The Impact of Urbanization on Current and Future Coastal Precipitation: A Case Study for Houston

Abstract

The approach of this study was to determine, theoretically, what impact current and future urban land use in the coastal city of Houston, Texas has on the space and time evolution of precipitation on a ‘typical’ summer day. Regional model simulations of a case study for 25 July 2001 were applied to investigate possible effects of urban land cover on precipitation development. Simulations in which Houston urban land cover was included resolved rain cells associated with the sea breeze front and a possible urban circulation on the northwest fringe of the city. Simulations without urban land cover did not capture the initiation and full intensity of the ‘hypothesized’ urban-induced rain cell. The response is given the terminology the ‘urban rainfall effect’ or URE. An urban growth model (UrbanSim) was used to project the urban land-cover growth of Houston, Texas from 1992 to 2025. A regional atmospheric-land surface model was then run with the 2025 urban land-cover scenario. Though we used a somewhat theoretical treatment, our results show the sensitivity of the atmosphere to urban land cover and illustrate how atmosphere — land interactions can affect cloud and precipitation processes. Two urban-induced features, convergence zones along the inner fringe of the city and an urban low-pressure perturbation, appear to be important factors that lead to enhanced rain clouds independently or in conjunction with the sea breeze. Simulations without the city (NOURBAN) produced less cumulative rainfall in the west-northwest Houston area than simulations with the city represented (URBAN). Future urban land-cover growth projected by UrbanSim (URBAN2025) led to a more expansive area of rainfall, owing to the extended urban boundary and increased secondary outflow activity. This suggests that the future urban land cover might lead to temporal and spatial precipitation variability in coastal urban microclimates. It was beyond the scope of the analysis to conduct an extensive sensitivity analysis of cause — effect relationships, though the experiments provide some clues as to why the rainfall evolution differs. This research demonstrates a novel application of urban planning and weather — climate models. It also raises viable questions concerning future planning strategies in urban environments in consideration of hydroclimate changes.

Sensitivity of the East Asian Summer Monsoon Circulation and Precipitation to an Idealized Large-Scale Urban Expansion

“…However, the magnitude and extent of the urbanization effect on wind field and precipitation are significantly reduced as the fractional urban cover decreases to 20%. The results concerning fractional coverage changes are consistent with experiments conducted for the Houston area by Shepherd et al (2010b). They used past, current, and future urban land cover in MM5 to evaluate sensitivity to land cover fraction and found that larger urban land cover produced the most significant and widespread changes in regional rainfall.…”

Urban impacts on air temperature and precipitation over The Netherlands

“…Similar results reported by Chen et al (2015) and Yang et al (2017) showed that higher UHI intensity might induce stronger convection and cause larger hourly precipitation in urban areas than in the rural areas in the late evening and night-time. Furthermore, pronounced precipitation difference during the night-time hours could be related to the interaction between the weakening sea breeze and the UHI (Shepherd et al 2010, Mitra et al 2012. It is of note that the catch efficiency of precipitation could be influenced by the location of stations.…”

Urbanization signature in the observed heavy rainfall climatology over India

“…While a number of studies provide a detailed analysis of the impact of urbanization on the local precipitation climatology for urban areas of developed countries such as Atlanta , Houston (Shepherd and Burian, 2003;Shepherd et al, 2009), Tokyo (Kusaka et al, 2000), Sydney (Gero and Pitman, 2006), Oklahoma City (Niyogi et al, 2006), Indianapolis Beijing (Zhou et al, 2004), and Mumbai (Lei et al, 2008), the impact of urbanization on continental-scale rainfall changes and large-scale systems such as Indian summer monsoon system has not been analyzed in adequate detail, and is the focus of this paper.…”

“…Cotton and Pielke (2007, Chapter 5;Pielke et al, 2007, Section 7) summarize numerous studies as to how urbanization alters rainfall patterns as a result of mesoscale circulations and through changes in convective available potential energy (CAPE). Moreover, recent research continues to show credible evidence that surface temperature increases (Kalnay and Cai, 2003), cloud enhancement (Inoue et al, 2004), and precipitation anomalies (Hand and Shepherd, 2009;Shem and Shepherd, 2009;Shepherd et al, 2009) may be linked to urban environments.…”

“…Spatial variations in the CAPE and CIN and in the mesoscale circulations that result from landscape heterogeneity, such as from urbanization, can focus on deep cumulus convection (Avissar and Liu 1996). Niyogi et al (2006), Shem and Shepherd (2008) and Shepherd et al (2009), using coupled atmosphereland models, quantified the relative changes in sensible and latent heat fluxes as a function of urban land cover for Oklahoma City, Atlanta and Houston respectively. Enhanced sensible heat flux was likely one factor related to the resolved urban-induced precipitation.…”