The Urban Heat-Island effect in Boston

In summer, buildings, roads, and other structures in cities absorb heat from sunshine and slowly release it. As a result, urban areas are typically several degrees warmer than greener and less densely developed areas that surround them. The difference can be especially noticeable at night, when cities are much slower to cool off. This phenomenon is the urban heat-island effect.

Urban Heat-Island satellite measurements

The figure below, from a group of researchers then at Boston University using satellite measurements made in 2001, shows the urban heat-island effect from Washington, D.C. to Boston. Colors indicate how much cooler average land surface temperatures from January through May in non-urban areas were than in urban centers.

Urban Heat Island effect (440)

X. Zhang et al. 2004. The footprint of urban climates on vegetation phenology. GEOPHYSICAL RESEARCH LETTERS, (31) L12209, doi: 10.1029/2004GLO20137, 2004.

Temperature variations between Boston, Worcester and Harvard Forest (Petersham, MA)

The below graphs show recent temperature data from Boston, Worcester, and Harvard Forest (located in Petersham, MA) as measured by the Boston ULTRA-EX project researchers at Boston University. Worcester is 50 miles and Harvard Forest is 70 miles inland from Boston. Temperature differences between them reflect the urban heat-island effect, the difference between coastal and non-coastal locations, and small-scale variability of weather patterns in New England. As is often the case with site-specific data from a brief span of time, patterns can be hard to discern.

May temp at BU, Harvard and Worcester (440)

May diel temp at BU, harvard and worcester (440)