Urban Climate of Southeast Asia/South Asia

    Until about 30 to 50 years ago, urban development primarily concentrated in mid- to high-latitude regions such as the United States and Europe. In recent years, however, rapid economic growth has driven accelerated urbanization in Southeast and South Asia. Previous studies have revealed that the impact of urbanization on climate (urban effects) varies significantly depending on the form of the city and the climatic zone in which it is located.

    Currently, the Kusaka Laboratory is conducting research on urban climates in major cities of Southeast Asia, including Jakarta (Indonesia), Bangkok (Thailand), and Manila (Philippines)—so-called "megacities"—as well as Ho Chi Minh City (Vietnam), Kuala Lumpur (Malaysia), and Singapore. This research goes beyond simply evaluating the presence or absence of urban areas; it includes comparisons between past and present urban climates using historical land use data, and projections of future urbanization and associated climate changes based on national urban development master plans.

    Some of these studies are collaborating with institutions such as the Vietnam Meteorological and Hydrological Administration (NCHMF) and the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG), with regular meetings to ensure close information sharing.

The Kusaka Laboratory has also hosted many international students from countries such as China, Vietnam, the Philippines, Malaysia, and Sri Lanka, each conducting urban climate research focused on their respective home countries. As a result, the urban climates of Southeast and South Asia have become one of the laboratory’s core research themes.

Urban Heat Island (UHI) Intensified by Urbanization

    In recent years, Southeast Asian cities experiencing rapid economic development have shown a growing trend of intensified urban heat island (UHI) effects, accompanied by rising urban temperatures. Doan and Kusaka (2016) evaluated the impact of urbanization over the past two decades in Ho Chi Minh City, Vietnam, where rapid urban growth is underway. Their study found that air temperatures increased by approximately 0.3°C in existing urban areas and by about 0.6°C in newly urbanized areas.

    Furthermore, based on a future urban development master plan, Doan et al. (2016) simulated future temperature changes under continued urbanization. The simulation projected surface air temperature increases of about 0.22°C in existing urban zones and approximately 0.41°C in emerging urban zones, indicating a likely further intensification of the UHI effect.

Urban Impacts During Heatwaves

    In recent years, tropical regions have experienced frequent heatwaves—periods of extreme high temperatures lasting for three or more consecutive days—leading to reported human casualties. While the impacts of heatwaves in tropical cities have not been thoroughly discussed until recently, the Kusaka Laboratory is actively addressing this issue as a key research focus.

Manila, the Philippines 

      In Manila, one of Southeast Asia’s megacities, Magnaye and Kusaka (2024) conducted a study using high-density observational data and an improved version of the WRF model. Their results revealed that urban heat island intensity (UHII) could reach up to 4°C, and that anthropogenic heat emissions from urban areas contributed approximately 10% to the UHII.

Kuala Lumpur, Malaysia

       For Kuala Lumpur, a city with a tropical rainforest climate, Syed Mahbar and Kusaka (2024) investigated changes in UHII before, during, and after heatwave events. Based on surface meteorological observations and WRF simulations, their findings showed that UHII intensified significantly during heatwaves compared to normal conditions.

Colombo, Sri Lanka

      In Colombo, a tropical city in South Asia, the urban thermal environment during heatwaves was strongly shaped by urbanization (Sathsara and Kusaka, 2025). The study also highlighted that accurately capturing the thermal environment during heatwave periods required the use of more recent and high-resolution land cover data.

Increased Cloud Cover Over Urban Areas

    Urban areas tend to experience increased cloud cover, as demonstrated in previous studies focusing on cities such as Tokyo and London. At the Kusaka Laboratory, we investigated the hypothesis that a similar phenomenon may occur in tropical cities as well.

    Syed Mahbar and Kusaka (2024) analyzed cloud characteristics in Kuala Lumpur, a major city with a tropical rainforest climate. The results showed that on hot and clear days, cloud cover tended to be greater over the urban area compared to surrounding regions.

List of Publications by City Studied So Far

(Written by: Nobuyasu Suzuki; Edited by: Coty CHENG)