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Earth at Night

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  1. Earth at Night Sue GrimmondInternational Association for Urban Climatewww.urban-climate.org

  2. Distinctiveness of Urban Areasfrom a Meteorological Perspective • Changes in surface morphology • Changes in surface cover • Additional anthropogenic sources of heat, water, other gases and particulates

  3. Variability in Morphology Implications, across & between cities, for: • Wind flow • Dispersion • Flux partitioning • BL height • Air quality • Surface runoff • Solar access • Radiative cooling Grimmond & Oke, 1999; JAM

  4. Variability of Surface Cover

  5. Variability Across a City Lodz, Poland Offerle et al. 2004a

  6. Variability Across a City RURAL .276 (.023) DOWNTOWN .210 (.020) SECTOR 29 .249 (.024) RURAL 313 (.8) DOWNTOWN 309 (1.6) SECTOR 29 312 (.6) Somgande S29 Tower Belle Vue ASTER surface reflectance (VNIR321) January 2001 Albedo Surface Temperature (K) Offerle et al. 2004b

  7. Regional Settings of Cities

  8. Common Methodology: “Urban” vs “Rural” Grimmond and Oke 1999: IAHS

  9. Urban Areas in their Region EcologicalFootprint SOURCE biophysical processes Depletion Pollution Disturbance CITY internal biophysical processes SINK biophysical processes Pollution Disturbance

  10. The Urban System Interactions between the city, human environment and biophysical environment INPUTS Energy Money Food Information Water Raw Materials Manufactured goods HUMAN THE CITY BIOPHYSICAL ENVIRONMENT ENVIRONMENT People Physical Structure Atmosphere & Energy Flows Ethnicity Building Type Hydrological Cycle Politics Layout Soils, Vegetation, Fauna Technology Geology & Landforms OUTPUTS Wastes Employment Liquids Wealth Solids Manufactured Goods Gases Degraded Energy LINKS TO Urban SystemsOTHER Rural Systems Regions Transport Communication From Bridgman et al. (1996)

  11. Scales in an Urban Environment

  12. Advantages of an Urban Ecosystem Approach Example: Planting trees to cool urban areas Need to consider multiple effects: • Trees require water to survive • Regional impact to supply that water • Ground water recharge • Salt water intrusion (coastal locations e.g. LA) • Management costs • e.g. likelihood of surviving wind storms, damage by roots to pavement, drains, growth into powerlines • Air quality impacts • Differences in VOC releases • Fraction of surface cover that is vegetated impacts boundary layer growth which impacts air quality • Fire hazard • Selection of trees may be based on only 1or 2 factors (e.g. shade and management of powerlines) rather than many issues (e.g. air quality, water needs)

  13. Key Limitations and Actions • Spatial variability exists in and between cities • Changes through time • Models need to account for this e.g. one urban class is not sufficient • Urban effects are not uni-directional (space and time) • Data availability often very limited • Not related to surface physical characteristics (morphology, land cover fractions, etc) • Airports • Fixed heights above the surface but ignores the morphology • e.g. 10 m wind speed measurement • Need routine data for model inputs and analysis • Need research programs to generate data to develop and evaluate models • Model evaluation of individual processes and multi-disciplinary linked systems • Establish communication between and within disciplines to ensure compatibility of information/data transfer • Careful attention is needed to the scale of processes compared to observations available