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Climate 2018, 6(4), 98; https://doi.org/10.3390/cli6040098

Observational Evidence of Neighborhood Scale Reductions in Air Temperature Associated with Increases in Roof Albedo

1
Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA
2
Heat Island Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
3
Altostratus, Inc., 940 Toulouse Way, Martinez, CA 94553, USA
*
Author to whom correspondence should be addressed.
Received: 14 October 2018 / Revised: 17 November 2018 / Accepted: 23 November 2018 / Published: 12 December 2018
(This article belongs to the Special Issue Climate Change Resilience and Urban Sustainability)
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Abstract

The effects of neighborhood-scale land use and land cover (LULC) properties on observed air temperatures are investigated in two regions within Los Angeles County: Central Los Angeles and the San Fernando Valley (SFV). LULC properties of particular interest in this study are albedo and tree fraction. High spatial density meteorological observations are obtained from 76 personal weather-stations. Observed air temperatures were then related to the spatial mean of each LULC parameter within a 500 m radius “neighborhood” of each weather station, using robust regression for each hour of July 2015. For the neighborhoods under investigation, increases in roof albedo are associated with decreases in air temperature, with the strongest sensitivities occurring in the afternoon. Air temperatures at 14:00–15:00 local daylight time are reduced by 0.31 °C and 0.49 °C per 1 MW increase in daily average solar power reflected from roofs per neighborhood in SFV and Central Los Angeles, respectively. Per 0.10 increase in neighborhood average albedo, daily average air temperatures were reduced by 0.25 °C and 1.84 °C. While roof albedo effects on air temperature seem to exceed tree fraction effects during the day in these two regions, increases in tree fraction are associated with reduced air temperatures at night. View Full-Text
Keywords: urban heat island; urban climate; Los Angeles; land use land cover; cool roofs; heat mitigation; vegetation; tree urban heat island; urban climate; Los Angeles; land use land cover; cool roofs; heat mitigation; vegetation; tree
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Mohegh, A.; Levinson, R.; Taha, H.; Gilbert, H.; Zhang, J.; Li, Y.; Tang, T.; Ban-Weiss, G.A. Observational Evidence of Neighborhood Scale Reductions in Air Temperature Associated with Increases in Roof Albedo. Climate 2018, 6, 98.

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