Urbanization effects on lake-land circulations in complex terrain

Area of Science:

• Atmospheric Science
• Environmental Science
• Urban Climatology

Background:

• Interactions between lake breezes, complex terrain, and urban environments are understudied.
• Understanding these interactions is crucial for local climate and air quality assessments.

Purpose of the Study:

• To investigate the aero- and thermodynamical interactions between Lake Geneva, its surrounding alpine terrain, and the urban areas of Lausanne and Geneva.
• To isolate and quantify the specific effects of urban land cover on these interactions.

Main Methods:

• Utilized the Weather Research and Forecasting (WRF) model for year-long simulations.
• Compared simulations of realistic urban land cover with hypothetical rural scenarios.
• Analyzed wind deceleration, anabatic wind regimes, and heat advection patterns.

Main Results:

• Urban areas caused minor wind deceleration due to increased surface drag, with negligible impact on the overall lake breeze evolution.
• Urban heat excess in Lausanne shifted anabatic wind onset by one hour and displaced flow collision points northward by 1 km.
• Urban heat advection altered air temperatures over the lake and along the lakeshore.

Conclusions:

• Mid-sized cities can exert significant influence on local wind and heat dynamics, comparable to larger cities.
• Urban land cover plays a role in modifying localized atmospheric circulations within complex terrain and lake environments.