Evidence of urban-induced precipitation variability in arid climate regimes

Abstract

The study employs a 1 OF(-year precipitation historical data record, global climate observing network observations and satellite data to identify possible anomalies in rainfall in and around two major arid urban areas, Phoenix, Arizona and Riyadh, Saudi Arabia. The analysis reveals that during the monsoon season, locations in northeastern suburbs and exurbs of the Phoenix metropolitan area have experienced statistically significant increases in mean precipitation of 12 to 14 percent from a pre-urban to post-urban ( 1950-2003) period. Further analysis of satellite-based rainfall rates suggests the existence of the anomaly region over a seven-year period. The anomaly cannot simply be attributed to maximum topographic relief and is hypothesized to be related to urban-topographic interactions and possibly irrigation moisture. Temperature records suggest that Riyadh has experienced an adjustment in mean temperature in response to the growth of urban surfaces (e.g., the so-called urban heat island effect).While ground-based precipitation records also indicate an upward trend in mean and total precipitation in and around Riyadh in the last 10-15 years, it is difficult to attribute the increase to urbanization because other less urbanized stations in Saudi Arabia also show a similar increase. Recent satellite-based precipitation estimates indicate an anomaly region 50-100 km north of Riyadh, but this study is not robust enough to conclusively link it to urbanization although certain climate-regime attributes suggests that it might be.

Remote sensing of the urban heat island effect across biomes in the continental USA

“…These results at least trend in the direction of a potential heat sink effect for arid cities postulated by some (e.g. Bounoua et al, 2009;Shepherd, 2005Shepherd, , 2006. Composite averaged summer day LST profiles across the Urban Core for the two urban areas are illustrated in Fig.…”

“…This means that the ecological context has consequences on both intensity and sign through its influence on the thermal characteristics of the rural area. A weak urban heat island or urban heat sink phenomenon, for example, has been observed in semi-arid and arid climates (where the rural areas are desert shrubland) despite high urban densities (Bounoua et al, 2009;Brazel et al, 2000;Lougeay et al, 1996;Pena, 2008;Shepherd, 2006). Furthermore, as a driving process at the landscape level, the nonrandom placement of urban infrastructure also has an effect.…”

Review of urban climate research in (sub)tropical regions

“…Latha and Badarinath (2005b) comment on solar radiation attenuation due to aerosols in Hyderabad. Rasul et al (2004) in Islamabad and Jauregui and Romales (1996) in Mexico City have analysed heavy rain events and long-term precipitation increase and Shepherd (2006) in Phoenix and Riyadh urban induced rainfall in arid cities. Humidity and evaporation in relation to the UHI intensity and other climatic variables have been explored in Mexico City (Jauregui and Luyando, 1998) and in relation to vegetation in Gaborone (Jonsson, 2004).…”

The Climate Change, Water Crisis and Forest Ecosystem Services in Beijing, China

“…Owing to the fast urbanization, natural ecosystems are being increasingly replaced by an impervious urban surface (Xiao et al, 2007). Impervious surfaces increase the speed and volume of water running off a site, while decreasing the quality of that water and highly modifying the hydrology of urban areas (Shepherd, 2006). A higher proportion of rainfall becomes surface-water runoff which results in increased peak flood.…”