Due to its nature; open public space involved a huge part of urban activities. One of the most important principles in designing open public spaces is con- sidering thermalcomfort in order to improve the quality of space and in- crease user’s satisfaction (Monam 2011). Only In the last 20 years the trans- fer of knowledge from climatologic and bio meteorologic studies to urban & architectural design tools has begun to take place (Akbari, Davis, Dorsano, Huang, & Winnett 1992; Brown 1995; Dessi 2002; Katzschner 2006; Ochoa De la Torre J. M. 1999) (Scudo 2005: 261). In urban areas, the great variety of different surfaces and sheltering obstacles produces a pattern of distinct microclimate systems. To simulate these local effects, micro scale surface– plant–air interaction schemes with a special extension to typical artificial urban boundaries are required (Bruse & Fleer 1998).
The way of designing urban fabric, has a major effect on reducing the temperature of open space and can be used in a manner that enables users to use space in a permanent and convenient way. Thus, the relationship between the qualitative and quantitative effects of various parameters should be considered based on the orientation of the streets and time. Design and development of the urban environment requires the application of its components for improving the performance of elements that can be either the buildings and their orientation and shape, or the smaller objects in micro level such as trees, water and floor coverings. Tehran has three urban fabrics including open spaces, high-rise buildings and urban intense fabric that each one has their own optimum performance in thermalcomfort. Since the street acts as a linear urban spaces and the main connector of noted texture, thermalcomfort is very important for its users. Micro scale design for pedestrians to benefit from the sufficient wind and temperature is equally effective as the height of masses, location and orientation of buildings to lead the wind flows and receive adequate radiation in an urban site. The main question is what is the role of these elements in a linear open space design? Some of the urban landscape features such as the trees and water features (stream in streets) and sidewalks floorings have an influence in the amount of solar energy and wind flow in different ways and they can be useful in helping energy efficiency. 2.1. Methods
From the Egyptian data considered in this paper, it is observed that the value of RI exceeds 85 only at urban and industrial areas during the summer months (July - August). It could be noticed that the serious hot discom- fort (85 ≤ RI) didn’t occur at all districts during the old non-urbanized period while during the recent urbanized period, both urban and industrial areas have values of RI exceeds 85 (366 hours for both them) during July and August and they occur afternoon (Figures 5-6). This is attributed to this time interval has maximum concentra- tion of traffic and go out of thousands employees in ad- dition to the giant and rapidly increase of industrializa- tion processes at Helwan area. It was found that serious hot discomfort (85 ≤ RI) didn’t occur at both rural and suburban areas during the two study periods.
Fig. 1. Location of Iraq and the neighbouring countries . Regarding the investigation study conducted in Iran (Tehran city) on the strategies to reduce the impact of Urban Heat Island on the human health , the results showed that the amount of vegetation placed on a building and its position (roofs, walls or both) is a more dominant factor than the orientation of the urban canyon. The canyon geometry with green roofs and walls that had a low thermal impact could play a more important role than the street orientation. Also, the study revealed that the heat sensation zones “hot” and “warm” are not achieved when urban roofs and walls are covered with vegetation, leading to more pleasant and comfort environments for the city residents. An investigation study was conducted of the warm core of Urban Heat Island in the highland zone of Muscat, Oman . The valley is surrounded by mountains formed of dark colored rocks that can absorb the short wave radiation and contribute to the existence of the warmth in the core of the urban area. The study emphasized the importance of the nature of rural baseline when assessing the urban effect on an urban area climate. A study was conducted in Bahrain City  to analyze the impact of the urbanization on the thermal behaviour of newly built environments. The results revealed that the recent process of the urbanization leads to an increase in the urban temperature by 2-5 ℃. The increase in temperature is enhanced by the urban activity such as on- going construction processes, shrinkage of green areas and the sea reclamation. Several studies indicate how the green effects have a crucial role in the process of sustainable cooling of the urban planning and in saving energy and
2016; Kántor, Égerházi, et al., 2012; Lin & Matzarakis, 2008; Lin, 2009; Mahmoud, 2011; Salata et al., 2016; Yang, Wong, & Zhang, 2013). Although this method was criticized by assuming that thermal sensation votes are continuous instead of ordinal data (Cheung & Jim, 2017), this impact was found to be insignificant (Salata et al., 2016). Few studies used the same method having the linear regression using different other thermalcomfort indexes (Pantavou et al., 2013; Yang, Wong, & Jusuf, 2013; Zhao, Zhou, Li, He, & Chen, 2016). PPET is the ultimate temperature in which the probabilities of users’ preferences towards having warmer and cooler changes are equivalent. To calculate PPET, a probit regression analysis for both warmer and cooler preferences is modelled and the intersection of both corresponds to the preferred temperature (Lin, 2009; Lin et al., 2011; Salata et al., 2016; Yang, Wong, & Jusuf, 2013; Yang, Wong, & Zhang, 2013; Zhao et al., 2016). TAR is the limit determining the temperature accepted by 80 or 90% of the respondents (ASHRAE, 2004). This range is generated from a quadratic regression between the thermal acceptability of the respondents and the temperature. Yang, Wong, and Jusuf (2013) calculated this range based on the assumption that 80% acceptability rate corresponds to the value of ±0.85 MTSV in the linear regression between the binned MTSV and the temperature as per ISO-7730 (2005). NPETR corresponds to the values ranging from -0.5 to +0.5 MTSV in the NPET linear regression (Chen et al., 2015; Kántor et al., 2016; Lai, Guo, Hou, Lin, & Chen, 2014; Liu et al., 2016; Salata et al., 2016). Different benchmarks obtained in similar OTC studies are summarised in Table 1, showing that the NPET is the most commonly used and the NPETR values are the least reported.
ii) U drugoj fazi koristi se komponenta Outdoor Solar Temperature Adjustor koja je takođe neophodna za računanje vrednosti UTCI indeksa i odnosi se na računanje prilagođene srednje temperature zračenja (engl. Solar Adjusted Mean Radiant Temperature - SAMRT). Ova komponenta sadrži deo sa ulaznim i izlaznim podacima (Slika 9). Za ulazne podatke neophodno je uključiti informacije iz komponente Weather data file o lokaciji područja (longitudu, latitudu i altitudu), difuznu i direktnu solarnu radijaciju, kao i temperaturu vazduha. Zatim, u okviru ove komponente neophodno je izvršiti podešavanje parametara koji podrazumevaju elemente koji se odnose na model tela čoveka za koga se računanje vrednosti UTCI indeksa vrši. Ti podaci podrazumevaju položaj tela, ugao rotacije tela, nivo odevenosti i lokaciju tela. Elementi izgrađenog okruženja koji svojom geometrijom utiču na ishod SAMRT temperature takođe su neophodni u procesu računanja. Zatim, refleksija parterne površine i period godine za koji se sprovodi analiza. Svaki od ovih parametara je detaljno objašnjen u daljem tekstu.
Street trees have several environmental benefits for urban citizens. Because of our focus on thermal condition and comfort in urban open spaces, we review the most important investigations on thermalcomfort. Coutts et al.  measured three east-west streets during heat waves in the temperature climate of Melbourne, Australia. They considered the Universal Thermal Climate Index (UTCI) for the calculation of outdoorthermalcomfort within the tree canopies. The maximum UTCI reduction by the trees were 6 ˚C. Moreover, they reported that the maximum air temperature reduction was 1.5 ˚C. A similar research done in Melbourne showed that Platanus trees led to a PET reduction of 6.6°C during a heat wave.
The assessment of an urban environment using computational fluid dynamics (CFD) could either involve an indoor or outdoor evaluation of the environmental quality such as the air quality and thermalcomfort. Many studies have been conducted using CFD to evaluate indoor and outdoor environmental conditions. These studies have cut across various environmental conditions such as air quality, thermalcomfort, and airflow characteristics in urban indoor and outdoor environments. Cheng and Zang (2004) studied the use of CFD tools for indoor environmental design and stressed the importance of proper validation studies, grid independence studies and proper handling of complex boundary conditions. Furthermore, CFD tool has been used extensively to evaluate Natural ventilation of indoor environments (Van Hoop and Blocken, 2013; Cook, et al. 2005; Yang, 2004, Mohammed et al. 2013, Meroney, 2009). However, many studies have also been conducted in the context of outdoorurban environments. CFD tool has been used by Blocken et al. (2012) to simulate pedestrian wind comfort and wind safety in urban areas (as shown in figure 4 above) and confirmed the considerable advantages of CFD compared to wind tunnel testing. McAlpine and Ruby (2004) in their study of air quality in microenvironments acknowledged the capability of CFD tools in allowing more accurate predictions. Moreover, Gousseau et al. (2011) also used CFD tool to study near-field pollutant dispersion in an urban environments, focusing both; on the prediction of pollutants concentration for pedestrian outdoor air quality and on building surface for ventilation system inlet and indoor air quality.
4.3. Computer simulations
In this study all the simulations were conducted using ENVI-met 3.1 , RayMan 1.2  and UMI . ENVI- met 3.1 is a three-dimensional non-hydrostatic microclimate model designed to simulate the surface, plant and air interactions in an urban environment with a typical spatial resolution of 0.5-10 m in space and 10 s in time. This program uses soil, radiative transfer, and vegetation models based on fundamental laws of fluid dynamics and thermodynamics that can simulate exchange processes of heat and vapor at horizont al and vertical surfaces around and between buildings. This program is capable of calculating meteorological parameters such as air temperature (°C), relative humidity (%), wind velocity (m/s), vapor pressure (hPa), and mean radiant temperature (°C) of the center of models. This program has been extensively used in order to study the effect of natural and built elements on urban microclimates in addition to the impacts of climate change.
-being could be related to climate and weather. Since park users would always look at weather conditions when doing outdoor activities, designers should apply the ergonomics factors as influential aspect for outdoor spatial design. In addition, urban parks offer the public some release from the pressures of urban environments and everyday living. Microclimatic condition wise, there may be limitations to the thermal conditions during daytime that may affect prolonged usage of the outdoor parks. An assessment of human responses to the outdoor environment and the individual user's experience is necessary to determine the people's understanding of the condition. The setting of an outdoor park pointedly influences how that space is perceived and used.
In the field of urban climate, Givoni  underlined how urban design may impact on comfort through urban heat island phenomenon. In 1998, Givoni  has also showed some regression equation concerning outdoor temperature in urban area which may influence of comfort in outdoor space, unfortunately he has not proposed equation of thermalcomfort perception for outdoor at that time. Some of the researchers who focus on outdoorthermalcomfort, have proposed regression equations to estimate the scale of outdoorthermalcomfort, where the regression is functions of climate variables such are: solar radiation, air temperature, air humidity, wind speed, and radiant temperature, as shown in Table 1. In the table it appears that there is no study of outdoorcomfort scale models that are specifically intended for the case of humid tropical climates. Some other researchers have also proposed the temperature index to measure the level of comfort for people who are at particular climatic environment. The temperature index (in 0 C) is known as PET (Physiologically Effective Temperature) which is then used as the standard calculation of the thermalcomfort of outdoor space in Germany , out_SET (Outdoor Standard Effective Temperature), and TEP (Effective Temperature Psychologically) by . But again, the temperature index was also obtained through the data from field study conducted in the area where the environment is not humid tropical climates, so it remains to be evaluated for increase its precision when applied on a broader climate situation.
As seen in Figs. 13 and 14 , observed T a and RH are different between SU and rural sites during the daytime, which can systematically cause an error in the modelled T mrt . For instance, the WR observed T a is 0.46 °C lower than the SU observed T a on average daytime and using the WR data roughly causes 2.1 °C underestimation of T mrt at SU, which is calculated by using the results of the SOLWEIG sensitivity test (Section 5.1 ). The BLUEWS/BLUMPS modelled variables are estimated for the local- scale, so the SOLWEIG air temperature and humidity are modiﬁed with the environmental lapse rate (0.0064 K m 1 ) to bring them to the level of interest. Alternatively, the additional resistance between the local and micro-scale could be used; however, this requires wind data to be transferred. This infor- mation is not currently needed within SOLWEIG. This new system showcases the potential to improve the modelling of T mrt by using meteorological variables more representative of urban areas instead of using the data from non-urban sites. The SU modelled T a is 0.36 °C higher than the WR observed T a on average during the daytime and results in a 1.7 °C higher T mrt than the WR used. These results show that the coupled models can provide more site-speciﬁc input data to the T mrt modelling.
observed during the ﬁeldwork. As it has been demonstrated that urban land surface models, like their rural counterparts, need to ensure appropriate soil moisture conditions ( Best and Grimmond, 2013 ), a spin up period of three times the study length was used. This is assumed to be most critical for SU and WR, as the natural grassland (DR) had extremely low (<2%) soil moisture, so an initial value of 1.5 mm was used. This proposed model has the advantage, compared to more complex models, that the addi- tional computer time is insigniﬁcant, whereas for others the constraint of inadequate spin up time may need to compromise performance.
2. Street wind orientation
The performance of each urban form, in relation to natural ventilation, greatly depends on the orientation of the streets’ grid and the buildings that line them on both sides. Street orientation could be parallel, oblique or perpendicular to the wind direction. When the major streets in a site are oriented parallel to the prevailing wind, the highest velocity could be obtained in the streets and the adjacent open spaces. Generally speaking, the optimal street orientation for ventilation purposes, which is advised by Givoni , , was found to be oblique to wind direction by approximately 20 - 30 o (see Fig. 1) with the narrowest buildings’ façades facing the wind . However, the real street orientation in the case study is almost 5º which means within the optimum street orientation range for natural ventilation as well as outdoorthermalcomfort.
Outdoorthermalcomfort, apart from climate conditions and clothing, is also aﬀected by the urban planning of the region. For outdoor conditions, humans are exposed to diﬀer- ent thermal aspects such as Urban Heat Island eﬀect (UHI; Santamouris 2014). Arid regions are characterized by low precipitation (Shepherd 2006) and elevated rates of evapora- tion (Razo et al. 2004). Le Houérou (1996) determined the maximum mean rainfall to be 150–450 mm per year while (Martin 2006) argued that there are periods where the amount can be less than 50 mm for 2 years. Qatar has an arid desert- like climate, characterized by hot summers, scarce precipita- tion, and warm winters with mean relative humidity (RH) ranging from 43% in June to 72% in December (Ghani et al. 2017). Highest historical recorded values of rainfalls vary from 0–155.4 mm for June and December, respectively (CAA 2013). In arid environments, Shashua-Bar et al. (2011) inves- tigated how vegetation aﬀects the sense of comfort neutral- ity concluding that shade and grass irrigation contributes to advanced thermal acceptability. In China, Xi et al. (2012) argued that speciﬁc design of campuses facilities can lower ambient temperature by 3°C, setting the thermalcomfort tem- perature at 24°C standard equivalent temperature (SET). To enhance outdoorthermalcomfort utilization of shaded areas from plantation or buildings are recommended. Cheng et al.
In this study, two thermalcomfort indices are employed to investigate outdoor human thermalcomfort within three major cities of different climates in Egypt. The indices are: the Discomfort Index (DI), and the Robaa Index (RI). The three considered cities are: Alexandria which is located in the north of Egypt, Cairo which is located in the middle and Aswan city which is located in the south of Egypt. The estimations of the two indices are based on the mean wind data of the three ci- ties, which covers the period from January 2010 to January 2011. The study results show that the thermalcomfort indices values can be employed to evaluate climate differences in urban areas. The calculated indices showed that; although extreme climate conditions are not reached in Egypt in general, the climate in the north is milder than in the south. In addition, the study results show that the RI is more practical than DI in assessing the human thermalcomfort in the outdoor envi- ronment.
This includes: pavilions, enclosed courtyard
pavilions, open square and open rectangular courtyard pavilions. Although the first type does not belong to a courtyard category, it has been included as this is the most common urban type in the case study area, Dhaka (Figure 1 (a)). It is therefore important to compare its performance with courtyard types. The second type is mostly suitable for hot-arid climate and also visible in many modern and historic building arrangements in hot-humid climates (Figure 1 (b)). The third urban type is an altered and urbanised pattern of rural housing arrangements in the case study area (Figure 1 (c)). In the latter, openings are provided in the corners of the courtyard, whereas in the former, opening is placed across the centre. The fourth type has been generated by elongating the third type along east-west direction since, building forms stretched out along the east- west direction are considered to be better suited for the majority of climates (Olgyay 1963).
The enthusiasm of scientists to study on ther- mal comfort condition of semi-outdoor and out- door spaces has been raised since recent decade but it is needed to focus on more details and locations. Through representing a review on the prior stud- ies, it is understood that although the evaluation of thermalcomfort in semi-outdoor spaces of various climates has been done up to now, the number of researches which specifically concentrate on to as- sess the human thermalcomfort in semi-open ar- eas are few. Particularly, there is a lack of research- es on assessing thermal conditions of semi-outdoor areas in hot-humid regions. Moreover, it is need- ed to find a proper universal thermal index for vari- ous climate conditions. This index can help urban planner to evaluate thermal condition of districts in the world in understandable range. Finally, to pro- pose the practical software for simulation the ther- mal comfort of semi-outdoor spaces in easy and us- er-friendly manner.
Among the urban design elements, archetypal urban form, density, and geometry have important implications in matters of urban planning, such as built potential, daylighting, passive cooling potential, and walkability. The sustainable performance of urban systems is measured upon these and many other factors. The question of which urban design performs best cannot have an absolute answer. When a large number of variables are taken into account, it is likely that conflicts will emerge amongst them; terms such as “best” and “optimal” will certainly embody value judgments. One thing that is certain, however, is the need to understand the principles and dynamics that govern such variables. Only then can the entirety of their implications –and potential benefits- be used for the betterment of the society around them.