Clear Summer Days Research Articles

Microclimate Modification by Urban Shade Trees – An Integrated Approach to Aid Ecosystem Service Based Decision-making

Since microclimate regulation is one of the most important services of vegetation that is directly perceived by urban population, many studies aimed to evaluate and map this service on different spatial scales. Most of the investigations focused on the modification of only one parameter, namely the reduction of air temperature. However, it is important to state that thermal sensation, health and well-being are influenced by more atmospheric parameters, including air humidity, wind velocity and the three-dimensional short- and long-wave radiation environment as well. This necessitates the assessment of the modification effect of urban vegetation on the thermal components separately. With the above mentioned objective, this paper presents the initial results of a microclimate investigation series carried out in Szeged, South-East Hungary. Systematic on-site measurements were carried out with a pair of special human-biometeorological stations on 20 clear summer days of 2015 in order to reveal the small-scale climate regulation potential of single trees in urban environment. Five healthy, mature trees were selected for the analysis, without the disturbing (additional shading) effect of any other trees or artificial objects. We compare separately the median values of the main thermal parameters – air temperature, relative humidity, as well as the short- and long-wave radiation components from the upper and lower hemisphere – measured under the canopy of the trees, and in the sun. Our results demonstrate that all of the five investigated tree specimens have significantly greater impact on the components of the radiation budget, while the modification of air temperature and humidity is rather small. Inter-species differences seem to be small in the warmest hours of the day, and may be attributed to the dimensional and canopy-characteristics. During the development of ecosystem service indicators it would be advisable to use integrated human-biometeorological indices which take into account all meteorological parameters that influence considerably human thermal comfort.

Monte Carlo modelling of daylight activated photodynamic therapy

The treatment of superficial skin lesions via daylight activated photodynamic therapy (PDT) has been explored theoretically with three dimensional (3D) Monte Carlo radiation transfer simulations. For similar parameters and conditions, daylight activated PDT was compared to conventional PDT using a commercially available light source. Under reasonable assumptions for the optical properties of the tissue, protoporphyrin IX (PpIX) concentration and a treatment dose of 75 J cm−2, it was found that during a clear summer day an effective treatment depth of over 2 mm can be achieved after 30 min of daylight illumination at a latitude of 56 degrees North. The same light dose would require 2.5 h of daylight illumination during an overcast summer day where a treatment depth of about 2 mm can be achieved. For conventional PDT the developed model suggests that 15 min of illumination is required to deliver a light dose of 75 J cm−2, which would result in an effective treatment depth of about 3 mm. The model developed here allows for the determination of photo-toxicity in skin tissue as a function of depth for different weather conditions as well as for conventional light sources. Our theoretical investigation supports clinical studies and shows that daylight activated PDT has the potential for treating superficial skin lesions during different weather conditions.

CFD simulation of an idealized urban environment: Thermal effects of geometrical characteristics and surface materials

Numerical fluid flow and heat transfer simulations of a street-scale urban environment are utilized to investigate the diurnal cycle of the urban thermal environment. Unsteady simulations forced with realistic solar load and wind and temperature profiles are performed based on Reynolds-averaged Navier–Stokes equations in the finite volume solver ANSYS/FLUENT 14.5. The simulations are carried out over an idealized geometry for a clear summer day in southern California. In comparison with previous studies, our model considers dynamic coupling of heat transfer and the flow field as well as non-uniform surface heating caused by solar insolation and building shadowing. Relative importance of urban design parameters, including urban aspect ratio (height-to-width of H/W=1/3–3/2), surface albedo (0.18–0.35), and wind direction (0°, 45° and 90°) and speed (2 and 3 ms-1 bulk flow) are investigated. Ground surface albedo is found to have the most influence on the urban facade temperature and the energy balance. Replacing asphalt with concrete as ground material decreased ground surface temperature by up to 8K and increased building wall temperature by 3.5K. In agreement with surface temperature Urban Heat Islands observations, high urban built-up density, specified by larger canyon H/W, increases the peak building wall temperature during the day, while the ground surface temperature is more sensitive to aspect ratio at night. Although the higher H/W decreases the penetration of direct solar radiation, an energy balance analysis suggests the wall temperature increase to be the result of decreasing convective cooling. For compact building configuration (canyon H/W of 1), rotating the wind direction 45° away from the canyon axis and increasing average bulk velocity at the inlet did not significantly influence the wind speed inside the canyon and therefore ground temperatures, while peak roof temperature is strongly influenced. Therefore urban built-up density outweighs the effects of wind speed and direction on the ground temperature.

Spring and summer night-time high ozone episodes in the upper Brahmaputra valley of North East India and their association with lightning

Simultaneous and round the clock measurement during thunderstorm and lightning has been used to study the impact of lightning generated NOx (LNOx) on O3 mixing ratio within the boundary layer during night-time. Lightning flash rate obtained from Lightning Image Sensor (LIS) on board TRMM over the Brahmaputra valley centred around Dibrugarh has been used to identify the events in which NOx was elevated with simultaneous dip in O3 for a short duration followed by subsequent elevation of O3 in spring and summer of 2012–2014. Seasonally averaged O3 attains higher values at night on thunderstorm days as compared to that on clear and cloudy days both in spring and summer i.e. as against a minimum night-time (1700–0500 h) values of ∼3 ppb on clear days, the mean night-time level on thunderstorm days is ∼18 ppb in spring and ∼12 ppb in summer. The estimated steady state O3 concentration is well correlated with the NO2/NO ratio and found to be ∼33% of the measured O3. One day isentropic concentration weighted trajectory (CWT) analysis carried out for the spring and summer seasons reveal that part of GWB and Bangladesh are the potential additional source of O3 in both the seasons. LNOx is found to contribute to ∼33% of the measured O3 during the study period. Enhancement of O3 is well correlated with the lightning radiance indicating direct photodissociation of O3 due to lightning. ΔO3 is independent of the location of the flash rather depends on flash intensity.

Erratum to: Outdoor open thin-layer microalgal photobioreactor: potential productivity

Figure 1 shown in the article does not represent real timecourse of algal growth in the photobioreactor during one fedbatch growth cycle. It was constructed as an ideal growth curve to estimate the maximum productivity using selected data obtained during clear summer days. Not included in the curve is the lower growth rate of the culture at the beginning of the curve. This would prolong the length of the cycle up to 12– 14 days and decreases the average daily net areal productivity in course of the growth cycle to about 29 g m d. Still, under ideal climate and growth conditions, yields of 80–100 t of dried Chlorella biomass per 1 ha area could be theoretically reached for a 300-day cultivation season. One of the major goals of algal biotechnology is to prove experimentally that such high biomass yields can be achieved in Chlorella strains with high starch content (50 % in biomass).

An Improved Three-Dimensional Simulation of the Diurnally Varying Street-Canyon Flow

The impact of diurnal variations of the heat fluxes from building and ground surfaces on the fluid flow and air temperature distribution in street canyons is numerically investigated using the PArallelized Large-eddy Simulation Model (PALM). Simulations are performed for a 3 by 5 array of buildings with canyon aspect ratio of one for two clear summer days that differ in atmospheric instability. A detailed building energy model with a three-dimensional raster-type geometry—Temperature of Urban Facets Indoor-Outdoor Building Energy Simulator (TUF-IOBES)—provides urban surface heat fluxes as thermal boundary conditions for PALM. In vertical cross-sections at the centre of the spanwise canyon the mechanical forcing and the horizontal streamwise thermal forcing at roof level outweigh the thermal forces from the heated surfaces inside the canyon in defining the general flow pattern throughout the day. This results in a dominant canyon vortex with a persistent speed, centered at a constant height. Compared to neutral simulations, non-uniform heating of the urban canyon surfaces significantly modifies the pressure field and turbulence statistics in street canyons. Strong horizontal pressure gradients were detected in streamwise and spanwise canyons throughout the day, and which motivate larger turbulent velocity fluctuations in the horizontal directions rather than in the vertical direction. Canyon-averaged turbulent kinetic energy in all non-neutral simulations exhibits a diurnal cycle following the insolation on the ground in both spanwise and streamwise canyons, and it is larger when the canopy bottom surface is paved with darker materials and the ground surface temperature is higher as a result. Compared to uniformly distributed thermal forcing on urban surfaces, the present analysis shows that realistic non-uniform thermal forcing can result in complex local airflow patterns, as evident, for example, from the location of the vortices in horizontal planes in the spanwise canyon. This study shows the importance of three-dimensional simulations with detailed thermal boundary conditions to explore the heat and mass transport in an urban area.

ERITEMINĖS ULTRAVIOLETINĖS SPINDULIUOTĖS POKYČIŲ ANALIZĖ

In this article the erythemally weighted UV radiation intensity variations during 2002-2011 were analysed. Also UV radiation intensity and total ozone data in this paper were analysed, because the UV index is directly dependent on the intensity of UV radiation, and most of the UV radiation is absorbed by stratospheric ozone. During 2002-2011 in the course of UV index - the upward trend was observed, and in the total ozone values - the downward trend was observed. During the investigated period in Lithuania the maximum UV index values (very high) on clear sky summer days were determined.

Developing a weather responsive internal shading system for atrium spaces of a commercial building in tropical climates

In response to the non-trivial problem of overheating in glass roofed buildings in low latitudes a study was undertaken to reduce discomfort and high energy consumption in a large atrium building in China. This paper reports on the development of a shading system designed for that building as a remedial solution to reduce temperatures while maintaining adequate levels of natural lighting in the atrium spaces of a large multifunctional commercial building. The effects of the shading system on both the physical indoor environment and its economic implications were analysed using implemented models. Calibrated with the data measured in the building during the hottest season, summer, the models were used to test both thermal and lighting performance of two shading arrangements: high and low level blinds in both open and covered modes on typical overcast days and clear days in summer and winter respectively. Also tested were two types of fabric used for the blinds.The performance of these tested cases was assessed for solar gain, cooling loads, internal surface temperatures, air temperatures and operative temperatures of both ground floor and surrounding walkways on various levels within the atrium, the major circulation areas. The results reveal that the high level shading, with blinds fixed close to the glazed roof are generally less effective in the provision of thermal and lighting conditions of the atrium, than the low level shading, where blinds are fixed 3–5 m below the glazed roof to form a ventilated void. The financial benefits of these remedial solutions were also assessed using standard economic analysis methods to provide recommendations on their costs and payback periods.

Analysis of ultraviolet radiation in Central China from observation and estimation

Measurements of UV (ultraviolet) and global solar radiation in Central China during 2006–2012 were first reported to investigate the UV radiation variability in different time scales and its UV fraction under different sky conditions. Both UV irradiation and UV fraction showed similar features that peaked in values at noon during summer (July) and reached their lowest in winter (January) with annual mean values being about 0.49 MJ m−2 d−1 and 4.35%, respectively. It was also discovered that there were inverse relationships between UV fractions and clearness indexes at all sky conditions; clouds, water vapor and seasonality were main factors causing the daily variations of UV irradiations. The maximum UV irradiances decreased by 51.14% (33.49%) in overcast days when compared to clear days in summer (winter). By analyzing the dependence of UV irradiances on cosine of solar zenith angle and clearness index, an efficient all-sky model has been developed for estimating UV values in Central China, which has also been tested at Sanjiang and Lhasa and produced satisfied estimations. UV dataset from 1961 to 2011 in Central China was then reconstructed and annual mean daily UV irradiation was about 0.488 MJ m−2 d−1. There was a significant decreasing trend (−0.018 MJ m−2 d−1 per decade) during the last 50 years, the decreases were sharpest in summer (−0.027 MJ m−2 d−1 per decade) with smallest decreases being observed in autumn (−0.001 MJ m−2 d−1 per decade). Meanwhile, it was also revealed that UV energy began to increase since 1990s (0.003 MJ m−2 d−1 per year).

Diurnal variation of photochemical oxidants over central Japan during clear summer days and the associated thermally-induced local circulation

Diurnal variation of photochemical oxidants over central Japan during clear summer days and the associated thermally-induced local circulation

Variability of solar UV-B irradiance: in situ monitoring and model calculation of the vitamin D synthetic capacity of sunlight

The prediction of the biological effects of solar radiation on human health, in particular involving terrestrial level of solar ultraviolet (UV) radiation, requires the development of an adequate methodological strategy for remote sensing. To date, it is well understood that, in appropriate doses, UV radiation is beneficial for people, specifically due to the production of vitamin D3 in the skin from its precursor 7-dehydrocholesterol. But as far as excessive UV exposure causes acute and chronic health effects, in most cases biological activity of solar UV radiation is calculated by weighting solar UV spectra with International Commission on Illumination (CIE) erythemal action spectrum. Yet the beneficial vitamin D synthetic capacity of sunlight cannot be correctly estimated in this way because of the significant difference between the erythemic and vitamin D synthesis action spectra. With due regard to the essential role of vitamin D3 for human health, in this article we examine the possibility of simplified estimation in situ of provitamin D3 photoconversion into previtamin D3 from the UV absorption spectra of an in vitro model of vitamin D synthesis upon exposure to sunlight. A large-scale linear correlation (R = 0.99) was found on a clear summer day between the concentration of accumulated previtamin D3 and maximum absorbance decline in the initial provitamin D3 absorption spectrum. However, long-term observations showed a poorer (R = 0.77) correlation, and a source of ambiguity of such indirect estimation of previtamin D3 concentration is discussed in detail. In addition, we propose a reliable algorithm for the direct calculation of previtamin D3 accumulation using solar UV spectra as input data to the reaction model of previtamin D photosynthesis and demonstrate the critical dependence of previtamin D3 accumulation on stratospheric ozone, season, latitude and cloudiness. The comparison of experimental and simulation data conforms to recent findings on Europe's darker atmosphere in the UV-B and implicates the practical certainty of the presented algorithm for the calculation of the vitamin D synthetic capacity from the remotely sensed solar spectra.

Coldest places on earth with angiosperm plant life

The highest elevation flowering plant ever recorded in Europe, a lush moss flora, one of the coldest places of permanent animal life (collembola, mites) and indications of mycorrhizal fungi were evidenced for the Dom summit (4,545 m, central Swiss Alps) between solid siliceous rock at 4,505-4,543 m, 46 degrees N. Cushions of Saxifraga oppositifolia were found at 4,505 to 4,507 m a.s.l. A large individual (possibly <30 years old) was in full bloom on 12 August 2009. The 14 C-dated oldest debris of the biggest moss, Tortula ruralis, suggests a 13 year litter turnover. The thermal conditions at this outpost of plant life were assessed with a miniature data logger. The 2008/09 growing season had 66 days with a daily mean rooting zone temperature <0 degrees C in this high elevation micro-habitat (2-3 cm below ground). The degree hours <0 degrees C during this period summed up to 4,277 degrees h corresponding to 178 degrees d (degree days), the absolute winter minimum was -20.9 degrees C and the absolute summer maximum 18.1 degrees C. The mean temperature for the growing period was +2.6 degrees C. All plant parts, including roots, experience temperatures below 0 degrees C every night, even during the warmest part of the year. On clear summer days, plants may be physiologically active for several hours, and minimum night temperatures are clearly above the freezing tolerance of Saxifraga oppositifolia in the active state. In comparison with climate data for other extreme plant habitats in the Alps, Himalayas, in the Arctic and Antarctic, these data illustrate the life conditions at what is possibly the coldest place for angiosperm plant life on earth.

Optimization of anti‐reflection moth‐eye structures for use in crystalline silicon solar cells

AbstractAn anti‐reflection (AR) moth‐eye structure made of acrylic resin and deposited on a polyethylene terephthalate (PET) substrate was optimized in the wavelength range from 400 to 1170 nm; crystalline silicon (c‐Si) solar cells function efficiently in this wavelength range. The rigorous coupled wave analysis (RCWA) method was used for optical simulation, and the Taguchi method was used for efficient optimization. The simulation results showed that the reflectance of the optimized structure over the above‐mentioned wavelength range was less than 0.87% and that a minimal reflectance of 0.1% was observed at 400 nm. Experimental results showed that the reflectance of a fabricated moth‐eye structure was less than 1.0% in the wavelength range and that a minimal reflectance of 0.55% was observed at 700 nm. A c‐Si solar cell, which was enclosed in a polyvinyl butyral (PVB) layer of uniform thickness, was coated with the fabricated moth‐eye film, and it was observed that the moth‐eye film increased electric generation (EG) up to 15%, depending on the incident angle. Further, a daily increase in EG of up to 8.7% was estimated on a clear summer day in Japan when the moth‐eye film was used. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Comparison of human radiation exchange models in outdoor areas

Results from the radiation components of seven different human thermal exchange models/methods are compared. These include the Burt, COMFA, MENEX, OUT_SET* and RayMan models, the six-directional method and the new Park and Tuller model employing projected area factors (fp) and effective radiation area factors (feff) determined from a sample of normal- and over-weight Canadian Caucasian adults. Input data include solar and longwave radiation measured during a clear summer day in southern Ontario. Variations between models came from differences in fp and feff and different estimates of longwave radiation from the open sky. The ranges between models for absorbed solar, net longwave and net all-wave radiation were 164, 31 and 187 W m−2, respectively. These differentials between models can be significant in total human thermal exchange. Therefore, proper fp and feff values should be used to make accurate estimation of radiation on the human body surface.

An experimental wick-type solar still system: Design and construction

A tilted wick-type solar still was designed and constructed. Its practical aspects and performance are presented. Charcoal cloth was used as an absorber/evaporator material and for saline water transport. The distillation system consists of five main parts: (1) the still, (2) main reservoir, (3) constant head device, (4) distillate bottle, and (5) brine reservoir. Indoor and outdoor experimental testings were carried out to investigate the effect of input water flow rate and salinity on the still productivity together with the variation of the solar still efficiency with absorber temperature. The representative daily efficiency of the still was about 53% on clear days in summer. It has been concluded that, the charcoal cloth is a good material for use as an absorber/evaporator and also as a water transport medium. Increase of the input water mass flow rate leads to a reduction in the efficiency of the wick-type solar still. The still efficiency decreased linearly with increase of salinity of the input saline water e.g. it decreased, by indoor testing, from 37.7% to 20% as the NaCl salt concentration increased from 0% to 10% by weight.

Modeling the Thermal Effects of Artificial Turf on the Urban Environment

Abstract The effects of artificial turf (AT) on the urban canopy layer energy balance, air and surface temperatures, and building cooling loads are compared to those of other common ground surface materials (asphalt, concrete, and grass) through heat transfer modeling of radiation, convection, and conduction. The authors apply the Temperatures of Urban Facets in 3D (TUF3D) model—modified to account for latent heat fluxes—to a clear summer day at a latitude of 33° over a typical coastal suburban area in Southern California. The low albedo of artificial turf relative to the other materials under investigation results in a reduction in shortwave radiation incident on nearby building walls and an approximately equal increase in longwave radiation. Consequently, building walls remain at a relatively cool temperature that is similar to those that are adjacent to irrigated grass surfaces. Using a simple offline convection model, replacing grass ground cover with artificial turf was found to add 2.3 kW h m−2 day−1 of heat to the atmosphere, which could result in urban air temperature increases of up to 4°C. Local effects of AT on building design cooling loads were estimated. The increased canopy air temperatures with AT increase heat conduction through the building envelope and ventilation in comparison with a building near irrigated grass. However, in this temperate climate these loads are small relative to the reduction in radiative cooling load through windows. Consequently, overall building design cooling loads near AT decrease by 15%–20%. In addition, the irrigation water conservation with AT causes an embodied energy savings of 10 W h m−2 day−1. Locally, this study points to a win–win situation for AT use for urban landscaping as it results in water and energy conservation.

라그랑지안 입자확산모델을 이용한 광양만 권역에서의 공기괴 재순환현상 수치모의

Air mass recirculation is a common characteristic in the coastal area as a result of the land-sea breeze circulation. This study simulates the recirculation of air mass over the Gwangyang Bay using WRF-FLEXPART and offers a basic information about the effective domain size that can reflect recirculation. For this purpose, WRF is set up four nested domains and three cases are selected. Subsequently FLEXPART is operated on the basis of WRF output. During the clear summer days with weak wind speed, particles that emitted from Yeosu national industrial complex and Gwangyang iron works flow into emission sources because of the land-sea breeze. When land-sea breeze is strengthen, the recirculation phenomena appears clearly. However particles aren't recirculated under weak synoptic condition. Also plume trajectory is analyzed and as a consequence, the smallest domain area have to be multiplied by 1.3 to understand recirculated dispersion pattern of particles.

Hydrogen generation under sunlight by self ordered TiO2 nanotube arrays

Abstract Highly ordered TiO 2 nanotube arrays generate a considerable interest for hydrogen generation by an electrochemical photocell, since ordered architecture of nanotube arrays provides a unidirectional electric channel for electron's transport. Here, we report the hydrogen generation by highly ordered TiO 2 nanotube arrays under actual sunlight in KOH electrolyte. The two-electrode electrochemical cell included an adjustable anode compartment capable of tracing the trajectory of the sun and a set of alkaline batteries connected with a rheostat for application of external bias. The results showed that the photocurrent responses of nanotube arrays match well with the intensity of solar irradiance on a clear summer day. Addition of ethylene glycol into KOH electrolyte as a hole scavenger enhanced the rate of hydrogen generation. A maximum photocurrent density of 31 mA/cm 2 was observed at 13:30 h, by focusing the sunlight with an intensity of 113 mW/cm 2 on the surface of the TiO 2 nanotube arrays in 1 M KOH electrolyte with 10 vol% ethylene glycol under an applied bias of 0.5 V. The observed hydrogen generation rate was 4.4 mL/h cm 2 under the focalized solar irradiance with an intensity between 104 mW/cm 2 and 115 mW/cm 2 from 10:00 to 14:20 h.

Abstract ED07-03: Role of Vitamin D in prevention of cancer: dose-response relationships

Abstract ED07-03: Role of Vitamin D in prevention of cancer: dose-response relationships

Outdoor open thin-layer microalgal photobioreactor: potential productivity

We have previously estimated the productivity and photosynthetic efficiency of the microalga Chlorella sp. grown in an outdoor open thin-layer photobioreactor under climate conditions typical of the Middle European region, i.e. with many days unsuitable for intensive growth of algae (cloudy and rainy days, low air temperature, low solar PAR input).To estimate the real potential productivity of the bioreactor, we collected data on algae yields obtained during clear summer day periods. Cultivation was performed in fed-batch cycles in a bioreactor with a 224 m2 culture area (length 28 m, slope 1.7%), and a 6–7 mm-thick layer of algal culture. The suspension volume in the bioreactor was 2,000 L. The mean values found for Třeboň (49°N), Czech Republic, as an average of several sunny summer cultivation periods in July, were: net areal productivity, Pnet = 38.2 g dry weight (DW) m-2 day-1; net volumetric productivity, Pvol, = 4.3 g algal DW L-1 day-1, photosynthetic efficiency (based on PAR), ηnet = 7.05%. The peak values were: Pnet about 50 g (DW) m-2 day-1, ηnet about 9%. Algal growth rate was practically linear up to high biomass densities (40–50 g DW L-1, corresponding to an areal density of 240–300 g DW m-2), at which point the culture was harvested. The concentration of dissolved oxygen increased from about 10 mg L-1 at the beginning to about 23 mg L-1 at the end of culture area at noon. Use of the above-described technology for economical production of bioethanol is proposed.