Improving Pedestrian Thermal Comfort Using Optimized Urban Trees Pattern in Aswan City

For long periods last years, the majority of cities suffer from exceptionally hot- dry climate. However, the most urban patterns within these cities are unsuitable for these severe occurrences and raise the value of the Urban Heat Island (UHI). The goal of this study is to see how UHI mitigation options affect outdoor human thermal comfort in three different forms of frequent urban trees patterns in the world’s most populous city in Egypt, Aswan. The ENVI-met model was utilised to assess meteorological using simulation climate program (Ecotect Analysis), buildings and vegetation distribution, using Pupulus Alba. All measurements were taken in a pedestrian walkway at the microclimate case study (case 1. without trees, case 2. distribution trees each 8m total coverage 50%, case 3. distribution trees each 12m total coverage 21.5% were conducted to measure, relative humidity, mean radiant temperature, wind speed, air temperature and prediction mean vote as a key indicator for human thermal comfort. This study provided a better understanding of the role of Urban Heat Island UHI mitigation strategies on human thermal comfort in the outdoor spaces of Aswan’s residential neighborhoods. The simulation results revealed high thermal comfort and discomfort after setting 3 cases for trees pattern for the climate and the possible vegetation (trees patterns). This result indicate that an optimized percentage of urban trees pattern can mitigate (UHI) effect and clear the role that urban trees serve in modifying microclimates.


Introduction
About 50 percent of the world's population live in cities and expected to rise to 80 percent in 2030 [1].Over 55% of the world's population already resides in cities, and by 2050, that number is projected to rise to 68% [2].Along with this challenge, the modern metropolis is also dealing with the effects of climate change, such as the Urban Heat Island (UHI) phenomena [3].The effects of climate change on urban planning are a growing concern for urban planners [4].They work tirelessly to preserve and enhance the quality of life for city dwellers by fostering a comfortable and welcoming atmosphere [5].Cities are essential locations for planning climate change adaptation because of the large concentration of infrastructure and people there, making metropolitan regions more sensitive to changes in precipitation patterns and temperature extremes.Proactive adaptation in cities can be highly cost effective: the National Institute of 1283 (2024) 012004 IOP Publishing doi:10.1088/1755-1315/1283/1/012004 2 Building Sciences estimates that every dollar invested in building resilience and reducing exposure to disaster risks (i.e., adaptation) saves $4 in disaster response and recovery [6].The factors impacting the arid microclimates, are compactness level, grass coverage, leaf area density, trees ground coverage, and asphalt and building areas.When creating the urban design comfort model, it is important to take into consideration the many mutual interactions between the built environment components, network, fabric and plants that influence the microclimate change.In fact, one of the key metrics to gauge the effectiveness of the urban microclimate is outdoor quality of life [7].In recent years, more focus has been placed on outdoor thermal comfort in an effort to address the UHI issue and create inviting outdoor spaces [8,9].thermal circumstances due to the effects of climate change caused by human activity, such as rising temperatures and midsummer heat waves, the outdoors will probably face significant changes in built-up regions [10,11].These facts have led to the development of a number of sciences that aim to improve the urban microclimate and increase thermal comfort in outdoor [12,13].Under the effect of urban overload, lack of plants, rising heat from human activities, and pollution, these urban microclimates have started to creep towards warmer temperatures and poor air quality [14].During the last century, numerous studies have attempted to assess thermal conditions, to define thermal comfort for humans and to categorize heat stress levels [15].
Nearly none of Egypt's planning or site design considers the climate landscape dimension, [16].Most Egyptian cities have lost their public squares, parks, and open areas over the past 50 years.Additionally, pedestrian walkways vanished, and the ancient gardens drastically declined [17].An enormous urban development project has been launched for the southern part of this Egyptian governorate, Aswan, which is located between the coordinates N 23° 58' and E 32° 46' and is known throughout the world for its cultural heritage and the open historical constructed environment that represents the monumental development that ancient Egypt had [18].ENVI-met is a three-dimensional microclimate simulation model that models soil, plant, building, and air interactions in constructed environments [19].The heat and vapour exchange between the plants and their environment is simulated and calculated, the model considered every aspect of the vegetation Additionally, it simulates photosynthesis, the cycle of evapotranspiration from the tree's roots to its foliage' stomata, and the temperature of the leaves.To simulate complex geometry, the ENVI-met software team created the 3D vegetal grid-based simulation model called Albero.Details are required for tree modeling (i.e.,Leaf Area Density, Leaf Area Index, geometry of the tree, the foliage albedo, and the depth and the diameter of the roots) [19,20].Various studies have verified the model's output.[21,22] and it has been verified to be reliable [20] The neighbourhood fabric and vegetation are two major factors that are vital in modifying arid microclimates in urban development [23].
Trees, on the other hand, are the best characteristics for controlling microclimates and increasing thermal comfort levels during the hot summer months because of their impact [24,25].In urban outdoor areas, air temperature, radiation temperature, air speed, and relative humidity are the main determinants of thermal comfort [26,27].The proper plant design should be developed, and the quantity of plants should be raised [28].Urban geometry and vegetation are the most important elements affecting the microclimate of an open region [29,30].
The purpose of this paper is to discuss urban thermal comfort, to guide planners to develop optimal trees pattern (Pupulus Alpa) in Aswan.Using ENVI-met V.5.1.1 simulation software to measure air temperature (Ta), mean radiant temperature (Tmrt), relative humidity (RH), wind speed (V) and predicted mean vote (PMV).

Method and Methodology
The current study examines the district's thermal comfort level in Aswan, Egypt (Latitude: 24.088938-Longitude: 32.899830)that is characterized by hot dry climat, Area about 344000 m² .
Three cases were studied in the residential block via microclimatic simulation in ENVI-met software (for 14hrs from sunrise to sunset).This study is limited to one sample day in summer (Average typical day6/6/2022) average air temperature 34.5˚C as analysed by Ecotect weather tool [31].The necessary meteorological information, such as wind direction and speed, minimum and maximum temperature as well as minimum and maximum relative humidity were retrieved from ECOTECT program.The simulation of the microclimate made use of this data as well as specific geographical characteristics like longitude, latitude, and altitude.The simulation's output parameters, including temperature, Tmrt, wind speed, humidity, and PMV, were quantified and shown graphically.The air plant, building, and soil interactions in constructed settings are simulated by the threedimensional microclimate simulation model ENVI-met [19].As it simulates and calculates the heat and vapour exchange between the plants and their surroundings, the model takes consideration every aspect of the vegetation.Air temperature (Ta) Figure 5. Change in air temperature in three cases of tree pattern.
Figure 5. showed that at peak time 13:00LST the best case for distribution the temperature degree was case 2 (29.49°C) and the highest temperature recorded 35.19°C with case one without trees.9 [32] showed that a method of prioritising street trees according to their breadth, direction, and aspect ratio in order to reduce high temperatures.
Mean Radiant Temperature (Tmrt) Figure 6.Change in air mean radiant temperature (Tmrt) with three cases of tree pattern.
The highest value of Tmrt was 70.25 °C at point 15:00 LST as a result for disapear of tree in case one it may due to radiation grace of trees and building shadow The lowest value of Tmrt was 39.12°C at the same point in case two Figure (6).
Shade in the open area was given at locations shaded by trees or buildings or both, depending on the effect on microclimatic variables and outdoor thermal comfort [33].
Relative Humidity (RH) Figure 7. Change in relative humidity percent with three cases of tree pattern.
The case two recorded the highest relative humidity 46.15% at 17:00 LST compared to other cases.Case one wase the lowest relative humidity 36.42% of sure the case without trees Figure (7).
Wind speed V Figure 8. Change in wind flow with three cases of tree pattern.
Figure (8) and table (4) showed that case one and case three value recorded maximum air flow among spaces approximately double the value of the case 2. It's necessary to feel the air movement to really understand how fresh green outdoor places seem.Considering every factor that prevents the airflow in outdoor areas, the size and imposing silhouette of the trees, the sense the draught in summer nearly impossible [34].Based on this finding, many studies have been done to make it possible for metropolitan areas to feel like the air is moving throughout the summer when researching the physical properties of every type of barrier, including tree position, morphology, and size [35,34].Regions that are shadowed by trees and buildings, these findings can be explained by the design of narrower streets with reduced wind speeds, which may have negative effects on Ta.Without airflow, the trees' evaporative cooling effect cannot be transferred from the shaded portions to the open spaces [36,37].Under the trees' canopy, the air became hotter due to static hot air.Due to a tree's evapotranspiration action, cooling is increased, which can be attributed to its water vapour carrying capacity while wind speed is catalysing evaporation, which is termed evaporative cooling of the surrounding air around the tree [37].

PREDICTED MEAN VOTE (PMV)
Figure 9. Change in PMV with three cases of tree pattern The PMV index, a gauge of thermal comfort, considers a number of variables, including air temperature, mean radiant temperature, humidity, and air velocity.The PMV value determines the range of temperature sensations that people feel about their surrounding environment.PMV indicates cold and warm sensations felt by humans with 7 scales; namely -3 (very cold), -2 (cold), -1 (cool), 0 (neutral), +1 (warm), +2 (hot), and +3 (very hot).This index is regarded as more sensitive than other thermal comfort indices [38].One of the tools most frequently used in thermal comfort studies, particularly for outdoor settings, is the PMV index.[39,40].
The PMV analysis was examined, the most suitable time interval for thermal comfort was at the morning in general.According to the outcomes of examination of the current situation and scenarios, when looking at the minimum range values (Figure 9,10), the case 2 better than case one and case three with the largest number of trees pattern, despite the increase in humidity.The highest drop was recorded at 7:00 and 19:00.The peak of PMV was at noon time 13: 00 and 15:00 as shown in (Table 4 and   Understanding exterior thermal comfort can be challenging due to the variety of contributing components and existing interactions.There are various factors that must be considered in thermal comfort study physical, physiological, psychological elements, and its interrelationships between the thermal conditions of the environment [41]. Three key attributes of vegetation-shading, evapotranspiration, and wind blockage-have a significant impact on the climate [42,37].The efficiency of vegetation in an urban canyon depends on the size, age, form, species, density and latitude of the plant [43].According to [44] In most of the receptor's points, there is a fluctuation in the PMV values shown in figure (2) due to the change in the overall arrangement Given that trees' moist effects are transferred by the wind to the receptor location, the random arrangement records superior PMV values.In the case of e receptor point (x) the level of comfort increases marginally at the model middle and (a) at northeast (figure 11,12).And receptor point (a) show the difference of three cases most clearest microclimate study which confirmed the validity of the result (figure 12).

Conclusion
At Aswan city, Pupulus Alba were distributed randomly in a residential area for absorbing solar energy and providing shade throughout the day.The primary simulations directed the recommended design in the direction of the random form with a ratio of 50% what the research improves pattern-optimizing method.Overall, the findings show that urban trees' shading effects can increase summertime thermal comfort levels, this is determined by calculating the distance between trees.
However these results were encouraging to use programs to analyse microclimate at new designs for present and future meteorological data.With using ENVI-met software we can simulate and find the best pattern for vegetation or trees and distribution ratio to increase thermal comfort.

Recommendation
Consequently, it is necessary to reassess and update the present planning methods and urban canopy designs, such as the vegetation, trees and the distance between them, while taking consideration for the very hot weather in Aswan.Following the configuration of the context's metrological data, ENVI-met software simulation is advised for the proposed refit.After adding trees before the installation phase, the outdoor PMV indicator will show that the improved quality of space.
This paper introduces an inventive solution to extremely hot-dry climate cities without vegetation that leverages the untapped potential of urban trees studied pattern, to ameliorate microclimate and mitigate heat rise stress.

Funding
There was no particular grant for this research was provided by funding organisations in the public, private, or not-for-profit sectors.

Figure 1 .
Figure 1.Meteorological measurements Aswan weather corresponding to hot summer typical day analyzed by Ecotect 2010 Figure (1,2) and Table (1,2): show the framework of the research.The Leonardo tool was utilised for inference and data analysis, while the ENVI-met guide was used for simulation.A post-processing programme called ENVI-met BioMet calculates thermal comfort indices for people.The utility instantly interacts with the output of ENVI-met to create a thermal comfort index without running 4 ENVI-met again.The tool requires input from both personal and climatic parameters.While personal characteristics like gender, , height, weight and level of exercise may be customised, climate parameters are dependent on simulation findings.The degree of thermal comfort was determined using the PMV indices.

Figure 3 .
Figure 3. Basic sitting and dimensions for the model

Figure 4 .
Figure 4. Reference (Albero -Envimet-V5.1.1)for Pupulus Alba Figure.10).The PMV values 12 slightly fluctuated in Table4.Because of change in humidity % effect of trees.High humidity led to feeling of high temperature in the early morning.The simulated PMV values in different hours scenario ranged between 0.8 and 4.04.In general, case one without trees resulted an increase in PMV values compare other scenarios throughout the simulation hours.

Figure 10 .
Figure 10.Different PMV values for different scenarios

Table 1 .
Input data for modelling and simulation Input

Table 2 .
ENVI-met configuration file setting

Table 4 .
Average of thermal comfort at effected times for the tree cases