Additionally, Pielke et al ( 2011) presented detailed documentation from recent studies related to how changes in LULC affect local climate, including rainfall. Shephard (2005) carefully reviewed and documented the past efforts taken to understand the effect of the urban environment on rainfall. Furthermore, many studies (Landsberg 1956, 1970, Atkinson 1968, Changnon 1968, Huff and Changnon 1972) then convinced the scientific community using case studies, climatological analysis around select cities, and field experiments that anthropogenic forces potentially alter the rainfall pattern over urban centers. ![]() Additionally, past studies emphasized understanding the impact of anthropogenic changes over rainfall extremes in different parts of the globe, such as India (Kishtawal et al 2010, Vittal et al 2013, Shastri et al 2015, Singh et al 2016, Paul et al 2018), Europe (Brunetti et al 2004), China (Zhai et al 2005, Zou and Ren 2015), and the Contiguous US (Shepherd et al 2002, Diem and Brown 2003, Niyogi et al 2011, 2017).Ī pioneering study by Horton ( 1921) reported the likelihood of occurrence of a thunderstorm modification over large cities compared to that in rural environments in the northeastern United States. Urbanization can affect the local to large-scale atmospheric composition, surface energetics, and water and carbon flux, further altering large-scale forcing that causes changes in the temporal and spatial patterns of temperature and rainfall (Oke 1982). Notably, in the United States (US), 80% of the total population lives in urban areas (Advisory Committee for Environmental Research and Education 2018), and the density of the impervious surface area across the Contiguous United States (US) exceeds 100 000 km 2 (Elvidge et al 2004). Recently, the scientific community (National Research Council 2012, Ramaswami et al 2016) identified a fundamental interdisciplinary need to understand the complex interactions between urban systems and local climate to improve the resilience of cities to the impacts of climate change. In response to the trade-off between global climate changes and local changes, particularly due to urbanization, studies such as Pielke et al ( 2007) reported that regional land use land cover (LULC) changes significantly affect local circulation and alter rainfall patterns. Changes in extreme rainfall characteristics have been evident in the past (Goswami et al 2006, Allan and Soden 2008, Zou and Ren 2015), and were primarily believed to be governed and dominated by large-scale circulation or greenhouse driven climatic changes. However, future effects from such events can be minimized through adaptation and risk management efforts informed by an improved understanding of their response to climate change. Rainfall extremes have caused severe disruption with widespread socio-economic impacts across the globe, and such events have been reported to become more frequent under warming conditions (Field et al 2012). Here, we show that urbanization, even though a local feature, influences the mesoscale meteorological setting and, is statistically associated with an intensification of rainfall extremes across the Contiguous United States. Statistical analyses highlight a positive relationship between changes in rainfall extremes and urbanization within a set of concentric ring buffers around rain gauge stations. ![]() Spatially, the changes in rainfall extremes over the central, northeast central, southeast, and northwest central zones were more pronounced due to urbanization. The results show a 2.7-fold higher probability of exceeding a 25% change in 50 year rainfall events over urban areas than over rural areas. This study presents the unexplored impacts of changes arising in urban areas on rainfall extremes over the Contiguous United States. Understanding the impact of urbanization on rainfall extremes is critical for both reliable climate projections as well as sustainable urban development. Anthropogenic changes are likely to intensify rainfall extremes, posing a risk to human, environmental and urban systems.
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