Understanding the Impact of Urbanization on Surface Urban Heat Islands—A Longitudinal Analysis of the Oasis Effect in Subtropical Desert Cities

Abstract

Abstract:We quantified the spatio-temporal patterns of land cover/land use (LCLU) change to document and evaluate the daytime surface urban heat island (SUHI) for five hot subtropical desert cities (Beer Sheva, Israel; Hotan, China; Jodhpur, India; Kharga, Egypt; and Las Vegas, NV, USA). Sequential Landsat images were acquired and classified into the USGS 24-category Land Use Categories using object-based image analysis with an overall accuracy of 80% to 95.5%. We estimated the land surface temperature (LST) of all available Landsat data from June to August for years 1990, 2000, and 2010 and computed the urban-rural difference in the average LST and Normalized Difference Vegetation Index (NDVI) for each city. Leveraging non-parametric statistical analysis, we also investigated the impacts of city size and population on the urban-rural difference in the summer daytime LST and NDVI. Urban expansion is observed for all five cities, but the urbanization pattern varies widely from city to city. A negative SUHI effect or an oasis effect exists for all the cities across all three years, and the amplitude of the oasis effect tends to increase as the urban-rural NDVI difference increases. A strong oasis effect is observed for Hotan and Kharga with evidently larger NDVI difference than the other cities. Larger cities tend to have a weaker cooling effect while a negative association is identified between NDVI difference and population. Understanding the daytime oasis effect of desert cities is vital for sustainable urban planning and the design of adaptive management, providing valuable guidelines to foster smart desert cities in an era of climate variability, uncertainty, and change.

Effects of urbanization on regional meteorology and air quality in Southern California

“…The world has been undergoing accelerated urbanization since the industrial revolution in the 19th century (Grimm et al, 2008;Seto et al, 2012). Urbanization leads to profound human modification of the land surface and its associated physical properties such as roughness, thermal inertia, and albedo (Fan et al, 2017) and land surface processes like irrigation (Vahmani and Hogue, 2014). These changes in land surface physical properties and processes alter corresponding surface-atmosphere coupling including exchange of water, momentum, and energy in urbanized regions (Vahmani and Ban-Weiss, 2016a;Li et al, 2017), which exerts an important influence on regional meteorology and air quality (Vahmani et al, 2016;Civerolo et al, 2007).…”

“…Land surface properties in surrounding rural areas can also affect urban-rural differences in temperature (Imhoff et al, 2010;Peng et al, 2012;Zhao et al, 2014). In particular, urban regions built in semiarid or arid surroundings tend to have a weak daytime UHI or even a UCI, whereas those built in moist regions tend to have a larger daytime UHI (Fan et al, 2017;Peng et al, 2012). Lastly, factors such as anthropogenic heat and atmospheric aerosol burdens can play an important role in urban heat or cool island formation in some regions (Oke, 1982;Wang et al, 2017).…”

Monitoring and Prediction of Land Use Land Cover Changes and its Impact on Land Surface Temperature in the Central Part of Hisar District, Haryana Under Semi-Arid Zone of India

“…Such a situation pertains to reduced evapotranspiration because of scanty vegetation cover in the rural surrounding during dry pre-monsoon summer. Presence of bare land in the form of fallow area, overgrazed land, lower moisture holding ability of thorny bushes are the dominant factors for the reduced evaporative cooling in the semi-arid regions (Fan et al, 2017;Shastri et al, 2017). Moreover, green cover in the form of parks, and plantation in the city becomes important contributor to lower mean LST because of high rates of evapotranspiration which has been termed 'oasis effect' in the cities located in the arid and semi-arid in earlier studies (Fan et al, 2017).…”

“…Presence of bare land in the form of fallow area, overgrazed land, lower moisture holding ability of thorny bushes are the dominant factors for the reduced evaporative cooling in the semi-arid regions (Fan et al, 2017;Shastri et al, 2017). Moreover, green cover in the form of parks, and plantation in the city becomes important contributor to lower mean LST because of high rates of evapotranspiration which has been termed 'oasis effect' in the cities located in the arid and semi-arid in earlier studies (Fan et al, 2017). Although, built-up area comprising high-rise buildings, roadways, industrial area with other constructions has also been detected with high mean LST because of the trapping of radiation and release of human-induced heat.…”

Trend Analysis of Urban Heat Island Intensity According to Urban Area Change in Asian Mega Cities

“…This phenomenon results in a cooler urban area when compared with its surrounding areas. This is attributed to urban morphological factors or seasonal surface characteristics, and existing studies have confirmed that this phenomenon occurs in urban areas whose surrounding areas are desert or agricultural land; moreover, this phenomenon is especially prominent in summer [46,47]. As of 2012, approximately 38.2% of the surrounding areas of Karachi were found to be cropland and bare areas.…”