Potential sensitivity of warm season precipitation to urbanization extents: Modeling study in Beijing‐Tianjin‐Hebei urban agglomeration in China

Abstract

In this study, we investigated how different degrees of urbanization affect local and regional rainfall using high-resolution simulations based on the Weather Research and Forecasting Model. The extreme rainfall event of 21 July 2012 in Beijing was simulated for three representative urban land use distributions (no urbanization, early urbanization level of 1980, and recent urbanization level of 2009). Results suggest that urban modification of rainfall is potentially sensitive to urban land use condition. Rainfall was increased significantly over the downwind Beijing metropolis because of the effects of early urbanization; however, recent conditions of high urban development caused no significant increase. Further comparative analysis revealed that positive urban thermodynamical effects (i.e., urban warming, increased sensible heat transportation, and enhanced convergence and vertical motions) play major roles in urban modification of rainfall during the early urbanization stage. However, after cities expand to a certain extent (i.e., urban agglomeration), the regional moisture depression induced by the prevalence of impervious urban land has an effect on atmospheric instability energy, which might negate the city's positive impact on regional rainfall. Additional results from regional climate simulations for 10 Julys confirm this supposition. Given the explosive urban population growth and increasing demand for freshwater in cities, the potential negative effects of the urban environment on precipitation are worth investigation, particularly in rapidly developing countries and regions.

Regional Patterns of Extreme Precipitation and Urban Signatures in Metropolitan Areas

“…The detected causal relationships are further supported by the physical mechanism of regional climate modeling under different scenarios of land use changes, which makes the findings even more convincing. Therefore, our study is a further extension of existing studies (Kaufmann et al, ; Song et al, ; J. Wang et al, ; Y. J. Yang et al, ).…”

Impact of Land-Use and Land-Cover Change on Meteorology in the Beijing–Tianjin–Hebei Region from 1990 to 2010

“…The CC of the observational and simulated daily precipitation in January was 0.76 and 0.8 in July, which meant that the simulation reflected various features well. In terms of the bias, the results from the observed values were higher than those from the simulation, which also appeared in Wang, Feng [16], who also noted why it was difficult to accurately simulate rainfall. This study focused on the difference in underlying surface changes affecting regional meteorology, and some model systematic errors can ultimately be offset by subtraction.…”

“…Because the vertical and horizontal air circulation were impacted, the precipitation decreased in this area. Because precipitation is a complex process, it is difficult to simulate its exact value [16]; however, LULC change is a factor that affects its trend.…”

Impact of Extensive Urbanization on Summertime Rainfall in the Beijing Region and the Role of Local Precipitation Recycling

“…The sharp decrease in relative humidity imposes a negative effect on the CAPE, which can negate and even overwhelm the promoting effects of urbanization on rainfall. Wang et al () partly explained the previous contradictory findings on the urban modification of rainfall. Nonetheless, it should be noted that most of these previous studies were based on the simulations of selected heavy rainfall cases and short‐term observational data, while few has examined the impact of urbanization on regional rainfall in a climatological sense.…”

“…Recent studies that focused on cities with high‐level urbanization situated in dry regions, such as the Beijing‐Tianjin‐Hebei metropolitan region, suggested that extensive urbanization could lead to a general reduction of regional rainfall (Feng et al, ; Guo et al, ; Wang et al, ; Zhang et al, , ; Zhong et al, ). Based on the analysis of rainfall data and numerical simulations for two selected heavy summer rainfall events, Zhang et al () revealed that the rapid urban expansion in Beijing is responsible for the reduction in summertime rainfall in the northeast areas of Beijing in the recent decades.…”