Micrometeorological Measurements Research Articles

A comprehensive study on wintertime outdoor thermal comfort of blue-green infrastructure in an arid climate: A case of Isfahan, Iran

Nowadays, one of the most critical objectives of cities in the face of population growth, energy consumption, and climate change is to provide a thermally comfortable urban environment through the creation of livable, healthy, and climate-responsive open spaces, among which urban blue-green infrastructures (UBGI) play a decisive role. While many studies have investigated the thermal comfort of UBGI in summer, limited research has been done to explore its synergistic effects during winter. To address this gap, this study aims to investigate the effects of UBGI on wintertime human thermal comfort through micrometeorological measurements and a questionnaire survey (426 participants) in the arid climate of Isfahan, Iran. The results illustrated: 1) Ta and Tmrt significantly impact people's thermal sensation. 2) A quadratic relationship (R2 = 0.99) exists between individuals’ thermal sensation and overall comfort. 3) An optimal integration of UBGI can improve human thermal comfort during winter. 4) UTCI (R2 = 0.90) and mPET (R2 = 0.86) are the most efficient thermal indices in this study and climate, followed by PET (R2 = 0.78). 5) Alliesthesia and incomplete adaptation are discussed in this study. These findings guide urban planners, designers, and environmental practitioners in creating sustainable and thermally comfortable environments.

Unraveling space and time variability in maximum water storage among sunflower organs: Implications for wetness duration

Vegetation wetness significantly alters the plant microclimate, thereby influencing plant functionality, growth, and yield. Prolonged wetness periods can exacerbate the risk of attack of various plant diseases. Maximum water storage capacity is a crucial parameter for modeling wetness duration, as it sets the upper limit for free water available for evaporation. This study aimed to achieve three main goals: (i) to investigate the maximum water storage capacity of distinct sunflower organs (leaves, stems, and capitula) and their constituent phytoelements, (ii) to establish relationships between maximum water storage and visible morphological characteristics, and (iii) to assess the impact of maximum water storage on phytoelement wetness duration. Morphological and micrometeorological measurements were conducted within a sunflower field plot. Maximum water storage capacity was determined in the laboratory using phytoelements collected from the field. For the capitula and its constituent phytoelements, this capacity was monitored throughout their development. Phytoelement size and orientation were quantified and correlated with their water storage capacity. The influence of phytoelement maximum water storage on wetness duration was investigated through simulation. Notably, we found that the maximum water storage capacity in leaf axils exceeded those in leaf lamina by 43 times. During the flowering and grain-filling stages, capitula exhibited greater water storage, primarily attributed to the contribution from the capitulum front. The area of leaves, stems, and capitula during the flowering stage had a greater impact on their maximum water storage capacity than their orientation. Simulation results revealed that certain phytoelements (e.g., leaf axils and capitulum disk) could remain wet for up to 20 h after most of the canopy, mainly leaves and stems, had dried. This study underscores the importance of examining variability in maximum water storage capacity and its impact on wetness duration within a sunflower canopy at the phytoelement level.

Interannual Variability of Water and Heat Fluxes in a Woodland Savanna (Cerrado) in Southeastern Brazil: Effects of Severe Drought and Soil Moisture

The Brazilian Cerrado biome is known for its high biodiversity, and the role of groundwater recharge and climate regulation. Anthropogenic influence has harmed the biome, emphasizing the need for science to understand its response to climate and reconcile economic exploration with preservation. Our work aimed to evaluate the seasonal and interannual variability of the surface energy balance in a woodland savanna (Cerrado) ecosystem in southeastern Brazil over a period of 19 years, from 2001 to 2019. Using field micrometeorological measurements, we examined the variation in soil moisture and studied its impact on the temporal pattern of energy fluxes to distinguish the effects during rainy years compared to a severe drought spell. The soil moisture measures used two independent instruments, cosmic ray neutron sensor CRNS, and FDR at different depths. The measures were taken at the Pé de Gigante (PEG) site, in a region of well-defined seasonality with the dry season in winter and a hot/humid season in summer. We gap-filled the energy flux measurements with a calibrated biophysical model (SiB2). The long-term averages for air temperature and precipitation were 22.5 °C and 1309 mm/year, respectively. The net radiation (Rn) was 142 W/m2, the evapotranspiration (ET) and sensible heat flux (H) were 3.4 mm/d and 52 W/m2, respectively. Soil moisture was marked by a pronounced negative anomaly in the 2014 year, which caused an increase in the Bowen ratio and a decrease in Evaporative fraction, that lasted until the following year 2015 during the dry season, despite the severe meteorological drought of 2013/2014 already ending, which was corroborated by the two independent measurements. The results showed the remarkable influence of precipitation and soil moisture on the interannual variability of the energy balance in this Cerrado ecosystem, aiding in understanding how it responds to strong climate disturbances.

The thermal perception of outdoor urban spaces in a hot arid climate: A structural equation modelling (SEM) approach

Human thermal comfort is linked to multi-sensory attributes and psychological cognition besides the influence of prominent meteorological parameters. To date, even the most advanced thermal comfort models like UTCI consider the interaction between human and external surroundings to be a heat transfer problem applying thermodynamic equations in the derivation behind thermal comfort indices. Machine learning (ML) models offer the advantage of improving the accuracy of predictor variable, but they fail to determine the relationship between the independent variables and data-driven prediction models. Structural Equation Modelling (SEM), an advanced modelling technique, can expose all hidden relationships among variables using latent variables while not being data-driven like ML. This study aimed to develop a structural framework which systematically explains these relationships and quantify the effects of 24 variables on outdoor thermal comfort using SEM due to its ability to represents the response of the dependent variable to a unit change in an explanatory variable. The method employed 635 structured interviews, observations, and wide-ranging micrometeorological measurements conducted concurrently in three Pedestrianized urban alleys in Cairo. The model statistically confirmed the hypothesis that overall thermal comfort in urban spaces is significantly influenced by multiple factors. Of these, background microclimatic conditions had the greatest relevance and certain urban features the least. 1 unit increase microclimate leads to a change in thermal comfort by 0.423 and 0.349 in summer and winter, respectively. In terms of thermal perception, the model shows that individuals are willing to tolerate a wider range if certain urban features are present such as shaded seating opportunities. These outcomes may aid to provide important guidance for urban designers to enhance thermal perception in urban streets.

Cover crop inclusion and residue retention improves soybean production and physiology in drought conditions

Soybean (Glycine max (L.) Merr.) planting has increased in central and western North Dakota despite frequent drought occurrences that limit productivity. Soybean plants need high photosynthetic and transpiration rates to be productive, but they also need high water use efficiency when water is limited. Crop residues and cover crops in crop rotations may improve soybean drought tolerance in northern Great Plains. We aimed to examine how a management practice that included cover crops and residue retention impacts agronomic, ecosystem water and carbon dioxide flux, and canopy-scale physiological attributes of soybeans in the northern Great Plains under drought conditions. The experiment consisted of two soybean fields over two years with business-as-usual (no-cover crops and spring wheat residue removal) and aspirational management (cover crops and spring wheat residue retention) during a drought year. We compared yield; aboveground biomass; green chromatic coordinates, and CO2 and H2O fluxes from eddy covariance, Phenocam images, and ancillary micrometeorological measurements. These measurements were used to derive ecosystem-scale physical, and physiological attributes with the ‘big leaf’ framework to diagnose underlying processes. Soybean yields were 29 % higher under drought conditions in the field managed in a system that included cover crops and residue retention. This yield increase was associated with a 5 day increase in the green-chromatic-coordinate defined maturity phenophase, increasing agronomic and intrinsic water use efficiency by 27 % and 33 %, respectively, increasing water uptake, and increasing the rubisco-limited photosynthetic capacity (Vcmax25) by 42 %. The inclusion of cover crops and residue retention into a cropping system improved soybean productivity because of differences in water use, phenology timing, and photosynthetic capacity. These results suggest that farmers can improve soybean productivity and yield stability by incorporating cover crops and residue retention into their management suite because these practices to facilitate more aggressive water uptake.

Modeling the atmospheric refractive index structure parameter using macrometeorological observations

The dynamic fluctuations in the atmospheric refractive index, commonly referred to as optical turbulence, cause phase distortions of the electromagnetic waves propagating through the atmosphere. The consequent scintillations have large implications for free-space optical communication, laser remote sensing, and directed energy applications. The refractive index structure parameter (C n 2), quantifying the strength of these fluctuations, is usually estimated using high-frequency micrometeorological measurements, employing sonic anemometer-thermometers or scintillometers. Despite providing highly accurate information, these systems are immensely complex and costly, especially for frequent field applications and remote locations. In this study, we have developed an empirical multinomial model for estimating C n 2 using three-year macrometeorological data and validated it against collocated and concurrent micrometeorological measurements, from a tropical semi-arid location. This simpler model would be handy for applications in remote locations having weather station measurements alone.

Dry-season length affects the annual ecosystem carbon balance of a temperate semi-arid shrubland

Semi-arid ecosystems have been shown to dominate over tropical forests in determining the trend and interannual variability of land carbon (C) sink. However, the magnitude and variability of ecosystem C balance remain largely uncertain for temperate semi-arid shrublands at the decadal scale. Using eddy-covariance and micro-meteorological measurements, we quantified the interannual variation in net ecosystem production (NEP) and its components, gross primary production (GPP) and ecosystem respiration (Reco, i.e., the sum of autotrophic and heterotrophic respiration), in a semi-arid shrubland of the Mu Us Desert, northern China during 2012–2022. This shrubland was an overall weak C sink over the 11 years (NEP = 12 ± 46 g C m−2 yr−1, mean ± SD). Annual NEP ranged from −66 to 77 g C m−2 yr−1, with the ecosystem frequently switching between being an annual C sink and a C source. GPP was twice as sensitive as Reco to prolonged dry seasons, leading to a close negative relationship between annual NEP and dry-season length (R2 = 0.80, P < 0.01). Annual GPP (R2 = 0.51, P = 0.01) and NEP (R2 = 0.58, P < 0.01) were positively correlated with annual rainfall. Negative annual NEP (the ecosystem being a C source) tended to occur when the dry season exceeded 50 d yr−1 or rainfall dropped below 280 mm yr−1. Increases in dry-season length strengthened the effects of low soil moisture relative to high vapor pressure deficit in constraining NEP. Both GPP and NEP were more closely correlated with C uptake amplitude (annual maximum daily values) than with C uptake period. These findings indicate that dry-season extension under climate change may reduce the long-term C sequestration in semi-arid shrublands. Plant species adapted to prolonged dry seasons should be used in ecosystem restoration in the studied area to enhance ecosystem functions.

Experimental and model-based comparison of wind tunnel and inverse dispersion model measurement of ammonia emission from field-applied animal slurry

Volatilization of ammonia from field-applied animal slurry is a significant problem. Accurate emission measurements are needed for inventories and research, but are not provided by all measurement methods. Wind tunnels may give emission values substantially above or below micrometeorological results, which have been shown to be accurate. This limitation reduces the utility of wind tunnel results, which make up a large fraction of available measurements. The present work focused on understanding wind tunnel measurement error by comparing micrometeorological and wind tunnel measurements with the aid of a semi-empirical model. Ammonia loss from digestate after field application was measured in high time resolution in three field trials using wind tunnels and the backward Lagrangian stochastic (bLS) dispersion technique simultaneously. Differences in measured emission were interpreted using the ALFAM2 model, and measurements were used to evaluate the model. Results showed that wind tunnel and bLS methods provided different cumulative emission estimates, although there were similarities in measured emission dynamics. The ALFAM2 model was generally able to reproduce emission dynamics for both measurement methods, but only when differences in mass transfer between the two methods were incorporated in an experimental parameter set. This important result suggests that: 1) the simple structure of the ALFAM2 model captures the essential physical and chemical processes controlling emission and 2) the two measurement methods differ only (or mainly) through mass transfer above the slurry/soil surface and rain. Therefore, with careful selection of wind tunnel air flow it should be possible to approximately match emission that occurs under open-air conditions. But without temporal variation in air flow, actual emission dynamics cannot be captured. This work provides a template for integrating and comparing measurements from different methods, and suggests it is possible to use wind tunnel measurements for model evaluation and even parameter estimation.

Microclimate impacts of neighborhood redesign in a desert community using ENVI-met and MaRTy

Municipalities often consider heat mitigation strategies to address urban overheating, but the location of implementation rarely is co-located with the communities that are carrying the majority of the heat burden in the city. The City of Phoenix, is redeveloping a public housing community with a focus on urban cooling as a desired outcome. This research uses in situ measurements (including the mobile micro-meteorological measurement cart, MaRTy) and ENVI-met microscale modeling of the neighborhood to assess air temperature (Tair) cooling capabilities of the planned redesigns to the neighborhood. After validating the ENVI-met model of the current neighborhood with fixed and mobile measurements with an index of agreement d > 0.9 and d > 0.8, respectively, analysis of the planned urban design shows some cool spots connected to new shade and vegetated corridors with Tair cooling magnitudes as high as 3 °C. Yet, some exposed and building-adjacent areas were identified as potential hot spots in the planned neighborhood. These hotspots underscore the importance of continued collaboration among the City, researchers, and the community to address the needs of the community for the creation of healthier urban environments.

Intercomparison of micrometeorological variables, surface energy fluxes, and evapotranspiration in different landscapes of the Brazilian semi-arid region

The comparison of energy exchanges between different landscapes is very valuable for understanding the consequences of deforestation and land use change on the climate. In this study, we analyzed micrometeorological variables, energy fluxes, and actual evapotranspiration over four landscapes of the Brazilian semi-arid region (preserved Caatinga – CAA, regenerating Caatinga – REGE, cactus landscape – CAM and deforested landscape – DEFA). Micrometeorological measurements (air temperature and relative humidity, vapor pressure deficit), net radiation (RN), latent heat (LE), sensible (H) and soil heat (G) fluxes, actual evapotranspiration (ET), and soil water storage variation (ΔS) were obtained in landscapes from October 2018 to September 2020. LE and H were calculated based on the Bowen ratio method. Significant differences were noted between micrometeorological variables (temperature and relative humidity, and vapor pressure deficit) and energy flux among the four landscapes. The four surfaces exhibited, on average, lower LE values when compared to H. At CAA landscape, 35% of the RN was used for LE, 64% for H, and 1% for G, versus 33% for LE, 65% for H, and 2% for G at REGE; 33% RN for LE, 65% for H and 2% for G at CAM, and 40% for LE, 59% for H and 1% for G at DEFA. The evapotranspiration for regenerating Caatinga (1.62 mm day−1), cactus (1.59 mm day−1), and deforested area (1.90 mm day−1) were higher than the preserved Caatinga (1.40 mm day−1). However, seasonal variations of the ET were more associated with fluctuations in RN, rainfall, and ΔS than with the type of land use. It is concluded that the removal of Caatinga by landscapes such as regenerating Caatinga, cactus plantations, and deforested area significantly modifies micrometeorological variables, energy fluxes, and the evapotranspiration, but their seasonality depends on the regime availability of water and energy.

Interannual variability of spring and summer monsoon growing season carbon exchange at a semiarid savanna over nearly two decades

Eddy covariance measurements of land-atmosphere energy, carbon, and water exchange now span multiple decades at some sites, supporting an improved understanding of flux interannual variability (IAV) and its ecophysiological and physical controls. Most eddy covariance IAV studies have focused on temperate forest ecosystems, where carbon fluxes are large and flux records are longest – but also where IAV is much lower than in dryland regions, which have been identified as an essential driver of the trend and variability in the global terrestrial carbon sink. In this study, we leveraged 19 years of continuous micrometeorological measurements at the AmeriFlux US-SRM mesquite savanna site in southern Arizona, USA to quantify the IAV, trends, and drivers of carbon fluxes during the distinct spring and summer growing seasons. We also assessed the ability of modern satellite and land surface models to capture the IAV of seasonal water and carbon fluxes. Annual net ecosystem production (NEP) was small and highly variable (23 +/- 64 gC m − 2 yr−1). Precipitation and associated measures of water availability determined most of the variability in NEP, largely through their influence on annual and seasonal gross ecosystem productivity (GEP) as opposed to ecosystem respiration (ER). Root-zone soil moisture captured between 73% (spring) and 85% (summer) of GEP variability and between 73% (spring) and 58% (summer) of ER variability. Throughout the study period, soil moisture and greenness increased with associated increases in GEP, ER and NEP. These trends were strongly influenced by very productive and wet summer growing seasons during the last two years, which were characterized by abundant understory grass cover. Typically, less than half of the variability in growing season GEP and evapotranspiration was captured by satellite-based estimates and land surface model simulations with local site forcing and calibration, highlighting the ongoing utility of long-term datasets to support careful model testing and improvement.

Stomatal ozone uptake of a Quercus serrata stand based on sap flow measurements with calibrated thermal dissipation sensors

The amount of ozone absorbed by the tree leaves is a critical factor determining the ozone effects on forest trees. Stomatal ozone uptake of a forest canopy can be estimated from the ozone concentration and canopy conductance (gc) determined by the sap-flow-based method. This method measures sap flow as a metric of crown transpiration and then derives gc. The thermal dissipation method (TDM) has been used to measure sap flow in most studies adopting this approach. However, recent studies have indicated that TDM may underestimate sap flow, especially in ring-porous tree species. In the present study, the accumulated stomatal ozone uptake (AFST) of a stand of Quercus serrata, a typical ring-porous tree species in Japan, was estimated by measuring sap flow using species-specific calibrated TDM sensors. Laboratory calibration of the TDM sensors revealed that the parameters (α and β) in an equation converting outputs from the sensors (K) to sap flux density (Fd) were substantially larger for Q. serrata than those originally proposed by Granier (1987). The Fd measured in the Q. serrata stand using calibrated TDM sensors were significantly larger than those obtained using non-calibrated sensors. The diurnal average of gc and daytime AFST (10.4 mm s−1 and 10.96 mmol O3 m−2 month−1) of the Q. serrata stand estimated by using calibrated TDM sensors in August 2020 were similar to those of forests dominated by Quercus species estimated by micrometeorological measurements in previous studies. In contrast, the gc and daytime AFST of the Q. serrata stand estimated by non-calibrated TDM sensors were remarkably lower than those estimated by micrometeorological measurements in previous studies, indicating severe underestimation. Therefore, it is strongly recommended that sap flow sensors are species-specifically calibrated when estimating the canopy conductance and ozone uptake of forests dominated by ring-porous trees based on sap flow measurements using TDM.

Optimal Frequency-Response Corrections for Eddy Covariance Flux Measurements Using the Wiener Deconvolution Method

We describe a new direct correction approach to accurately restore frequency attenuated eddy covariance (EC) measurements. The new approach utilizes the Wiener deconvolution method to optimally estimate the original signal from noisy atmospheric measurements. Key features over conventional EC spectral correction methods include (i) the use of physics-based response functions, (ii) the ability to account for the non-linear phase contributions, and (iii) the direct restoration of the original signal rather than simulating the effect on an ideal reference spectrum. The new correction approach is compared to conventional spectral correction methods in a numerical simulation where the magnitude of the key limitations of conventional methods is explored under conditions relevant to common EC set-ups. The simulation results showed that the spectral correction methods commonly used for calculating EC fluxes introduced systematic error up to 10% to the restored fluxes and substantially increased their random uncertainty. The errors are attributed to the effect of using inappropriate response functions, failing to account for the contribution of the non-linear phase, and due to the assumption of spectral similarity on the scale of averaging intervals. The Wiener deconvolution method is versatile, can be applied under non-ideal conditions, and provides an opportunity to unify analytical and “in-situ” spectral correction methods by applying existing transfer functions to directly restore attenuated spectra. Furthermore, the Wiener deconvolution approach is adaptable for use with various micrometeorological measurement techniques such as eddy accumulation and flux profile measurements.

The difference in thermal comfort between southern and northern Chinese living in the Xi'an cold climate region.

A year-long longitudinal survey regarding perceptions of outdoor thermal conditions and thermal comfort was conducted in Xi'an, a City in a Chinese cold region. The survey included micrometeorological measurements and a longitudinal questionnaire. The thermal comfort and adaptability of southern Chinese (people from Changsha and Guangzhou) and northern Chinese (people from Xi'an) in Xi'an were studied from the three aspects of psychological, physiological, and behavioral differences. The results of similar studies in other regions were compared with those of this study. Regarding psychological differences, northerners were more adapted to Xi'an's climate than southerners, with an expected temperatures of 20.7℃ and 24.1℃ for northerners and for southerners, respectively. Regarding physiological differences, the neutral temperature of the northern population was 22.12℃, while that of the southern population was 21.12℃. The neutral temperature for the southern population in Xi'an is similar to that of northern people living in Xi'an. Regarding behavioral differences, northerners were more likely than southerners to maintain their thermal comfort by adjusting their clothing when they experienced a change in the outdoor environment. This study not only indicates that there were differences regarding the thermal comfort of people originating different regions but also provided support for fully explaining the mechanism of climate adaptation of human thermal comfort. In addition, this work provides basic data regarding formulating outdoor thermal comfort standards and provided data support for personalized thermal comfort.

Outdoor thermal comfort of urban river landscape belt in China's cold region: A case study of Xi'an

The outdoor thermal sensation and comfort questionnaires was conducted on the River Ba landscape belt of Xi'an city located in the cold region of China. The survey included objective micrometeorological measurements and subjective questionnaire surveys in winter, summer and spring. The study contrasted the outdoor thermal comfort of the river landscape belt in different seasons in cold region. Physiological equivalent temperature (PET) was used as a thermal comfort index to quantitatively analyze the thermal comfort range of urban river in Xi'an. The 80% thermal acceptable PET range in Xi'an was 14.3 °C–19.9 °C in winter, 17.3 °C–24.6 °C in spring, and 17.6 °C–31.8 °C in summer. During winter, spring, and summer, the neutral PET was 21.7 °C, 20.5 °C, and 18.9 °C, respectively. Due to seasonal adaptation, “slightly warm” in spring and winter was considered the most comfortable thermal sensation, while “neutral to cool” was regarded as the most comfortable in summer. The importance of thermal experience and psychological adaptation was found, thermal sensation voting was lower in early spring than in winter for the same PET, and the locals were acceptable even if not within the comfort PET range.

Dosadašnji značaj i uloga Poljoprivrednog fakulteta u Beogradu na razvoj i primenu melioracija u Republici Srbiji

The development of agriculture in Serbia would not have been possible without the implementation of ameliorative measures. Measures to improve the soil water regime in our country have existed throughout modern era, but very significant ameliorative practices have been implemented in the last 100 years, coinciding with the establishment of the Faculty of Agriculture at the University of Belgrade. In Serbia, after the First World War, extensive work was carried out in the field of drainage, which underwent a real expansion after the Second World War. In the period from 1950 to 1970, drainage systems were built on about 1.5 million hectares, and by 1990 the total drained area exceeded 2.01 million hectares. Alongside the construction of drainage systems, dams were built on the major rivers to protect coastal areas from flooding. A significant achievement is the construction of the Danube-Tisza-Danube water system (1947-1977), which involved complex and versatile water management in Vojvodina. The introduction of irrigation in agriculture progressed much more slowly than drainage. The total irrigated area in 1990 was about 120,000 hectares, and today, after the crisis-ridden 1990s, it amounts to about 100,000 hectares. Nowadays, it is necessary to design additional drainage systems where problems of this kind arise, whereas the potential areas for irrigation are considerably larger. Until the beginning of the 21st century, various ameliorative activities were the focus of technical and research activity: soil surveys, investigation of the soil physical and water characteristics, soil chemical amelioration , the application of horizontal pipe drainage, soil recultivation, soil conservation, introduction of large machines for pressurised irrigation and application of drip irrigation methods. More recently, modern technologies and contemporary global trends such as the use of GIS, remote sensing, soil water balance monitoring, crop cover monitoring, micrometeorological measurements, automation of irrigation systems and crop growth modelling have been introduced alongside the application of traditional methods. The last decade has been marked by researches focused on the effects of climate change on agricultural production. The importance of the Soil and Water Management department is reflected in the training of professionals who are able to keep pace with technological changes and apply them to the management of soil and water resources, from the planning and implementation of new hydromeliorative systems to the maintenance of old systems and the management of crop production.

Micrometeorological measurements of air temperature in part of the northern slope of the Western Rhodopes (preliminary results)

The present study characterizes some microclimatic differences on the northern slope of the Western Rhodopes Mountains. The data for the analysis are based on the observations at three points: Brestovitsa at the foot, Bryanovshtitsa on the slope and Vurhovruh hut on the ridge, during July and August. Average temperatures, average minimum and maximum temperatures as well as the absolute minimum and maximum temperatures were established. They decrease naturally in accordance with altitude change, showing a dependence on synoptic conditions and microclimatic differences. The vertical temperature gradient is calculated for the studied parameters, with the largest values for the absolute maximum temperature amounting to 1.1 °C and the smallest for the absolute minimum and mean minimum temperature amounting to 0.5 °C. The largest values of the vertical temperature gradient for all parameters were observed between Brestovitsa and Bryanovstitsa.

Estimating crop coefficients and actual evapotranspiration in citrus orchards with sporadic cover weeds based on ground and remote sensing data

Accurate estimations of actual crop evapotranspiration are of utmost importance to evaluate crop water requirements and to optimize water use efficiency. At this aim, coupling simple agro-hydrological models, such as the well-known FAO-56 model, with remote observations of the land surface could represent an easy-to-use tool to identify biophysical parameters of vegetation, such as the crop coefficient Kc under the actual field conditions and to estimate actual crop evapotranspiration. This paper intends, therefore, to propose an operational procedure to evaluate the spatio-temporal variability of Kc in a citrus orchard characterized by the sporadic presence of ground weeds, based on micro-meteorological measurements collected on-ground and vegetation indices (VIs) retrieved by the Sentinel-2 sensors. A non-linear Kc(VIs) relationship was identified after assuming that the sum of two VIs, such as the normalized difference vegetation index, NDVI, and the normalized difference water index, NDWI, is suitable to represent the spatio-temporal dynamics of the investigated environment, characterized by sparse vegetation and the sporadic presence of spontaneous but transpiring soil weeds, typical of winter seasons and/or periods following events wetting the soil surface. The Kc values obtained in each cell of the Sentinel-2 grid (10 m) were then used as input of the spatially distributed FAO-56 model to estimate the variability of actual evapotranspiration (ETa) and the other terms of water balance. The performance of the proposed procedure was finally evaluated by comparing the estimated average soil water content and actual crop evapotranspiration with the corresponding ones measured on-ground. The application of the FAO-56 model indicated that the estimated ETa were characterized by root-mean-square-error, RMSE, and mean bias-error, MBE, of 0.48 and -0.13 mm d−1 respectively, while the estimated soil water contents, SWC, were characterized by RMSE equal to 0.01 cm3 cm−3 and the absence of bias, then confirming that the suggested procedure can produce highly accurate results in terms of dynamics of soil water content and actual crop evapotranspiration under the investigated field conditions.

A Field Study of Outdoor Human Thermal Perception in Three Seasons in Shanghai, China

The locality of landscape design needs to obtain human thermal perception in different cities or regions. Previous studies in Shanghai have focused on a single season and ignored the seasonal characteristics of hot summers and cold winters. The objective of this research was to examine the outdoor human thermal perception in three seasons—summer, autumn, and winter. For this purpose, a field survey was conducted in two urban squares in Shanghai, and during three seasons, an outdoor human thermal perception questionnaire survey was completed combined with micrometeorological measurements. In the questionnaire, the thermal sensation and thermal comfort of interviewees were evaluated through the 9-point scale and the 4-point break scale, respectively. Regression lines gave the possibility to calculate the neutral ranges and the comfort ranges. A neutral PET (physiological equivalent temperature) range of 13.0~28.6 °C and a comfort PET range of 14.2~32.6 °C were obtained for three seasons. In addition, the relationships between personal (gender and age of respondents) and microclimatic (air temperature, relative humidity, wind velocity, and solar radiation) factors on thermal sensation votes (TSV) and thermal comfort votes (TCV) were evaluated. The results of multiple regression analysis showed that the variables affecting TSV and TCV changed with the season. The findings of this research enhance our understanding of outdoor human thermal perception and can contribute to more friendly outdoor open space design in Shanghai.

Preliminary results of outdoor and indoor air quality and micrometeorological measurements in an inflatable football arena

Preliminary results of outdoor and indoor air quality and micrometeorological measurements in an inflatable football arena