Loss of a lake system in a megacity: The impact of urban expansion on seasonal meteorology in Mexico City

Abstract

The Mexico City Metropolitan Area (MCMA) has undergone significant urban expansion in a closed basin that once supported a large lacustrine system. While urbanization has been mentioned as a factor in observed meteorological trends, a systematic study of the effects of land use-land cover change (LULCC) on seasonal meteorology is lacking. In this study, we utilize the Weather Research and Forecasting (WRF) system to determine the spatiotemporal changes in near-surface air temperature, precipitation, and boundary layer conditions induced by the modern-day urban landscape relative to presettlement conditions. We capture the MCMA extent through an improved Landsat-based multicategory urban classification and therefore account for intraurban spatial heterogeneity and further conduct additional experiments to examine the sensitivity to anthropogenic heating within WRF. We find that accounting for these factors produced the best simulations of thermal conditions, with RMSE values less than 1.5°C at all measurement stations, and an improved diurnal cycle of air temperature and precipitation. We then assessed the impacts of LULCC in the MCMA, finding that thermal changes were largest during daytime hours, with temperature increasing, on average, by more than 4°C. Furthermore, we utilize these simulations to mechanistically link the built environment-induced increase in air temperature to simulated increases in rainfall during the evening hours. To our knowledge, this study provides the first dynamical and thermodynamical evidence to support the rainfall enhancements documented through observations in the MCMA and link it quantitatively to the warming effects associated with urbanization. These results have important implications for understanding the meteorological conditions leading to widespread urban flooding in the MCMA.

Urban resilience efforts must consider social and political forces

“…2). For example, 600 years of urbanization has led to substantial increases in rainfall over large portions of Mexico City (8). This alone has likely exacerbated overall flood risk in the city during the rainy season.…”

The impact of an urban canopy and anthropogenic heat fluxes on Sydney's climate

“…Note that the effects of the urbanization on local climate vary with the pre‐settlement land cover type. For example, Benson‐Lira et al () found that the loss of lake cover due to urbanization in Mexico city led to daytime warming of >4 °C and night warming of ∼1 °C.…”

“…Note that the effects of the urbanization on local climate vary with the pre-settlement land cover type. For example, Benson-Lira et al (2016) found that the loss of lake cover due to urbanization in Mexico 267 city led to daytime warming of >4 ∘ C and night warming of ∼1 ∘ C. In winter, a cooling effect due to UCE is simulated during night and day. This cooling is due to the reduction of Rnet (Figure 5(b)) and a greater portion of Rnet being allocated to heat storage, which offsets the reduction in LH (Figures 5(f) and (d)).…”

Modeling the Impacts of Urbanization on Summer Thermal Comfort: The Role of Urban Land Use and Anthropogenic Heat

“…Recently, the Weather Research and Forecasting (WRF) model (Skamarock et al, ) coupled with an urban canopy model (UCM; Kusaka et al, ) is widely used as a community tool for studying urban climatic and environmental issues (Chen et al, ). However, previous WRF/UCM simulations usually used the default (e.g., Chen et al, ; Wang et al, ) or spatially uniform AH profiles in the UCM (e.g., Benson‐Lira et al, ; Grossman‐Clarke et al, ), or even ignored the AH effect (e.g., Zhang, Gao, et al, ; Zhou & Shepherd, ; Zhang et al, ; Wang et al, ). Using the WRF/UCM model and simple setting of AH values, previous studies suggested that the contribution of AH emission to the UHI under hot weather conditions was about 22%–30% in Hangzhou and Nanjing (Chen et al, ; Chen, Zhang, & Wang, ), which are respectively the provincial capitals of Zhejiang and Jiangsu in YRD.…”