Implementation of a direct Implementation of a direct sensitivity method into CMAQsensitivity method into CMAQ

Daniel S. Cohan, Yongtao Hu, Amir Hakami, Daniel S. Cohan, Yongtao Hu, Amir Hakami, M. Talat Odman, Armistead G. RussellM. Talat Odman, Armistead G. RussellGeorgia Institute of Technology, Atlanta, GAGeorgia Institute of Technology, Atlanta, GA

Presentation to Models-3 Users’ WorkshopPresentation to Models-3 Users’ WorkshopOctober 22, 2002October 22, 2002

( )( )CMAQCMAQ

( )( )CMAQCMAQ

ΔΔ

ΔΔSIMULATIONSIMULATION SENSITIVITYSENSITIVITY

Uses of SensitivityUses of Sensitivity

• Policy development:Policy development: – Impact of emission control measuresImpact of emission control measures– Impact of new emittersImpact of new emitters

• Uncertainty analysis: Uncertainty analysis: – Dependence of model results on assumptionsDependence of model results on assumptions

• Inverse modeling (“Area of Influence”):Inverse modeling (“Area of Influence”):– Which emitters affect a receptorWhich emitters affect a receptor

Sensitivity MethodsSensitivity Methods • ““Brute-Force” Method:Brute-Force” Method:

– Run CMAQ once for a “base case”Run CMAQ once for a “base case”– Run CMAQ again for each of N perturbationsRun CMAQ again for each of N perturbations

• Direct Decoupled Method:Direct Decoupled Method: (Dunker 1981, Yang et al., 1997)(Dunker 1981, Yang et al., 1997)

– Solve for sensitivities decoupled from concentrations, Solve for sensitivities decoupled from concentrations, using the same numerical routines in a single CMAQ using the same numerical routines in a single CMAQ runrun

– Local, first-order sensitivities:Local, first-order sensitivities:

0

0

pp

CCS

n

nn

nn p

CS

Sensitivity Parameter(e.g., NOx Emissions)

Conc.(e.g., O3)

DDM

Sensitivity = tan()

pj

BF

∆Ci

DDM DDM andand Brute ForceBrute Force

I.C., B.C.,Emissions

Advection &Diffusion

Chemistry

ConcentrationsConcentrations(t)(t)

SensitivitiesSensitivities(t)(t)

Chemistry

Direct Decoupled MethodDirect Decoupled Method

ConcentrationsConcentrations (t+(t+ΔΔt)t)

SensitivitiesSensitivities(t+(t+ΔΔt)t)

Pros & ConsPros & ConsBrute Force:Brute Force:

▲ Simple

▲ Captures non-linearities

▼ Inefficient for large N

▼ Inaccurate for small perturbations

DDM:DDM:

▲ Efficient for large N

▲ Accurate for small perturbations

▼ Does not capture non-linearities

Demonstration of CMAQ-DDMDemonstration of CMAQ-DDM

Fall-Line Air Quality Study:Fall-Line Air Quality Study:• Focus on GeorgiaFocus on Georgia• 12 km horizontal; 13 layers12 km horizontal; 13 layers• SAPRC-99 chemistrySAPRC-99 chemistry• SAMI emissions inventorySAMI emissions inventory

DDM (implemented so far):DDM (implemented so far):• gas-phasegas-phase• first-orderfirst-order• emissions, I.C., & B.C.emissions, I.C., & B.C.

DDM: ODDM: O33 to Isoprene & NO to Isoprene & NOxx

Sensitivity to point NO emissionsSensitivity to point NO emissions

DDM to Actual NO EmissionsDDM to Actual NO Emissions DDM to 1 mol/s, Layer 6 EmissionDDM to 1 mol/s, Layer 6 Emission

DDM vs. Brute Force:DDM vs. Brute Force: Ozone Initial Conditions Ozone Initial Conditions

DDMDDM Brute ForceBrute Force

DDM vs. Brute Force:DDM vs. Brute Force: Domainwide NO Domainwide NOxx Emissions Emissions

DDMDDM Brute ForceBrute Force

DDM vs. Brute Force:DDM vs. Brute Force:Single Point NOSingle Point NODDMDDM Brute ForceBrute Force

Area of InfluenceArea of Influence

RR

EE EE

AOI

EE

DDM

DDMDDM

EE

DDMDDM shows impact of one shows impact of one emitter on concentrations emitter on concentrations domainwidedomainwide

To compute the receptor-To compute the receptor-based “Area of based “Area of Influence”:Influence”:

1.1. Compute Compute DDMDDM for for unit emissions unit emissions from various from various emitters emitters EE

2.2. Interpolate to Interpolate to obtain obtain AOIAOI of of receptor receptor RR to to every emitter every emitter EE

3.3. Scale to amount Scale to amount of emissions at of emissions at each each EE

AOI: Atlanta Ozone to NOAOI: Atlanta Ozone to NO

Response to 1 mol/s NO sourceResponse to 1 mol/s NO source Scaled by NO emissionsScaled by NO emissions

AOI: Macon Ozone to NOAOI: Macon Ozone to NO

Response to 1 mol/s NO sourceResponse to 1 mol/s NO source Scaled by NO emissionsScaled by NO emissions

ConclusionsConclusions

• DDM and Area of Influence enhance DDM and Area of Influence enhance the functionality of CMAQthe functionality of CMAQ

• Strong agreement with brute force, Strong agreement with brute force, even for fairly large perturbationseven for fairly large perturbations

• Future work will incorporate:Future work will incorporate:– higher-order sensitivitieshigher-order sensitivities– aerosolsaerosols– further exploration of AOIfurther exploration of AOI