Microclimatic Variables Research Articles

Urban morphology and prediction models of microclimatic phenomena in dry atmospheric context

The morphological configuration of cities has a direct influence on microclimatic variation. The predominant built composition in certain areas, the high rates of waterproofed surfaces, vegetation scarcity and water surfaces can have a significant impact on the temperature and humidity values on inhabited areas, often exposing the population on unhealthy environments. The aim of this paper is to elaborate a prediction microclimatic model variation of four different Local Climate Zones (LCZ) exposed to a dry atmospheric condition in an altitude tropical region. The method was developed on three stages, the first one, refers to a collect campaign of temperature and humidity variation in four different urban environments, LCZ D, LCZ 1, LCZ 5 and LCZ 9 in São José do Rio Preto, Brazil. The representative microclimatic behavior of each area of ​​the city in relation to the performance of a dry air mass was recorded. The second stage involved the microclimatic collected data, which were submitted to a statistical analysis with ANOVA tests, serving as the basis for the development of prediction microclimatic models variation for each LCZs. After validating the models, it was verified, in the third stage, the urban area that presented morphological characteristics that allow the occurrence of high temperature waves and reduced indexes of relative humidity. The produced models for predicting urban microclimatic show a very high capacity of representation to estimate the temperature values in different areas of the city, since in all cases values of R exceed 80%. The results showed that the area with LCZ5 presents the longest periods of heat exposure, which should receive more attention from planners in relation to investments in urban green infrastructure.

Evidence of a Climate-Change-Induced Shift in European Beech Distribution: An Unequal Response in the Elevation, Temperature and Precipitation Gradients

Climate is a strong predictor of the geographic distribution of tree species, and thus climate change may trigger shifts in the distribution of a tree species and/or its demographic structure. In the study, we aim to comprehensively compare the distributions of four life stages of European beech (Fagus sylvatica) (i.e., regeneration, recruitment, young trees and mature trees) in forests in Slovenia, Central Europe, which are characterized by strong gradients of elevation (ELV), temperature (TEMP) and precipitation (PREC) to detect possible shifts in distribution and demography. Beech life stages were surveyed on 3366 plots. To depict disparities between ELV, TEMP and PREC distributions of beech life stages, we applied several non-parametric methods: basic statistical tests to study differences in medians, means, and 1st and 9th deciles; generalized additive models to study shifts in the optimum; and extreme value analysis to study shifts at the trailing and leading edges. A substantial shift in juvenile beech stages upward and toward colder sites was detected. However, the shift was not uniform along the distributions; the most significant shift was detected at the leading edge of ELV (+73 m) and TEMP (−2.6 °C), but surprisingly there was no beech movement identified at the trailing edge. The observed shift may be a result of the interplay between climate change, high spatial variability in microclimate, unexceptional droughts in the recent past, changes in forest use and possible limitations in the migration ability of beech and its adaptation capacity.

Disparate responses of soil-atmosphere CO2 exchange to biophysical and geochemical factors over a biocrust ecological succession in the Tabernas Desert

There is growing evidence that dryland soils could act as substantial but so far disregarded carbon sinks at the global scale. In drylands, potential abiotic processes of CO2 uptake are still debated while estimates of the biotic contribution of photosynthetizing biocrusts to the net carbon uptake remain uncertain. This uncertainty is partly attributable to a common neglect of the underlying soil and spatiotemporal variability of soil CO2 fluxes. Moreover, it is still unknown how those fluxes evolve during the ecological succession of biocrusts and which factors control them. Therefore, in this study, we aimed to (1) identify those factors and use them for predictions, and (2) explain the inter-annual variation of cumulative CO2 fluxes over the succession. We conducted 2 years of continuous measurements of the topsoil CO2 molar fraction (χs) and microclimatic variables and estimated the soil-atmosphere CO2 flux using the gradient method. Statistical spatiotemporal models were developed of χs dynamics and cumulative annual fluxes. A soil CO2 uptake potentially due to coupled gypsum dissolution-calcite precipitation was consistently detected at night, with cumulative values ranging from −4 to −65 gC m−2 depending on succession stage. In comparison, cumulative soil CO2 emissions ranged from 101 to 307 gC m−2 depending on succession stage. The succession stage, soil water content (ϑw), and temperature (Ts) and the interactions of these variables explained and efficiently predicted the daily averaged χs dynamics. Soil CO2 emissions were more sensitive to ϑw and Ts in late successional stages, apparently because of organic carbon accumulation and higher porosity. Our measurements suggest that CO2 consumption processes were progressively counterbalanced by the increase in biological CO2 production during succession. That is probably why those processes could mainly be detected in early successional stages and more generally in drylands, as they sustain a low biological activity. However, such processes could be ubiquitous in ecosystems but difficult to detect. We discuss the implication of those results for the extensive dryland soils in the context of climate change.

Modification of the microclimate and water balance through the integration of trees into temperate cropping systems

Climate change scenarios predict an increased occurrence of droughts and heatwaves, as well as extreme rainfall events in Central Europe. Alley cropping, which is the inclusion of rows of trees and shrubs in agricultural land, could enhance the resilience of cropping systems, as these systems are expected to positively modify the microclimate and water balance of croplands. This review analyses the effect of alley cropping on the microclimate and water balance, based on the available evidence from temperate alley cropping systems. Within alley cropping systems, the tree rows generate gradients in microclimatic variables, whereby strongest effects are observed in or close to the tree rows. Field-scale studies on light intensity (n=20), wind speed (n=4) and surface runoff (n=3) all reported a reduction compared to sole cropping systems. Effects on air temperature (n=10), relative humidity (n=5) and evapotranspiration (n=6) varied among studies, with the majority reporting a decrease in daytime temperatures (50% of studies), variable effects on relative humidity (60%) and an increase in evapotranspiration (50%) due to higher evapotranspiration by trees. Highest variation among studies was found for soil moisture, with 41% of studies reporting temporal and spatial differences within the system. This variation among studies likely depends on the purpose of the trees (short rotation coppice vs. fruit and/or timber trees) and design of the system. Also site context, such as topography, landscape diversity and climate, could play a role, but these factors are rarely taken into account. Only few studies investigated landscape-scale effects (n=3), such as groundwater recharge and moisture recycling. Future research should investigate the role of site context in the functioning of alley cropping systems and quantify landscape-scale effects. The process understanding gained from those studies will contribute to designing alley cropping systems that enhance the climate change resilience of current central European cropping systems.

Canopy height impacts on the growing season and monthly microclimate in a burned forest of British Columbia, Canada

Forest canopies can buffer seedlings from extreme climate conditions. Yet, how disturbed forest canopies influence microclimate is not well understood, despite the important implications of microclimate for seedling establishment and post-disturbance successional trajectories. Better understanding of the relationship between a forest canopy and sub-canopy temperature and moisture conditions requires easily acquired and continuous forest canopy data, which is increasingly available due to new technology. Here, we measured canopy height using a remotely piloted aircraft (RPA) and monitored microclimate with low-cost temperature and soil moisture sensors in a sub-boreal forest impacted by fires of variable severity. We used regression models to investigate how differences in canopy height influenced microclimate variables. Mean growing season temperatures at -8 cm (soil), 0 cm (surface), and 15 cm (near-surface) relative to the ground surface were higher under shorter more disturbed canopies. Soil temperature was most sensitive to canopy height differences: linear models for the observed data range predicted a 2.0 °C increase in mean growing season soil temperature with every 10 m decrease in canopy height. We observed a weak negative relationship between canopy height and mean growing season soil moisture. We found that canopy height summarized at moderate resolution (15 m) better explained differences in temperature in our disturbed landscape. This work informs future methods to produce gridded microclimate datasets and outlines the impact of disturbed forest structure on microclimate variables. Our results show that the characteristics of the forest canopy remaining after a burn impact microclimates, which has important implications for post-fire ecosystems.

Mobile measurements of microclimatic variables through the central area of Singapore: An analysis from the pedestrian perspective

High-density cities, such as Singapore, are currently facing the urban heat island (UHI) effect, a phenomenon that leads to higher air and surface temperatures within the urban area in comparison to the surroundings and is one of the most critical anthropogenic climate change-related environmental issues for contemporary high-density cities. This study aims to investigate the effect of different urban morphologies such as high-rise and low-rise buildings, green areas, and water bodies on the urban microclimate in Singapore. Mobile measurements taken from a pedestrian perspective were conducted for the first time in the central area of Singapore to explore the severity of the UHI effect through distinctive urban morphologies. The Sky View Factor (SVF) was the metric used to quantify these characteristics. During daytime, the air temperature was higher when SVF increased, except for the water body area. Shading showed to be an important factor to decreasing air temperature in the tropics. Reductions by up to 4.5 ºC were observed due to the buildings shading during daytime, while the cooling effect of vegetation reduced the air temperature by up to 4 ºC during the daytime and 1 ºC at night-time. Thus, this study revealed a strong relationship between the decrease in air temperature and greenery coverage in the city. Therefore, understanding the relationship between urban morphology and microclimate conditions may better drive sustainable urban planning and development in the tropics. Finally, it was demonstrated the importance of using mobile monitoring to retrieve granular data that allows identifying specific environmental issues on a hyperlocal scale, which would not be recognised through other monitoring techniques.

SOIL RESPIRATION UNDER DIFFERENT LAND USE SYSTEMS IN THE KUMAON REGION OF CENTRAL HIMALAYA, INDIA

Soil respiration (SR) is chiefly controlled by microclimatic conditions, microbial activity, and land use management practices of the particular ecosystem. In the present study, SR was measured under three different land-use systems viz. arable land (AL), a kitchen garden (KG), and peach orchard (PO) in the Almora and Nainital districts of Uttarakhand to observe the effect of soil temperature (ST) and soil moisture (SMC) on the rate of SR. The cumulative seasonal mean SR rate (g CO 2 m -2 h -1 ) was 2.67 ± 0.33, 4.3 ± 0.06, 8.29 ± 2.59 for the year 2017‒18, and 1.37 ± 0.28, 1.85 ± 0.05 and 2.27 ± 0.03 for the year 2018‒19 in AL, KG and PO respectively. The highest SR was found in PO followed by KG and AL. This study also found the spatial and temporal variations of SR in the selected land-use systems. The SR was positively correlated with SMC but negatively correlated with ST. Thus the ST explained the maximum variability of SR in the selected land-use systems. Overall, the results of this study clearly indicate that the microclimatic variables and land use management practices have a greater role in changes in SR of the studied region.

Microclimate influences plant reproductive performance via an antagonistic interaction

Climatic conditions can influence plant reproduction directly, but also via changes in plant traits, interactions with animals, and the surrounding environment. Such indirect effects can often be complex and involve multiple steps including climatic effects on interacting species, and on the context in which these interactions occur. The joint effects of climatic variation and indirect effects in terms of plant-animal interactions have sometimes been assessed at larger spatial scales. However, less is known about how microclimatic variation affects within-population variation in reproductive performance, in spite of that it is becoming increasingly clear that variation in climatic conditions can occur over very short distances. We studied the direct and indirect effects of microclimate on within-population variation in reproductive performance of the plant Gentiana pneumonanthe in presence of the myrmecophagous and seed predator butterfly Phengaris alcon. We found that microclimatic effects on plant performance were mainly indirect, and that effects of temperature and moisture were interactive. The number of seeds per flower of G. pneumonanthe decreased in cold and moist microsites, and these effects were mediated by an increased oviposition by P. alcon in these microsites. The effects of soil temperature and moisture on the incidence of oviposition and plant performance were mediated by effects on plant phenology, density and phenology of neighbouring host plants, and host ant abundance. Plants that flowered earlier and where host ants were more abundant, and especially plants surrounded by fewer and later-flowering neighbours, produced fewer seeds per flower because of a higher incidence of oviposition. Our results demonstrate that effects of microclimatic variation on plant reproductive performance can be mostly indirect and largely mediated by species interactions. These findings highlight that among individual variation in small-scale environmental conditions within populations can cause variation in individual plant performance through multiple pathways.

Climate change and cocoyam (Colocasia esculenta (L.) Schott) production: assessing impacts and potential adaptation strategies in Zimbabwe

Tropical root and tuber crops such as cocoyam (Colocasia esculenta (L.)) are important for food security and livelihoods and yet neglected in climate change impact studies and large-scale crop improvement programs. The aim of this study was to apply the maximum entropy modelling approach to assess production potential for the orphan crop cocoyam under current and projected climatic conditions by 2050 and 2070 in Zimbabwe. A robust model fit was achieved (AUC > 0.9) with variable importance showing that precipitation-related factors were most important in determining the suitability of cocoyam. About 4.3% of the country is suitable for cocoyam production in Zimbabwe under current climatic conditions with the most suitable areas in eastern districts of Chipinge, Chimanimani, Mutare, Mutasa, Nyanga and Makoni. By 2050, model means project a decrease of 6%, 9%, 10% and 15% under RCP2.6, RCP4.5, RCP6.0 and RCP8.5, respectively. More drastic decreases are projected by 2070 with almost a quarter (23%) of the current suitable areas having lost their suitability for cocoyam production. There is a general model agreement in the direction of impacts except for RCP2.6 where CCSM4 model projects increases in suitability for cocoyam in the country while other models project decreases. We find that regulating canopy microclimate variation increases potential for cocoyam production under climate change and can be implemented to ensure resilience of cocoyam production systems. Therefore, stabilizing or improving orphan crops systems will substantially contribute to local food security and reduction of malnutrition especially during the lean season.

Effect of Climate Variability on Water Footprint of Some Grain Crops under Different Agro-Climatic Regions of Egypt

The water footprint (WF), based on irrigation water quality, is important as a decision-making tool for crop selection based on the comparative advantage of water consumption and yield to maximize agricultural water productivity and sustainably improve water use efficiency. This paper presents a generic link between climate variability and water footprint. To support this link, a case study is presented for wheat and maize in different agro-climate zones in Egypt. In this study, the three agro-ecological zones, Nile Delta, Middle Egypt, and Upper Egypt, were selected to represent three different microclimates. The climate data were analyzed to estimate reference evapotranspiration (ETo) and calculate crop water use (CWU) for wheat and maize from 2015 through 2019. Cultivated area and yield data were analyzed during the study period. Water footprint (WF) was calculated for old land (clay soils) and new lands (sandy soils) in three climate regions based on blue and grey water. Green water was excluded due to negligible rainfall depths in Egypt. The results showed that the mean values of WF for maize were 1067, 1395, 1655 m3/ton in old land and 1395, 1634, 2232 m3/ton in new land under the three climate regions, respectively, while it was 923, 982, 1117 m3/ton in old land and 1180, 1258, 1452 m3/ton for wheat in new land for the three regions, respectively. The results show that the crop water use fluctuated over regions due to climate variability where the CWU values were 6211, 7335, 8007 m3/ha for maize and 4348, 4825, 5774 m3/ha for wheat in the three regions, respectively. The results show an 11% and 33% increase in maize and an 18% and 29% increase in wheat CWU in Middle and Upper Egypt regions comparing to what was observed in Nile Delta due to an increase in solar radiation, temperature, and wind speed. The Egypt mean value of wheat water footprint was 1152 m3/ton and mean value of maize water footprint was 1563 m3/ton. The data clearly show the effect of microclimate variability on WF and irrigation requirements between regions. The methodology and results from this study provide a pathway to help the policy makers to mitigate climate change impacts on crop yield and to enhance water resources management in major crop production regions by redistribution of the cropping patterns based on the comparative advantages of each crop within each region. The crop choices relative to the soil water retention characteristics could also contribute to the moderation of microclimate, which affects ETo and ETc and the water footprint.

Canopy self-replacement in Pinus sylvestris rear-edge populations following drought-induced die-off and mortality

In recent years, Pinus sylvestris die-off and mortality events have occurred across all its range of distribution, usually associated with recurrent droughts induced by climate change. A shift in canopy dominance towards other better adapted co-existing species can be expected, especially in populations located close to their climatic tolerance limits. Herein, we tested, along a local elevational gradient, whether canopy opening resulting from die-off and mortality favours the growth of a non-dominant co-existing tree species (Quercus pubescens) established in the sub-canopy, in comparison to P. sylvestris sub-canopy trees. We also tested whether the growth of both species is associated with local climatic suitability for these species (extracted from SDMs) or, alternatively, with direct measures of micro-climatic variables. Finally, the effect on tree growth of other micro-local factors such as competition, canopy closure and micro-topography was also tested. Sub-canopy tree growth was enhanced overall by canopy opening resulting from P. sylvestris canopy die-off, but this response was stronger in P. sylvestris trees, reinforcing the self-replacement of this species after die-off. This higher growth rate is related to modifications in the micro-local climate (higher temperatures in the wettest quarter). Conversely, Q. pubescens is less sensitive to micro-local climate conditions but it can grow faster than P. sylvestris on stands with no canopy die-off or mortality. In contrast, climatic suitability extracted from SDMs was negatively related to sub-canopy P. sylvestris growth and had no effect on Q. pubescens. These contrasting results support observations at plot scale that P. sylvestris self-replacement is better explained by local environmental conditions than by values of climatic suitability obtained from regional-scale data-sets. Nevertheless, these climatic suitability measures remain consistent with the overall pattern of low seedling recruitment observed in previous works at the rear edge of species' distribution. This study reveals that short-term shifts in species dominance at a local scale will not necessarily occur in the studied P. sylvestris forests following die-off. This finding endorses the notion that micro-local environment and species traits (i.e., light and temperature tolerance, life-history strategies) modulate the capacity for resilience in rear-edge populations that would probably be prone to collapse otherwise.

The potential of natural shade provided by Brazilian savanna trees for thermal comfort and carbon sink

This study looked at the potential of thermal comfort provided to animals by four different Brazilian savanna (Cerrado) native trees, as well as their potential for carbon sink. The evaluations were carried out during the summer of 2020, which consisted of the collection of microclimate variables. The Mean Radiant Temperature (TMR, °C) was derived from the shaded and unshaded areas under the trees, and from that, the Radiant Heat Load (RHL, W m−2) was calculated as an index of thermal comfort. Solar radiation was estimated considering the sum of the direct, diffuse, and reflected components (W m−2), and carbon stock from trees biomass for CO2 sequestration was estimated from an allometric model applied to the native Cerrado tree species. The shade of the native trees reduced the meteorological variables such as dry bulb and black globe temperatures, to values considered adequate for the thermal comfort of animals, with an average reduction respectively equal to 1.3 °C and 6.4 °C. This represents a significant difference compared to the unshaded area as well as among tree species (P < 0.05), reflecting in lower values of TMR and RHL in the shaded area provided by each species. Carbon sequestration individually estimated by each native tree species was on average 8.85 Mg per tree. These results demonstrate the great potential for native tree species in the Cerrado biome to be used in agroforestry systems to provide higher levels of thermal comfort to animals and to combat climate change through their aptitude of CO2 sink.

A multi-perspective analysis of microclimate dynamics for air-based solar hydrogen production

Navigating the microclimatic environment for the optimal control of water-from-air devices could be a challenge. An example of such a device is an air-based solar hydrogen production device. Such a device promises the ability for off-grid, easily deployable and modular hydrogen production for on-site consumption. Novel analysis techniques, such as wavelet transform coherence analysis, could assist in better understanding the microclimate in which air-based hydrogen production devices might function. The analysis becomes complicated when a system is evaluated at the microclimatic level, especially when it is considered that the performance of air-based solar hydrogen devices are not only dependent on solar radiation, but also on humidity levels in the air. To get a grasp of the interactions that take place within a microclimatic system, a two-tiered approach is presented. It has been shown that relative humidity and temperature is stratified close to the ground, and that the stratification undergoes an inversion twice per day. A possible link between absolute humidity and wind direction is observed and humidity rallies are identified. Using microclimate monitoring and wavelet transform coherence analysis, an attempt is made to disentangle microclimatic variables by pointing out regions of high coherence and regions of low coherence between different variables. It is furthermore suggested that the propagation direction of a humidification process within the microclimate can be determined by considering the phase angle between relative humidity timeseries at different heights above the ground, using wavelet transform coherence analysis. It has been demonstrated that wavelet transform coherence analysis, in conjunction with a comprehensive microclimate monitoring process, could support the understanding of the complex processes that occur within the microclimatic environment and therefore support the management of water-from-air systems. In this regard a management framework is also presented.

Different factors limit early- and late-season windows of opportunity for monarch development.

Seasonal windows of opportunity are intervals within a year that provide improved prospects for growth, survival, or reproduction. However, few studies have sufficient temporal resolution to examine how multiple factors combine to constrain the seasonal timing and extent of developmental opportunities. Here, we document seasonal changes in milkweed (Asclepias fascicularis)–monarch (Danaus plexippus) interactions with high resolution throughout the last three breeding seasons prior to a precipitous single‐year decline in the western monarch population. Our results show early‐ and late‐season windows of opportunity for monarch recruitment that were constrained by different combinations of factors. Early‐season windows of opportunity were characterized by high egg densities and low survival on a select subset of host plants, consistent with the hypothesis that early‐spring migrant female monarchs select earlier‐emerging plants to balance a seasonal trade‐off between increasing host plant quantity and decreasing host plant quality. Late‐season windows of opportunity were coincident with the initiation of host plant senescence, and caterpillar success was negatively correlated with heatwave exposure, consistent with the hypothesis that late‐season windows were constrained by plant defense traits and thermal stress. Throughout this study, climatic and microclimatic variations played a foundational role in the timing and success of monarch developmental windows by affecting bottom‐up, top‐down, and abiotic limitations. More exposed microclimates were associated with higher developmental success during cooler conditions, and more shaded microclimates were associated with higher developmental success during warmer conditions, suggesting that habitat heterogeneity could buffer the effects of climatic variation. Together, these findings show an important dimension of seasonal change in milkweed–monarch interactions and illustrate how different biotic and abiotic factors can limit the developmental success of monarchs across the breeding season. These results also suggest the potential for seasonal sequences of favorable or unfavorable conditions across the breeding range to strongly affect monarch population dynamics.

Tracheid buckling buys time, foliar water uptake pays it back: Coordination of leaf structure and function in tall redwood trees.

Tracheid buckling may protect leaves in the dynamic environments of forest canopies, where rapid intensifications of evaporative demand, such as those brought on by changes in light availability, can result in sudden increases in transpiration rate. While treetop leaves function in reliably direct light, leaves below the upper crown must tolerate rapid, thermally driven increases in evaporative demand. Using synchrotron-based X-ray microtomography, we visualized impacts of experimentally induced water stress and subsequent fogging on living cells in redwood leaves, adding ecological and functional context through crown-wide explorations of variation in leaf physiology and microclimate. Under drought, leaf transfusion tracheids buckle, releasing water that supplies sufficient temporal reserves for leaves to reduce stomatal conductance safely while stopping the further rise of tension. Tracheid buckling fraction decreases with height and is closely coordinated with transfusion tissue capacity and stomatal conductance to provide temporal reserves optimized for local variation in microclimate. Foliar water uptake fully restores collapsed and air-filled transfusion tracheids in leaves on excised shoots, suggesting that trees may use aerial water sources for recovery. In the intensely variable deep-crown environment, foliar water uptake can allow for repetitive cycles of tracheid buckling and unbuckling, protecting the tree from damaging levels of hydraulic tension and supporting leaf survival.

Energy Balance, Microclimate, and Crop Evapotranspiration of Winter Wheat (Triticum aestivum L.) under Sprinkler Irrigation

Understanding the impact of sprinkler irrigation on field energy balance, microclimate, and crop evapotranspiration is of great importance for optimizing irrigation scheduling and enhancing crop growth. In this study, the microclimate variables, energy, and water flux were measured using an eddy covariance system during four wheat (Triticum aestivum L.) growing seasons in a sprinkler-irrigated field of North China Plain. The variation patterns of microclimate, energy balance (net solar radiation Rn, soil heat flux G, latent heat LE, and sensible heat H) and crop evapotranspiration (ET) were analyzed during and after sprinkler irrigation events. A novel quantitative model using a stepwise regression method was developed to predict the change in microclimate after sprinkler irrigation by considering irrigation, weather, meteorology, and crop traits. The results showed that the reflectance rate of the wheat canopy decreased by 0.01, and the daily LE/Rn increased by 0.19–0.23 in the 1–3 days after sprinkler irrigation with 40–50 mm water, which finally resulted in crop ET increased by 1.8–4.7 mm during irrigation interval, and seasonal total ET could increase by 9–24 mm when five normal sprinkler irrigations were implemented in a wheat season. The mean daily H/Rn decreased by 0.06–0.17, indicating weak energy exchange between canopy and environment. The measured daily minimum (Tmin), maximum temperatures (Tmax) and daily mean vapor pressure deficit (VPD) decreased by approximately 0.8 °C, 0.9 °C, and 0.25 kPa, respectively, and daily mean relative humidity increased by approximately 7.5% on the first 3 days after sprinkler irrigation; and these changes decreased and were negligible on the 5th–7th days. The decreases in daily Tmin, Tmax, and mean VPD after sprinkler irrigation could change more under higher irrigation amounts and sunny days with a larger crop leaf area index based on the fitted models.

Effects of spatial scale of atmospheric reanalysis data on clear-sky surface radiation modeling in tropical climates: A case study for Singapore

Solar resource assessments most generally require atmospheric information, which is customarily acquired from gridded datasets. The spatial scale mismatch problem, i.e., the difference in spatial representativeness of gridded data and in situ measurements, therefore becomes relevant. This study examines how the gridded data used as inputs to clear-sky radiation models can affect their performance at urban scale. The tropical island of Singapore is selected for the case study. Aerosol optical depth at 550 nm (AOD550), Å ngström exponent (AE), and precipitable water (PW) from both the MERRA-2 reanalysis and ground-based stations (AERONET and SuomiNet) are collected between 2013–2020. Firstly, it is found that, relatively to the AERONET ground truth, the bias in MERRA-2’s AOD550 is more prominent than that in AE or PW. Next, the bias propagation from the gridded inputs (AOD550, AE, and PW) to clear-sky radiation predictions is explored using various models. The estimated clear-sky direct normal irradiance (DNIcs) is more sensitive to AOD550 variation than the clear-sky global horizontal irradiance (GHIcs). Six clear-sky radiation models, five of which accept MERRA-2 gridded inputs, are compared with each other, and with the in situ irradiance measurements recorded at 9 sites. The inter-model difference across Singapore is remarkably consistent because the whole island fits inside a single MERRA-2 grid cell. Under high-AOD550 situations, however, the inter-model deviation becomes large for both GHIcs and DNIcs. The conventional model-versus-measurement comparison shows that each model achieves very different site-to-site performance, largely because the spatially-averaged inputs cannot fully represent the micro-climatic variability. Relatively speaking, no clear-sky radiation model significantly outperforms its peers. The simple MAC2 model and the empirical (locally derived) Yang GHIcs-only model are recommended for Singapore.

CHANGES IN LIGHT RADIATION AND MICROCLIMATIC CONDITIONS ALTER THE POMEGRANATE CUTTINGS PHOTOMORPHOGENESIS TREATED WITH AQUEOUS EXTRACT OF Cyperus rotundus

Technological advances in agriculture make it possible to manage the light spectrum radiation in a protected environment and generate improvements in plant photomorphogenesis, which can be a promising strategy for the supply of seedlings of pomegranate qualities. It aimed to evaluate whether the microclimatic environmental changes, due to the management of light spectrum radiation, modify the photomorphogenesis and water consumption by pomegranate cuttings treated with aqueous C. rotundus (nutsedge) extract, as well as determine the most important variables to explain such effects. A completely randomized design, in a 4x4 factorial scheme, and with three replications. Four light spectrum radiation (white, blue, red, and extreme red lights) and four nutsedge extract concentrations (0, 25, 50, and 100%) were applied. Throughout the experimental period, the environments were monitored to establish the illuminance, average air temperature, relative air humidity, average soil temperature and evapotranspiration water consumption by the cuttings. The numbers of shoots were recorded weekly, numbers of roots and shoots were calculated 60 days after cutting planting. All microclimatic variables were influenced by light conditions. Shoots were observed on the cuttings under white and blue lights with application of 0, 25, 50, and 100% of nutsedge extract concentrations. Variations in light spectrum radiation promote environmental microclimate changes and influence photomorphogenesis and water consumption by pomegranate cuttings treated with aqueous extract of nutsedge. All variables studied were considered as important to explain the influence of environmental microclimate changes, due to light spectrum variation, on photomorphogenesis and water evapotranspiration and consumption by pomegranate cuttings.

Long Term Microscale Decadal Analysis of Coastal Rainfall Pattern: An Indication of Microclimatic Variation in South India

There are drastic variations in the intensity and the pattern of rainfall and temperature globally. The variations thus reflect the variation in the microclimatic signatures. The current study aims to assess the climatic changes in the coastal region of Ramanathapuram using the monthly rainfall and temperature average along the coastal region. The microscale rainfall and temperature trend have been analysed for three decades (30 years), representing 1990 to 2019. The study was divided into three different periods: first (1990-1999), second (2000-2009), and the third decade (2010-2020). The study infers that 467 km2 of the area receives an average of 676 mm of rain in decade-I. In decade-II, 39 km2 of the area is noted with 637.6 mm rainfall, 48 km2 of the study area is reported to have 821 mm rainfall, and only 29 km2 area receives normal rainfall of 992 mm, but 351 km2 receives “excess” rainfall of above 1000 mm. In decade-III, less than 750 mm rainfall is recorded at 202 km2, with 43 km2 recorded “deficit” rainfall, and 24 km2 area received an “excess” rainfall. The variation in the amount of rain during the recent period was observed. Similarly, the temperature was comparatively elevated during the Ist Decade (1990-1999). The intensity of rain events, number of rainy days and frequency of rainfall reflected variations. The land surface temperatures also indicated minor variations and increased inter-monsoonal periods. The variation in the rainfall amount, the shift in monsoonal periods and the change in temperature indicate the microclimatic variation in the region.

Smart greenhouses as the path towards precision agriculture in the food-energy and water nexus: case study of Qatar

Greenhouse farming is essential in increasing domestic crop production in countries with limited resources and a harsh climate like Qatar. Smart greenhouse development is even more important to overcome these limitations and achieve high levels of food security. While the main aim of greenhouses is to offer an appropriate environment for high-yield production while protecting crops from adverse climate conditions, smart greenhouses provide precise regulation and control of the microclimate variables by utilizing the latest control techniques, advanced metering and communication infrastructures, and smart management systems thus providing the optimal environment for crop development. However, due to the development of information technology, greenhouses are undergoing a big transformation. In fact, the new generation of greenhouses has gone from simple constructions to sophisticated factories that drive agricultural production at the minimum possible cost. The main objective of this paper is to present a comprehensive understanding framework of the actual greenhouse development in Qatar, so as to be able to support the transition to sustainable precision agriculture. Qatar’s greenhouse market is a dynamic sector, and it is expected to mark double-digit growth by 2025. Thus, this study may offer effective supporting information to decision and policy makers, professionals, and end-users in introducing new technologies and taking advantage of monitoring techniques, artificial intelligence, and communication infrastructure in the agriculture sector by adopting smart greenhouses, consequently enhancing the Food-Energy-Water Nexus resilience and sustainable development. Furthermore, an analysis of the actual agriculture situation in Qatar is provided by examining its potential development regarding the existing drivers and barriers. Finally, the study presents the policy measures already implemented in Qatar and analyses the future development of the local greenhouse sector in terms of sustainability and resource-saving perspective and its penetration into Qatar’s economy.