A microphysical investigation of different convective cells during the precipitation event with sustained high-resolution observations

The growth and breakup processes of raindrops within a cloud influence the rain intensity and the sizes of raindrops on the surface.The Doppler velocity spectrum acquired by a vertically pointing radar(VPR)contains information on atmospheric turbulence and the size classification of falling hydrometeors.In this study,the four types of Convective Cells(CC)during precipitation events with more than 700 mm of precipitation in southern China are described.The characteristics of four types of CCs correspond to the isolated convection,the early stage,the mature stage,and the decline stage of organizational convection,in that order.Microphysical analysis using retrieval of vertical air motion(Vair)and raindrop evolution in clouds from Doppler velocity spectra collected by C-band VPR revealed the growth and breakup of falling raindrops with dynamic impact.Larger raindrops appear in the early stages and are accompanied by ice particles,which are impacted by the falling path᾽s downdraft.Raindrop aggregation,which is primarily related to the alternation of updraft and downdraft,accounts for the mature stage᾽s high efficiency of surface rainfall.The CCs in the decline stage originate from the shallow uplift in the weak and broad downdraft under conditions of enough water vapor.The updraft dominates the stage of isolated convection.Observations of convective cells could be more accurately represented in model evaluations.

Predictability and dynamics of the rapid intensification of Super Typhoon Lekima (2019)

This study explores the effect of the initial axisymmetric wind structure and moisture on the predictability of the peak intensity of Typhoon Lekima(2019)through a 20-member ensemble forecast using the WRF model.The ensemble members are separated into Strong and Weak groups according to the maximum 10-m wind speed at 48 h.In our study of Lekima(2019),the initial intensity defined by maximum 10-m wind speed is not a good predictor of the intensity forecast.The peak intensity uncertainty is sensitive to the initial primary circulation outside the radius of maximum wind(RMW)and the initial secondary circulation.With greater absolute angular momentum(AAM)beyond the RMW directly related to stronger primary circulation,and stronger radial inflow,Strong group is found to have larger AAM import in lowlevel,helping to spin up the TC.Initial moisture in innercore is also critical to the intensity predictability through the development of inner-core convection.The aggregation and merger of convection,leading to the TC intensification,is influenced by both radial advection and gradient of system-scale vortex vorticity.Three sensitivity experiments are conducted to study the effect of model uncertainty in terms of model horizontal grid resolution on intensity forecast.The horizontal grid resolution greatly impacts the predictability of Lekima’s intensity,and the finer resolution is helpful to simulate the intensification and capture the observed peak value.

PFC^(2D)-based investigation on the mechanical behavior of anisotropic shale under Brazilian splitting containing two parallel cracks

A validated particle flow code(PFC^(2D))-based model was developed to investigate the indirect tensile mechanical behavior of shale containing two central parallel cracks under Brazilian splitting test conditions.The results show that preexisting cracks have a significant and insignificant influence on the tensile strength of shale under LPL and LVL conditions,respectively.When L≥10 mm,changing the L and H values has little effect on the tensile strength of shale.However,the inclusion of preexisting cracks have a positive effect on reducing the anisotropy of the shale specimens,and in the case of an L/D ratio of 0.3,the shale anisotropy is the lowest.Four failure modes were formed at differentβandθvalues under LPL conditions.In the case ofβ≥60°,the failure mode is mainly affected byβ,and whenβ≤45°,the failure mode is more complicated than in the case ofβ≥60°.Only three major failure modes were observed under LVL conditions;in the case of 45°≤β≤75°andθ≤30°,the most complex failure mode occurred.

Climate change impact and adaptation on wheat yield, water use and water use efficiency at North Nile Delta

Investigation of climate change impacts on food security has become a global hot spot.Even so,efforts to mitigate these issues in arid regions have been insufficient.Thus,in this paper,further research is discussed based on data obtained from various crop and climate models.Two DSSATcrop models(CMs)(CERESWheat and N-Wheat)were calibrated with two wheat cultivars(Gemiza9 and Misr1).A baseline simulation(1981-2010)was compared with different scenarios of simulations using three Global Climate Models(GCMs)for the 2030s,2050s and 2080s.Probable impacts of climate change were assessed using the GCMs and CMs under the high emission Representative Concentration Pathway(RCP8.5).Results predicted decreased wheat grain yields by a mean of 8.7%,11.4%and 13.2%in the 2030s,2050s and 2080s,respectively,relative to the baseline yield.Negative impacts of climatic change are probable,despite some uncertainties within the GCMs(i.e.,2.1%,5.0%and 8.0%)and CMs(i.e.,2.2%,6.0%and 9.2%).Changing the planting date with a scenario of plus or minus 5 or 10 days from the common practice was assessed as a potentially effective adaptation option,which may partially offset the negative impacts of climate change.Delaying the sowing date by 10 days(from 20 November to 30 November)proved the optimum scenario and decreased further reduction in wheat yields resulting from climate change to 5.2%,6.8%and 8.5%in the 2030s,2050s and 2080s,respectively,compared with the 20 November scenario.The planting 5-days earlier scenario showed a decreased impact on climate change adaptation.However,the 10-days early planting scenario increased yield reduction under projected climate change.The cultivar Misr1 was more resistant to rising temperature than Gemiza9.Despite the negative impacts of projected climate change on wheat production,water use efficiency would slightly increase.The ensemble of multi-model estimated impacts and adaptation uncertainties of climate change can assist decision-makers in planning climate adaptation strategies.

Terrain relief periods of loess landforms based on terrain profiles of the Loess Plateau in northern Shaanxi Province,China

The Loess Plateau is densely covered by numerous types of gullies which represent different soil erosion intensities.Therefore,research on topographic variation features of the loess gullies is of great significance to environmental protection and ecological management.Using a5 m digital elevation model and data from a national geographic database,this paper studies different topographical areas of the Loess Plateau,including Shenmu,Suide,Yanchuan,Ganquan,Yijun,and Chunhua,to derive representative gully terrain profile data of the sampled areas.First,the profile data are standardized in MATLAB and then decomposed using the ensemble empirical mode decomposition method.Then,a significance test is performed on the results;the test confidence is 95% to 99%.The most reliable decomposition component is then used to calculate the relief period and size of the gullies.The results showed that relief periods of the Chunhua,Shenmu,Yijun,Yuanchuan,Ganquan,and Suide gullies are 1110.14 m,1096.85 m,1002.49 m,523.48 m,498.12 m,and 270.83 m,respectively.In terms of gully size,the loess landforms are sorted as loess fragmented tableland,aeolian and dune,loess tableland,loess ridge,loess hill and loess ridge,and loess hill,in descending order.Taken together,the gully terrain features of the sample areas and the results of the study are approximately consistent with the actual terrain profiles.Thus,we conclude that ensemble empirical mode decomposition is a reliable method for the study of the relief and topography of loess gullies.

The investigation of fly ash based asphalt binders using atomic force microscope

Atomic Force Microscope （AFM） is a relatively new technique for investigation of construction materials. In this study AFM was used to investigate the interaction of asphalt binder with fly ash. Fly ash is a coal combustion byproduct of electric power utilities having pozzolanic properties and commonly used in Portland cement concrete. In this study, an investigation was made by using different types of fly ash with two types of asphalt binders such as PG 58-28 and PG 64-28. Asphalt microstructure is divided into four subgroups such as Saturates, Aromatics, Resins and Asphaltenes （SARA）. These four phases can be distinguished by the atomic force microscope. The interaction of these phases affected by introducing fly-ash was investigated and correlation with rheological properties was observed.

Temporal and spatial changes of residential land in the Yuyang desert region of northern Shaanxi Province in recent 20 years

It is very important to understand the temporal and spatial changes of residential land for the improvement of human settlement environment. Based on the three TM images of 1986, 1996 and 2005 and other assistant maps, the temporal and spatial characteristics of residential land in the Yuyang desert region of northern Shaanxi Province of China were analyzed by using geographical information System （GIS） and remote sensing （RS） technology. Some important conclusions were obtained, which mainly contained four aspects as follows. 1） The area of residential land in the Yuyang desert region increased 956.07 hm2 in total, and the changes of residential land among the townships were different with four various change trends. The expansion speeds in the Yuyang Township and Qinhe Township were the biggest from 1986 to 1996 and from 1996 to 2005, respectively. The expansion intensities in other townships were below 0.1%, except the Yuyang Township. 2） The number of residential land patches increased 2847, while the average area and perimeter of residential land patches decreased 0.304 hm2 and 60.78 m during 1986-2005, respectively. The residential land patches also displayed four different changes from 1986 to 2005 among the townships. 3） The residential land mainly distributed in the middle of Yuyang Township and Mahe Township, and the interface of Jinjitan Township and Mengjiawan Township. The total spatial pattern of residential land was relative stability, but the significant changes of residential land were found in the Yuyang Township and its vicinities during 1986-2005. 4） Three distribution patterns of residential land at the micro scale were categorized from the 100 typical villages in the study area. The number of villages in the pattern 1 increased, while the pattern 2 and pattern 3 decreased in recent 20 years, which implicated the adaptation of humans to the habitation environment. This research would provide scientific references fbr harmonizing the human-land relationship, optimizing the residential land spatial distribution patterns and constructing the well human settlement environment in the desert regions.

Characteristics and evolution of faults in the north-central Yin’e Basin and the effects on the coal-seam in the Cretaceous strata

Research on the characteristics of faults and their evolutionary history since the Cretaceous in the Suhongtu-Dagu depressions can provide a theoretical basis for geological evaluation of the coal seams in the Suhongtu Formation in the northern-central region of the Yin’e Basin.Using 3-D seismic-logging inversion techniques,seismic stratigraphic calibration,stratigraphic sequence delineation,and thickness calculations on the Suhongtu-Dagu depressions were carried out to clarify the planar and profile distributions of the faults,as well as the evolutionary history of these faults and the tectonic history of the depressions.The results of this study revealed that the distribution of the faults in the Suhongtu-Dagu depressions in the northern part of the Yin’e Basin varies with region,and the fault system was multi-period,orthotropic,north-east-trending,and north-north-east-trending,with a certain degree of inheritance in terms of the geological setting.Three types of faults were identified:Y-shaped fractures,reverse Y-shaped fractures,and parallel fractures,which can be classified as Paleozoic-Cenozoic continuous syncline faults and intra-depression faults from the top of the Permian to the Upper Cretaceous series and inter-stratigraphic adjustment faults within the Cretaceous System,respectively.The evolution of these faults can be divided into three phases:the controlling faults were the faults that existed before the Early Cretaceous and had been active since then;synclinal faults that formed during the Early Cretaceous;and modified faults that formed since the Early Cretaceous.The development and modification of the coal seams in the Cretaceous Suhongtu Formation in the Hari,Kuanzihu,and Babei sags were strongly controlled and influenced by a multi-phase complex fault system.

Research on the pressure variation law and enhancing CBM extraction application effect of CO_(2) phase transition jet coal seam fracturing technology

Due to the limited permeability and high methane content of the majority of China’s coal seams,significant coal mining gas disasters frequently occur.There is an urgent need to artificially improve the permeability of coalbed methane(CBM)reservoirs,enhance the recovery efficiency of CBM and prevent mine gas accidents.As a novel coal rock fracture technology,the CO_(2) phase transition jet(CPTJ)has been widely used due to its advantages of safety and high fragmentation efficiency.In this study,to ascertain the effects of the pressure of CPTJ fracturing,the influence of its jet pressure on cracked coal rock was revealed,and its effect on CBM extraction was clarified.In this research,the law of CPTJ pressure decay with time was investigated using experimental and theoretical methods.Based on the results,the displacement and discrete fracture network law of CPTJ fracturing coal rock under different jet pressure conditions were studied using particle flow code numerical simulation.Finally,field experiments were conducted at the Shamushu coal mine to assess the efficiency of CPTJ in enhancing CBM drainage.The results showed that the pressure of the CPTJ decreased exponentially with time and significantly influenced the number and expansion size of cracks that broke coal rock but not their direction of development.CPTJ technology can effectively increase the number of connected microscopic pores and fractures in CBM reservoirs,strongly increase the CBM drainage flow rate by between 5.2 and 9.8 times,and significantly reduce the CBM drainage decay coefficient by between 73.58%and 88.24%.

Rapid flood inundation mapping by differencing water indices from pre-and post-flood Landsat images

Following flooding disasters,satellite images provide valuable information required for generating flood inundation maps.Multispectral or optical imagery can be used for generating flood maps when the inundated areas are not covered by clouds.We propose a rapid mapping method for identifying inundated areas based on the increase in the water index value between the pre-and post-flood satellite images.Values of the Normalized Difference Water Index(NDWI)and Modified NDWI(MNDWI)will be higher in the post-flood image for flooded areas compared to the pre-flood image.Based on a threshold value,pixels corresponding to the flooded areas can be separated from non-flooded areas.Inundation maps derived from differencing MNDWI values accurately captured the flooded areas.However the output image will be influenced by the choice of the pre-flood image,hence analysts have to avoid selecting pre-flood images acquired in drought or earlier flood years.Also the inundation maps generated using this method have to be overlaid on the post-flood satellite image in order to orient personnel to landscape features.Advantages of the proposed technique are that flood impacted areas can be identified rapidly,and that the pre-existing water bodies can be excluded from the inundation maps.Using pairs of other satellite data,several maps can be generated within a single flood which would enable emergency response agencies to focus on newly flooded areas.

Building damage mapping based on Touzi decomposition using quad-polarimetric ALOS PALSAR data

Building damage assessment is of great significance to disaster monitoring.Polarimetric Synthetic Aperture Radar(SAR)can record the polarization scattering measurement matrix of ground objects and obtain more abundant ground object information,meaning that they can be used for assessing damage to buildings.In this paper,a new approach is proposed to assess building damage using the Touzi incoherent decomposition and SAR-based characteristics of buildings before and after damage.The March 11th,2011 earthquake that struck the coast of northeast Japan serves as the demonstration of the technique using quad-polarimetric ALOS PALSAR data acquired before and after the disaster.The analysis shows that after the buildings are damaged,there is a clear decrease in theαs1(the dominant scattering-type magnitude)components and the degree of this reduction corresponds to the degree of building damage.This means that theαs1 components obtained by Touzi decomposition can effectively reflect the degree of building damage.On this basis,a model based on Touzi decomposition was established to evaluate the degree of damage to buildings,and the accuracy of the model was validated using high-resolution optical data acquired before and after the earthquake.The experimental results show that Touzi decomposition can be effectively used for damage assessment mapping in built-up areas.

Effects of sea level rise on storm surge and waves within the Yangtze River Estuary

Sea level rise (SLR) can cause water depth increase (WDI) and coastal inundation (CI).By applying the coupled FVCOM + SWAN model,this study investigates the potential impacts of WDI and CI,induced by a 1.0 m SLR,on storm surge and waves within the Yangtze River Estuary.A 1.0 m WDI decreases the maximum storm surge by 0.15 m and increases the maximum significant wave height by 0.35 m.The CI effect size is smaller when compared with WDI.CI decreases the maximum storm surge and significant wave height by 0.04 and 0.07 m,respectively.In the near-shore area,WDI significantly alters the local hydrodynamic environment,thereby stimulating changes in maximum storm surges and wave heights.Low-lying regions are negatively impacted by CI.Conversely,in deep-water areas,the relative change in water depth is minimal and the effect of CI is gradually enhanced.The combined effect of WDI and CI decreases the maximum surge by 0.31 m and increases the maximum significant wave height by 0.21 m.As a result,CI may be neglected when designing deep-water infrastructures.Nonetheless,the complex interactions between adoption and neglect of CI should be simulated to achieve the best seawall flood control standards and design parameters.

Scale characters analysis for gully structure in the watersheds of loess landforms based on digital elevation models

Scale is the basic attribute for expressing anddescribing spatial entity and phenomena. It offerstheoretical significance in the study of gully structureinformation, variable characteristics of watershed mor-phology, and development evolution at different scales.This research selected five different areas in China＇s LoessPlateau as the experimental region and used DEM data atdifferent scales as the experimental data. First, the changerule of the characteristic parameters of the data at differentscales was analyzed. The watershed structure informationdid not change along with a change in the data scale. Thiscondition was proven by selecting indices of gullybifurcation ratio and fractal dimension as characteristicparameters of watershed structure information. Then, thechange rule of the characteristic parameters of gullystructure with different analysis scales was analyzed bysetting the scale sequence of analysis at the extractiongully. The gully structure of the watershed changed withvariations in the analysis scale, and the change rule wasobvious when the gully level changed. Finally, the changerule of the characteristic parameters of the gully structure atdifferent areas was analyzed. The gully fractal dimensionshowed a significant numerical difference in differentareas, whereas the variation of the gully branch ratio wassmall. The change rule indicated that the developmentdegree of the gully obviously varied in different regions,but the morphological structure was basically similar.

Evaluation of the environmental impact of the urban energy lifecycle based on lifecycle assessment

Energy resources have environmental impact through their entire lifecycle. The evaluation of the environmental impacts of the energy lifecycle can contribute to decision making regarding energy manage- ment. In this paper, the lifecycle assessment （LCA） method is introduced to calculate the environmental impact loads of different types of energy resources （including coal, oil, natural gas, and electricity） used in urban regions. The scope of LCA includes the production, transportation, and consumption processes. The pollutant emission inventory is listed, and the environmental impact loads are acquired through the calculation of environmental impact potentials, normalization, and weighted assessment. The evaluation method is applied to Beijing, China, revealing that photochemical oxidant formation and acidification are the primary impact factors in the lifecycle of all energy resources and that the total environmental impact load increased steadily from 132.69 million person equivalents （PE） in 1996 to 208.97 million PE in 2010. Among the energy types, coal contributes most to the environmental impact, while the impacts caused by oil, natural gas, and electricity have been growing. The evaluation of the environmental impact of the urban energy lifecycle is useful for regulating energy structures and reducing pollution, which could help achieve sustainable energetic and environmental development.

River basin water resource compensation characteristics by set pair analysis： the Dongiiang example

Flood and drought coexist in many river basins, thus analyses of water resource compensation characteristics become important, since they are the foundation for rational utilization of floodwaters. In this research, set pair analysis （SPA）, a relatively new uncertainty analysis method, is used to study the dry and wet compensation characteristics of water resource para- meters. In addition, fuzzy membership and grey correlation degree are adopted to test the result of set pair analysis. The Dongjiang River is taken as an example and the analyzed parameters include precipitation and mean discharge from different hydrological stations. The results show that there is a high homeotype-encountering chance for precipitation and mean discharge between different stations for both dry and wet conditions; thus the compensation capacity is small. Although the mean discharge is synchronous with the precipitation in the river basin, there exists a certain degree of shift, indicating possible utilization of floodwater on a small scale. The results from SPA are consistent with that from a traditional analysis method, showing that SPA is a promising alternative method for studying river basin water resource compensation characteristics, in particular for exploring potential complements embedded in non- complementary general features.

Intersection delay estimation from floating car data via principal curves： a case study on Beijing＇s road network

It is a pressing task to estimate the real-time travel time on road networks reliably in big cities, even though floating car data has been widely used to reflect the real traffic. Currently floating car data are mainly used to estimate the real-time traffic conditions on road segments, and has done little for turn delay estimation. However, turn delays on road intersections contribute significantly to the overall travel time on road networks in modem cities. In this paper, we present a technical framework to calculate the turn delays on road networks with float car data. First, the original floating car data collected with GPS equipped taxies was cleaned and matched to a street map with a distributed system based on Hadoop and MongoDB. Secondly, the refined trajectory data set was distributed among 96 time intervals （from 0：00 to 23： 59）. All of the intersections where the trajectories passed were connected with the trajectory segments, and constituted an experiment sample, while the intersections on arterial streets were specially selected to form another experiment sample. Thirdly, a principal curve-based algorithm was presented to estimate the turn delays at the given intersections. The algorithm argued is not only statistically fitted the real traffic conditions, but also is insensitive to data sparseness and missing data problems, which currently are almost inevitable with the widely used floating car data collecting technology. We adopted the floating car data collected from March to June in Beijing city in 2011, which contains more than 2.6 million trajectories generated from about 20000 GPS-equipped taxicabs and accounts for about 600 GB in data volume. The result shows the principal curve based algorithm we presented takes precedence over traditional methods, such as mean and median based approaches, and holds a higher estimation accuracy （about 10%-15% higher in RMSE）, as well as reflecting the changing trend of traffic congestion. With the estimation result for the travel delay at intersections, we analyzed the spatio-temporal distribution of turn delays in three time scenarios （0： 00-0： 15, 8： 15-8：30 and 12： 00-12： 15）. It indicates that during one＇s single trip in Beijing, average 60% of the travel time on the road networks is wasted on the intersections, and this situation is even worse in daytime. Although the 400 main intersections take only 2.7% of all the intersections, they occupy about 18% travel time.

An artificial neural network approach to estimate evapotranspiration from remote sensing and AmeriFlux data

A simple and accurate method to estimate evapotranspiration （ET） is essential for dynamic monitor- ing of the Earth system at a large scale. In this paper, we developed an artificial neural network （ANN） model forced by remote sensing and AmeriFlux data to estimate ET. First, the ANN was trained with ET measurements made at 13 AmeriFlux sites and land surface products derived from satellite remotely sensed data （normalized difference vegetation index, land surface temperature and surface net radiation） for the period 2002-2006. ET estimated with the ANN was then validated by ET observed at five AmeriFlux sites during the same period. The validation sites covered five different vegetation types and were not involved in the ANN training. The coefficient of determination （RE） value for comparison between estimated and measured ET was 0.77, the root-mean- square error was 0.62 mm/d, and the mean residual was - 0.28. The simple model developed in this paper captured the seasonal and interannual variation features of ET on the whole. However, the accuracy of estimated ET depended on the vegetation types, among which estimated ET showed the best result for deciduous broadleaf forest compared to the other four vegetation types.

Complementarity of lacustrine pollen and sedimentary DNA in representing vegetation on the central-eastern Tibetan Plateau

Plant environmental DNA extracted from lacustrine sediments(sedimentary DNA,sedDNA)has been increasingly used to investigate past vegetation changes and human impacts at a high taxonomic resolution.However,the representation of vegetation communities surrounding the lake is still unclear.In this study,we compared plant sedDNA metabarcoding and pollen assemblages from 27 lake surface-sediment samples collected from alpine meadow on the central-eastern Tibetan Plateau to investigate the representation of sedDNA data.In general,the identified components of sedDNA are consistent with the counted pollen taxa and local plant communities.Relative to pollen identification,sedDNA data have higher taxonomic resolution,thus providing a potential approach for reconstructing past plant diversity.The sedDNA signal is strongly influenced by local plants while rarely affected by exogenous plants.Because of the overrepresentation of local plants and PCR bias,the abundance of sedDNA sequence types is very variable among sites,and should be treated with caution when investigating past vegetation cover and climate based on sedDNA data.Our finding suggests that sedDNA analysis can be a complementary approach for investigating the presence/absence of past plants and history of human land-use with higher taxonomic resolution.