Cover Ratio Research Articles

Agrivoltaic: How much electricity could photovoltaic greenhouses supply?

In regions where the land available is scarce it is of special interest to deploy agrivoltaic systems. The combined use of greenhouses to produce food and energy at the same time increases farmers’ income, converting farming into a more attractive sector. The farming sector could benefit from agrivoltaic, since farmers could profit from a double source of incoming: vegetables and energy. The aim of this research is to establish how relevant agrivoltaic can be in terms of energy production at regional scale. For this purpose, a methodology is developed to: (i) identify greenhouses using cartographic information systems, (ii) estimate how much of these areas could be covered by solar photovoltaic panels without decreasing the crops production, thus, estimating the optimal photovoltaic cover ratio for different type of crops under different solar conditions by developing a novel set of equations and (iii) evaluate the corresponding photovoltaic power and production. This methodology has been applied to one regional practical case, the Canary Islands, and the results are surprising in terms of the potentiality of agrivoltaic, which could cover rates as high as 30% of the annual regional electricity demand depending on, among others, the transmittance value of the greenhouse material and the adequate determination of the cover ratio.

Design and Application of Zero Poisson Large Deformation Superstructure

The variant wing can adapt to more complicated operating environment. There often need large thickness deformation and wingspan change in the process of wing deformation. Meanwhile, the deformation process should not affect other components, which requires that both the wing structure and the outer panel cover have the function of zero poisson’s ratio and large deformation. For this reason, this work designed a two-dimensional poisson’s ratio structure based on the topology optimization and variable density method. Then, optimization design method was adopted to meet the demand of zero poisson’s ratio and large deformation of wing cover. Furthermore, the equivalent elastic tensor of zero poisson’s ratio structure with large deformation was predicted using energy homogenization method, and the mechanical properties of zero poisson’s ratio structure were verified. Finally, numerical simulation method was conducted to predict the mechanical properties of zero poisson’s ratio wing covering lattice structure. To summarize, a kind of wing cover structure with zero poisson’s ratio and large deformation in this study was obtained and the application of this structure in aerospace was also demonstrated.

Seasonal hydrogen storage for residential on- and off-grid solar photovoltaics prosumer applications: Revolutionary solution or niche market for the energy transition until 2050?

Appropriate climate change mitigation requires solutions for all actors of the energy system. The residential sector is a major part of the energy system and solutions for the implementation of a seasonal hydrogen storage system in residential houses has been increasingly discussed. A global analysis of prosumer systems including seasonal hydrogen storage with water electrolyser, hydrogen compressor, storage tank, and a fuel cell studying the role of such a seasonal household storage in the upcoming decades is not available. This study aims to close this research gap via the improved LUT-PROSUME model, which models a fully micro sector coupled residential photovoltaic prosumer system with linear optimisation for 145 regions globally. The modelling of the cost development of hydrogen storage components allows for the simulation of a residential system from 2020 until 2050 in 5-year steps in hourly resolution. The systems are cost-optimised for either on– or off-grid operation in eight scenarios including battery electric vehicles, which can act as an additional vehicle-to-home electricity storage for the system. Results show that implementation of seasonal hydrogen systems only occurs in least cost solutions in high latitude countries when the system is forced to run in off-grid mode. In general, a solar photovoltaic plus battery system including technologies that can cover the heat demand is the most economic choice and can even achieve lower cost than a full grid supply in off-grid operation for most regions until 2050. Additional parameters including the self-consumption ratio, the demand cover ratio, and the heat cover ratio can therefore not be improved by seasonal storage systems if economics is the main deciding factor for a respective system. Further research opportunities and possible limitations of the system are then identified.

The evaluation of the nutritional quality of common wild edible fungi in Yunnan Province

There are huge resource reserves of wild edible fungi richer in their varieties in Yunnan Province which is located on plateau of low latitude and possesses unique various climate environments and bigger vegetative cover ratios. Moreover, nutrients and flavor substances in the same or various species of wild edible fungi differ greatly with the influence on different components from habitats and geographic areas. So, 5 common wild edible fungi were collected from different areas in Yunnan Province, and several findings were made from this research. Above all, through the evaluation of amino acids, these 5 fungi met the criteria for ideal protein by WHO/FAO, and the nutritional value of protein was ranked as matsutake>truffle>collybia albuminosa>bolete>chanterelle. Next, after the analysis of taste activity values, the ranking of taste was bolete>collybia albuminosa>truffle>matsutake>chanterelle. Subsequently, the ranking of characters was truffle>collybia albuminosa >bolete>matsutake>chanterelle through principal component analysis. Finally, truffle could be completely divided by Fisher discrimination analysis with a bigger difference from others, main in ash, protein, sugar, and polysaccharide, meanwhile, truffle and bolete could be completely divided by orthogonal projections to latent structures discrimination analysis, main in protein, crude fiber, fat, and amino acid. So, there was a more conspicuous difference in nutrients among fungi, through which nutrients combined with multivariate statistics analysis made possible the correct differentiation of small range categories in wild edible fungi, and the correct classification of small range of them could effectively be realized.

Richness of arbuscular mycorrhizal fungi increases with ecosystem degradation of temperate eucalypt woodlands

PurposeDegraded ecosystems can be maintained by abiotic and biotic legacies long after initial disturbances, preventing recovery. These legacies can include changes in arbuscular mycorrhizal fungi (AMF). To inform potential restoration pathways, we aimed to elucidate differences in AMF between intact and degraded ecosystems, their responses to modified soils, and interactions with invasive plants.MethodsWe used a state-and-transition framework to characterise AMF communities, native and exotic plant cover, and soil physicochemical properties across little-modified reference states and degraded states, which were carbon (C) and nitrogen (N) -depleted, intermediate, and CN-enriched, in temperate eucalypt woodlands of south-eastern Australia.ResultsMost ground-layer states differed significantly in their AMF communities, with the CN-enriched states being most distinct. All states had unique taxa and characteristic indicator taxa, but intermediate and CN-enriched states harboured four-to-five times more indicator taxa than the reference state. Consistent with this, richness of AMF was higher in the intermediate and CN-enriched states than in reference states, driven by higher richness of Archaeosporaceae, Diversisporaceae, Glomeraceae, and Paraglomeraceae. Pathway analysis indicated that differences in AMF communities among states were strongly related to differences in native:exotic plant cover ratio, mediated by soil organic matter and nutrients.ConclusionOur results indicate that ecosystem degradation is associated with both loss of AMF taxa and introduction of ‘weedy’ AMF, which in turn potentially contribute to maintenance of degraded ecosystems. We argue that our state-and-transition approach to characterising AMF communities improved our understanding of the different pathways of degradation, elucidating possible constraints to ecosystem recovery.

Fractional vegetation cover ratio estimated from radiative transfer modeling outperforms spectral indices to assess fire severity in several Mediterranean plant communities

The obtention of wall-to-wall fire severity estimates through reliable remote sensing-based techniques that align with management needs is a critical factor in post-fire decision-making processes. In this paper, we novelty proposed a multi-date change detection framework based on the variation in fractional vegetation cover (FCOVER), with enough ecological sense and physical basis to be generalizable across different plant communities and burned landscapes with varying environmental conditions. This framework meets the definition of fire severity operationally used in the field as a biophysical indicator when fire effects on the understory and overstory layers are linked. The FCOVER was retrieved from Sentinel-2 surface reflectance scenes by inverting PROSAIL-D radiative transfer model (RTM) simulations using the random forest regression algorithm. FCOVER retrievals were validated in the field using burned and unburned control plots. We computed the FCOVERr metric as the ratio of post-fire to pre-fire FCOVER. We tested the relationship of the FCOVERr and the most common bi-temporal spectral indices in the literature, i.e. the differenced Normalized Burn Ratio (dNBR), the Relative dNBR (RdNBR) and the Relativized Burn Ratio (RBR), with the Composite Burn Index (CBI) measured in field plots for validation purposes in two case-study wildfires in the western Mediterranean Basin. We also calculated the transferability of FCOVERr and the spectral indices between different plant communities within each site, as well as between sites. The predictive errors of pre and post-fire FCOVER retrievals were found to be low (RMSE ≈ 10%) for the two study sites. Overall, the FCOVERr metric provided more accurate CBI estimations (R2 = 0.87 ± 0.04) than spectral indices (R2 = 0.71 ± 0.13). The CBI was linearly related with the FCOVERr metric for both sites, whereas the type of relationship with spectral indices was not consistent, which translated into better transferability performance of the FCOVERr metric (nRMSE = 14.27% ± 3.75%) than that of the spectral indices (nRMSE = 21.97% ± 8.09%), not only between different Mediterranean plant communities within sites, but also between the two sites. Spectral indices underestimated moderate to high fire severity to a greater extent than FCOVERr in the CBI field plots, and misclassified fire severity in several areas with patchiness fire effects identified in the field. The FCOVERr product proposed in this study may be a sound choice for the operational identification of priority areas for post-fire management.

Analisis Kesesuaian Penggunaan Lahan pada Sempadan Danau Batur, Provinsi Bali

Batur lake is one of the lakes designated as world cultural heritage considering the importance and role of Batur lake and its environment culturally, economically and ecologically. Various activities from various sectors grow around Batur lake which could change the land use and have a negative impact on the panorama of the lake. Therefore, this study aims to determine the boundary of Batur lake viewed from the development of water level rise to describe the suitability of land use in the Batur lake border, as well as to develop strategies for land use mismatches that occur. Data were collected through primary and secondary surveys. Statistical-descriptive analysis techniques in the form of data processing digitization with geospatial information systems and land use evaluations were carried out based on land suitability analysis, followed by comparing existing land use with the direction of activities in related regulations. Results shows the direction of land suitability on Batur lake border, are the buffer area and the development of annual plants. The land cover ratio of each direction is still in accordance with the maximum limit. In addition, there are land uses that are not suitable, such as plantation agriculture and non-annual crops, as well as trade and services, in the form of tourism accommodation.

The impacts of carbon trading policy on China's low-carbon economy based on county-level perspectives

Under the background of “carbon peak” and “carbon neutrality”, the important role of Carbon Trading Policy (CTP) played in China's micro-level low-carbon economy cannot be ignored. However, discussions on the CTP's impacts on China's county-level low-carbon economic quality are insufficient due to limited data availability. Hence, this paper estimated the quality of China's county-level quality of low-carbon economy based on satellite data during 2006–2018. In particular, the quality of low-carbon economy was evaluated by the ratio of low-carbon GDP to real GDP, which considers forest carbon sinks, CO2 emissions and real gross domestic product revised by the nighttime light data. Subsequently, this study examined how CTP affected China's county-level low-carbon economy using difference-in-difference-in difference (DDD) method. The results show that (1) CTP significantly improved the quality of low-carbon economy in county-level regions with high proportion of high-emissions energy consumption or secondary industry's output; (2) mechanism analysis shows that administrative intervention currently promoted the quality of low-carbon economy, while the market mechanism had lagged and positive effects; and (3) the ratio of forest land cover to total land cover and technological progress were also significant channels for CTP to improve the quality of low-carbon economy.

Solar Tracker: Performance Analysis and Optimisation of Efficiency

Solar energy is one of the richest source of renewable energy on Earth, thus its harnessing is very much necessary for the useful conversion of light energy into electric energy. Solar panels are developed in this direction. Many scientists have developed various methods to gather the solar irradiation in order to maximize the extraction of electric power from the Photovoltaic generators. However, the problem with the solar power is that it is directly dependent on light intensity. The main hindrance with solar panels is their low efficiency with huge investment. Studies show that a solar panel converts 20-40% of energy incident on it to electrical energy. The solution is to use a tracking system1, 7 that maintains the panel’s position orthogonal with the light source. There are many tracking systems designs available including passive and active systems with one or two axes of freedom.8, 9 It has been found that the overall efficiency gain in single-axis solar tracker designed in10 is 27% than that of fixed mechanism. We had optimised the tracker efficiency by performing the experiment with solar tracker for consecutive three days and thus results were analysed by using stat-ease software. Moreover, the testing showed that the power used by the tracking system was much less than that of power gained by tracking system. While working on the developed set-up, focus was given on the incremental efficiency of the solar power generation system. In the present work, further performance analysis is taken up with the help of various parameters viz. Specific Energy Production (SEP), Performance Ratio (PR), Ground Cover Ratio (GCR) and Surface Performance Ratio (SPR)11 to further elaborate the efficiency enhancement in solar trackers as compared to fixed systems.

The 30-year impact of post-windthrow management on the forest regeneration process in northern Japan

The frequency and intensity of typhoons are expected to increase over time due to climate change. These changes may expose forests to more windthrow in the future, and increasing the resilience of hemiboreal forests through forest management after windthrow is important. Here, we quantified forest structure recovery using aerial photos and light detection and ranging (LiDAR) data after catastrophic windthrow events. Our aims are to test the following three hypotheses: (1) forest structure will not recover within 30 years after windthrow, (2) forest recovery will be affected not only by salvaging but also pre-windthrow attributes and geographical features, and (3) various post-windthrow management including salvaging will drastically alter tree species composition and delay forest recovery. Our results revealed that hypothesis (1) and (2) were supported and (3) was partially supported. The ordination results suggested that more than 30 years were needed to recover canopy tree height after windthrow in hemiboreal forests in Hokkaido, Japan. Salvage logging did not delay natural succession, but it significantly decreased the cover ratio of conifer species sites (0.107 ± 0.023) compared with natural succession sites (0.310 ± 0.091). The higher the elevation, the steeper the site, and the higher the average canopy height before windthrow, the slower the recovery of forest stands after windthrow and salvaging. Scarification and planting after salvage logging significantly increased the number of canopy trees, but those sites differed completely in species composition from the old growth forests. Our study thus determined that the choice and intensity of post-disturbance management in hemiboreal forests should be carefully considered based on the management purpose and local characteristics.

Enhancing the feasibility of airport PPP projects with hybrid funding

In transport infrastructure concessions, the sources of revenue to the private partner (or concessionaire) may include (i) the infrastructure users (e.g., landing fees, in the case of airports), (ii) the government (e.g. through availability payments), and (iii) both users and government, which might be called a hybrid concession. An example of the latter is a highway concession where the concessionaire charges tolls to the road users but, because of relatively low revenues, the government agency complements the toll revenue with availability payments.Focusing on airports, this paper summarizes the cases where it may be justified for the government to complement users’ revenues and describes a model developed for the financial assessment of airport concessions involving payments by both the government and airport users, through the collection of several charges. The methodology described in the paper is also used to review the flexibility in new or ongoing airport concessions to mitigate traffic risks, which have been aggravated by the COVID-19 pandemic. The methodology can also be applied to other forms of transport infrastructure.A practical application of the model is demonstrated in the paper, using publicly available information, as well as basic assumptions, to build case studies for the Larnaca and Paphos airports in Cyprus. The model can also be used to carry out sensitivity analyses of the impact of key input parameters on outputs such as the investor's return on equity and annual debt service cover ratio.

Electrical Impedance Tomography Image Reconstruction With Attention-Based Deep Convolutional Neural Network

Electrical impedance tomography (EIT) is a promising functional and structural imaging method in process tomography. However, due to the ’soft-field’ nature and the high dependence on the prior information, it often suffers serious artifacts in quantitative analysis. Most recently, EIT image quality has improved significantly because of the state-of-the-art deep learning-based models in the aspect of solving the inverse problem, especially fully convolutional networks (FCN) and V-Net variants. Despite their success, these deep convolutional networks (CNNs) have two limitations: (1) The long-range information transition is frequently lost and the reverse gradient often disappears in deep CNNs; (2) Some novel skip connections, such as residual and dense connections, often occupy substantial computational resources. To overcome these two limitations, we propose V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net, a new neural architecture based on redesigned feature transited connections by the terms of (1) A pre-reconstructor based on the iterative Newton-Raphson method, which maps the nonlinear function between the measurements and the initial images, (2) Dual cascaded V-Net are combined, which play the role of an encoder and a decoder, respectively, (3) A new parallel attention mechanism via channel attention and coordinate attention to learn the conductivity distributions and boundary-shaped feature separately, and (4) the light-weight skip connections reduce the computational resources (or accelerate the inference speed) of EIT imaging. The V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net is evaluated by using the multi-phase flow industrial applications, and the results demonstrate that (1) V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net has better performance in shape reconstruction with sharp ’corner’, (2) V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net could reconstruct the model accurately where it has some low-contrast conductivity distributions, (3) V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net enhances the quality of interfaces with the stratified flow, and (4) the pruned V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> A-Net achieves significant speedup compared with the VDD-Net or V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> DNet. The analyses show that the average relative error is 0.05, the average correlation coefficient is 0.92, the average structural similarity is 0.92 on the testing datasets. In addition, the average relative cover ratio is 0.97 and the average relative contrast ratio is 0.98 on the testing datasets.

Estimation of Soil Losses in Çapakcur Watershed (Bingol, Turkey) Using RUSLE Method and Comparison of Predicted Soil Losses with Sediment Yield

The present study aimed to determine the total and net erosion in the Capakcur watershed, which has a high erosion risk. Accordingly, annual soil loss in the Capakcur watershed was estimated using RUSLE method. Net erosion was determined directly by measuring the monthly flow rate and sediment concentrations of the Capakcur stream, which originated from the Capakcur watershed and flowed into the Murat River throughout 2019. Estimated soil loss in the Capakcur watershed was 96916.20 ton yr-1, and the amount of soil transported from the Capakcur stream was 68656.09 ton yr-1. Sediment delivery ratio (SDR) was calculated as 0.78. This ratio was well above the average SDR of Turkey (0.23). Topographic factors such as slope length and degree, rainfall, and low vegetation cover ratio in the watershed are the main causes of the high SDR. Due to the high SDR, the fertile surface soil layers of lands in the basin are carried to the streams. This causes both decrease in fertility in soils and pollution of the limited freshwater resources. In order to improve vegetation and management practices in the watershed, soil protection practices such as afforestation and terraces, wire cages and stone walls in gullies should be increased.

Useful indicators and models for assessing erosion control ecosystem service in a semi-arid forest landscape.

Forests provide a large array of ecosystem services (ESs) such as wood supply, extreme natural event prevention, and ecotourism opportunities. The quantitative characterization of ESs is a crucial but costly task for environmental managers. The aim of this study was to develop easily applicable models and indicators for assessing erosion control ES in a semi-arid landscape. In order to accomplish this, 107 randomly selected plots were visited for field measurements and topsoil sampling. Several parametric tests were then used to analyze the field data. The findings revealed that (i) normalized difference vegetation index (NDVI), (ii) cover management (C) factor of the Revised Universal Soil Loss Equation (RUSLE), (iii) soil organic matter content, (iv) canopy cover ratio, and (v) land use/land cover (LULC) types could be used as useful performance indicators of erosion control ES. Two regression models were developed based on these indicators and compared to RUSLE results for the study area. Using the first model, we were able to estimate the soil protection performance of different LULC types by NDVI at the pixel level (R2adj = 0.90, p < 0.05). The second model estimated annual potential soil loss using NDVI and ground slope values (R2adj = 0.57, p < 0.05). Based on the ES indicators framework, a practical approach was proposed in this study for rapid assessment of the soil erosion problem without running RUSLE. Thus, environmental managers are expected to make well-informed landscape planning decisions and improve their ES provision application capabilities at a reduced cost.

Clipping decreases plant cover, litter mass, and water infiltration rate in soil across six plant community sites in a semiarid grassland

Water infiltration in the soil is a crucial hydrological function in the land water cycle, especially in the semiarid region where water is relatively scarce. The semiarid grassland in Northern China represents the regional vegetation in the vast area of Eurasian continent and is sensitive to land use change. However, no clear patterns exist regarding the comprehensive examination of water infiltration in relation to clipping across six plant community sites. This study aimed to test the effect of clipping and plant community sites, which were dominated by Agropyron cristatum, Stipa krylovii, Leymus chinensis, Potentilla tanacetifolia, Artemisia frigida, or Lespedeza davurica, on the water infiltration rate in the semiarid grassland. Clipping significantly decreased the water initial, steady, and average infiltration rates by 39.13, 4.36, and 12.46 mm h−1, respectively, across the six plant community sites. Clipping-induced changes in the average infiltration rate positively correlated with the changes in the plant cover (r = 0.60, P < 0.01), litter mass (r = 0.53, P < 0.01), forb functional group ratio (r = 0.46, P = 0.03), and total porosity (r = 0.49, P = 0.02), and negatively with water-holding capacity (r = −0.45, P = 0.03). Further, the water infiltration rate significantly differed among the six plant community sites. The L.davurica site had the highest water initial infiltration rate with a value of 137.63 ± 17.76 mm h−1, while the L. chinensis site had the lowest rate with a value of 74.08 ± 5.26 mm h−1. Principal component analysis showed that the total porosity, litter mass, plant cover, and forb functional group ratio were the main factors affecting water infiltration rates in the control grassland. Overall, our findings suggested that local governments and herders should implement unclipping as a potential sustainable management for improving hydrological function in the semiarid grassland.

Invariant aluminum CHF under electron beam irradiation conditions for downward-facing flow boiling

It is well-known that irradiation may alter the surface morphology of metal materials, thus greatly changing the heat transfer characteristics, especially in nucleate boiling. In this study, electron beam irradiation effects of critical heat flux (CHF) on aluminum surfaces in downward-facing saturated flow boiling were investigated. It was found that although the contact angle decreased greatly after irradiation, no obvious CHF and heat transfer coefficient change was observed up to a total dose of 3000 kGy. Then the bubble cover ratio was calculated, and we believed that the bubble coverage was strongly associated with the boiling crisis. The insensitivity CHF of aluminum was likely to be related to the easy oxidation on aluminum surface. This founding may be helpful for the future heat transfer design and anti-accident counter-measurements in radiation environment.

Heat-prone neighbourhood typologies of European cities with temperate climate

• Compact mid-rise areas are the most heat-prone in Amsterdam, London, and Paris • Within one local climate zone, morphological variance needs to be considered. • Combinations of seven morphological parameters are analysed. • Four neighbourhood typologies are developed using K-means cluster analysis. • Street orientation and Height-to-Width ratio are the most variant parameters. Outdoor microclimates vary among different urban neighbourhoods depending on their morphological variations. The Local Climate Zone (LCZ) framework is a well-developed typomorphological classification used to capture the variation that characterises neighbourhood microclimates. However, it does not include detailed morphological parameters within neighbourhoods that have synergistic effects on microclimates. It is thus essential to develop neighbourhood typologies with detailed spatial descriptions. This study first identifies the LCZ in Amsterdam, London and Paris with the highest Land Surface Temperature (hereinafter referred to as the most heat-prone areas). Subsequently, parameters which are not covered by the LCZs were analysed, including building block's floor area ratio and shape factor, street canyon's orientation and Height-to-Width ratio, street total length, green space area, and tree cover ratio. The results show that LCZ 2-compact mid-rise areas are the most heat-prone. Employing K-means cluster analysis, four neighbourhood typologies are distinguished within the LCZ 2: mainly wide streets with N-S and E-W orientations, mainly narrow streets with N-S and E-W orientations, mainly narrow streets with NE-SW and NW-SE orientations, mainly wide streets with four orientations divided by 45°. These generalised neighbourhood typologies can be used as the basis for design interventions aiming at climate adaptation in heat-prone urban areas.

Summer urban heat island mitigation strategy development for high-anthropogenic-heat-emission blocks

• Results from 33 measurement points in 5 selected urban districts were analyzed. • Urban morphology explains 34% of the variation in air temperature. • Suggested morphological indices are proposed to mitigate the high temperature. • 20m buffer zone is proper to analyze microclimate in high anthropogenic heat areas. • The microclimatic prediction models were established for sustainable development. The negative impacts of urban heat island (UHI) have attracted more and more academic attention. Currently, few studies have considered the effects of anthropogenic heat emission (AHE) in different urban districts. To explore the spatial and temporal differences in microclimate in high-AHE areas, five high-anthropogenic-heat-emission blocks in Xi'an, China were selected, and the microclimatic indices of air temperature (AT) and relative humidity (RH) were measured in 33 urban points in the five typical urban blocks. Meanwhile, the urban morphological indices of 33 points were calculated in the 20 m and 50 m buffer areas (BAs). Results show that the green cover ratio (GCR), the impervious surface area ratio (ISAR), sky view factor (SVF) and reflectivity (REF) were important variables affecting microclimate. These indices explained up to 35% and 31% of the changes in AT and RH, respectively. In addition, the ISAR should be controlled within 44% and the REF should be controlled above 21.5%, in order to ensure that the maximum AT remained less than 37°C (high-temperature orange warning) inside the block on a typical summer day. This study improves the prediction method of high summer temperatures in high-AHE blocks and provides hints for developing UHI mitigation strategies.

Verification of PCSWMM's LID processes and their scalability over time and space

IntroductionThis paper explores the scalability of PCSWMM's Low Impact Development (LID) modeling tools within the urban stormwater computer model.MethodsThe scalability is assessed for a variety of spatial and temporal scales and for event (50-year return storm) and continuous inputs (daily rainfall for an 11 month period), and with a focus on bioretention cells. The model is calibrated for a moderate to large scale, semi-urban watershed on Vancouver Island, British Columbia, Canada. Sensitivity analysis and specialized metrics are used to verify internal model processes at a variety of scales.ResultsWith regard to spatial scaling, changes in flow path length and slope derived from Digital Elevation Models were the most impactful spatial information when modeling flood event and the model's surface layer was the dominant contributor to peak flowrate and volume mitigation by the bioretention cell. However, when modeling the continuous rainfall inputs, storage layer related parameters dominated model outputs. Aside from the soil layer's depth, soil layer parameters such as hydraulic conductivity, showed negligible influence on response to time series rainfall. Parameters that are kept static by the model such as vegetation cover, hydraulic conductivity and storage void ratio (but are naturally dynamic), were tested for their impact on response if allowed to change seasonally or with excessive loading. Runoff coefficients were greatly impacted by storage layer parameter dynamics with very little impact from vegetation. For event simulations, the berm height in the surface layer was the dominant player in reducing peak flow as well as total volume. An analysis to help illustrate sensitivity across spatial scales is proposed.DiscussionThe Spatial Dynamic Sensitivity Analysis shows that parameter sensitivity changes dynamically as LID implementation percentage changes. In particular, the clogging factor, which is a parameter associated with the storage layer, was highly influential for time series rainfall analysis. The LID model concepts in PCSWM seem appropriate for events because the surface layer dominates the response for very large storms. For smaller storms, continuous time series, and larger spatial scales, the model could be revised to better represent soil layer dynamics and vegetation cover, which were both currently inconsequential to the model's output.

The impact of urban morphology on the spatiotemporal dimension of estate-level air temperature: A case study in the tropics

This research evaluated the spatiotemporal dimension of the thermal environment of urban microclimate system in Singapore through a case study. To provide a holistic assessment of air temperature due to urban morphology, for the spatial dimension, correlations between different urban morphology variables and estate-level air temperature were examined through machine learning models to test nonlinear assumption. Different urban morphologies were measured and calculated including shading coefficient of buildings, shading coefficient of greenery, green plot ratio, building height, building cover ratio, building wall area, impervious ground surface fraction, and ground albedo. The temporal dimension of air temperature changes was examined at hourly resolution. The test score of hourly temperature predictions using nonlinear algorithm ranged from 0.24 °C to 0.67 °C, with RMSE above 0.5 °C occurring at T8-T17. Furthermore, this research aggregated hourly temperature prediction into an average cumulative temperature increase (ACTI). A heatmap was created showing ACTI on a university campus with a maximum temperature difference of 2 K between cold and hot spots. Based on the investigation, this study further proposed guidelines for low carbon urban planning for greenery, painting or pavement material, and active system.