Albedo, Land Cover, and Daytime Surface Temperature Variation Across an Urbanized Landscape

Abstract

Land surface albedo is a key parameter controlling the local energy budget, and altering the albedo of built surfaces has been proposed as a tool to mitigate high near‐surface temperatures in the urban heat island. However, most research on albedo in urban landscapes has used coarse‐resolution data, and few studies have attempted to relate albedo to other urban land cover characteristics. This study provides an empirical description of urban summertime albedo using 30 m remote sensing measurements in the metropolitan area around Boston, Massachusetts, relating albedo to metrics of impervious cover fraction, tree canopy coverage, population density, and land surface temperature (LST). At 30 m spatial resolution, median albedo over the study area (excluding open water) was 0.152 (0.112–0.187). Trends of lower albedo with increasing urbanization metrics and temperature emerged only after aggregating data to 500 m or the boundaries of individual towns, at which scale a −0.01 change in albedo was associated with a 29 (25–35)% decrease in canopy cover, a 27 (24–30)% increase in impervious cover, and an increase in population from 11 to 386 km−2. The most intensively urbanized towns in the region showed albedo up to 0.035 lower than the least urbanized towns, and mean mid‐morning LST 12.6°C higher. Trends in albedo derived from 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) measurements were comparable, but indicated a strong contribution of open water at this coarser resolution. These results reveal linkages between albedo and urban land cover character, and offer empirical context for climate resilient planning and future landscape functional changes with urbanization.

Impacts of Land Cover/Use on the Urban Thermal Environment: A Comparative Study of 10 Megacities in China

“…As shown in other studies [3,4,11,82,83], an increasing amount of high-albedo IS materials are currently utilized in building urban infrastructure. For instance, in Adelaide [84], Athens [85], Boston [86] and Guangzhou [11], these megacities have been recommended to optimally cool down the urban temperature and mitigate the UHI effect by adopting the high-albedo building materials. This is a critical step toward alleviating the release of urban heat and facilitating infrastructure construction in low-temperature corridors, because the heat behavior of high-albedo IS causes solar radiation to be reflected rather than absorbed.…”

Using Satellite-Borne Remote Sensing Data in Generating Local Warming Maps with Enhanced Resolution

“…The global average temperature of the Earth has increased, but year-to-year variability in local climates impedes the identification of clear changes in observation and human experience [5]. It is expected that urbanization could expand globally to triple its extent in the year 2000 by 2030 due to the projected urban population increase to nearly five billion [6,7]. In fact, urbanization modifies local land cover, habitats, hydrology, biochemistry, and surface energy balance [8].…”

“…In fact, urbanization modifies local land cover, habitats, hydrology, biochemistry, and surface energy balance [8]. Such rapid urbanization causes land fragmentation [9,10], and creates urban heat islands (UHI), i.e., a suite of localized climate shifts, due to densely built impervious land cover [7,11]. The temperature across the urban landscape can vary at the finer spatial scale due to the presence of various land covers, such as buildings, parking lots, roads, parks, etc., within a given small area [7].…”

“…Such rapid urbanization causes land fragmentation [9,10], and creates urban heat islands (UHI), i.e., a suite of localized climate shifts, due to densely built impervious land cover [7,11]. The temperature across the urban landscape can vary at the finer spatial scale due to the presence of various land covers, such as buildings, parking lots, roads, parks, etc., within a given small area [7]. Even the temperature could vary within a single building perimeter, for example, areas of a building facing towards the sun and the corresponding building shadow areas would not have a similar temperature.…”

“…Even the temperature could vary within a single building perimeter, for example, areas of a building facing towards the sun and the corresponding building shadow areas would not have a similar temperature. Such local variations and the overall urban UHI would affect the local to regional surface energy balance [6,7,11]. Therefore, it becomes important to map the temperature variations over urban areas (in other words, local warming) at a finer spatial resolution for urban planners and decision makers to maintain sustainable environmental quality and human well-being.…”