Why Small Built Parks Matter: Evidence that Small Urban Vegetation Improves Thermal Comfort in Hyper-arid Cities

Muscat, the capital of Oman is a hyper-arid city characterized by intensive solar radiation for most part of the year similar to the neighboring Gulf cooperation countries (GCC). Outdoor Thermal Comfort (OTC) is critical for livability, was assessed. A field survey was carried out in vegetated and non-vegetated area in summer where objective and subjective parameters were simultaneously collected. The former represents environmental parameters measured using a Kestrel 5400 Heat Stress Tracker, while the later was assessed through a structured face-to-face questionnaire. A total of 415 respondents were involved to assess their thermal sensation vote (TSV) and environmental parameters preference using ASHRAE 7-point scale and Mclntyre scale respectively. The computation of the Physiological Equivalent Temperature (PET) was performed via RayMan pro version 3.1 software. The Physiological Equivalent Temperature (PET) range of 23.6°C- 30.8°C and neutral PET of 27.2°C was obtained. PET is moderately correlated (R = 0.7, R ²  = 0.50) with thermal sensation votes and it is significant at the 0.01 level (2-tailed). A linear regression model specific to the country's climatic zone and the national dress code of the citizens was established as: TSV= (0.14×PET) -3.8. The majority of respondents (96.2%) in vegetated area felt, the temperature to be more thermally acceptable and comfortable, while the percentage fall to quarter in non-vegetated area. This study emphasizes the importance of human thermal comfort in urban areas contributing to knowledge on the influence of microclimate in hot arid climatic zones, and cities in those zones can adapt by transforming the urban spaces.