{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:2078"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:2078","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Dependence of outdoor thermal comfort on street design in hot and dry climate","abstract":"The present work addresses the contribution of street design toward the development of a comfortable microclimate at street level for pedestrians. The work is design-oriented and seeks to provide a quantitative knowledge readily interpretable from the perspective of urban designers. Street geometries are investigated, including various aspect ratios, i.e. height-to-width ratio H/W, solar orientations and a number of design details. First, symmetrical urban canyons with H/W equal to 0.5, 1, 2 and 4 and for different solar orientations (i.e. E-W, N-S, NE-SW and NW-SE) are studied. Secondly, asymmetrical profiles with different openness to the sky are investigated together with the role of ar-chitectural details such as galleries, horizontal overhangs on façades and rows of trees, considered as possible ways to improve the outdoor thermal comfort further in the summertime. Moreover, the analysis focuses on the local differences in the thermal sen-sation across the street, i.e. street centre vs. street sides, which influence the frequenta-tion of the street. A special emphasis is placed on a human bio-meteorological assess-ment of these microclimates by using the thermal index PET, Physiologically Equiva-lent Temperature.
The investigation is carried out by using the three-dimensional numerical model ENVI-met 3.0, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for typical summer conditions in Ghardaia, Algeria (32.40° N, 3.80° E), a subtropical region characterized by a hot and dry climate. Additionally, short-term field measurements are carried out in Freiburg, Germany, and in Ghardaia (Beni-Isguen), Algeria, during the summer 2003. In the former site, the microclimate changes due to geometry and the effects of the street irradiation patterns on the heat gained by a human body are dealt with in detail. In the latter site, a quantitative evaluation of the thermal effectiveness of existing architectures in a hot-dry climate is the focus.
The simulations show that the thermal comfort is difficult to reach passively in such an extreme climate but improvements are possible by means of appropriate geometrical forms. All investigated urban describers are found to influence the final thermal sensa-tion. Contrasting patterns in the comfort situation are found between shallow and deep urban streets as well as between the various orientations studied.
Wide streets (H/W 0.5) are highly uncomfortable for both orientations. Yet, N-S ori-entation shows some advantage over E-W orientation, and this benefit increases as the aspect ratio increases.
Explicitly, this is expressed by a shorter period of heat stress and lower PET maxima. Moreover, heat stress can effectively be mitigated if galleries, trees or textured façades are appropriately combined with the aspect ratio and solar orientation.
A comparison of all case studies reveals that the duration, the period of day of extreme heat stress, as well as the spatial distribution of PET across the canyon depend strongly on aspect ratio and on street orientation. This is crucial since this will directly influence the design choices in relation to street usage, e.g. streets exclusively planned for pedes-trian use or including motor traffic, and also the time of frequentation of urban spaces. The simulations as well as the on-site measurements also confirmed the dominant role of the radiation fluxes expressed by the mean radiant temperature Tmrt for summer con-ditions. The human body absorbs energy from the irradiated surrounding surfaces and from a direct exposure of his body. This fact points out the necessity of shading as a main strategy for keeping the street area in comfort range. Air temperature and wind speed are secondary factors with respect to comfort as these vary less with urban ge-ometry changes in comparison to Tmrt. The issue of solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs and draw attention on the double role of the street, i.e. as interface of urban and architectural scales. Design recommendations are also outlined for designing a comfortable urban street.
Methodologically, ENVI-met revealed to be a good tool for the prognosis of the urban microclimate changes within urban areas, and also in the assessment of outdoor comfort through a satisfactory estimation of the mean radiant temperature. A number of eventual refinements of the model are mentioned to improve its accuracy.
The work also highlights the necessity of more on-site measurements and more subjec-tive votes of people for validating the simulations results and in order to strengthen a practice-oriented knowledge about comfort in urban areas.","abstract_html":"The present work addresses the contribution of street design toward the development of a comfortable microclimate at street level for pedestrians. The work is design-oriented and seeks to provide a quantitative knowledge readily interpretable from the perspective of urban designers. Street geometries are investigated, including various aspect ratios, i.e. height-to-width ratio H/W, solar orientations and a number of design details. First, symmetrical urban canyons with H/W equal to 0.5, 1, 2 and 4 and for different solar orientations (i.e. E-W, N-S, NE-SW and NW-SE) are studied. Secondly, asymmetrical profiles with different openness to the sky are investigated together with the role of ar-chitectural details such as galleries, horizontal overhangs on façades and rows of trees, considered as possible ways to improve the outdoor thermal comfort further in the summertime. Moreover, the analysis focuses on the local differences in the thermal sen-sation across the street, i.e. street centre vs. street sides, which influence the frequenta-tion of the street. A special emphasis is placed on a human bio-meteorological assess-ment of these microclimates by using the thermal index PET, Physiologically Equiva-lent Temperature. <br>The investigation is carried out by using the three-dimensional numerical model ENVI-met 3.0, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for typical summer conditions in Ghardaia, Algeria (32.40° N, 3.80° E), a subtropical region characterized by a hot and dry climate. Additionally, short-term field measurements are carried out in Freiburg, Germany, and in Ghardaia (Beni-Isguen), Algeria, during the summer 2003. In the former site, the microclimate changes due to geometry and the effects of the street irradiation patterns on the heat gained by a human body are dealt with in detail. In the latter site, a quantitative evaluation of the thermal effectiveness of existing architectures in a hot-dry climate is the focus. <br>The simulations show that the thermal comfort is difficult to reach passively in such an extreme climate but improvements are possible by means of appropriate geometrical forms. All investigated urban describers are found to influence the final thermal sensa-tion. Contrasting patterns in the comfort situation are found between shallow and deep urban streets as well as between the various orientations studied. <br>Wide streets (H/W  0.5) are highly uncomfortable for both orientations. Yet, N-S ori-entation shows some advantage over E-W orientation, and this benefit increases as the aspect ratio increases. <br>Explicitly, this is expressed by a shorter period of heat stress and lower PET maxima. Moreover, heat stress can effectively be mitigated if galleries, trees or textured façades are appropriately combined with the aspect ratio and solar orientation. <br>A comparison of all case studies reveals that the duration, the period of day of extreme heat stress, as well as the spatial distribution of PET across the canyon depend strongly on aspect ratio and on street orientation. This is crucial since this will directly influence the design choices in relation to street usage, e.g. streets exclusively planned for pedes-trian use or including motor traffic, and also the time of frequentation of urban spaces. The simulations as well as the on-site measurements also confirmed the dominant role of the radiation fluxes expressed by the mean radiant temperature Tmrt for summer con-ditions. The human body absorbs energy from the irradiated surrounding surfaces and from a direct exposure of his body. This fact points out the necessity of shading as a main strategy for keeping the street area in comfort range. Air temperature and wind speed are secondary factors with respect to comfort as these vary less with urban ge-ometry changes in comparison to Tmrt. The issue of solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs and draw attention on the double role of the street, i.e. as interface of urban and architectural scales. Design recommendations are also outlined for designing a comfortable urban street. <br>Methodologically, ENVI-met revealed to be a good tool for the prognosis of the urban microclimate changes within urban areas, and also in the assessment of outdoor comfort through a satisfactory estimation of the mean radiant temperature. A number of eventual refinements of the model are mentioned to improve its accuracy. <br>The work also highlights the necessity of more on-site measurements and more subjec-tive votes of people for validating the simulations results and in order to strengthen a practice-oriented knowledge about comfort in urban areas.","abstract_has_math":false,"creators":["Ali-Toudert, Fazia"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Mayer, Helmut"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:33Z","subjects":["Straßenschlucht","human-biometeorologie","PET","Himmelrichtung","Freiräume","urban canyon","aspect ratio","street orientation","ENVI-met","gallery","overhangs","urban vegetation"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/2078","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Mayer, Helmut"]},{"key":"dc:creator","label":"Author","values":["Ali-Toudert, Fazia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Straßenschlucht","human-biometeorologie","PET","Himmelrichtung","Freiräume","urban canyon","aspect ratio","street orientation","ENVI-met","gallery","overhangs","urban vegetation"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The present work addresses the contribution of street design toward the development of a comfortable microclimate at street level for pedestrians. The work is design-oriented and seeks to provide a quantitative knowledge readily interpretable from the perspective of urban designers. Street geometries are investigated, including various aspect ratios, i.e. height-to-width ratio H/W, solar orientations and a number of design details. First, symmetrical urban canyons with H/W equal to 0.5, 1, 2 and 4 and for different solar orientations (i.e. E-W, N-S, NE-SW and NW-SE) are studied. Secondly, asymmetrical profiles with different openness to the sky are investigated together with the role of ar-chitectural details such as galleries, horizontal overhangs on façades and rows of trees, considered as possible ways to improve the outdoor thermal comfort further in the summertime. Moreover, the analysis focuses on the local differences in the thermal sen-sation across the street, i.e. street centre vs. street sides, which influence the frequenta-tion of the street. A special emphasis is placed on a human bio-meteorological assess-ment of these microclimates by using the thermal index PET, Physiologically Equiva-lent Temperature.
The investigation is carried out by using the three-dimensional numerical model ENVI-met 3.0, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for typical summer conditions in Ghardaia, Algeria (32.40° N, 3.80° E), a subtropical region characterized by a hot and dry climate. Additionally, short-term field measurements are carried out in Freiburg, Germany, and in Ghardaia (Beni-Isguen), Algeria, during the summer 2003. In the former site, the microclimate changes due to geometry and the effects of the street irradiation patterns on the heat gained by a human body are dealt with in detail. In the latter site, a quantitative evaluation of the thermal effectiveness of existing architectures in a hot-dry climate is the focus.
The simulations show that the thermal comfort is difficult to reach passively in such an extreme climate but improvements are possible by means of appropriate geometrical forms. All investigated urban describers are found to influence the final thermal sensa-tion. Contrasting patterns in the comfort situation are found between shallow and deep urban streets as well as between the various orientations studied.
Wide streets (H/W 0.5) are highly uncomfortable for both orientations. Yet, N-S ori-entation shows some advantage over E-W orientation, and this benefit increases as the aspect ratio increases.
Explicitly, this is expressed by a shorter period of heat stress and lower PET maxima. Moreover, heat stress can effectively be mitigated if galleries, trees or textured façades are appropriately combined with the aspect ratio and solar orientation.
A comparison of all case studies reveals that the duration, the period of day of extreme heat stress, as well as the spatial distribution of PET across the canyon depend strongly on aspect ratio and on street orientation. This is crucial since this will directly influence the design choices in relation to street usage, e.g. streets exclusively planned for pedes-trian use or including motor traffic, and also the time of frequentation of urban spaces. The simulations as well as the on-site measurements also confirmed the dominant role of the radiation fluxes expressed by the mean radiant temperature Tmrt for summer con-ditions. The human body absorbs energy from the irradiated surrounding surfaces and from a direct exposure of his body. This fact points out the necessity of shading as a main strategy for keeping the street area in comfort range. Air temperature and wind speed are secondary factors with respect to comfort as these vary less with urban ge-ometry changes in comparison to Tmrt. The issue of solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs and draw attention on the double role of the street, i.e. as interface of urban and architectural scales. Design recommendations are also outlined for designing a comfortable urban street.
Methodologically, ENVI-met revealed to be a good tool for the prognosis of the urban microclimate changes within urban areas, and also in the assessment of outdoor comfort through a satisfactory estimation of the mean radiant temperature. A number of eventual refinements of the model are mentioned to improve its accuracy.
The work also highlights the necessity of more on-site measurements and more subjec-tive votes of people for validating the simulations results and in order to strengthen a practice-oriented knowledge about comfort in urban areas.","Die vorliegende Untersuchung beschäftigt sich mit dem Beitrag, den das Straßendesign zur Ausbildung eines komfortablen Mikroklimas für Menschen im Straßenbereich leisten kann. Der Schwerpunkt liegt bei subtropischen Klimabedingungen, d.h. bei heißem und trockenem Klima. Die Arbeit wurde anwendungsorientiert durchgeführt. Sie versucht, quantitative Ergebnisse bereitzustellen, die aus der Sicht eines Stadtplaners leicht verstanden und interpretiert werden können. Verschiedene Geometrien von Straßenschluchten werden untersucht. Sie schließen ein variables H/W-Verhältnis, unterschiedliche Richtungen und spezifische Designausführungen (z.B. Überhänge od. Straßenbegleitgrün) ein.
Am Anfang werden symmetrische Straßenschluchten mit H/W = 0.5, 1, 2 und 4 analysiert, die in E-W, N-S, NE-SW und NW-SE verlaufen. Daran schließt sich die Untersuchung von asymmetrischen Straßenschluchten an. Hier werden zusätzlich die Effekte von planerischen Details, wie Galerien, Überhänge und Straßenbegleitgrün, berücksichtigt, da sie eine weitere Möglichkeit zur Verbesserung der thermischen Komfortbedingungen im Außenbereich darstellen. Bei den Ergebnissen erfolgt eine räumliche Differenzierung im thermischen Empfinden von Menschen quer zur Straße.
Zur human-biometeorologischen Bewertung des thermischen Komforts wird die physiologisch äquivalente Temperatur PET verwendet. Die zur Berechnung von PET erforderlichen Variablen werden in hoher räumlicher und zeitlicher Auflösung über die Anwendung des 3D Modells ENVI-met 3.0, ermittelt.
Als Untersuchungsgebiet, das im Sommer heiße und trockene Klimabedingungen repräsentiert, dient die Region Ghardaia (32.40 °N, 3.80 °E) in Algerien.
In Ergänzung zu den numerischen Simulationsuntersuchungen erfolgten im Sommer 2003 kurzzeitige Messungen der thermophysiologisch relevanten meteorologischen Variablen in Freiburg und in Beni-Isguen (Ghardaia), Algerien.
Die Simulationsergebnisse zeigen, dass thermischer Komfort für Menschen unter den gegebenen, extremen klimatischen Verhältnissen schwer erreichbar ist. Verbesserungen sind jedoch über geeignete geometrische Anordnungen von Straßenschluchten möglich. Gegensätzliche Muster der Komfortbedingungen treten zwischen Straßenschluchten mit sehr hohem und niedrigem H/W-Verhältnis sowie mit unterschiedlicher Orientierung auf. Breite Straßenschluchten weisen einen hohen thermischen Diskomfort auf. Dabei sind Straßenschluchten in N-S Richtung etwas günstiger als solche in E-W Richtung zu beurteilen. Angezeigt durch einen kürzeren Zeitraum während des Tages mit Wärmebelastung und niedrigere PET Maxima nimmt dieser Vorteil der Straßenschluchten in N-S Richtung mit ansteigendem H/W-Verhältnis zu. Es ließ sich auch quantifizieren, wie sich die Wärmebelastung, die in Straßenschluchten auf Menschen wirkt, durch die Berücksichtigung von weiteren Varianten des Straßendesigns, wie Galerien, Überhänge oder Straßenbegleitgrün, in Kombination mit dem H/W-Verhältnis und der Richtung der Straßenschlucht reduzieren lässt.Im subtropischen Klima, der Tageszeitraum mit extremer Wärmebelastung und die räumliche Verteilung von PET in der Straßenschlucht am stärksten vom H/W-Verhältnis und von der Richtung der Straßenschlucht abhängen. Das hat Auswirkungen auf die Möglichkeiten zur optimierten Nutzung von Straßenschluchten (z.B. ausschließliche Nutzung durch Fußgänger oder einschließlich von Kraftfahrzeugverkehr) und auf die Zeiten der häufi-gen Nutzung dieser urbanen Freiräume.
In Bezug auf den thermischen Komfort von Menschen im Sommer im Freien bestätigen die Simulationsberechnungen und experimentellen Fallstudien die dominierende Rolle der Strahlungsflüsse, die durch die mittlere Strahlungstemperatur Tmrt der Umgebung parametrisiert werden. Stehende Menschen in Straßenschluchten absorbieren tagsüber hauptsächlich Strahlungswärme von bestrahlten Umgebungsflächen, während der Wärmegewinn aus der direkten Sonnenstrahlung von zweitrangiger Bedeutung ist. Daraus ergibt sich, dass nur über die Abschattung der direkten Sonnenstrahlung die klimatischen Bedingungen in Straßenschluchten verbessert werden. Lufttemperatur und Windgeschwindigkeit können in Bezug auf thermischen Komfort im Sommer in den Subtropen als meteorologische Variable von zweiter Bedeutung aufgefasst werden, da ihre räumliche und zeitliche Variabilität in Straßenschluchten deutlich geringer als diejenige von Tmrt ist.
Ein zusätzliches Kriterium für das Straßendesign, auf das kurz eingegangen wird, ist die Verfügbarkeit von Strahlung in Innenräumen im Winter. Unter Berücksichtigung der Anforderungen im Winter an das Design von Straßenschluchten werden Empfehlungen an die Planung von Freiräumen in Straßenschluchten gegeben.
Insgesamt hat sich das mikroskalige Modell ENVI-met als ein sehr gutes Werkzeug für diese Untersuchung herausgestellt. Vor allem wird Tmrt in zufriedenstellender Weise simuliert. Zweckmäßig wären allerdings weitere Validierungen von ENVI-met über geeignete experimentelle Fallstudien."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Dependence of outdoor thermal comfort on street design in hot and dry climate","Abhängigkeit des thermischen Komforts unter heißen und trockenen Klimabedingungen vom Straßendesign"]}]}],"canonical_facts":{"dc:contributor":["Mayer, Helmut"],"dc:creator":["Ali-Toudert, Fazia"],"dc:description.abstract":["The present work addresses the contribution of street design toward the development of a comfortable microclimate at street level for pedestrians. The work is design-oriented and seeks to provide a quantitative knowledge readily interpretable from the perspective of urban designers. Street geometries are investigated, including various aspect ratios, i.e. height-to-width ratio H/W, solar orientations and a number of design details. First, symmetrical urban canyons with H/W equal to 0.5, 1, 2 and 4 and for different solar orientations (i.e. E-W, N-S, NE-SW and NW-SE) are studied. Secondly, asymmetrical profiles with different openness to the sky are investigated together with the role of ar-chitectural details such as galleries, horizontal overhangs on façades and rows of trees, considered as possible ways to improve the outdoor thermal comfort further in the summertime. Moreover, the analysis focuses on the local differences in the thermal sen-sation across the street, i.e. street centre vs. street sides, which influence the frequenta-tion of the street. A special emphasis is placed on a human bio-meteorological assess-ment of these microclimates by using the thermal index PET, Physiologically Equiva-lent Temperature.
The investigation is carried out by using the three-dimensional numerical model ENVI-met 3.0, which simulates the microclimatic changes within urban environments in a high spatial and temporal resolution. Model calculations are run for typical summer conditions in Ghardaia, Algeria (32.40° N, 3.80° E), a subtropical region characterized by a hot and dry climate. Additionally, short-term field measurements are carried out in Freiburg, Germany, and in Ghardaia (Beni-Isguen), Algeria, during the summer 2003. In the former site, the microclimate changes due to geometry and the effects of the street irradiation patterns on the heat gained by a human body are dealt with in detail. In the latter site, a quantitative evaluation of the thermal effectiveness of existing architectures in a hot-dry climate is the focus.
The simulations show that the thermal comfort is difficult to reach passively in such an extreme climate but improvements are possible by means of appropriate geometrical forms. All investigated urban describers are found to influence the final thermal sensa-tion. Contrasting patterns in the comfort situation are found between shallow and deep urban streets as well as between the various orientations studied.
Wide streets (H/W 0.5) are highly uncomfortable for both orientations. Yet, N-S ori-entation shows some advantage over E-W orientation, and this benefit increases as the aspect ratio increases.
Explicitly, this is expressed by a shorter period of heat stress and lower PET maxima. Moreover, heat stress can effectively be mitigated if galleries, trees or textured façades are appropriately combined with the aspect ratio and solar orientation.
A comparison of all case studies reveals that the duration, the period of day of extreme heat stress, as well as the spatial distribution of PET across the canyon depend strongly on aspect ratio and on street orientation. This is crucial since this will directly influence the design choices in relation to street usage, e.g. streets exclusively planned for pedes-trian use or including motor traffic, and also the time of frequentation of urban spaces. The simulations as well as the on-site measurements also confirmed the dominant role of the radiation fluxes expressed by the mean radiant temperature Tmrt for summer con-ditions. The human body absorbs energy from the irradiated surrounding surfaces and from a direct exposure of his body. This fact points out the necessity of shading as a main strategy for keeping the street area in comfort range. Air temperature and wind speed are secondary factors with respect to comfort as these vary less with urban ge-ometry changes in comparison to Tmrt. The issue of solar access indoors has been briefly discussed as an additional criterion in designing the street by including winter needs and draw attention on the double role of the street, i.e. as interface of urban and architectural scales. Design recommendations are also outlined for designing a comfortable urban street.
Methodologically, ENVI-met revealed to be a good tool for the prognosis of the urban microclimate changes within urban areas, and also in the assessment of outdoor comfort through a satisfactory estimation of the mean radiant temperature. A number of eventual refinements of the model are mentioned to improve its accuracy.
The work also highlights the necessity of more on-site measurements and more subjec-tive votes of people for validating the simulations results and in order to strengthen a practice-oriented knowledge about comfort in urban areas.","Die vorliegende Untersuchung beschäftigt sich mit dem Beitrag, den das Straßendesign zur Ausbildung eines komfortablen Mikroklimas für Menschen im Straßenbereich leisten kann. Der Schwerpunkt liegt bei subtropischen Klimabedingungen, d.h. bei heißem und trockenem Klima. Die Arbeit wurde anwendungsorientiert durchgeführt. Sie versucht, quantitative Ergebnisse bereitzustellen, die aus der Sicht eines Stadtplaners leicht verstanden und interpretiert werden können. Verschiedene Geometrien von Straßenschluchten werden untersucht. Sie schließen ein variables H/W-Verhältnis, unterschiedliche Richtungen und spezifische Designausführungen (z.B. Überhänge od. Straßenbegleitgrün) ein.
Am Anfang werden symmetrische Straßenschluchten mit H/W = 0.5, 1, 2 und 4 analysiert, die in E-W, N-S, NE-SW und NW-SE verlaufen. Daran schließt sich die Untersuchung von asymmetrischen Straßenschluchten an. Hier werden zusätzlich die Effekte von planerischen Details, wie Galerien, Überhänge und Straßenbegleitgrün, berücksichtigt, da sie eine weitere Möglichkeit zur Verbesserung der thermischen Komfortbedingungen im Außenbereich darstellen. Bei den Ergebnissen erfolgt eine räumliche Differenzierung im thermischen Empfinden von Menschen quer zur Straße.
Zur human-biometeorologischen Bewertung des thermischen Komforts wird die physiologisch äquivalente Temperatur PET verwendet. Die zur Berechnung von PET erforderlichen Variablen werden in hoher räumlicher und zeitlicher Auflösung über die Anwendung des 3D Modells ENVI-met 3.0, ermittelt.
Als Untersuchungsgebiet, das im Sommer heiße und trockene Klimabedingungen repräsentiert, dient die Region Ghardaia (32.40 °N, 3.80 °E) in Algerien.
In Ergänzung zu den numerischen Simulationsuntersuchungen erfolgten im Sommer 2003 kurzzeitige Messungen der thermophysiologisch relevanten meteorologischen Variablen in Freiburg und in Beni-Isguen (Ghardaia), Algerien.
Die Simulationsergebnisse zeigen, dass thermischer Komfort für Menschen unter den gegebenen, extremen klimatischen Verhältnissen schwer erreichbar ist. Verbesserungen sind jedoch über geeignete geometrische Anordnungen von Straßenschluchten möglich. Gegensätzliche Muster der Komfortbedingungen treten zwischen Straßenschluchten mit sehr hohem und niedrigem H/W-Verhältnis sowie mit unterschiedlicher Orientierung auf. Breite Straßenschluchten weisen einen hohen thermischen Diskomfort auf. Dabei sind Straßenschluchten in N-S Richtung etwas günstiger als solche in E-W Richtung zu beurteilen. Angezeigt durch einen kürzeren Zeitraum während des Tages mit Wärmebelastung und niedrigere PET Maxima nimmt dieser Vorteil der Straßenschluchten in N-S Richtung mit ansteigendem H/W-Verhältnis zu. Es ließ sich auch quantifizieren, wie sich die Wärmebelastung, die in Straßenschluchten auf Menschen wirkt, durch die Berücksichtigung von weiteren Varianten des Straßendesigns, wie Galerien, Überhänge oder Straßenbegleitgrün, in Kombination mit dem H/W-Verhältnis und der Richtung der Straßenschlucht reduzieren lässt.Im subtropischen Klima, der Tageszeitraum mit extremer Wärmebelastung und die räumliche Verteilung von PET in der Straßenschlucht am stärksten vom H/W-Verhältnis und von der Richtung der Straßenschlucht abhängen. Das hat Auswirkungen auf die Möglichkeiten zur optimierten Nutzung von Straßenschluchten (z.B. ausschließliche Nutzung durch Fußgänger oder einschließlich von Kraftfahrzeugverkehr) und auf die Zeiten der häufi-gen Nutzung dieser urbanen Freiräume.
In Bezug auf den thermischen Komfort von Menschen im Sommer im Freien bestätigen die Simulationsberechnungen und experimentellen Fallstudien die dominierende Rolle der Strahlungsflüsse, die durch die mittlere Strahlungstemperatur Tmrt der Umgebung parametrisiert werden. Stehende Menschen in Straßenschluchten absorbieren tagsüber hauptsächlich Strahlungswärme von bestrahlten Umgebungsflächen, während der Wärmegewinn aus der direkten Sonnenstrahlung von zweitrangiger Bedeutung ist. Daraus ergibt sich, dass nur über die Abschattung der direkten Sonnenstrahlung die klimatischen Bedingungen in Straßenschluchten verbessert werden. Lufttemperatur und Windgeschwindigkeit können in Bezug auf thermischen Komfort im Sommer in den Subtropen als meteorologische Variable von zweiter Bedeutung aufgefasst werden, da ihre räumliche und zeitliche Variabilität in Straßenschluchten deutlich geringer als diejenige von Tmrt ist.
Ein zusätzliches Kriterium für das Straßendesign, auf das kurz eingegangen wird, ist die Verfügbarkeit von Strahlung in Innenräumen im Winter. Unter Berücksichtigung der Anforderungen im Winter an das Design von Straßenschluchten werden Empfehlungen an die Planung von Freiräumen in Straßenschluchten gegeben.
Insgesamt hat sich das mikroskalige Modell ENVI-met als ein sehr gutes Werkzeug für diese Untersuchung herausgestellt. Vor allem wird Tmrt in zufriedenstellender Weise simuliert. Zweckmäßig wären allerdings weitere Validierungen von ENVI-met über geeignete experimentelle Fallstudien."],"dc:format.medium":["application/pdf"],"dc:subject":["Straßenschlucht","human-biometeorologie","PET","Himmelrichtung","Freiräume","urban canyon","aspect ratio","street orientation","ENVI-met","gallery","overhangs","urban vegetation"],"dc:title":["Dependence of outdoor thermal comfort on street design in hot and dry climate","Abhängigkeit des thermischen Komforts unter heißen und trockenen Klimabedingungen vom Straßendesign"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:33Z"}