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Urban Heat Island Analysis


Tools Used: Mosaic, Reclassify, Raster Calculator

Skills Used: Obtaining Landsat data, raster analysis

View of Downtown Sacramento and the  Sacramento River

The Problem:  During hot weather urbanized areas can experience higher temperatures, greater pollution levels and more negative health impacts compared to surrounding rural areas. This is known as an urban heat island effect. Heat islands occur due to a combination of factors: roads, parking lots, buildings, and roofs that absorb heat; vehicle engines and industrial generators that produce heat; and the absence of trees and shrubs that provides shade and cooling through evapotranspiration or water bodies that cool through evaporation. Daytime temperatures in urban areas can be about 1–7°F higher than temperatures in outlying areas and nighttime temperatures about 2–5°F higher. (Source)

Project Description: This analysis asks the question of how has the urban heat island index changed in the study are over 30 years due to changes in impervious surfaces. The purpose of this study was to map and detect changes in surface land temperature in Sacramento, CA  from 1999 to 2019. The methodology was to conduct a raster analysis using raw data and spatial analysis tools, specifically reclassifying as an ordinal rank, then reclassifying the data as a binary, and then comparing the decades.

The data used were Landsat Provisional Surface Temperature satellite data, at 30-meter spatial resolution. The goal was to create a series of heat maps that show the temperature difference over time at the neighborhood range. The results show an increase in warming areas, primarily in the suburban areas surrounding the city of Sacramento.

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