Synoptic patterns and heatwaves: Intensifying urban heat islands in the Mexico Basin

Modifying urban heat islands (UHI) by weather patterns in complex terrain remains to be seen. UHI and heatwaves (HW) contribute to extreme heat events that can severely impact human health. Studying the interaction between these phenomena, especially concerning synoptic patterns, is crucial for advancing our understanding of urban climate change and its effects. This research is focused on studying the impact of synoptic conditions on the development of UHI and heatwaves, and their potential mechanisms in the Mexico Basin for the dry-warm season (February-March-April). We use observations, ERA5 reanalysis, a weather pattern (WP) classification proposed by Diaz-Esteban et al., (2022), and WRF numerical experiments to get the required mesoscale fields at the Mexico Basin from 1990 to 2019. Results show that UHI and HW over the Mexico Basin are strongly affected by seven WP, which we further classify into two groups: WP group 1 with well-defined anticyclonic circulation and WP group 2 with a mix of anticyclonic and cyclonic circulations. WP group 1 allows for considerable intensification of the UHI but not with the combined effect of UHI intensification under HW. This latter phenomenon is exhibited mainly by WP group 2. In a group classification, HW events intensify the UHI by 0.1 degrees C to 0.3 degrees C. In the first group this intensification is caused by stagnation in the lower troposphere, while in the second group, it results from horizontal advection. Both mechanisms play a significant role in amplifying the UHI effect. Our findings have implications for forecasting extreme temperature events at a subseasonal scale, public health strategies, and climate adaptation.