AERMET 8 TH Modeling Conference RTP, NC September 22 – 23, 2005 Presented by: Desmond T. Bailey [email protected].

AERMETAERMET

88THTH Modeling Conference Modeling ConferenceRTP, NCRTP, NC

September 22 – 23, 2005September 22 – 23, 2005

Presented by: Desmond T. Bailey [email protected]

The Planetary Boundary Layer (PBLThe Planetary Boundary Layer (PBL))

Surface LayerSurface Layer 0 to 0.1 Z0 to 0.1 Zii (mixing height) (mixing height) Dominated by frictionDominated by friction M-O Similarity appliesM-O Similarity applies

Mixed LayerMixed Layer Capped by a stable layer aloftCapped by a stable layer aloft Develops due to heating from belowDevelops due to heating from below Wind speed is constant with heightWind speed is constant with height

AERMET ScienceAERMET Science The Planetary Boundary Layer (PBL)The Planetary Boundary Layer (PBL)

Convective Boundary Layer (CBL)Convective Boundary Layer (CBL)• Driven by surface heatingDriven by surface heating• Develops during the dayDevelops during the day• Moderate to strong vertical mixingModerate to strong vertical mixing

Stable Boundary Layer (SBL)Stable Boundary Layer (SBL)• Driven by surface coolingDriven by surface cooling• Develops at nightDevelops at night• Little to no vertical mixingLittle to no vertical mixing

AERMET ScienceAERMET Science

Properties of the PBL affecting dispersionProperties of the PBL affecting dispersion vertical profiles ofvertical profiles of

• Wind speedWind speed• TemperatureTemperature• Vertical turbulenceVertical turbulence• Lateral turbulenceLateral turbulence

Depth of mixingDepth of mixing

AERMET ScienceAERMET Science Surface LayerSurface Layer

Similarity TheorySimilarity Theory Applies in the surface layerApplies in the surface layer

Important scaling parametersImportant scaling parameters

• Friction velocityFriction velocity fn (wind shear, zfn (wind shear, z00))• Convective velocity scaleConvective velocity scale fn (H, Zfn (H, Zii, , θθ ) )• Monin-Obukhov lengthMonin-Obukhov length fn (H, ufn (H, u**, , θθ ) )• Temperature ScaleTemperature Scale fn (H, u fn (H, u* * )) • Mixing heightMixing height

CBL RegimesCBL Regimes

Surface LayerSurface Layer Depth 0 to 50 mDepth 0 to 50 m Dominated by frictionDominated by friction M-O similarity theory appliesM-O similarity theory applies Turbulence depends on roughness and M-O lengthTurbulence depends on roughness and M-O length

Mixed LayerMixed Layer Depth up to 3000 mDepth up to 3000 m Wind speed is constant with heightWind speed is constant with height Turbulence depends on convective velocity scaleTurbulence depends on convective velocity scale

CBL CharacteristicsCBL Characteristics

Monin-Obukhov length < 0Monin-Obukhov length < 0 Depth increases during the day due to Depth increases during the day due to

surface heatingsurface heating Shear and buoyancy contribute to Shear and buoyancy contribute to

turbulenceturbulence Capped by a stable layer Capped by a stable layer

Modeling the CBLModeling the CBL

Estimate the sensible heat flux using an Estimate the sensible heat flux using an energy balance approachenergy balance approach

Given the heat flux, calculate the friction Given the heat flux, calculate the friction velocity and M-O length using an iterative velocity and M-O length using an iterative approachapproach

Determine the growth of the mixed layer Determine the growth of the mixed layer by integrating heat flux over timeby integrating heat flux over time

SBL CharacteristicsSBL Characteristics

Monin-Obukhov length > 0Monin-Obukhov length > 0 Develops when surface begins to coolDevelops when surface begins to cool Turbulence is shear drivenTurbulence is shear driven Turbulence decays with heightTurbulence decays with height Mixing is weakMixing is weak ProblematicProblematic

Not as well understood as the CBLNot as well understood as the CBL

Modeling the SBLModeling the SBL

Extension of CBL method for estimating Extension of CBL method for estimating friction velocity and M-O length friction velocity and M-O length problematic due to small negative heat problematic due to small negative heat flux.flux.

Alternative method uses the Bulk Alternative method uses the Bulk Richardson NumberRichardson Number

Bulk Richardson NumberBulk Richardson Number

AdvantagesAdvantages Does not require cloud coverDoes not require cloud cover

Required measurementsRequired measurements Wind speed at one level in surface layerWind speed at one level in surface layer Vertical Temperature gradient in the surface Vertical Temperature gradient in the surface

layerlayer

Evaluation of Bulk Richardson ApproachEvaluation of Bulk Richardson Approach

Problems were found with the approach used in Problems were found with the approach used in AERMET 02222AERMET 02222

An evaluation was funded to resolve the problemAn evaluation was funded to resolve the problem

Several alternative implementations were consideredSeveral alternative implementations were considered

These were tested using the Kansas, Prairie Grass, and These were tested using the Kansas, Prairie Grass, and Cinder Cone Butte data basesCinder Cone Butte data bases

Evaluation of Bulk Richardson ApproachEvaluation of Bulk Richardson Approach

Problems were found with the approach used in Problems were found with the approach used in AERMET 02222AERMET 02222

An evaluation was funded to resolve the problemAn evaluation was funded to resolve the problem

Several alternative implementations were consideredSeveral alternative implementations were considered

These were tested using the Kansas, Prairie Grass, and These were tested using the Kansas, Prairie Grass, and Cinder Cone Butte data basesCinder Cone Butte data bases

Evaluation of Bulk Richardson ApproachEvaluation of Bulk Richardson Approach

Presented at the 8th AMS/AWMA Joint Conference in Vancover, BC

Evaluation of Bulk Richardson ApproachEvaluation of Bulk Richardson Approach

Presented at the 8th AMS/AWMA Joint Conference in Vancover, BC

Process meteorological data Process meteorological data for use in AERMODfor use in AERMOD

Raw Data

QA Merge ProcessExtract

Model ready files

Surface DataSurface Data

Supported FormatsSupported Formats SAMSONSAMSON CD 144CD 144 TD 3280TD 3280 HUSWOHUSWO TD 3505 (ISHD)TD 3505 (ISHD) SCRAMSCRAM

Upper-Air DataUpper-Air Data

Supported FormatsSupported Formats

FSLFSL

TD 6201TD 6201

Stage 1 ExtractStage 1 Extract

Stage 2 MergeStage 2 Merge

Stage 3 Process for AERMODStage 3 Process for AERMOD

Audit Report Surface DataAudit Report Surface Data

Stage 2 Merge ReportStage 2 Merge Report