时空特征识别了全球景观变化的功能权衡关系和景观多功能性.结果表明,全球大部分NCPs的高值仅在局地出现.1992~2018年,6个调节型NCP、3个物质型NCP和2个非物质型NCP下降.29种调节型和物质型NCP组合(总共有54种组合)的主导流域占全球76%的陆地面积,而无NCP主导的流域占全球陆地面积的22%.NCPs变化的协同关系比权衡关系更为常见,但调节型和物质型NCP之间的关系普遍处于权衡状态.过渡气候地区的NCP相对少,并具有强烈的权衡关系;而低纬度地区NCPs之间的高度协同关系可能受到未来气候变化的影响.研究结果提供了对全球NCP空间变化规律的总体认知,可用于科学支撑区域景观功能的关系调控和景观多功能性提升,以增强全球人类福祉.展开更多
The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show t...The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.展开更多
基金supported by the National Natural Science Foundation of China(42301127)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2023D01C185).
文摘Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to climate change.Using remote sensing and meteorological data,this study revealed the spatiotemporal characteristics of leaf area index(LAI)in the north of China during 1982–2022,clarified the response of LAI change to different meteorological factors,quantified the impacts of climate change and human activities on LAI change,and predicted the future trends in LAI change.From 1982 to 2022,the vegetation in the north of China generally showed a greening trend with a change rate of 0.0071 m2/(m2•a).Temperature was strongly positively correlated with LAI and was the main climate factor driving LAI change.Residual analysis revealed that vegetation improvement occurred in across 74.53%of the study area,and vegetation improvement in about 96.83%of the improved zone was attributed to a combination of climate change and human activities.The regions where anthropogenic contribution exceeded 60.00%covered 36.83%of human-affected areas,while the regions where climatic contribution exceeded 60.00%covered 19.77%of climate-affected areas,demonstrating that human activities influenced the intensity of LAI change more deeply despite the broad spatial impact of climate change.Human activities such as afforestation and the Three-North Protective Forest Program played the dominant role in vegetation greening compared to climate change.Hurst index analysis indicated that 80.30%of vegetation in the north of China is expected to experience a non-sustained improvement in the future.These findings will provide a scientific basis for optimizing the protection strategies of the national ecological barrier areas and evaluating the effectiveness of major ecological projects.
文摘The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.
基金The Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract No.2016-04-03the National Key Research and Development Program of China under contract No.2016YFC1402701
文摘The seasonal and inter-annual variations of Arctic cyclone are investigated. An automatic cyclone tracking algorithm developed by University of Reading was applied on the basis of European Center for Medium-range Weather Forecasts（ECMWF） ERA-interim mean sea level pressure field with 6 h interval for 34 a period. The maximum number of the Arctic cyclones is counted in winter, and the minimum is in spring not in summer.About 50% of Arctic cyclones in summer generated from south of 70°N, moving into the Arctic. The number of Arctic cyclones has large inter-annual and seasonal variabilities, but no significant linear trend is detected for the period 1979–2012. The spatial distribution and linear trends of the Arctic cyclones track density show that the cyclone activity extent is the widest in summer with significant increasing trend in CRU（central Russia）subregion, and the largest track density is in winter with decreasing trend in the same subregion. The linear regressions between the cyclone track density and large-scale indices for the same period and pre-period sea ice area indices show that Arctic cyclone activities are closely linked to large-scale atmospheric circulations, such as Arctic Oscillation（AO）, North Atlantic Oscillation（NAO） and Pacific-North American Pattern（PNA）. Moreover,the pre-period sea ice area is significantly associated with the cyclone activities in some regions.
基金supported by the National Key Research and Development Program of China(2017YFA0604701)the National Natural Science Foundation of China(41991235)+1 种基金the Australian Research Council Future Fellowship(FT200100096)the Fundamental Research Funds for the Central Universities in China。
文摘自然对人类的贡献(nature’s contributions to people,NCP)是指大自然对人类生活质量的一切积极贡献和消极影响,分为10个调节型NCP、4个物质型NCP和4个非物质型NCP.但目前这些NCP的全球时空分布及其相互作用规律尚不清楚,直接制约了加强自然界多种有益贡献的生态系统管理实践.本研究构建基于指标体系的评价方法,结合生态系统演变、气候变化与人类活动全球尺度多源空间数据集,在全球范围内对1990~2018年所有18个NCPs进行空间制图,在15,204个流域单元上识别主导了NCP组合,并基于NCPs时空特征识别了全球景观变化的功能权衡关系和景观多功能性.结果表明,全球大部分NCPs的高值仅在局地出现.1992~2018年,6个调节型NCP、3个物质型NCP和2个非物质型NCP下降.29种调节型和物质型NCP组合(总共有54种组合)的主导流域占全球76%的陆地面积,而无NCP主导的流域占全球陆地面积的22%.NCPs变化的协同关系比权衡关系更为常见,但调节型和物质型NCP之间的关系普遍处于权衡状态.过渡气候地区的NCP相对少,并具有强烈的权衡关系;而低纬度地区NCPs之间的高度协同关系可能受到未来气候变化的影响.研究结果提供了对全球NCP空间变化规律的总体认知,可用于科学支撑区域景观功能的关系调控和景观多功能性提升,以增强全球人类福祉.
基金Project supported by the National Natural Science Foundation of China and Hong Kong under Grant Nos. 40275004,4001161948.
文摘The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.
