The Study of Urban Impacts on Rainfall and Fog/Haze (SURF) Project: Prof. Bornstein's Scientific Conception and Practice (Invited Presentation)

Half the global population will be in cities by 2025, many having more than 10 million people.  Urbanization modifies atmospheric energy and moisture balances, forming local climates, e.g. urban heat islands (UHIs) and enhanced precipitation.  These produce significant challenges to science and society, e.g. flooding, heat waves strengthened by UHIs, and air pollutant hazes.  The Beijing megacity experiences such severe events, e.g., 2012 flooding killed 79 and caused losses of $2B.

Despite significant research into urban effects on weather and air quality, important science issues remain, e.g., urban-thermodynamic and aerosol impacts on summer convective precipitation and interactions between urban and regional climate changes.  Observations are fundamental for understanding these interactions, improving forecasts, and providing useful information to end-users.  Previous large urban field campaigns have not been coordinated by a group such as the Beijing Institute of Urban Meteorology (IUM), with its responsibilities for both boundary layer research and real time urban weather forecasting.  The overall science objective of the 2014-8 SURF Project is thus a better understanding of urban, terrain, convection, and aerosol interactions for improved forecast accuracy.  Beijing is a test case, but the improved understandings are transferable to many large cities globally.

Specific objectives include:

• Promote cooperative international-research to improve understanding of urban weather-systems via summer thunderstorm-rainfall and winter aerosol field studies
• Improve high-resolution (∼1 km grid) urban weather and air quality forecast-models
• Enhance urban weather forecasts for societal applications, e.g., health, energy, hydrologic, climate change, air quality, urban planning, emergency-response management.

Preliminary climatological and case studies show that urban rainfall impacts are sensitive to UHI intensity. Beijing shows two kinds of urban effects: thunderstorm initiation vs. bifurcation. Urban aerosols (haze) have important impacts on radiation, and potentially on the timing, intensity, and location of precipitation.