Urban Test Beds:Productivity, Problems, and Progress

Measurement Networks, Logistics, and Models

William J. Shaw12th GMU Conference on Transport and DispersionJuly 9, 2008

Urban Test Bed—Definition and Analogy

Urban Test Bed

“A multifunctional infrastructure that provides multiyear continuous measurement and archival of environmental data, across a metropolitan area and through the atmospheric boundary layer, supporting improvements in a range of activities from scientific research to user applications.”Williamson et al., 2007, AMS Seventh Symposium on the Urban Environment.

Analogy: ARM Cloud and Radiation Test Bed (CART; now ACRF)

Logistical Challenges

CostThe ARM annual budget for operating the Central Facility in Oklahoma is multiple $MStart-up costs for instruments, including negotiating terms of their location, can be substantialThis is a challenge to agencies supporting urban test beds, because it requires a substantial commitment over many budget cycles, especially since long-term measurements do not carry the immediacy and excitement of campaigns

Instrument OversightFor instruments to provide reliable data, they must be regularly monitored and calibrated.For more sophisticated instruments, continuing development of processing techniques is an important component of success

Logistical Resources

Surface Meteorological NetworksMany are already in placeThe coverage in urban areas is remarkably denseMany urban surface network data already collected and at least roughly QA’d (by MesoWest and now by NOAA’s MADIS)

Upper-air MeteorologyThis remains largely a gapProfilers are useful (but not dense or everywhere)Current Doppler radar data may be especially helpful

ModelsIt will never be possible to measure “everything, everywhere, all of the time”Routine mesoscale modeling with data assimilation are and will be essential to establishing information such as inflow conditions for urban CFD investigations

Scientific Challenges

FocusIt is unlikely that a single test bed can adequately address all needs for operations and research in urban fire, air quality, dispersion, severe weather, etc. Can we prioritize the needs that urban test beds will serve?

Multiple LocationsBecause of the highly nonlinear behavior of many essential processes, multiple disparate test bed locations will be needed.

Thinking Long-termScientists’ DNA seems to carry a campaign geneTo be truly valuable, test beds must have adequate observations and well-defined scientific uses for their long-term data

Some Key Long-term Data Needed from Urban Test Beds

Diurnal and spatial variability of mixing layer depthTurbulence structure of the mixing layer, especially under stable stratification and in the urban core.

This is also a science question.

Wind and stability structure of the urban boundary layer, especially inflow conditions to the urban core (models)

Test beds should be sited to allow for better understanding of the urban boundary layer where the inflow is complicated by complex terrain

Regular tracer releases and samplingNeeded to evaluate behavior of meteorological and dispersion models over a range of conditions beyond the idealized.

Needed to understand indoor–outdoor exchange

Political Challenges

Data SensitivityData that define indoor-outdoor exchange for specific buildings or air flow in subways, for example, can be highly sensitive.

These data are essential for understanding some outdoor dispersion measurements.

How will test beds make such data available to scientists in order to make fundamental progress?