Poster Paper: Urban Heat Island Effect and Extreme Heat Event in Southern California

Friday, March 9, 2018
Burkle Lobby, First Floor (Burkle Family Building at Claremont Graduate University)

*Names in bold indicate Presenter

Mengdi Li, University of California, Irvine

Massive urbanization and intensified development activities have brought urban heat island effect (UHI) to many cities in Southern California by converting natural land cover to impervious dark artificial surfaces and urban settings that accumulate heat. UHI will negatively affect the living condition of people in Southern California by exaggerating extreme heat events and raising energy consumption during summer. This paper analyzed the spatial and temporal characteristics, the influence, the mitigation strategies of UHI as well as related public policies promoting this sustainable development approach. To analyze the distribution of UHI in the Los Angeles County (LA County) and Orange County (OC), the Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day Land Surface Temperature (LST) in 2001, 2006 and 2011 were collected and averaged to derive monthly LST maps of each county. And then monthly LSTs were merged with respective land cover data in each year of National Land Cover Database (NLCD). Results showed that there was no temperature difference observed between developed and undeveloped area in North LA County, while UHI was detected in South LA County and OC and the largest temperature differences were in spring and summer. The average temperature differences between developed area and green space in 2001, 2006 and 2011 were 6 °F, 7 °F, and 6°F respectively in South LA County. The overall temperature difference between developed area and green space was around 4°F constantly in 2001, 2006 and 2011 in Orange County. Temperature differences among different development intensities were also considerable in South LA County and OC. In South LA County, high and medium development intensities associated with hottest temperature through year, followed by lower-intensive developed area, and then developed open space. In OC, temperature in higher-intensity developed area was warmer than lower-intensity developed area. UHI will exaggerate extreme heat events and will increase the rate of heat-related mortality in hot summer days. To quantify extreme heat event in LA County and OC, daily air temperature from 42 weather stations in 1961 to 2016 were collected and temperature threshold was defined as the 85th percentile of historical air temperature from 1961 to 1990. Extreme heat event happened more in inland cities than in coastal cities. From 1961 to 1995, the number of extreme heat event days in City of Irvine was always lower than that of City of Los Angeles. After 1995, the number of extreme heat event days in Irvine was almost the same with or even more than that in Los Angeles.