CALPUFF Modeling System

Science and Implementation Is

Roger W. Brode

U.S. EPA/OAQPS

Air Quality Modeling Group

9th Conference on Air Quality Modeling

October 9, 2008

Research Triangle Park, NC
Outline

• Assessment of VISTAS version of CALPU• Unresolved technical issues with v5.8• Near-field Clarification Memo• Some examples of complex wind situations• Discussion of technical issues and concern

to CALPUFF near-field applications

• Other CALPUFF implementation and scien• Summary and conclusions 
CALPUFF Update Proce

• Incumbent upon EPA to perform an 

independent assessment of CALPUwhen updating to new versions

• CALPUFF requires extensive asses

and understanding of changes madeapprovals made by EPA, not develo

• CALPUFF Update Tool – Introduced 

Modeling Conference in Sept 2005
CALPUFF Update Too

• Compares 2 CALPUFF versions; 

proposed (beta) vs. current version 

• Determines code changes and differ

in results across 10 scenarios

• Provides a standardized methodolog

evaluating changes in model codes
Analysis

Tool

Sources

Meteorology

Terrain

Differences

?

Reso

BETABASE

CALPUFF Update Too
CALPUFF Update Process

Initial Assessments of v5.75

Table 1: Range of Maximum Absolute Percent 

Differences by Scenario for Initial Application of 

Assessment Tool 

Scenario 1 -22.0 to +23.3 Scenario 2 -0.2 to +83.4 Scenario 3 -17.7 to +60.8 Scenario 4 -13.6 to +28.1 Scenario 5 -46.0 to +21.1 Scenario 6 -10.3 to +6.3 Scenario 7 -1.7 to +1.0 Scenario 8 -10.0 to +5.4 Scenario 9 -1.2 to +1.0 Scenario 10 No differences 

EPA, 2008: Assessment of the “VISTAS” Version of the CALPUFF ModSystem, EPA-454/R-08-007, available on SCRAM website.
CALPUFF Update Process

Additional Assessments of v5

• TRC provided the following interim ve

to facilitate isolating impacts due to (fixes and (2) non-optional technical enhancements:

– CALMET v5.53c = CALMET v5.53a + bug fix– CALMET v5.53c2 = CALMET v5.53c + non-op

technical enhancements

– CALPUFF v5.711c = CALPUFF v5.711a + bug 
CALPUFF Update Process

Additional Assessments of v5

• EPA conducted several tests in order 

compare and isolate affects of the folcategories of changes:

– Bug fixes– Non-optional technical enhancements– New default parameters for optional tec

enhancements
CALPUFF Update Process

Summary of Significant Find

• Significant differences attributed to each 

three known factors: 

– Bug Fixes– Non-optional Technical Enhancements– New Default Parameters for Optional Technic

Enhancements

• Of the three known factors, the New Defa

Parameters for Optional Technical Enhancaused the largest differences overall

• Differences varied significantly across dif

scenarios and source types, with no signoverall bias evident
CALPUFF Update Proces

Summary of Differences – v5.8 

Scenario 10 No differences No differences No differences 

Scenario 9 No differences > |0.01| -1.2 to +1.0 No differences > |0.01| 

Scenario 8 -1.4 to +0.6 -2.0 to +3.1 -12.1 to +5.5 

Scenario 7 No differences > |0.01| -1.7 to +1.0 0.0 to +0.4 

Scenario 6 -1.4 to +0.6 -2.0 to +6.3 -12.6 to +5.5 

Scenario 5 -32.4 to +9.5 -9.2 to +0.6 -41.8 to +20.9 Scenario 4 -18.4 to +8.4 -0.7 to +4.2 -3.2 to +30.5 Scenario 3 -5.1 to +6.0 -0.8 to +1.7 -19.3 to +60.8 Scenario 2 -15.4 to +27.8 -30.5 to +0.7 -21.8 to +118.3 Scenario 1 -1.0 to +22.6 -18.6 to +1.9 -22.0 to +24.4 

Te

B

Test 7 – New Default

Parameters

Test 6 – Non-Optional

Test 5 – Bug Fixes Technical Enhancements

Range of Maximum Absolute Percent Differences by Scenario

1Test 8 differences are due to bug fixes, but include some additional bug fixes comp
Table 6. CALPUFF Comparison Results for Scenarios 1 - 5 for Base v5.711a vs

Scenario

5

-0.88 -32.43

65 m Point Source

34 8.40 -4.55 -4.95

.

 No differences in highest ranked (design) values

0.68

99 m Point S

Source Type

Area Source Volume Source 30 m Point Source

-5.10 -7.36

12

-21.78 -6.71

0.02 -0.300.32 0.12

-18.37 

 Differences in one or more design values 

-0.02 0.00 -0.05 7.26 -3.98

2.35 0.58 25.24

-2.84 29.24

0.480.28

7.59

22.63

0.12

0.41

0.201.07
CALPUFF Assessment Results from Previous Up

v5.7 to 5.711a
Scenario 2 - 65m Point Source, Salem Location

Percent Difference - 1st Highest, 1-Hour Averages

-400 -300 -200 -100 0 100 200 300 400

-400-300-200-100

0

100200300400
Figure 1: Contour Plot of Percent Differences for Scenario 2

Jordan Valley 65m Point Source; 4th-Highest 24-Hour Averages

Test 4 - CALPUFF (5.711c) and CALMET (5.53c2) vs. VISTAS (5.756/5.726) 

(with modified inputs to override new default parameter)

0 100 200 300

-200-100

0

100200
CALPUFF Update Process

Unresolved Issues with v5

• EPA has unresolved technical concerns re

how the optional technical enhancements mixing height have been implemented in C

• These concerns are related to the new de

parameters THRESHL and THRESHW for threshold buoyancy energy flux over land water, respectively

• These new thresholds were implemented 

the MMS-sponsored enhancements, to preunlimited growth of the convective boundaover water
CALPUFF Update Process

Unresolved Issues with v5

• These new thresholds are defined (in the 

documentation available) as the “threshold buoyancy flux required to sustain convectiheight growth”

• However, the code indicates that when the 

heat flux falls below the threshold, the conmixing height is immediately assigned to 0that grid cell, eliminating convective turbul

• A new convective boundary layer may form 

subsequent hours
CALPUFF Update Process

Unresolved Issues with v5

• This behavior is masked somewhat by oth

defaults within CALMET, including the defminimum mixing height of 50m, the use of maximum of convective and mechanical mheights as the overall mixing height, and toption for upwind averaging of mixing heig

• The default threshold is 0.05 W/m

2/m.

– For example, if Zic = 3000m at 2pm, and H = 1

at 3pm, then Zic = 0m at 3pm. A new CBL wilat 4pm.

• The following figures from Scenario 4 illus

behavior
CALMET v5.8 Convective Boundar

Heights (THRESHL = 0.05)
Time series of convective mix

height from CALMET 
CALPUFF Update Process

Resolution of Issues (Partia

• TRC agreed to implement the following c

in the CALPUFF modeling system code, EPA to approve v5.8:

– Incorporate the non-optional technical enhancements 

optional technical enhancements, removing non-optioenhancements as a potential source of differences;

– Incorporate a new regulatory default switch (MREG=1

to allow the optional technical enhancements to be incmodel, but to require the user to override the default oexercise these optional technical enhancements; and

– Modify the CALPUFF model code to include the minim

of 0.5 m/s over water as part of the regulatory default 
CALPUFF Update Proces

Summary of Differences – v5.8 

Scenario 10 No differences No differences No differences 

Scenario 9 No differences > |0.01| -1.2 to +1.0 No differences > |0.01| 

Scenario 8 -1.4 to +0.6 -2.0 to +3.1 -12.1 to +5.5 

Scenario 7 No differences > |0.01| -1.7 to +1.0 0.0 to +0.4 

Scenario 6 -1.4 to +0.6 -2.0 to +6.3 -12.6 to +5.5 

Scenario 5 -32.4 to +9.5 -9.2 to +0.6 -41.8 to +20.9 Scenario 4 -18.4 to +8.4 -0.7 to +4.2 -3.2 to +30.5 Scenario 3 -5.1 to +6.0 -0.8 to +1.7 -19.3 to +60.8 Scenario 2 -15.4 to +27.8 -30.5 to +0.7 -21.8 to +118.3 Scenario 1 -1.0 to +22.6 -18.6 to +1.9 -22.0 to +24.4 

Te

B

Test 7 – New Default

Parameters

Test 6 – Non-Optional

Test 5 – Bug Fixes Technical Enhancements

Range of Maximum Absolute Percent Differences by Scenario

1Test 8 differences are due to bug fixes, but include some additional bug fixes comp

EPA, 2008: Assessment of the “VISTAS” Version of the CALPUFF Modeling SystemEPA-454/R-08-007, available on SCRAM website.
CALPUFF Implementation Iss

• Lack of adequate documentation

– New MREG option in CALMET not well-documented; CALMET

input file indicates “no default” and assigns value of MREG = 0enforce regulatory defaults

– Many important technical details are not documented, except i

• Magnitude of differences between v5.8 of CALPU

previous version raises questions regarding “validoriginal model evaluations for CALPUFF

• PG vs. turbulence dispersion option in CALPUFF

– Addressed in March 2006 Model Clearinghouse Memo: not an 

switch with promulgation of AERMOD, requires separate asse

– Assessment is underway, but has uncovered other PG-class d

with turbulence option

• Pending assessment of v5.8’n’ and v6 updates

– Currently “on hold” due to need to address broader issues

• CALPUFF near-field Clarification Memo
CALPUFF Near-field

Clarification Memorandum

• Summary of Key Points: – The EPA-preferred model for near-field regulatory applications (le

kilometers) for simple and complex terrain is AERMOD. The AERM

be used for all near-field regulatory applications, unless an adequate dmade that AERMOD is not appropriate for that application or is clearly 

than an alternative model. [See paragraph 4.2.2(b) of Appendix W – “Fregulatory applications in all types of terrain, the recommended model 

– CALPUFF is not the EPA-preferred model for near-field application

considered as an alternative model on a case-by-case basis for neapplications involving “complex winds,” subject to approval by thauthority. The approval of CALPUFF for near-field regulatory applicat

based on case-specific justification, including necessary documentation determination that AERMOD is not appropriate or clearly less appropria

CALPUFF. Generalized approval of CALPUFF for near-field applicatio

reference to other cases where CALPUFF has been approved for near

acceptable, unless such cases are similar enough to the application unapplicable, and are adequately documented to support that determinat

paragraph 7.2.8(a) of Appendix W – “the CALPUFF modeling system (

Appendix A) may be applied on a case-by-case basis for air quality estcomplex non-steady-state meteorological conditions.”]
CALPUFF Near-field

Clarification Memorandum

• From Preamble to April 2003 FR 

promulgating CALPUFF:

– “We will require approval to be obtained prior t

accepting CALPUFF for complex wind situationwill ensure that a protocol is agreed to between parties involved, and that all are willing to acceresults as binding. As experience is gained in uCALPUFF for complex wind situations, acceptabecome clear and those cases that are problembe better identified.” (pp. 18441-2)
CALPUFF Near-field

Clarification Memorandum

• From Section 7.2.8 of Appendix W

– “The setup and application of the model should 

determined in consultation with the appropriate authority (paragraph 3.0(b)) consistent with limparagraph 3.2.2(e).”

– Reference to paragraph 3.2.2(e) places CALPU

status of an alternative model.
CALPUFF Near-field

Clarification Memorandum

• Paragraph 3.2.2(e) of Appendix W:

“e. Finally, for condition (3) in paragraph (b) of this subse

[preferred model is less appropriate for the specific ap

there is no preferred model], an alternative refined moused provided that:

i. The model has received a scientific peer review;ii. The model can be demonstrated to be applicable to the 

theoretical basis;

iii. The data bases which are necessary to perform the ana

available and adequate;

iv. Appropriate performance evaluations of the model have 

the model is not biased toward underestimates; and 

v. A protocol on methods and procedures to be followed h

established.”
CALPUFF Near-field

Clarification Memorandum

• Summary of main steps:

1) a determination that treatment of complex winds is cri

estimating design concentrations;

2) a determination that the preferred model is not approp

appropriate than CALPUFF; and 

3) a demonstration that the five criteria listed in paragrap

for use of an alternative model are adequately addres

• Each of these steps involves case-s

considerations
CALPUFF Near-field

Clarification Memorandum

• Importance of consistency, spelled 

paragraph 1(b) of the Guideline:

“The model that most accurately estimates concentrations in the aralways sought. However, it is clear from the needs expressed by th

EPA Regional Offices, by many industries and trade associations, adeliberations of Congress, that consistency in the selection and models and data bases should also be sought, even in case-byanalyses. Consistency ensures that air quality control agencies anpublic have a common basis for estimating pollutant concentrationscontrol strategies and specifying emission limits. Such consistency promoted at the expense of model and data base accuracy. The Gprovides a consistent basis for selection of the most accurate mode

bases for use in air quality assessments.”
Examples of Complex Wind

• Examples of complex winds are described 

paragraph 7.2.8(a) of Appendix W:

– “a. Inhomogeneous Local Winds. In many parts 

United States, the ground is neither flat nor is thcover (or land use) uniform. These geographicacan generate local winds and circulations, and mprevailing ambient winds and circulations. Geogeffects are most apparent when the ambient winlight or calm. In general these geographically incirculation effects are named after the source lothe winds, e.g., lake and sea breezes, and mouvalley winds. In very rugged hilly or mountainoualong coastlines, or near large land use variatiocharacterization of the winds is a balance of varforces, such that the assumptions of steady-staline transport both in time and space are inappr
Examples of Complex Wind

• Valley flows

– Down-slope/down-valley flows under light 

stable conditions

– Cross-valley circulations due to differentia

under convective conditions

– Valley channeling, may be driven by diffe

conditions

– Stagnation conditions– Significant horizontal and vertical disconti

wind, temperature, etc.

– Grid resolution and availability of represen

data may be significant issues
Slope Flows

• Part of local 

wind pattern thermally ind

• Formation is 

under weak spressure gra

• Depends upo

surface tempcontrasts due daytime heatnighttime coo
Mountain-Plain Circulatio

• Mountain-Plain 

circulations also develop due to thermal effects. 

• Rising air over mountains 

as upslope winds develop create a weak pressure gradient which causes air from the plains to flow toward the mountain to compensate for the rising 

• At night, the circulation 

reverses, and the winds flow from the mountains onto the plains. 
Nocturnal Thermal Structu

• As air over mountain 

cools, it becomes mthan its surrounding environment and bedrain down the gradterrain slopes. 

• Cold air accumulate

valley basin and cretemperature inversiotop of the valley. 

• Air within valley is st

stratified and pollutiobecome trapped and accumulate.
Examples of Complex Wind

• Coastal influences

– Land/sea-breeze (lake-breeze) circulatio

by differential heating between land and 

– Thermal internal boundary layer (TIBL) n

during daytime onshore flow

– Grid resolution and representative met da

be significant issues

– TIBL effects most important for elevated 

near the coast, and may be addressed thsubgrid-scale modules
Complex Winds - Issues

• General issues

– Complex wind influences will vary signific

based on source characteristics and loca

– Plume recirculation may occur under var

conditions, such as cross-valley and coacirculations and stagnation

– Availability of representative meteorologi

to “inform” the system

– Ability of modeling system to effectively u

site-specific information

– Model performance/uncertainty for spatio

pairing of model results is not well documunderstood
Complex Winds - Issues

• More specific issues

– Near-field, localized plume terrain interac

may be significantly misrepresented due resolution limitations

– Ability of modeling system to effectively u

site-specific information appears to be significantly lacking – important informatibe effectively destroyed or misrepresente

– Recent Staff Memorandum, dated Septe

2008, provides additional details regardinissues
Complex Winds – Performa

Evaluations

• CALPUFF modeling system performa

near-field complex wind applications well-documented

• IWAQM Phase 2 report includes som

CALPUFF evaluation results for Kincterrain) and Lovett (complex terrain)

• Evaluation results for Lovett show go

performance
CALPUFF Lovett Evaluation R

from IWAQM Phase 2 Repo
Complex Winds – Performan

Evaluations

• However, CALPUFF was applied with CTD

met inputs, bypassing CALMET

• This is not consistent with motivation for C

near-field applications under paragraph 7.2Appendix W, which is to “fully treat the time space variations of meteorology effects on and dispersion.”

• Therefore, these evaluation results are not 

to near-field applications under paragraph Appendix W
CALPUFF/CALMET Evalua

for Lovett

• Various methods, including graphical and statistica

measures, are used for evaluating model performanear-field regulatory models, such as AERMOD or Industrial Source Complex (ISC) models.

• The Cox-Tikvart method uses the Fractional Bias (

statistical measure of agreement between the obspredicted concentration;

– The FB is bounded between -2 and +2, with a v

(zero) indicating perfect agreement. An absoluless than 0.667 for FB indicates agreement withof 2
Near-Field Evaluation 

Procedure Cont’d

• Fractional bias calculated from Robust Highest 

Concentration (RHC):

• Model comparisons based on Composite Perfor

Measure (CPM) and Model Comparison Measur

[

] ,

2

3N

-

1 RHC

= X(N)

+

X

- X(N) ⎥

⎦⎤ ⎢

⎣⎡ ln

( ) 

2

(AFB

)

+(AFB

)

32 AFB

+

3

1 CPM

=

3 

r , s 

⎢⎣⎡

MCM

= CPM

(

1

)

−CPM

(

2

) ,
Lovett Near-Field Compl

Terrain

• CALMET 3-D Windfields Developed

– 3 Level Tower (10m, 50m, 100m) simulated as 3 surfa

with corresponding anemometer heights

– Upper air data from Albany, NY– 125 meter grid spacing using SRTM-1 (terrain) and NL

(landuse).

• Various CALPUFF configurations tested 

– P-G– AERMOD turbulence– Plume Half-Height Adjustment– CALPUFF Strain Based Adjustment– AERMOD surface and profile data
Model Configurations Evalu

• CALPUFF1: 

– P-G Dispersion– Plume Half Height Adjustment

• CALPUFF2: 

– AERMOD Turbulence– Plume Half Height Adjustment

• CALPUFF3: 

– P-G Dispersion– CALPUFF Strain Based Adjustment 

• CALPUFF4: 

– AERMOD Turbulence– CALPUFF Strain Based Adjustment

• CALPUFF5: 

– AERMOD Profile Data– Plume Half Height Adjustment

• AERMOD (Version 07026)
Robust Highest Concentrat

AERMOD 190.79 -2.202E-02

CALPUFF5 170.94 8.778E-02

CALPUFF4 498.73 -0.9107

CALPUFF3 215.26 -0.1424

CALPUFF2 331.69 -0.5597

CALPUFF1 270.83 -0.3681OBSERVED 186.63

MODEL RHC FB

AERMOD 52.19 CALPUFF5 45.20 

CALPUFF4 88.91 

CALPUFF3 80.19 CALPUFF2 50.03 

CALPUFF1 79.98 OBSERVED 51.77

MODEL RHC 

3-Hour 24-Hour
Composite Performance Measure (C

Model CPM +/- C.I. +/- C.I.

90% 95% 

CALPUFF1 0.5956 0.1280 0.1526 CALPUFF2 0.6005 0.1708 0.2036 CALPUFF3 0.4763 0.1210 0.1442 CALPUFF4 0.7884 0.2349 0.2800 CALPUFF5 0.4382 0.1008 0.1202 AERMOD 0.4234 0.0980 0.1168 
Model Comparison Meas

(MCM)

Model - Model MCM +/- C.I. 

90% 

CALPUFF1-CALPUFF2 -4.943E-03 0.3247 CALPUFF1-CALPUFF3 0.1192 0.1709 CALPUFF1-CALPUFF4 -0.1928 0.3939 CALPUFF1-CALPUFF5 0.1574 0.3377 CALPUFF1-AERMOD 0.1722 0.2679 CALPUFF2-CALPUFF3 0.1242 0.3195 CALPUFF2-CALPUFF4 0.1879 0.4114 CALPUFF2-CALPUFF5 0.1624 0.3563 CALPUFF2-AERMOD 0.1771 0.3353 CALPUFF3-CALPUFF4 -0.3120 0.3897 CALPUFF3-CALPUFF5 3.819E-02 0.3319 CALPUFF3-AERMOD 5.295E-02 0.2619 CALPUFF4-CALPUFF5 0.3503 0.4839 CALPUFF4-AERMOD 0.3650 0.4344 CALPUFF5-AERMOD 1.476E-02 0.2107 
3-Hour Q-Q Plot - Lovet
24-Hour Q-Q Plot - Love
Observations – Near Field 

Evaluation

• CALPUFF model performance exhibits significa

sensitivity to dispersion and terrain options.

• More “advanced” options (turbulence and strain

terrain adjustment) exhibited poorest performan

• CALPUFF with AERMOD profiles (i.e. no CALM

performed best of CALPUFF configurations.

• CAVEAT: These evaluation results are very pre

and will be updated based on additional insights 

treatment of tower data in CALMET
Questions?