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Initial Study of HPAC Modeled Dispersion Driven by MM5 With and Without Urban Canopy ParameterizationsDr. Chris Kiley – NGCDr. Jason Ching - ARL, NOAA, RTP CDR Stephanie Hamilton - DTRA

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Outline of Presentation

•Overview of HPAC •Objective of Study•Preliminary Results •Next Steps

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DTRA

• Defense Threat Reduction Agency• Mission is to safeguard the USA (and its allies) from weapons

of mass destruction (WMD) (chemical, biological, radiological, nuclear, and high yield explosives) by providing capabilities to reduce, eliminate, or counter such threats and mitigate its effects.

• DTRA’s Hazard Prediction and Assessment Capability (HPAC) • Automated software system provides the means to accurately

predict the effects of hazardous material releases into the atmosphere and its impact on civilian and military populations.

• The system models hazard areas produced by military or terrorist incidents and industrial accidents using:

• integrated source terms • high-resolution weather forecasts• particulate transport analyses

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Weather and Environment Data Input Process for HPAC

Land Cover(Landscan)

Land Cover(Landscan)

Interpolationto

Uniform Grid

Interpolationto

Uniform Grid

Terrain Data(Landscan)

Terrain Data(Landscan)

Weather Data(Many sources)

Weather Data(Many sources)

Transport&

Dispersion

Transport&

Dispersion

SourceData

SourceData

Concentrationin spaceand time

Concentrationin spaceand time

Calculate Mass-Consistent Wind

Field

Calculate Mass-Consistent Wind

Field

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Meteorological Input Considerations

• Primary influence on Atmospheric Transport and Dispersion (ATD)

• Compatible spatial resolution for the venue of the hazardous release

• Operational: Rapid calculations• Is it Urban? This is the “Problem” we

are to address.

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Model Resolution

Coarser resolution (5 km) reveals little detail in the wind field

Higher resolution (1.67 km) reveals additional wind field structure

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Urban AT&D

• Urban environment greatly affects local meteorology• Wind velocity and direction• Turbulence profiles• Thermal characteristics

• NWP models not well suited to simulate urban areas• Grid resolutions, detailed building

information, parameterization, operational timeliness of forecasts, etc.

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Urban AT&D

• Urban meteorology and AT&D is a current area of focused R&D• Not well understood yet highest probability of

terrorist attack

• NWP does not currently handle urban areas well

• AT&D systems include simplified assumptions that describe the influence of urban environment• Mass consistent adjustments to underlying building

topography• CFD solutions as computational capabilities

advance• Coupled CFD/NWP models• Urban dispersion models

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UDM and other approaches

• Urban Dispersion Model (UDM)• Dstl (UK)• Operationally Fast• Current Urban Capability within HPAC

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Urban Dispersion Model (UDM)

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Yellow arrows show wind speed and direction

At 50 m above the ground, the flow is from the north or north-northeast at a steady speed

UWM Winds @ 50m Height

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At 7 m above the ground, the flow is channeled around Capitol Hill and down the Mall, with strong winds

Weaker winds in built-up parts of the city

UWM Winds @ 7m Height

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HPAC now driven by modeled meteorology (MM5): Sensitivity study to grid size and to urbanization with Reynolds Averaging vs detailed Urban Canopy Parameterization versions. Preliminary results for Houston include:

• 4 km MM5• 4 km MM5 with UDM• 1 km MM5• 1 km MM5 with UDM• 1 km MM5 Urban Canopy Model• Date: August 29, 2000• Time of Release: 0700 EDT• Duration of release: 4 hours

Study Description

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Houston Case Study

• 12 UTC (7 AM) 29 August 2000• GB Release, location arbitrarily chosen

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4 km

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4 km with UDM

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1 km

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1 km with UDM

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1 km Urbanized MM5

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Status of Study, Preliminary Findings & Caveats

• Successfully linked urbanized MM5 with HPAC.• Only limited results performed at this time • UDM appears to slow spread as expected• Relative reduction in agent spread due to

enhanced grid resolution not evident for early morning release

• Urbanized MM5 comparative reduction in spread also not pronounced at 0700

• Results pending for different time of day release times

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Future investigations continues to:

• Examine and understand sensitivity to different times of release, different release locations and different duration of puff travel in order to appreciate differences in flow and turbulence fields due to grid size and urban descriptions.

• Understand mesoscale modeling abilities to simulate effect of urbanization on land-lake/sea breeze, boundary layer and heat island structures on HPAC simulations.

• Develop operational (fast) and R&D versions.

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The EndThank you for your attention

Disclaimer: The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. This work constitutes a contribution to the NOAA Air Quality Program. Although it has been reviewed byEPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.