Highlights from the 2016 Guideline on Air Quality Models Conference

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Highlights from the 2016 Guideline

on Air Quality Models Conference

Rocky Mountain States Section of the Air & Waste

Management Association - Denver, CO

April 21, 2016

Sergio A. Guerra, Ph.D. – CPP Inc.


Outline

• Updates on AERMOD modeling system

• Building Downwash

• Prognostic meteorological data

• Ozone and Secondary PM2.5

• Long Range Transport

• What’s next?


Background• Revisions to Appendix W were proposed by

EPA on July 29, 2015

• Public comment closed on October 27, 2015

• Final rulemaking by July 7 or 8th of 2016

• References:

– 11th Modeling Conference Presentations

https://www3.epa.gov/ttn/scram/11thmodconfpres.htm

– Guideline on AQ Models: The New Path, 6th

Specialty Conferencehttps://www3.epa.gov/ttn/scram/11thmodconfpres.htm


AERMOD Updates

EPA has proposed that the following options be incorporated

into the regulatory versions of AERMOD and AERMET:

• The ADJ_U* option in AERMET;

• The LOWWIND3 option in AERMOD;

• The BUOYLINE option in AERMOD for modeling buoyant line

sources; and

• The POINTCAP and POINTHOR source type options in

AERMOD to model capped and horizontal stacks.

• NOx-NO2 conversion

– ARM2

– PVMRM2


AERMET/AERMOD ADJ_U*

• The Beta ADJ_U* option in AERMET associated

with the Bulk Richardson Number (BULKRN)

option has been modified to include a more

refined method for calculating THSTAR and

extending its applicability for very stable/low

wind conditions, based on Luhar and Raynor

(BLM, v132, 2009);

• The updated ADJ_U* option with BULKRN also

includes modifications to subroutine TGINIT in

AERMOD to calculate THSTAR;

• EPA has proposed that the ADJ_U* option (with

or without BULKRN) be incorporated into the

regulatory version of AERMET.


AERMET/AERMOD ADJ_U*

• Friction velocity (u*) computed by

AERMET.

• u* used to calculate mixing height,

initial horizontal and vertical

dispersion (sigma-y and sigma-z)

• EPA noted in 2007 issues with high

concentrations due to treatment of

light winds.

• AERMOD users started to identify

highest impacts associated with low

wind speeds (i.e., <1 m/s) during

night hours.


AERMOD-Low Wind Options

AERMOD v15181 includes a new LOWWIND3 (LW3) non-DFAULT/BETA

option:

• LOWWIND3 increases minimum value of sigma-v from 0.2 to 0.3

m/s, consistent with the LOWWIND2 option, but eliminates upwind

dispersion, consistent with the LOWWIND1 option;

• The LOWWIND3 option uses an “effective” sigma-y value that

replicates the centerline concentration accounting for meander,

but sets concentrations to zero (0) for receptors more than

6*sigma-y off the plume centerline, similar to the FASTALL option;

• EPA has proposed in that the LOWWIND3 option be incorporated

into regulatory version, while the LOWWIND1 and LOWWIND2

options are still available for testing & evaluation purposes.


Capped and Horizontal Stacks

Draft/BETA options for capped & horizontal stacks have been

incorporated in AERMOD (beginning with v06341):

• Source types POINTCAP & POINTHOR used to trigger BETA options;

• User inputs actual stack exit velocity (Vs) and stack diameter (Ds);

• The Model Clearinghouse procedure is used for non-downwash

sources;

• For the POINTHOR option with downwash the exit velocity is

assigned as the initial horizontal velocity of the plume;

• For the POINTCAP option with downwash, the initial plume radius is

assigned as 2*Ds to account for initial plume spread from the cap,

and the initial horizontal velocity of the plume is assigned as the

initial exit velocity specified by the user divided by 4 to account for

suppressed momentum and buoyancy.


NOx to NO2 Conversion

• EPA has proposed that the ARM2 and

PVMRM2 options be incorporated as

regulatory options.

http://www.atmos.washington.edu/~lbaylon/research.html


Buoyant Line Sources

• Beginning with v15181, AERMOD includes an option to model

buoyant line sources, using the BUOYLINE source type;

• The BUOYLINE option in AERMOD model allows for modeling

of buoyant line sources using meteorological data processed

through the AERMET meteorological processor;

• The BUOYLINE option in AERMOD also allows use of the

processing options to support the form of the 1-hr NO2, 1-hr

SO2 and 24-hr PM2.5 NAAQS.


Mobile Source Modeling

• Proposal includes replacement of CALINE3,

CAL3QHC, and CAL3QHCR with AERMOD as

the Appendix A preferred dispersion model

for all mobile source modeling of inert

pollutants

• Technical Support Document (TSD) for

Replacement of CALINE3 with AERMOD for

Transportation Related Air Quality Analyses,

EPA Document EPA-454/B-15-002 http://www.epa.gov/ttn/scram/11thmodconf/CAL3_A ERMOD_Replacement_TSD.pdf


Model Clearinghouse Activity

• On use of ARM2

– July 16, 2015; Region 2

– December 22, 2015; Region 4

• On use of Adj-u* beta option and POINTHOR&POINTCAP

– February 10, 2016; Region 10

• Upcoming concurrence

– Definition of minimum ambient ratio in ARM2; Region 6

– Use of Adj-u* for tall stack in complex terrain; Region1

– Use of wind tunnel derived building dimensions; Region 4

– Informal memo on use of Adj-u* and LOWWWIND3 options


Use of Beta Options

• Clarification on the Approval Process for

Regulatory Application of the AERMOD

Modeling System Beta Options• https://www3.epa.gov/ttn/scram/guidance/clarification/AERMOD_Beta_Options_Memo-20151210.pdf


Building Downwash

• Priority for EPA’s OAQPS and ORD

• Upcoming clearinghouse memo from Region 4

• PRIME2 Advisory Committee


PRIME

AERMOD’s Building Downwash Algorithm

• Used EPA wind tunnel data

base and past literature

• Developed analytical

equations for cavity height,

reattachment, streamline

angle, wind speed and

turbulence

• Developed for specific

building dimensions

• When buildings outside of

these dimensions, theory falls

apart


BPIP Diagnostic Tool

http://bit.do/cppwind-BPIPDiagnosticLikely Overprediction Factor for each Flow Vector

Source 1


ComplianceCompliance

CPP’s EBDCPP’s EBD

BPIP Diagnostic

ToolBuilding Geometry

Meteorological Data

Terrain Data

AERMET

AERMAP

Operating Parameters AERMODOther Inputs

Building

Inputs

BPIP Diagnostic Tool


Summary of Needed Updates to

PRIMEFlaws that may cause overpredictions:

1. Building wake growth starts at wrong location – leads overestimated wake

height and building downwash zone.

2. Start of building downwash occurs at the wrong location – leads to

overstated downwash.

3. Height of building downwash zone (high turbulence) is overestimated.

4. Reduced velocity calculation in wake needs improvement – leads to

incorrect plume rise calculation.

5. Streamlines for porous structures should be horizontal and wake velocity

and turbulence parameterization is not correct.

6. Streamlines and wakes velocity/turbulence parameterization incorrect for

streamlined structures.

7. Transition back to ambient turbulence is questionable.

More information is available in papers and presentations #34 and #25

(Petersen and Guerra, 2016)


AERMOD/PPRIME

Overestimates

Downwash

Reality

Summary of Needed Updates to

PRIME


Refinery Structures Upwind

Solid BPIP Structure Upwind

No Structures

Streamlines for Lattice Structures


PRIME2 Advisory Committee

Subcommittee of the Atmospheric Modeling and

Meteorology Committee (APM) of the Technical

Council of the Air and Waste Management Association

(AWMA).

The two purposes of this committee include to:

1. Provide a technical review forum to improve the

PRIME building downwash algorithms

2. Establish a mechanism to review, approve and

implement new science into the model for this and

future model improvements


PRIME2 Advisory Committee

– EPA mentioned that building downwash is a

priority

– Had about 40-50 people attend the initial meeting

– Got an update from ORD about some of their

work related to building downwash

– EPA is looking into publishing a technical paper

soon

– EPA’s ORD will be collaborating with this

committee


Meteorological Data• Prognostic meteorological data

– No representative NWS station and infeasible to

collect site-specific data

– No fewer than 3-years of data

– Mesoscale Model Interface Program (MMIF)

developed to read prognostic data (i.e., WRF) to

create data for input into AERMET and AERMOD,

as well as other dispersion models

• Draft guidance and evaluation of MMIF

available https://www3.epa.gov/ttn/scram/11thmodconf/Draft_MMIF_Guidance.pdf


Ozone and PM2.5 Formation

Included in Chapter 5 of proposed

Appendix W as a tiered approach:

• First Tier:

– Use of existing technical information

such as previous photochemical

modeling

– Model Emission Rates for Precursors

(MERPs) is a Tier 1 tool

– MERPS will not replace SERs

– Guidance will be forthcoming


Ozone and PM2.5 Formation

• Tier 2 relates to using models

to assess impacts from single

sources on ozone and PM2.5

formation

– Use of chemical models is

recommended including:

• Eulerian (e.g., CAMx, CMAQ)

• Lagrangian (e.g., CALPUFF,

SCICHEM)


Single Source Impacts

• Source impact estimation approaches

– Brute force approach

– Decoupled direct method (DDM) sensitivity

– Source apportionment


Source Impact Estimation

Approaches

Baker, K. Estimating Ozone and Secondary PM2.5 for Permit Related Programs, A&WMA’s 6th Specialty Conference -

Chapel Hill, NC, April 12, 2006


Long Range Transport

• EPA proposing that Appendix W no longer contain

language requiring use of CALPUFF or other

Lagrangian model for LRT assessments.

• For NAAQS demonstrations: Near-field modeling is

sufficient to address whether a source will cause

of contribute to a NAAQS violation so EPA does

not consider a LRT assessment beyond 50 km

necessary for inert pollutants.

• EPA recognizes that LRT assessments may be

necessary in limited situations for PSD increment

and proposes a screening approach where

CALPUFF or other appropriate model/tool may be

used.


IWAQM Update

• Interagency Workgroup on AQ Modeling

• FLAG Guidance is being updated

• Current guidance tied to Appendix W

• Plan is to have it be a stand alone document

• CALPUFF will likely continue to be used for the

next 3-5 years

• MMIF documentation will be emphasized


What's Coming?

The good

• Some beta options in AERMOD are

expected to become default

– Horizontal/capped stack

– Adjusted surface roughness in AERMET

– LOWWIND3 option

– ARM2 and PVMRM2 for NOx to NO2

conversion


What's Coming?

Ozone and PM2.5 formation

• Uncertainty

– For Tier 1 and Tier 2 ozone and PM2.5

evaluations

– Long Range Transport

• More time and expense

• Analyses more vulnerable to legal

challenge


Sergio A. Guerra, PhD

[email protected]

Mobile: + 612 584 9595

CPP, Inc.

2400 Midpoint Drive, Suite 190

Fort Collins, CO 80525

+ 970 221 3371

www.cppwind.com @CPPWindExperts

Thanks!

Engineering

Highlights from the 2016 Guideline on Air Quality Models Conference