Spatial Characteristic Scales Research Articles

Characteristic Scales of Magnetic Switchback Patches Near the Sun and Their Possible Association With Solar Supergranulation and Granulation

Abstract Parker Solar Probe (PSP) data recorded within a heliocentric radial distance of 0.3 au have revealed a magnetic field dominated by Alfvénic structures that undergo large local variations or even reversals of the radial magnetic field. They are called magnetic switchbacks, they are consistent with folds in magnetic field lines within a same magnetic sector and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either in the low solar atmosphere through magnetic reconnection processes or result from the evolution of turbulence or velocity shears in the expanding solar wind. In this work, we investigate the temporal and spatial characteristic scales of magnetic switchback patches. We define switchbacks as a deviation from the nominal Parker spiral direction and detect them automatically for PSP encounters 1, 2, 4, and 5. We focus in particular on a 5.1 day interval dominated by switchbacks during E5. We perform a wavelet transform of the solid angle between the magnetic field and the Parker spiral and find periodic spatial modulations with two distinct wavelengths, respectively consistent with solar granulation and supergranulation scales. In addition we find that switchback occurrence and spectral properties seem to depend on the source region of the solar wind rather than on the radial distance of PSP. These results suggest that switchbacks are formed in the low corona and modulated by the solar surface convection pattern.

Impacts of the grain for Green Program on the spatial pattern of land uses and ecosystem services in mountainous settlements in southwest China

The Grain for Green Program which is an important part of the strategy of Western development was initiated to protect the ecological environment and mitigate disasters. The upper reaches of the Min River basin is one of the key pilot regions for Grain for Green Program implementation in the mountainous areas of Sichuan Province, southwestern China. Therefore, monitoring the effect of the Grain for Green Program on the ecosystem services (ESs) in the montainous areas is important. Especially, several authors have emphasized the need to quantify spatial characteristics and evaluate ES values of land uses in mountainous areas from spatial and temporal perspectives. In this study, we firstly analyzed the spatial pattern of land uses in mountainous settlements before and after implementation of Grain for Green Program in the upper reaches of Min River, Sichuan Province of China. Based on lacunarity analysis, we explored the spatial characteristics of land uses including spatial heterogeneityand cluster. The results suggested that the spatial characteristics of land uses occurred at different scales, and there is strong relationship between spatial characteristic scales and the different distribution pattern of land use. We then quantified the relationships between geometrical features for land use pacthes and vegetation habitat suitability by multilevel Bayesian model. We found that the vegetation habitat suitability significantly affected on spatial location, size, and complexity of different land use patches in mountainous settlements. Based on assignment method of ES value per unit area, we finally quantitatively analyzed and compared the changes in ES values of land uses in mountainous settlements caused by Grain for Green Program from spatial and temporal scales. It is an important indicator for defining ecological potential by quantifying the change in ES value. After implementation of Grain for Green Program, the total ES value dramatically increased because of increase in forest and pasture areas. It suggests that the Grain for Green Program could bring effectively ecological benefit on protecting ecosystem functions in some degree. Application of spatial characteristics analysis of land uses and ES valuation in mountainous settlements to study the spatial structure of land use and service supplies should provide a better understanding of service provision and enable evaluation of the ecological integrity of land uses in mountainous areas.

Assessing the high impacts of land use change: spatial characteristics of land uses and ecological compensation based on payment for ecosystem services model in a mountainous area, China

Most impacts on ecosystem services (ESs) are related to land use changes that may cause ecosystem fragmentation and loss of ecosystem functions. Spatial planning focused on sustainable landscape development should consider the local potential for providing ESs as well as ecological conservation due to land use changes. To better address the issues that are related to ecological and the ecological and environmental conservation, ecological compensation could coordinate the development of the energy, the economy, and the environment by internalizing environmental externalities and adjusting for the relationships with stakeholders’ benefits. In this study, we developed a framework for analyzing the spatial characteristics of land uses and calculating ecological compensation based on pay for ecosystem services (PESs) from 1995 to 2010 in the upstream of Min River, China. In terms of lacunarity analysis, we firstly explored the spatial patterns of land uses in these two periods that occurred at different spatial characteristic scales. We also observed a strong relationship between lacunarity values and the different distribution patterns of land uses. We then investigated changes in ESs in response to land use change through the assignment of per unit area ecological service value (ESV) method. The total value of ESs dropped from 449.97 billion yuan in 1995 to 441.35 billion yuan in 2010, exhibiting decreasing rate, mainly due to the degradation of woodlands. Soil formation and retention, gas regulation, and biodiversity protection were the three largest ESs, contributing about 50% of the total ESV. Considering the changed relation between social and economic indicators and ESV based on spatial visualization and analysis, we finally constructed a quantitative estimate model for ecological compensation taking a village as study unit and determined standard value so as to evaluate ecological compensation from 1995 to 2010. Spatial differences of the ecological compensation were significant among all the villages and towns. The maximum ecological compensation account (ranged from 1.68 to 8.54 billion yuan) appeared in the villages approximated to Li County, Heishui County, and Songpan County, Sichuan, People’s Republic of China. This proposed framework provides a better understanding of spatial characteristic scales of land uses and enables evaluation of the ecological integrity of landscapes. It also fills up the gap in the field of quantitative evaluation of regional ecological compensation and provides a feasible way to reconcile the conflicts among benefits in the economic, social, and ecological sectors.

Spatial characteristics of land uses and ecological compensations based on payment for ecosystem services model from 2000 to 2015 in Sichuan Province, China

The ecosystem services provision is constantly under threat by anthropogenic pressures, especially which is mainly related to land use changes. A solution proposed to address these issues is the implementation of spatial characteristics of land uses and ecological compensation (based on Payment for Ecosystem Services) programs. In this study, we developed a framework for analyzing the spatial characteristics of land uses and calculating ecological compensation from 2000 to 2015 in Sichuan Province, China. We firstly examined the utility of lacunarity analysis for detecting spatial characteristic scales of pattern of land uses. Due to large-scale and regular distribution, the spatial heterogeneity of cropland, woodland and grassland were higher than that of water body, construction land and unused land. We then investigated changes in ecosystem services in response to land use change through assignment of per unit area ecosystem service value method. The total ecosystem service value is about 10,780 billion yuan·year−1, and the woodland and grassland ecosystems contributed more to the total ecosystem service value. The critical areas (with higher ecosystem service value) for management purpose were identified depending on the heterogeneity of use services learned from spatially explicit measures. Considering the changed relationship between social and economic indicators and ecosystem service value based on spatial visualization and analysis, we finally constructed a quantitative estimate model for ecological compensation taking city (state) as study unit, and determined standard value so as to evaluate ecological compensation from 2000 to 2015. Spatial differences of the ecological compensation were significant among all the cities (states). The average payment standards of ecological compensation based on the population, ecological compensation based on city (state) area, and corrected ecological compensation were − 117.10 billion yuan, 4.41E-13 billion yuan, and − 58.55 billion yuan, respectively. The negative values suggested that the stakeholders of Sichuan Province should pay for ecological compensation, and the positive value meant the residents in the Sichuan Province can obtain the amount of ecological compensation. This proposed innovative framework provides a better understanding of spatial characteristic scales of land uses and enables evaluation of the ecological integrity of landscapes. It also fills up the gap in the field of quantitative evaluation of regional ecological compensation and provides a feasible way to reconcile the conflicts among benefits in the economic, social and ecological sectors.

Kinetic analysis of the ionization ratio effects on a three‐species plasma

In partially ionized plasmas, the energy transferred to electrically charged species by the electromagnetic field can be partly channelized to the population of neutrals, due to interspecies collisional processes. Depending on the relative density of neutrals, these effects may govern the collective plasma dynamics by drastically modifying particle dynamics and energy‐transport processes with respect to the fully ionized plasma‐approximation models. In this work, the influence of the ionization ratio ri on a partially ionized plasma is analysed by means of a three‐species one‐dimensional kinetic model to compute transient and steady state velocity‐dependent distribution functions. The conservative collision operators accounting for charge–charge and charge–neutral interactions allow studying several plasma scenarios with the same entire number of particles per unit of volume but for an increasing ri parameter, in the presence of a modulated signal‐like electric field. For a sequence of plasma scenarios of fixed ri, ranging from typical weakly ionized to highly ionized plasma values ri ∼ 10−7–10−4, the mass species flows are examined. These flows behave linearly with respect to ri up to a value ri ≃ 10−5 from which the quasi‐linear dependence is critically altered. The convection–diffusion equations are solved with the semianalytical Propagator Integral Method, which behaves well to deal with conservative operators, density, and field discontinuities, allowing for the use of collision terms of disparate time and spatial characteristic scales. The results can be relevant to a wide class of plasma systems and to analyse the ionization ratio effects on transport coefficients.

Horizontal spatial correlation of the ionospheric TEC derived from GPS global ionospheric maps

The spatial correlations of ionospheric day-to-day variability are investigated by statistical analysis on TEC production that provided by the Jet Propulsion Laboratory (JPL). First, we use the monthly-averaged TEC over the world to calculate the deviation of the TEC and then the spatial correlation coefficient matrix of the deviation is also derived. According to the definition of correlation distance in statistics, the spatial characteristic scale is retrieved in the Zonal and meridian directions, and their variation of solar activity levels, geomagnetic field configuration conditions and seasonal conditions are investigated in details. Our study indicates strong correlations between geomagnetic conjugate points, which are large at low-latitudes than at mid-latitudes. Furthermore, in the equatorial anomaly region, due to the process of forming double crest structure, the electron distribution at low-latitudes will be affected by the upwelling of the plasma, thus the anomaly of correlation scale is notable. The correlation scale, which usually increases in LT 6:00, peaks at LT 12:00 and LT 14:00 and then decreases. It is overall larger in the daytime and smaller in the nighttime. These spatial correlations are important for understanding the physical mechanisms that cause ionospheric weather variability. For the potential application in development of ionospheric data assimilation model, the spatial correlations are fitted by elliptic Gaussian formula scale. In general, the correlation scale is regressed better in the Zonal direction than in the Meridional direction, better in low-latitude than in middle-latitude, and better in spring and autumn than in winter and summer. These results can help us to accurately construct the background field error covariance matrix in ionospheric data assimilation.

Assessing high impacts of climate change: spatial characteristics and relationships of hydrological ecosystem services in northern Japan (Teshio River watershed)

Ecosystem services (ESs) provide information on the tendency of ecosystems to reach and form a state of equilibrium. The process of ES changes is important in order to identify the climate change-related causes that occur regionally to globally. ES-based management plays an important role in mitigation strategies for the negative impact of global climate change on ecosystem. Therefore, it is necessary to evaluate spatial characteristics and relationships among these multiple services from different spatial scales which could aid in multiple ES sustainable development from local to global scales. In this study, we developed a framework for analyzing the spatial characteristics and interactive relationships of multiple ESs. We analyzed the spatial distributions of six hydrological ESs that are important in the northernmost part of Japan (Teshio River watershed) by using hydrology and nutrient model (Soil and Water Assessment Tool, SWAT) under baseline climate conditions and climate change derived from the global circulation model (GCM). We then explored the spatial characteristic scales of ESs by multiscale analysis (lacunarity estimation) to reveal provision flow and spatial distribution characteristics for hydrological ESs. We observed a strong relationship between the spatial characteristics of land uses and ES provision. The spatial characteristics of individual hydrological ESs were totally different and had different spatial homogeneity and cluster (indicated by initial lacunarity index and lacunarity dimension). The results also showed trade-offs between inorganic nutrient retention (provision ESs) and organic nutrient and sediment retentions (regulating ESs), and synergies between organic nutrient retention and sediment retention under all climate change scenarios. The different stakeholders will take different mitigation programs (e.g., establishing riparian vegetation, planning nutrient management practices, and integrating climate change model into systematic conservation planning of ESs) to avoid negative impacts of climate change on ESs. Application of this proposed framework to study the spatial characteristics and relationships of hydrological ESs under climate change could provide understanding on the impact of climate change on ES changes and solutions to mitigate strategies to cope with those changes in the future.

An experimental study of a turbulent jet impinging on a flat surface

The flow characteristics of an isothermal turbulent jet impinging normally on a flat plate was studied experimentally using hot-wire anemometry. The air jet discharged from a round pipe with an inner diameter D and the distance between the pipe exit and the flat impingement plate was 9D. The Reynolds number, based on the jet centerline velocity at pipe exit and the pipe inner diameter, was 10,338. Measurements were performed in the free- and wall-jets, mean velocity, RMS, Reynolds shear stress, higher-order moments of velocity fluctuations, dissipation spectrum as well as spatial characteristic scale results being presented. Moreover, a multiscale analysis method based on wavelet transform was applied to gain deeper insight into the multiscale turbulent structures and to extract the most essential scales governing the development of the turbulent flow structures of the impinging jet. The experimental results show that the normal velocity fluctuations have the greatest skewness and the highest intermittency in the mixing region and this characteristic is more prominent downstream the pipe exit. The radial velocity fluctuations at a small distance from the flat surface trend towards Gaussian values far away the jet centerline. The strongest dissipation structures grows with larger scales and lower frequencies far away from the pipe exit, and the frequency range of the dissipation structures is reduced far away from the jet centerline together with the spatial distribution of the dissipation structures expanding with larger scales and lower frequencies. The scales in the center of the mixing region have the most energy, from which the scales belonging to the inertial range have a trend to shift to the larger scales with the increasing radial traverse, thus the scales of the coherent structures belonging to the dissipation region get more as well as larger. The scales belonging to the inertial range in the wall-jet region tend to the larger scales with the increasing normal traverse.

Large-scale periodicity in the distribution of QSO absorption-line systems

The spatial-temporal distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is investigated on the base of our updated catalog of absorption systems. We consider so called metallic systems including basically lines of heavy elements. The sample of the data displays regular variations (with amplitudes ~ 15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution, where eta is a dimensionless line-of-sight comoving distance, relatively to smoother dependences. The eta-distribution reveals the periodicity with period Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20) h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a spatial interpretation of the results treating the pattern obtained as a trace of an order imprinted on the galaxy clustering in the early Universe.

Characteristic space scales and timescales in hydrology

We analyzed spatial and temporal variograms of precipitation, runoff, and groundwater levels in Austria to examine whether characteristic scales exist and, if so, how big they are. In time, precipitation and runoff are stationary with characteristic scales on the order of a day and a month, respectively, while groundwater levels are nonstationary. In space, precipitation is almost fractal, so no characteristic scales exist. Runoff is nonstationary but not a fractal as it exhibits a break in the variograms. An analysis of the variograms of catchment precipitation indicates that this break is due to aggregation effects imposed by the catchment area. A spatial variogram of hypothetical point runoff back calculated from runoff variograms of three catchment size classes using aggregation statistics (regularization) is almost stationary and exhibits shorter characteristic space scales than catchment runoff. Groundwater levels are nonstationary in space, exhibiting shorter‐scale variability than precipitation and runoff, but are also not fractal as there is a break in the variogram. We suggest that the decrease of spatial characteristic scales from catchment precipitation to runoff and to groundwater is the result of a superposition of small‐scale variability of catchment and aquifer properties on the rainfall forcing. For comparison, TDR soil moisture data from a comprehensive Australian data set were examined. These data suggest that in time, soil moisture is close to stationary with characteristic scales of the order of 2 weeks while in space soil moisture is nonstationary and close to fractal over the extent sampled. Space‐time traces of characteristic scales fit well into a conceptual diagram of Blöschl and Sivapalan [1995]. The scaling exponents z in T ∼ Lz (where T is time and L is space) are of the order of 0.5 for precipitation, 0.8 for runoff from small catchments, 1.2 for runoff from large catchments, 0.8 for groundwater levels, and 0.5 for soil moisture.