aermet 8 th modeling conference rtp, nc september 22 – 23, 2005 presented by: desmond t. bailey...
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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