Earth at Night

Sue GrimmondInternational Association for Urban Climate

www.urban-climate.org

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

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, PolandVariability Across a City

Offerle et al. 2004a

Belle Vue

S29 Tower

DOWNTOWN

.210 (.020)

SECTOR 29

.249 (.024)

RURAL

.276 (.023)

RURAL

313 (.8)

DOWNTOWN

309 (1.6)

SECTOR 29

312 (.6)

Albedo

Surface Temperature (K)

ASTER surface reflectance (VNIR321) January 2001Variability 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

CITYinternal biophysical processes

SINKbiophysical processesPollutionDisturbance

SOURCEbiophysical processesDepletionPollutionDisturbance

Ecological Footprint

The Urban System Interactions between the city, human environment and biophysical environment

INPUTSEnergy MoneyFood InformationWater Raw MaterialsManufactured goods

HUMAN THE CITY BIOPHYSICALENVIRONMENT ENVIRONMENTPeople Physical Structure Atmosphere & Energy FlowsEthnicity Building Type Hydrological CyclePolitics Layout Soils, Vegetation, FaunaTechnology Geology & Landforms

OUTPUTSWastes EmploymentLiquids WealthSolids Manufactured GoodsGases Degraded Energy

LINKS TO Urban SystemsOTHER Rural 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