Local impact of trees on thermal comfort of pedestrians in streets
Bibliographic record
Abstract
Urban thermal comfort can be improved by trees. A better understanding of the effects of trees on urban climate in streets can provide better guidelines on the optimized use of vegetation in cities to moderate temperatures. In this study, we explore and quantify both improvement and deterioration of urban thermal comfort due to street trees, modeled based on a common street tree in Montreal, by varying planting patterns, street orientation and wind direction. The impact of trees on outdoor thermal comfort is studied at street level and at balcony level for multistoried residential buildings over 24-hour cycles. The study is performed with a suite of urban climate models based on OpenFOAM, considering turbulent and buoyant air flow, heat and moisture transport in porous media and short- and long-wave radiative exchanges. Results are presented in terms of Universal Thermal Climate Index (UTCI). To quantify zones and periods of impact of trees on thermal comfort during day and night, we introduce several new comfort indices: the cooling and heating indices, that describe the level of thermal comfort improvement or deterioration, respectively, and the cooling and heating areas, indicating which areas of the street are affected. We show that tree canopies can be strong assets during the day, as trees intercept solar radiation and provide shading. However, as a counterpoint, they may cause deterioration of thermal comfort during night, stretching sometimes into the morning. Street orientation is found to have a larger impact on thermal comfort than wind direction, while wind flow parallel to the street leads to more comfortable conditions than perpendicular wind. We identify street orientations and tree planting patterns that enhance thermal comfort. • New metrics are proposed to better describe the thermal comfort impact of trees. • Shadowing effects should be maximized through planting patterns and street orientations. • Street orientation has a larger impact on thermal comfort than wind direction. • Trees negatively affect nighttime thermal comfort by blocking cooling of hot surfaces. • Depending on their locations, trees can deteriorate or improve resident thermal comfort.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".