Earth at Night Sue Grimmond International Association for Urban Climate

Distinctiveness of Urban Areas from a Meteorological Perspective  Changes in surface morphology  Changes in surface cover  Additional anthropogenic sources of heat, water, other gases and particulates

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

Variability of Surface Cover

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

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

Regional Settings of Cities

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

Urban Areas in their Region CITY internal biophysical processes SINK biophysical processes Pollution Disturbance SOURCE biophysical processes Depletion Pollution Disturbance Ecological Footprint

The Urban System Interactions between the city, human environment and biophysical environment INPUTS EnergyMoney Food Information WaterRaw Materials Manufactured goods HUMANTHE CITYBIOPHYSICALENVIRONMENT PeoplePhysical StructureAtmosphere & Energy Flows EthnicityBuilding TypeHydrological Cycle PoliticsLayoutSoils, Vegetation, Fauna TechnologyGeology & Landforms OUTPUTS WastesEmployment Liquids Wealth SolidsManufactured Goods GasesDegraded Energy LINKS TOUrban Systems OTHERRural Systems Regions Transport Communication From Bridgman et al. (1996)

Scales in an Urban Environment

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)

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