Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and...Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and is crucial to extract high-precision data. In particular, orthometric and ellipsoid elevations, surveyed at different moments in time, can be compared to yield information on vertical movements when geoid anomalies are known. However, a data checking procedure must be applied if archival orthometric elevations are used, because long-term measurements for many historical benchmarks may have been lost and/or replaced with other points, but at different elevations. This type of checking can be carried out over an area without gravimetric anomalies by modeling geoid undulations and vertical displacements in the time-span used for analysis, excluding points with anomalous values. This procedure was tested and applied in the Po Delta area (northern Italy), historically subject to high subsidence rates: the leveling benchmarks of 1983 were measured with the GPS technique in 2008. After checking of archival data and transformation from ellipsoid to orthometric elevations, comparisons of the same points and interpolations on the study area provided a subsidence map for the 1983-2008 period.展开更多
The aim of this work is to research the influence of natural climatic changes on the evolution of the coastal zone in modern times and the possible implication of human activities on the configuration of the present c...The aim of this work is to research the influence of natural climatic changes on the evolution of the coastal zone in modern times and the possible implication of human activities on the configuration of the present coastline.Comparison of data of two very far and different areas , the Po River delta, Adriatic Sea and the Huanghe River delta, Bohai Sea, reveals the planetary diffusion of climatic fluctuations and their effects on coastal evolution .展开更多
Saltwater intrusion along rivers is a complex process controlled by multiple factors and thus fluctuates with a highly nonlinear nature and time-varying characteristics.It is challenging to monitor saltwater intrusion...Saltwater intrusion along rivers is a complex process controlled by multiple factors and thus fluctuates with a highly nonlinear nature and time-varying characteristics.It is challenging to monitor saltwater intrusion.The objective of this study was to clarify the spatial-temporal variation of saltwater intrusion and its potential impact on agriculture in the Po River Delta(Italy).2006 was the most severe year of saltwater intrusion in the period we considered.2022 was even worse,but the data are still under processing.In this study,the Hilbert-Huang transform(HHT)and rescaled range(R/S)were used to identify the multi-time scales and change trends of the salinity and discharge in 2006.After that,the time-dependent intrinsic correlation(TDIC)was used to depict intrinsic relationships between salinity and discharge at different time scales.The results showed that discharge and salinity exhibited behav-iours of positive long-range correlation during different periods.The temporal series of salinity and discharge was decomposed into six intrinsic mode functions(IMF)and residuals based on the ensemble empirical mode decomposition(EEMD).The sum of variance contribution rates of IMF1(4 days),IMF2(10 days),and IMF3(12.1 days)of salinity was more than 75%.All measured TDICs have highlighted strong correlations between salinity and discharge.Furthermore,we used spatial interpolation tech-niques to map salinity data along rivers.This allowed the investigation of dynamic changes in saltwater intrusion patterns during periods of severe drought.Outcomes show a significant negative correlation between salinity and normalized difference vegetation index(NDVI),indicating that the study area's agricultural greening was affected by saltwater intrusion.展开更多
文摘Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and is crucial to extract high-precision data. In particular, orthometric and ellipsoid elevations, surveyed at different moments in time, can be compared to yield information on vertical movements when geoid anomalies are known. However, a data checking procedure must be applied if archival orthometric elevations are used, because long-term measurements for many historical benchmarks may have been lost and/or replaced with other points, but at different elevations. This type of checking can be carried out over an area without gravimetric anomalies by modeling geoid undulations and vertical displacements in the time-span used for analysis, excluding points with anomalous values. This procedure was tested and applied in the Po Delta area (northern Italy), historically subject to high subsidence rates: the leveling benchmarks of 1983 were measured with the GPS technique in 2008. After checking of archival data and transformation from ellipsoid to orthometric elevations, comparisons of the same points and interpolations on the study area provided a subsidence map for the 1983-2008 period.
文摘The aim of this work is to research the influence of natural climatic changes on the evolution of the coastal zone in modern times and the possible implication of human activities on the configuration of the present coastline.Comparison of data of two very far and different areas , the Po River delta, Adriatic Sea and the Huanghe River delta, Bohai Sea, reveals the planetary diffusion of climatic fluctuations and their effects on coastal evolution .
基金funding from the European Union Next-GenerationEU(PIANO NAZIONALE DI RIPRESA E RESILIENZA(PNRR)-MISSIONE 4 COMPONENTE 2,INVESTIMENTO 1.4-D.D.103217/06/2022,CN00000022)supported by the Start-up funding from Inner Mongolia University(21800-5223728).
文摘Saltwater intrusion along rivers is a complex process controlled by multiple factors and thus fluctuates with a highly nonlinear nature and time-varying characteristics.It is challenging to monitor saltwater intrusion.The objective of this study was to clarify the spatial-temporal variation of saltwater intrusion and its potential impact on agriculture in the Po River Delta(Italy).2006 was the most severe year of saltwater intrusion in the period we considered.2022 was even worse,but the data are still under processing.In this study,the Hilbert-Huang transform(HHT)and rescaled range(R/S)were used to identify the multi-time scales and change trends of the salinity and discharge in 2006.After that,the time-dependent intrinsic correlation(TDIC)was used to depict intrinsic relationships between salinity and discharge at different time scales.The results showed that discharge and salinity exhibited behav-iours of positive long-range correlation during different periods.The temporal series of salinity and discharge was decomposed into six intrinsic mode functions(IMF)and residuals based on the ensemble empirical mode decomposition(EEMD).The sum of variance contribution rates of IMF1(4 days),IMF2(10 days),and IMF3(12.1 days)of salinity was more than 75%.All measured TDICs have highlighted strong correlations between salinity and discharge.Furthermore,we used spatial interpolation tech-niques to map salinity data along rivers.This allowed the investigation of dynamic changes in saltwater intrusion patterns during periods of severe drought.Outcomes show a significant negative correlation between salinity and normalized difference vegetation index(NDVI),indicating that the study area's agricultural greening was affected by saltwater intrusion.
