The focus of this study is a coastal high-resolution (2′ X 2′ ) two-waycoupled wave-tide-surge interaction model, including three main physical mechanisms. Comparisons andanalysis of simulated and measured wave heig...The focus of this study is a coastal high-resolution (2′ X 2′ ) two-waycoupled wave-tide-surge interaction model, including three main physical mechanisms. Comparisons andanalysis of simulated and measured wave heights and sea level considered two moderate storm casesfor the Huang-he Delta coastal area. The effects of different physical mechanisms on wave heightsare mainly influenced by wave-current interaction, including radiation stress. Wave-age dependentsurface wind stress and radiation stress mechanisms in the coupling wave-tide-surge interactionmodel show positive impact on sea level, and the wave-current interaction bottom stress mechanismshows negative impact on seal level. The comprehensive effects of the three main physical mechanismsshow positive net impact on seal level and increase sea level by around 20cm for the stormsconsidered. Overall, the results we show that the wave heights and sea levels simulated by thecoupled wave-tide-surge model agree better with the measured values than uncoupled model results,particularly for peak storm conditions.展开更多
Net primary productivity（NPP）, as an important variable and ecological indicator in grassland ecosystems, can reflect environmental change and the carbon budget level. The Ili River Valley is a wetland nestled in th...Net primary productivity（NPP）, as an important variable and ecological indicator in grassland ecosystems, can reflect environmental change and the carbon budget level. The Ili River Valley is a wetland nestled in the hinterland of the Eurasian continent, which responds sensitively to the global climate change. Understanding carbon budget and their responses to climate change in the ecosystem of Ili River Valley has a significant effect on the adaptability of future climate change and sustainable development. In this study, we calculated the NPP and analyzed its spatio-temporal pattern of the Ili River Valley during the period 2000–2014 using the normalized difference vegetation index（NDVI） and an improved Carnegie-Ames-Stanford（CASA） model. Results indicate that validation showed a good performance of CASA over the study region, with an overall coefficient of determination（R2） of 0.65 and root mean square error（RMSE） of 20.86 g C/（m^2·a）. Temporally, annual NPP of the Ili River Valley was 599.19 g C/（m^2·a） and showed a decreasing trend from 2000 to 2014, with an annual decrease rate of –3.51 g C/（m^2·a）. However, the spatial variation was not consistent, in which 55.69% of the areas showed a decreasing tendency, 12.60% of the areas remained relatively stable and 31.71% appeared an increasing tendency. In addition, the decreasing trends in NPP were not continuous throughout the 15-year period, which was likely being caused by a shift in climate conditions. Precipitation was found to be the dominant climatic factor that controlled the inter-annual variability in NPP. Furthermore, the correlations between NPP and climate factors differed along the vertical zonal. In the medium-high altitudes of the Ili River Valley, the NPP was positively correlated to precipitation and negatively correlated to temperature and net radiation. In the low-altitude valley and high-altitude mountain areas, the NPP showed a negative correlation with precipitation and a weakly positive correlation with temperature and net radiation. The results suggested that the vegetation of the Ili River Valley degraded in recent years, and there was a more complex mechanism of local hydrothermal redistribution that controlled the growth of vegetation in this valley ecosystem.展开更多
文摘The focus of this study is a coastal high-resolution (2′ X 2′ ) two-waycoupled wave-tide-surge interaction model, including three main physical mechanisms. Comparisons andanalysis of simulated and measured wave heights and sea level considered two moderate storm casesfor the Huang-he Delta coastal area. The effects of different physical mechanisms on wave heightsare mainly influenced by wave-current interaction, including radiation stress. Wave-age dependentsurface wind stress and radiation stress mechanisms in the coupling wave-tide-surge interactionmodel show positive impact on sea level, and the wave-current interaction bottom stress mechanismshows negative impact on seal level. The comprehensive effects of the three main physical mechanismsshow positive net impact on seal level and increase sea level by around 20cm for the stormsconsidered. Overall, the results we show that the wave heights and sea levels simulated by thecoupled wave-tide-surge model agree better with the measured values than uncoupled model results,particularly for peak storm conditions.
文摘[目的]准确了解2010年以来扎龙自然保护区生态变化,为提高湿地生态系统服务价值评估能力提供数据支持和理论参考。[方法]基于遥感、气象、地面协同观测数据,利用CASA(Carnegie-Ames-Stanford Approach)模型、GSMSR(Geostatistical Model of Soil Respiration)模型和回归分析等统计方法,分析气候变化对2010—2020年扎龙自然保护区土地覆盖、植被生态质量、净生态系统生产力(NEP)等的影响。[结果](1)扎龙自然保护区的主要土地覆盖类型为有水草甸,占保护区面积的37.24%,主要分布在核心区,但面积总体呈下降趋势;(2)植被覆盖度呈波动增长趋势,年最高植被覆盖度平均为74.62%;(3)植被生态质量指数呈增加趋势,2019,2020年处于“好”等级;NEP平均为253.59 g/(m^(2)·a)(以C计),呈现东高西低的空间分布特征;(4)生长季平均固碳量为5.69×10^(5) t/a,释氧量1.52×10^(6) t/a,均存在上升趋势;(5)气温对生态监测指标的影响大于降水量。[结论]扎龙自然保护区是嫩江流域生态最为脆弱的区域,植被生产力受气候影响大,需要加强生态保护和修复。
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19030204)the West Light Program of Chinese Academy of Sciences(2015-XBQN-B-17)
文摘Net primary productivity（NPP）, as an important variable and ecological indicator in grassland ecosystems, can reflect environmental change and the carbon budget level. The Ili River Valley is a wetland nestled in the hinterland of the Eurasian continent, which responds sensitively to the global climate change. Understanding carbon budget and their responses to climate change in the ecosystem of Ili River Valley has a significant effect on the adaptability of future climate change and sustainable development. In this study, we calculated the NPP and analyzed its spatio-temporal pattern of the Ili River Valley during the period 2000–2014 using the normalized difference vegetation index（NDVI） and an improved Carnegie-Ames-Stanford（CASA） model. Results indicate that validation showed a good performance of CASA over the study region, with an overall coefficient of determination（R2） of 0.65 and root mean square error（RMSE） of 20.86 g C/（m^2·a）. Temporally, annual NPP of the Ili River Valley was 599.19 g C/（m^2·a） and showed a decreasing trend from 2000 to 2014, with an annual decrease rate of –3.51 g C/（m^2·a）. However, the spatial variation was not consistent, in which 55.69% of the areas showed a decreasing tendency, 12.60% of the areas remained relatively stable and 31.71% appeared an increasing tendency. In addition, the decreasing trends in NPP were not continuous throughout the 15-year period, which was likely being caused by a shift in climate conditions. Precipitation was found to be the dominant climatic factor that controlled the inter-annual variability in NPP. Furthermore, the correlations between NPP and climate factors differed along the vertical zonal. In the medium-high altitudes of the Ili River Valley, the NPP was positively correlated to precipitation and negatively correlated to temperature and net radiation. In the low-altitude valley and high-altitude mountain areas, the NPP showed a negative correlation with precipitation and a weakly positive correlation with temperature and net radiation. The results suggested that the vegetation of the Ili River Valley degraded in recent years, and there was a more complex mechanism of local hydrothermal redistribution that controlled the growth of vegetation in this valley ecosystem.
