RESEARCH ARTICLE
MODIS Summer SUHI Cross-sections Anomalies over the Megacities of the Monsoon Asia Region and Global Trends

Evidence has accumulated in recent years regarding the scope of local and global climate changes attributed to exacerbating anthropogenic factors such as accelerating population growth, urbanization, industrialization, traffic and energy use. Remote space monitoring, unlike ground-based measurements, has the advantage of providing global coverage on a daily basis.

MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra 1°×1° spatial resolution as well as the 1 km higher resolution of Aqua-MODIS were investigated for a global overview of megacities temperature variations, as well as the recent trends of the 10 largest Monsoon Asian megacities.

The average Land Surface Temperature (LST) cross-sections of the 10 Asian megacities were examined for June-August 2002-2014. Temperature variations fit a spatial bell-shaped curve, with a pronounced maximum over the city center. Nighttime data indicated sharp LST decreases with distance from the city center, particularly in the coldest cities, those of Tokyo, Seoul, Osaka and Beijing.

Daytime latitudinal (E-W) and longitudinal (N-S) Surface Urban Heat Islands (SUHI) have steeper gradients than for nighttime data. During daytime, the SUHI gradients are largest in Tokyo, Seoul, Osaka and Beijing with values reaching 15^oC followed by the cities of Shanghai and Guangzhou with ~11^oC, and Karachi with ~5^oC SUHI. Nighttime SUHIs were more moderate, 4-6^oC in Tokyo, Seoul ~5^oC, Osaka 5-7^oC and Beijing ~7^oC. Only in the three largest megacities, i.e., Tokyo, Guangzhou and Shanghai, did the nighttime LST trends decline.