Quantifying influence of rainfall events on outdoor thermal comfort in subtropical dense urban areas

Abstract

Existing research on outdoor thermal comfort in urban areas focuses on meteorological factors such as temperature, relative humidity, wind speed, and radiation on sunny or cloudy days. However, climate conditions before, during, and after rainfall events can cause changes in meteorological factors in subtropical regions. Rainfall is an atmospheric condition with a large influence on thermal comfort, particularly in subtropical areas with abundant rain.

Big data on temperature, relative humidity, wind speed, precipitation, and total cloud cover from the Taipei Weather Station under the Central Weather Administration from June to August each year from 2011 to 2020 were analyzed, dividing the data into categories based on precipitation. Using a k-means clustering algorithm, we quantified the relationships between meteorological factors and apparent temperature as well as physiological equivalent temperature in different rainfall scenarios.

The results indicate that rainfall in the summers of subtropical oceanic climates indeed influence outdoor thermal comfort in urban areas: 37.7% of the rainfall weather patterns improved thermal comfort and 62.3% of the rainfall weather patterns reduced thermal comfort. RWP 46 represent the weather conditions that most significantly improve thermal comfort, at 1:00 PM, with a rainfall of 15 mm, there is a decrease in ΔAT by 14.4 °C and ΔPET by 22.1 °C. With the hot, humid, and rainy climate conditions in Taiwan, apparent temperature is the most accurate index of thermal comfort.

KEY POLICY HIGHLIGHTS

• Rainfall events may affect outdoor thermal comfort in subtropical cities.

• Different rainfall weather patterns have different impacts on urban outdoor thermal environments.

• 62.3% of rainfall weather patterns resulted in worsened thermal comfort, for low and concentrated rainfall resulting in a stuffier thermal environment.

Keywords:

• Rainfall event
• subtropics
• Taiwan
• outdoor thermal comfort
• enthalpy

Acknowledgement

This study is grateful for support and research grants from Research Center of Energy Conservation for New Generation of Residential, Commercial, and Industrial Sectors and the NSTC Project No. 110-2221-E-027-018-MY2.

Data availability

The data that support the findings of this study are available in [CWA Observation Date Inquire Service] at [https://codis.cwa.gov.tw/], reference number [7]. These data were derived from the following resources available in the public domain: [https://codis.cwa.gov.tw/].

Disclosure statement

The authors declare that there is no conflict of interest between the research in this paper and its authors and publishers.