Urban effects on local cloud patterns

Abstract

Urbanization extensively modifies surface roughness and properties, impacting regional climate and hydrological cycles. Urban effects on temperature and precipitation have drawn considerable attention. These associated physical processes are also closely linked to clouds’ formation and dynamics. Cloud is one of the critical components in regulating urban hydrometeorological cycles but remains less understood in urban-atmospheric systems. We analyzed satellite-derived cloud patterns spanning two decades over 447 US cities and quantified the urban-influenced cloud patterns diurnally and seasonally. The systematic assessment suggests that most cities experience enhanced daytime cloud cover in both summer and winter; nocturnal cloud enhancement prevails in summer by 5.8%, while there is modest cloud suppression in winter nights. Statistically linking the cloud patterns with city properties, geographic locations, and climate backgrounds, we found that larger city size and stronger surface heating are primarily responsible for summer local cloud enhancement diurnally. Moisture and energy background control the urban cloud cover anomalies seasonally. Under strong mesoscale circulations induced by terrains and land–water contrasts, urban clouds exhibit considerable nighttime enhancement during warm seasons, which is relevant to strong urban surface heating interacting with these circulations, but other local and climate impacts remain complicated and inconclusive. Our research unveils extensive urban influences on local cloud patterns, but the effects are diverse depending on time, location, and city properties. The comprehensive observational study on urban–cloud interactions calls for more in-depth research on urban cloud life cycles and their radiative and hydrologic implications under the urban warming context.

Variation the in relationship between urban tree canopy and air temperature reduction under a range of daily weather conditions

“…Trees help mitigate the lethality [ 3 , 4 ] of the worsening urban heat island effect from climate change [ 5 ] through shading [ [6] , [7] , [8] ] and evapotranspiration [ 7 , 9 ]. The effects of these different cooling mechanisms vary across space and over time [ 10 , 11 ], and interact with other aspects of the built environment [ 8 , [12] , [13] , [14] , [15] ] and regional meteorology [ 16 ].…”

“…Under cloudy conditions, the former effect is minimal and it is not well understood how much transpirational cooling persists under these conditions. Interestingly, it has been shown that cities even create clouds: they draw moisture in through advection and then a combination of turbulence from urban surface roughness and abundant urban aerosols create more clouds [ 16 ]. Excluding clouds prevents us from understanding the role of trees’ cooling under cloudy conditions.…”

Satellite Clear‐Sky Observations Overestimate Surface Urban Heat Islands in Humid Cities

“…of 10 associated with surface heating in urban areas can impact atmospheric dynamics, fostering the condensation of water vapor into clouds (Chen et al, 2011;Vo et al, 2023). Additionally, the augmented concentration of anthropogenic emissions in urban settings, stemming from industrial activities and vehicular traffic, introduces additional particulate matter and aerosols into the atmosphere (Z. H. Zhang et al, 2017).…”

Observational Evidence Reveals Compound Humid Heat Stress‐Extreme Rainfall Hotspots in India

“…Zhang et al, 2023), but also affects local weather patterns, such as enhancement of mean rainfall and short-duration extreme rainfall by increasing vertical uplift and moisture convergence (Ali et al, 2021;Fischer & Knutti, 2016;Y. Li et al, 2020;Liu & Niyogi, 2019;Vo et al, 2023). This amplifies the likelihood of "preconditioned" compound extremes, that is, the sequential occurrence of humid heatwaves and extreme rainfall (C. Li et al, 2023;W.…”