The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite (OMPS) flying onboard the Suomi National Polar-orbiting Partnership satellite (S-NPP) launched as a part of the Joint Polar Satellite System (JPSS) program between NOAA and NASA. Since NOAA is already operationally processing OMPS nadir total ozone products, evaluations were made in this study on the total column ozone research products generated by NASA’s science team, utilizing the latest version of their Backscatter Ultraviolet (BUV) retrieval algorithms, to provide insight into the performance of the operation system. Comparisons were made with globally distributed ground-based Brewer and Dobson spectrophotometer total column ozone measurements. Linear regressions show fair agreement between OMPS and ground-based total column ozone measurements with a root-mean-square error (RMSE) of approximately 3% (10 DU). The comparison results indicate that the OMPS total column ozone data are 0.59% higher than the Brewer measurements with a standard deviation of 2.82% while 1.09% higher than the Dobson measurements with a standard deviation of 3.27%. Additionally, the variability of relative differences between OMPS and ground total column ozone were analyzed as a function of latitude, time, viewing geometry, and total column ozone value. Results show a 2% bias over most latitudes and viewing conditions when total column ozone value varies between 220 DU and 450 DU.
Comparisons between observations and background fields indicate that amplitude and phase differences in oscillations result in a non-Gaussian distribution in observation minus background vectors (OMB). Empirical Orthogonal Function (EOF) quality control (QC) and Fast Fourier Transform (FFT) quality control are proposed from the perspective of data assimilation and are applied to the surface specific humidity from ground-based stations. The QC results indicate that the standard deviation between observations and background is reduced effectively, and the frequency distribution for the observation increment is closer to a normal distribution. The specific humidity outliers occur primarily in mountainous and coastal regions. Comparing the two QC methods, it is found that the EOF QC performs better than the FFT QC as it can keep large scale of fluctuation information from the original field, preventing these waves from entering into the residual field and being removed by the QC process.
A three-dimensional hydrodynamic model with the capability to deal with changing land water boundaries was developed based on ECOMSED in this study. The model was configured to numerically study the water flushing characteristics of Dahuofang Reservoir in China through the determination of spatially distributed residence times. The model successfully reproduced the intra-annual water level variations, as well as the temporal evolution and spatial distribution of water temperature. Through a series of numerical experiments, it can be concluded that (1) the water flushing of the reservoir is both temporally and spatially variable; and (2) inflows and withdrawals are the decisive factors influencing the water flushing characteristics. Heat fluxes are the controlling factors of the water flushing of a strong stratified reservoir. Wind has the weakest effect, but it still should be considered in determination of reservoir water flushing characteristics.
The diffusion of pore fluid pressures may create both spatial and temporal effective stress gradients that influence or control the development and evolution of fractures within rock masses. To better understand the controls on fracturing behavior, numerical simulations are performed using a progressive fracture modeling approach that shares many of the same natural kinematic features in rocks, such as fracture growth, nucleation, and termination. First, the pinch-off breaking test is numerically performed to investigate the tensile failure of a rock specimen in a uniform pore pressure field. In this numerical simulation, both mechanical and hydrological properties of a suite of rocks are measured under simulated laboratory conditions. The complete tensional failure process of the rock specimen under pore pressure was reproduced. Second, a double-notched specimen is numerically extended to investigate how the water flow direction or pore pressure gradient influences the fracture growth. An exhaustive sensitivity study is conducted that examines the effects of varying both hydrological and mechanical boundary conditions. The simulation results indicate that local fluid pressure gradients strongly influence the state of stress in the solids and, thereby, fracture growth. Fracture and strength behavior is influenced not only by the pore pressure magnitude on a local scale around the fracture tip, but also by the orientation and distribution of pore pressure gradients on a global scale. Increasing the fracture growth rate increases the local model permeability and decreases the sample strength. The results of this study may provide useful information concerning the degree of hydrological and mechanical coupling action under geologic conditions.
In this paper, we introduce the method of Wavelet Multi-scale Decomposition (WMD) combined with Power Spectrum Analysis (PSA) for the separation of regional gravity and magnetic anomalies. The Songliao Basin is situated between the Siberian Plate and the North China Plate, and its main structural trend of gravity and magnetic anomaly fields is NNE. The study area shows a significant feature of deep collage-type construction. According to the feature of gravity field, the region was divided into five sub-regions. The gravity and magnetic fields of the Songliao Basin were separated using WMD with a 4th order separation. The apparent depth of anomalies in each order was determined by Logarithmic PSA. Then, the shallow high-frequency anomalies were removed and the 2nd–4th order wavelet detail anomalies were used to study the basin’s major faults. Twenty-six faults within the basement were recognized. The 4th order wavelet approximate anomalies were used for the inversion of the Moho discontinuity and the Curie isothermal surface.
Satellite microwave emission mixed with signals from active sensors is referred to as radio-frequency interference (RFI). RFI affects greatly the quality of data and retrieval products from space-borne microwave radiometry. An accurate RFI detection will not only enhance geophysical retrievals over land but also provide evidence of the much-needed protection of the microwave frequency band for satellite remote sensing technologies. It is difficult to detect RFI from space-borne microwave radiometer data over winter land, because RFI signals are usually mixed with snow in mid-high latitudes. A modified principal component analysis (PCA) method is proposed in this paper for detecting microwave low frequency RFI signals. Only three original variables, one RFI index (sensitive to RFI signal) and two scattering indices (sensitive to snow scattering), are included in the vector for principal component analysis in this modified method instead of the nine or seven RFI index original variables used in a normal PCA algorithm. The principal component with higher correlation and contribution to the original RFI index is the RFI-related principal component. In the absence of a reliable validation data set of the “true” RFI, the consistency in the identified RFI distribution obtained from this method compared to other independent methods, such as the spectral difference method, the normalized PCA method, and the double PCA method, give confidence to the RFI signals’ identification over land. The simple and reliable modified PCA method could successfully detect RFI not only in summer but also in winter AMSR-E data.
Landslides are among the most serious of geohazards in the Xi’an Region, Shaanxi, China, and are responsible for extensive human and property loss. In order to understand the distribution of landslides and assess their associated hazards in this region, we used a combination of frequency analysis, logistic analysis, and Geographic Information System (GIS) analysis, with consideration of the spatial distribution of landslides. Using the GIS approach, the five key factors of surface topography, including slope gradient, topographic wetness index (TWI), height difference, profile curvature and slope aspect, were considered. First, the distribution and frequency of landslides were considered in relation to all of the five factors in each of three sub-regions susceptible to landslides (Qin Mountain, Li Mountain, and Loess Tableland). Secondly, each factor’s influence was determined by a logistic regression method, and the relative importance of each of these independent variables was evaluated. Finally, a landslide susceptibility map was generated using GIS tools. Locations that had recorded landslides were used to validate the results of the landslide susceptibility map and the accuracy obtained was above 84%. The validation proved that there is sufficient agreement between the susceptibility map and existing records of landslide occurrences. The logistic regression model produced acceptable results (the areas under the Receiver Operating Characteristics (ROC) curve were 0.865, 0.841, and 0.924 in the Qin Mountain, Li Mountain and Loess Tableland). We are confident that the results of this study can be useful in preliminary planning for land use, particularly for construction work in high-risk areas.
In this study, based on environmental quality monitoring data on 22 pollutants from 490 control sections, we analyzed the spatial distribution and temporal changes of water quality in ten Chinese river basins (watersheds) to reveal the trends from 2005 to 2010. We used a comprehensive water pollution index (WPI) and the proportions of this index accounted for by the three major pollutants to analyze how economic development has influenced water quality. Higher values of the index represent more serious pollution. We found that WPI was much higher for the Hai River Basin (1.83 to 5.60 times the averages in other regions). In the Yangtze River Basin, WPI increased from upstream to downstream. The indices of some provinces toward the middle of a basin, such as Hebei Province in the Hai River Basin, Shanxi Province in the Yellow River Basin, and Anhui Province in the Huai River Basin, were higher than those of upstream and downstream provinces. In the Songhua, Liao, and Southeast river basins, WPI decreased during the study period: in 2010, it decreased by 33.9%, 44.3%, and 67.2%, respectively, compared with the 2005 value. In the Pearl River, Southwest, and Inland river basins, WPI increased by 23.1%, 47.7%, and 38.5% in 2010, compared with 2005. A comparison of WPI with the GDP of each province showed that the water pollution generated by economic development was lightest in northwestern, southwestern, and northeastern China, and highest in central and eastern China, and that the water environment in some coastal regions were improving. However, some provinces (e.g., Shanxi Province) were seriously polluted.
To assess the impacts of mowing on N2O and CH4 fluxes emissions from the meadow-steppe grasslands of Inner Mongolia, China, two regimes were investigated: unmown since 2005 (UM), and mown once every three years since 2009 (M3). On-site measurements were conducted continuously during a year-round period (August 2011 to August 2012). During the observation period, three diurnal cycles were also measured. In addition, a targeted laboratory experiment was conducted to make up for the few measurements in winter. A large pulse of N2O emissions related to freeze-thaw cycles was observed at M3 during the spring thaw. Results showed that the meadow-steppes played a role as a sink for CH4 and a source for N2O. Significantly lower mean CH4 uptake at UM (40.3 μg C·m-2·h-1) as compared to M3 (70.5 μg C ·m-2·h-1) (p<0.01), and significantly higher mean N2O efflux at UM (6.3 μg N·m-2·h-1) as compared to M3 (4.3 μg N·m-2·h-1) (p<0.05) were found. The laboratory experiment results revealed that mowing changed the soil conditions that favor the activity of denitrifiers during thawing periods. The CH4 and N2O fluxes were significantly correlated with soil temperature (p<0.05). Mowing affected CH4 uptake and N2O emission mainly through its effect on vegetation types and some soil properties, such as soil inorganic N content, soil temperature, and soil moisture content, while soil inorganic N and moisture were not leading factors. Our results also suggested that mowing could mitigate the potential global warming in terms of CH4 uptake and N2O emissions.
Climate change affects the heat and water resources required by agriculture, thus shifting cropping rotation and intensity. Shanghai is located in the Taihu Lake basin, a transition zone for various cropping systems. In the basin, moderate climate changes can cause major shifts in cropping intensity and rotation. In the present study, we integrated observational climate data, one regional climate model, land use maps, and agricultural statistics to analyze the relationship between heat resources and multi-cropping potential in Shanghai. The results of agro-climatic assessment showed that climate change over the past 50 years has significantly enhanced regional agro-climatic resources, rendering a shift from double cropping to triple cropping possible. However, a downward trend is evident in the actual multi-cropping index, caused principally by the increasing costs of farming and limitations in the supply of labor. We argue that improving the utilization rate of the enhanced agro-climatic resources is possible by introducing new combinations of cultivars, adopting more laborsaving technologies, and providing incentives to farmers.
The Jilantai Salt Lake (JSL), a lake of importance due to its salt production in China since the early Qing dynasty, is surrounded by sand dunes. Exploration of the development of these sand dunes will be helpful for identifying the forces underlying the desert landscape and for identifying a solution to protect the salt resources. Through field investigation, we found sand dunes overlying either lacustrine and bog deposits on the lake bed at a lower altitude or littoral sediments on the higher lakeshores. Optically Stimulated Luminescence (OSL) dating results indicate that sands started to accumulate around the JSL as early as the early Holocene (around 11 ka), while the rapid development of sand dunes occurred within the latest 0.1 ka. By comparison with climatic documents and human activities in adjacent regions, the initiation of sand accumulation around the JSL as early as the early Holocene is considered to be the result of low effective moisture in the Jilantai area. However, the rapid development of the sand dunes in the vast area surrounding the JSL was likely initiated by the intensified human activities which occurred within the latest 0.1 ka under warm and dry climatic conditions.
The morphology in the Liaodong Bay has undergone a marked change over the past decades due to the cutoff of nearby rivers. The fine sediment of the bay consists of both non-cohesive and cohesive fractions with relatively small particles over the seabed. Thus, a three-dimensional morphodynamic model accounting for non-cohesive and cohesive fractions is established to investigate the morphological change without sediment input from nearby rivers. A representative wave is chosen to compute the wave distribution in the Liaodong Bay and depth-dependent wave radiation stresses are employed by the hydrodynamic model. The advection-diffusion equation is used to simulate the fine sediment transport under the representative wave and tidal currents. The erosion flux of non-cohesive and cohesive sediment is taken into account. The simulated results of tidal level, velocities, directions, and sediment concentrations are in agreement with the measured data. The results demonstrate that the present model, which takes the erosion flux of both non-cohesive and cohesive fractions into account, gives more reasonable values than when accounting for cohesive sediment alone. When the three-dimensional morphodynamic model is applied to predict morphological change over the course of a year, the deposition is shown to be relatively small and the range of the erosion is increased compared to previous results of sediment input from the river. It can be concluded that the erosion in the Liaodong Bay is increasing due to the cutoff of the river, and that morphological evolution must be taken into account if any type of coastal construction plans are to be carried out over the seabed.
This paper presents a new method for recovering paleoporosity of sandstone reservoirs and quantitatively defines the evolution process of porosity. This method is based on the principle that the present is the key to the past. We take the middle Es3 member in Niuzhuang Sag, Dongying Depression, and Bohai Bay Basin as an example. The method used in this study considers the present porosity as a constraint condition, and the influences of both constructive diagenesis and destructive diagenesis to divide the porosity evolution process into two independent processes, namely porosity increase and porosity decrease. An evolution model of sandstone porosity can be established by combining both the pore increase and pore decrease effects. Our study reveals that the porosity decrease model is a continuous function of burial depth and burial time, whereas the porosity increase model mainly occurs in an acidified window for paleotemperature of 70°C to 90°C. The porosity evolution process can be divided into the following phases: normal compaction, acidification and pore increase, and post-acidification compaction. Thus, the porosity evolution model becomes a piecewise function of three subsections. Examples show that the method can be applied effectively in recovering the paleoporosity of sandstone reservoirs and simulating the porosity evolution process.
Quantifying and mapping the distribution patterns of ecosystem services can help to ascertain which services should be protected and where investments should be directed to improve synergies and reduce trade-offs. Moreover, the indicators of urbanization that affect the provision of ecosystem services must be identified to determine which approach to adopt in formulating policies related to these services. This paper presents a case study that maps the distribution of multiple ecosystem services and analyzes the ways in which they interact. The relationship between the supply of ecosystem services and the socio-economic development in the Taihu Lake Basin of eastern China is also revealed. Results show a significant negative relationship between crop production and tourism income (p<0.005) and a positive relationship between crop production, nutrient retention, and carbon sequestration (p<0.005). The negative effects of the urbanization process on providing and regulating services are also identified through a comparison of the ecosystem services in large and small cities. Regression analysis was used to compare and elucidate the relative significance of the selected urbanization factors to ecosystem services. The results indicate that urbanization level is the most substantial factor inversely correlated with crop production (R2 = 0.414) and nutrient retention services (R2 = 0.572). Population density is the most important factor that negatively affects carbon sequestration (R2 = 0.447). The findings of this study suggest the potential relevance of ecosystem service dynamics to urbanization management and decision making.
In this research, a new method is developed to determine the optimal contract load for a hydropower reservoir, which is achieved by incorporating environmental flows into the determination process to increase hydropower revenues, while mitigating the negative impacts of hydropower generation on riverine ecosystems. In this method, the degree of natural flow regime alteration is adopted as a constraint of hydropower generation to protect riverine ecosystems, and the maximization of mean annual revenue is set as the optimization objective. The contract load in each month and the associated reservoir operating parameters were simultaneously optimized by a genetic algorithm. The proposed method was applied to China’s Wangkuai Reservoir to test its effectiveness. The new method offers two advantages over traditional studies. First, it takes into account both the economic benefits and the ecological needs of riverine systems, rather than only the economic benefits, as in previous methods. Second, although many measures have been established to mitigate the negative ecological impacts of hydropower generation, few have been applied to the hydropower planning stage. Thus, since the contract load is an important planning parameter for hydropower generation, influencing both economic benefits and riverine ecosystem protection, this new method could provide guidelines for the establishment of river protection measures at the hydropower planning stage.
Rhizomes are essential organs for growth and expansion of Phragmites australis. They function as an important source of organic matter and as a nutrient source, especially in the artificial land-water transitional zones (ALWTZs) of shallow lakes. In this study, decomposition experiments on 1- to 6-year-old P. australis rhizomes were conducted in the ALWTZ of Lake Baiyangdian to evaluate the contribution of the rhizomes to organic matter accumulation and nutrient release. Mass loss and changes in nutrient content were measured after 3, 7, 15, 30, 60, 90, 120, and 180 days. The decomposition process was modeled with a composite exponential model. The Pearson correlation analysis was used to analyze the relationships between mass loss and litter quality factors. A multiple stepwise regression model was utilized to determine the dominant factors that affect mass loss. Results showed that the decomposition rates in water were significantly higher than those in soil for 1- to 6-year-old rhizomes. However, the sequence of decomposition rates was identical in both water and soil. Significant relationships between mass loss and litter quality factors were observed at a later stage, and P-related factors proved to have a more significant impact than N-related factors on mass loss. According to multiple stepwise models, the C/P ratio was found to be the dominant factor affecting the mass loss in water, and the C/N and C/P ratios were the main factors affecting the mass loss in soil. The combined effects of harvesting, ditch broadening, and control of water depth should be considered for lake administrators.
In general, coastal habitat conditions are extremely harsh, with the ecological equilibrium inextricably related to the plant community. Understanding the natural vegetation features of a coastal zone with little human disturbance could provide a reference for future vegetation restoration and ecosystem maintenance services. In this study, the vegetation patterns of Wangzi Shell Ridge Island in the Yellow River Delta were investigated. A total of 35 taxa of vascular plants were documented, representing 15 families and 33 genera (of which most were mono-specific). Surveys identified only one to eight taxa in each plot. From sea to land, the vegetation showed a typical zonal distribution pattern. There was a correlation between the landform and important factors that influenced the plants including soil factors and distance from the sea. Thus, the taxa distribution and vegetation had a significant correlation with landform. The dune crest, backdune and interdune lowlands were areas with weak storm surges and were the important locations for the taxa to be become established. Plants along the high-tide line formed important defenses from large waves and high winds. The significant protection provided a suitable living environment for many organisms with high medicinal value. Special attention and protection could be provided to this area by reducing the use of the beach road and enclosing the complete section from sea to land with a protective fence. In addition, vegetation protection and restoration on Shell Ridge Island would aid in the formulation and implementation of reintroduction strategies for similar vegetation in similar habitats.
The Qiandao Lake Area (QLA) is of great significance in terms of drinking water supply in East Coast China as well as a nationally renowned tourist attraction. A series of laws and regulations regarding the QLA environment have been enacted and implemented throughout the past decade with the aim of negating the harmful effects associated with expanding urbanization and industrialization. In this research, an assessment framework was developed to analyze the eco-environmental vulnerability of the QLA from 1990–2010 by integrating fuzzy analytic hierarchy process (FAHP) and geographical information systems (GIS) in an attempt to gain insights into the status quo of the QLA so as to review and evaluate the effectiveness of the related policies. After processing and analyzing the temporal and spatial variation of eco-environmental vulnerability and major environmental issues in the QLA, we found that the state of eco-environmental vulnerability of the QLA was acceptable, though a moderate deterioration was detected during the study period. Furthermore, analysis of the combination of vulnerability and water quality indicated that the water quality showed signs of declination, though the overall status remained satisfactory. It was hence concluded that the collective protection and treatment actions were effective over the study period, whereas immediately stricter measures would be required for protecting the drinking water quality from domestic sewage and industrial wastewater. Finally, the spatial variation of the eco-environmental vulnerability assessment also implied that specifically more targeted measures should be adopted in respective regions for long-term sustainable development of the QLA.