# Final Report: Fourth Peer Review of the CMAQ Model

Submitted to:

Community Modeling and Analysis System Center

Carolina Environmental Program

The University of North Carolina at Chapel Hill

Submitted by:

Nancy J. Brown Lawrence Berkeley National Laboratory
David T. Allen University of Texas, Austin
Praveen Amar Clean Air Task Force George Kallos University of Athens, Greece Richard McNider University of Alabama, Huntsville Armistead G. Russell Georgia Tech William R. Stockwell Howard University

September 28, 2011

### Table of Contents

1. Introduc tion................................................................................................................... ................. 3

2. Major Developments since the third peer review (December 2006)......................... 4

3. Specific recommendations of third peer review panel and response to prior

review......................................................................................................................... ............................... 6

4. Panel Response to charge questions ..................................................................................... 7

4.1 What is the overall quality of the applied scientific research in the CMAQ Modeling

Pro ram?....................................................................................................................... .......................................7 g
4.2 Charge Question 2: What are the strengths and weaknesses of the science being
used within the components of the CMAQ Model development program? ............................... 11

4.3 What is the quality and relevance of the model development, application, and
evaluation being conducted as part of the CMAQ Modeling program to the four ITR

Pro rams?......................................................................................................................................................... 13 g
4.4 What are your perceptions of the integration across different elements of the CMAQ modeling program (links among model development, applications, evaluation)? What is

your perception of the usefulness of the CMAQ modeling program to the EPA, states, other

customer needs, and research community?......................................................................................... 15
4.5 Are there any modeling research areas that are relevant to the EPA’s regulatory

program needs not being addressed or given insufficient attention within the CMAQ Modeling Program? Are there any current areas of research emphasis that could be given

a lower priority or eliminated to help advance the above four ITR areas? Are the

resources made available to the CMAQ Modeling Program being used effectively in terms
of the choice and quality of the applied research being conducted at AMAD in support of
the four ITR areas? ......................................................................................................................... ............... 17

5.0 Comments on the Review Process ......................................................................................18

6.0 Panel Recommendati ons .......................................................................................................18

7.0 References..................................................................................................................... ..............19

### 1. Introduction

The CMAQ Model External Peer Review Panel co nducted a two and a half day review view on June 27, 28, and 29, 2011. This report summarizes its findings, and follows other reviews conducted in 2004, 2005, and 2006 [Amar et al., 2004; 2005 and 2007].

The report is written from the perspectives represented by the seven-member review panel: David Allen, Praveen Amar, Nancy Brown, George Kallos, Richard McNider, Armistead (Ted) Russell, and William Stockwell. Panel members read a considerable volume of material on CMAQ provided by EPA and attended two days of presentations on CMAQ by the EPA staff (see the Appendix for meeting agenda).

The Atmospheric Modeling and An alysis Division (AMAD) of the National Exposure Research Laboratory (NERL) develops opera tional state-of-the-art air qual ity models and modeling tools for use in policy and regulatory analyses. Th is review focused on the work conducted by the group of 21 staff scientists (the CMAQ gr oup) within AMAD. The 2011 Peer Review emphasized an assessment of the meteorological, physical, and chemical process aspects of the Community Multiscale Air Qual ity (CMAQ) modeling program, as well as applications, refinements, and considerable evaluations of mo del performance. The review panel focussed its attention on the current community version of CMAQ, version 4.7.1, which was released in January, 2011 as well as the future version, CMAQ 5.0, to be released in October, 2011.

Within the context of the AMAD’s mission to develop air quality models for regulatory, research, and operational purposes, the panel was ch arged with evaluating the overall quality of the applied scientific research in the CMAQ Mo deling Program. The panel evaluated: 1) the overall quality of the applied scientific re search in the CMAQ Modeling program; 2) the strengths and weaknesses of the science being used within th e components of the CMAQ Model development program; 3) the quality and relevanc e of the model development, applications and
evaluations that are conducted as part of the CMAQ Modeling Pr ogram to the four Integrated Transdisciplinary Research (ITR) programs; and 4) the integration of different elements of the CMAQ modeling program and its usefulness to the EPA, states, and other customer needs as well as the research community. The panel al so evaluated the relevance of the AMAD’s modeling program elements in view of the res ources available to the CMAQ Modeling Program. The panel was requested to identify relevant modeling research areas that are not being addressed or are given insufficient attention. The panel also identified curr ent research areas that should be given lower priority or eliminated to help advance the four EPA Office of Research and Development (ORD) ITR areas. The four ITR ar eas are: Air, Climate, and Energy (ACE), Chemical Safety for Sustainability (CSS), Su stainable and Healthy Communities (SHC), and
Safe and Sustainable Water Reso urces (SSWR). The panel was also asked to consider whether

3the resources made available to the CMAQ Mode ling Program are being used effectively in terms of the choice and quality of the applied research being conducted at AMAD in support of
the four ITR areas.

CMAQ is the central tool for its user community throughout the US and the world that is being used in regulatory and scientif ic applications by researchers an d the EPA, states, regional, and local agencies in State Implementation Planning (S IP) processes. The community is at ease with using it at its current state of development, even as more difficult policy-oriented demands are being placed on the model (e.g., simulating ozone at lower concentration levels and in the winter).

As noted, even though the CMAQ modeling system is used throughout the US for regulatory purposes, by EPA, states, and regional and local agencies, there are also other models used by many of these entities for SIP activities that are often provided by the air quality consulting community outside the CMAQ framew ork. There is a need for the nation to have the very best tools for air quality decision making; hence, it would seem appropriate that the CMAQ group should also strive, when feasible , to make subcomponents of CMAQ available to the larger U.S. modeling community. In the past, the CMAQ group has achieved this successfully with biogenic emission modules, and more recently, with th e development of model evaluation tools.

The consensus of the panel was that the CM AQ group is doing an exceptional job selecting research topics and conducting their research; hence, we will not comment further on the choice
of scientific directions that the group has pursued. The panel was impressed that they have used
model error and control strategy sensitivity as a basis for guiding the selection of research
directions.



### 2. Major Developments since the third peer review (December 2006)

CMAQ has evolved significantly since the last review in 2006. The aerosol/particulate matter simulation capabilities have advanced dramatical ly. The descriptions of the secondary organic aerosol (SOA) formation routes ar e significantly enhanced, and while still biased on the low side, they capture reasonably the diurnal trends and the sc ientifically identified routes. Dust emissions are also more realistically treated. Sea salt aerosol emissions from the coastal zone are simulated. Additional species are included in the thermodynamic treatment and reactive gases
are now modeled to interact wi th coarse particles in a dyna mically correct fashion. The chemistry has been updated from older to cu rrent versions of the CB, SAPRC and RACM chemical mechanisms. In spite of the model becoming more comprehensive and complex, the group is also making strides to make it more user-friendly.

4Other areas where there has been sign ificant progress are indicated below:

Model Evaluation

The Air Quality Model Evaluation International Initiative (AQMEII) has played a key role in making the model evaluation more systematic by including operational, diagnostic, dynamic and probabilistic evaluation methods. Pr obabilistic evaluation is the ne west approach and is still under development within the modeling community.

Chemistry

Chemical mechanisms options have been upgr aded to include SAP RC07 and CB05. Isoprene chemistry, toluene chemistry, and the kinetics as sociated with key inorganic reactions OH + NO 2

→ HNO 3 and HO + SO 2 → H 2 SO 4 + HO 2 have been revised. The inline calculation of photolysis rate constants has been improved and implemented for testing. Work is in progress to incorporate a more realistic aqueous-phase chemistry mechanism.

Aerosols (Particulate Matter)

There is an improved treatment of the heterogeneous reaction of N 2 O 5 to HNO 3 . There has been substantial improvement of the SOA module. There is dynamic mass transfer for coarse aerosols.

Emissions

Improvements have been made in the treatments of estimating biomass burning emissions and anthropogenic fugitive dust. The addition of “lightning NO x emissions” to CMAQ significantly improves agreement between simulations and measurements.

Transport

Work is in progress to achieve consistenc y between CMAQ and the Weather Research and Forecasting (WRF) meteorological model. For exam ple, the new mass continuity treatment in CMAQ uses the WRF vertical velocity calculation, which still requires additional attention especially when modeling at finer scales (of a ki lometer or less). Since th e inherent problem is related to both grid and/or st encil differences, there are likely to be differences in CMAQ and WRF vertical velocities especi ally relating to the selection of an appropriate top boundary
condition.

Air-Surface Interactions

The CMAQ group has adapted a two-la yer (vegetation & soil) resist ance model for bidirectional exchange for ammonia and mercury. They have c ontinued their excellent work comparing model deposition to field observations.

5Two-Way Coupled WRF-CMAQ Model

An efficient and flexible coupled meteorol ogy-chemistry modeling system based on the WRF and CMAQ models has been developed and is be ing tested. The current one-way and off-line coupling of WRF and CMAQ has the advantage th at one only has to run the meteorological model once for multiple control strategy tests. This means that CMAQ and WRF can continue separate internal development tasks. However, ultimately this approach may limit the application of the CMAQ model when small scales (e.g., le ss than 1 km) are required, where turbulent eddies begin to be resolved by the model. It is difficult to see how the chemistry model can accommodate the segregated effects without usin g true time-step coupling. Coupling of the chemistry and physics should be required when pl ume behavior is dominated by the resolvable eddies. The “vertical velocity problem” menti oned previously may also be of concern for applications at the small scales. While the glob al modeling community has been less concerned about this, the same issues appear to arise when trying to translate the effects of cloud convective transport from the physical model to the chemical model.



### 3. Specific recommendations of third peer review panel and response to prior
review

Recommendations of the Third Peer Review Panel and EPA Response:

The 2006 peer review panel made several key recommendations to improve CMAQ performance and the CMAQ group has made a number of modificat ions in response. The key “high priority” recommendations included: 1) improvement in the treatment of N 2 O 5 chemistry, 2) reduction of the uncertainty in chemical mechanisms for aromatic chemistry, 3) improvement of the representation of SOA production from biogenics and aromatics, and 4) improvement of the evaluation of different mechanisms to quantif y their impact on pollu tant predictions and responses to precursor reductions.

In response to the above recommendations, th e CMAQ group has made substantial efforts to include development of a new parameterization scheme for N 2 O 5 chemistry and conducted model comparisons with field measurements. C onsistent with the pa nel’s recommendation, a parameterized version of aromatic chemistry (including an updated toluene mechanism in the CB05 version) has been implemented. To improve SOA treatment, new SOA precursors (isoprene, benzene, and sesquiterpenes) have been added, and new pathways have been incorporated (e.g., acid enhan cement of isoprene SOA). The panel recommendation relating to responses to precursor reductions is important from a regulat ory standpoint and the group’s
recent work found that both CBM and SAPRC m echanisms exhibited similar responses. The CMAQ group is commended for its work with EPA Office of Air Quality Planning and Standards (OAQPS) in this policy-relevant effort.

6In responses to other recommendations of “mediu m and low priority” a number of actions were also taken. For example, for dry deposition, good progress has been made in the important area
of a bidirectional flux treatment for ammonia a nd mercury that includes comparisons with data
from intensive field studies.



### 4. Panel Response to charge questions

4.1 What is the overall quality of the applied scientific research in the CMAQ Modeling Program?

Evaluation (quality of science)

The CMAQ group is to be complimented on the extensive efforts they have made to evaluate CMAQ, and to provide the evaluatio n tools to the user community. Th eir research in this area is of very high quality and they are the world leader in air quality model evaluation activities. These efforts provide a foundation for the more reliable use of the CMAQ modeling system, not only for traditional applications, but also as th e model is used for new and more challenging applications. If the National Ambient Air Qual ity Standard (NAAQS) for ozone becomes more stringent, new evaluation efforts may be required by the CMAQ group to demonstrate the model’s ability to capture correct ly the model response to air pollution control strategies at “midhigh” ozone levels. While the gr oup is arguably the world leader in this area, there are cases where they will need to be even more forward-looking. They need to support the NAAQS review process (e.g., the primary and secondary ozone standards, new primary PM and NOx/SOx standards, and future secondary standards for SOx/NOx) by pr oviding the modeling tools and requisite analyses.

Chemistry (quality of science)

The overall quality of the chemistry component s is high. It is commendable that the CMAQ group has been developing alternative gas-phase mechanisms to the carbon bond mechanism. These new options will allow CMAQ to be used reliably for a wider range of conditions and applications. Chemical mechanism options have been upgraded to include SAPRC07 and CB05. Appropriate attention is bei ng given to the chemistry of biogenically emitted organic compounds. Photolysis is a major driver of at mospheric chemistry and is very dependent on meteorological conditions; thus the inline calcula tion of photolysis rate constants in CMAQ is a significant improvement.

Particulate Matter (quality of science)

The overall quality of applied scientific rese arch on particulate matter in the CMAQ modeling program is excellent. The CMAQ group has made significant scientific progress in developing

7methods for tracking, within CMAQ, sources of primary and secondary aerosol. These advances
will enable much more focused efforts to improve CMAQ’s under-prediction of Secondary Organic Aerosol (SOA) formation and over-prediction of “other”, unspeciat ed particulate matter (PM) components. The team has also incor porated state of the science descriptions of heterogeneous chemistry into CMAQ gas phase chemistry modeling, particularly for N 2 O 5

.

While progress has been significan t, there is a need for impr ovement in the following areas:

• Review of the soil dust schemes currently included in limited area models and not those in GCMs (schemes in the GCMs are not refined and less accurate).

• Addition of heterogeneous chemistry processe s (e.g., primarily processes associated with SOA formation).

• Treatment of the conversion from concentra tions to number density and size distribution, which is especially important if tighter c oupling between the met a nd chemical transport models is required to treat the physics and chemistry of aerosol indirect effects.

Meteorology (quality of science)

The meteorological model (WRF) used in the coupled system is ma ture and provides the necessary meteorological fields to drive CMAQ using the recently developed coupler. WRF has 2-way nesting capability but CMAQ does not. This imposes some restrictions on how to do coupling. A one-way nesting config uration was applied for most cas es where the coupled system is used. The coupler also works in a limite d fashion in the reverse way by supplying the necessary information to estimate the direct effects of aerosols on radiation. This is a useful step towards better coupling.

Retrospective studies in which ai r quality is simulated at locati ons that exceeded NAAQS in the past are used to evaluate the impact of different emission control strategies. These studies have been a cornerstone of control strategy devel opment for SIPs under the Clean Air Act. The EPA has used such retrospective studies for outli ning general population e xposures, for designing observation/monitoring networks to observe changes in air qualit y and to determine what might be possible in terms of atmospheric response as frameworks for new standards are being established. The CMAQ team has made significant contributions in developing techniques for recreating the meteorology and physical atmospheres for these retrospective studies.

In particular they have embraced Four Dimens ional Data Assimilation (FDDA) in the MM5 (the model that preceded WRF) framework in the free at mosphere as a way to constrain the model to observations and remove the model drift, which is inherent in a free forecast. Most importantly they have worked with the WRF community to include these FDDA techniques within the WRF
framework. Data assimilation in WRF is a us eful tool for hindcas ting (and forecasting)

8simulations and this has been clearly demonstrated in their work. Additionally, they have used a new generation of observations incl uding radar profilers and satellite data to improve the fidelity of representing the atmospheri c conditions and parameters.

They have led the way by demonstrating, in retros pective studies, that simple models constrained by observations are preferable to more comp lex models that contain many uncertain and unknown parameter values. Near-surface temperatures are highly dependent on land characteristics of highly uncertain quantities such as soil moisture, soil heat capacity and deep soil temperatures. Their indirect methods of adjus ting soil moisture in a si mple two-layer surface model based on model error in the morning and sim ilar schemes to adjust the deep soil substrate temperatures at night to improve surface temperat ures are two examples of this approach. The corresponding surface flux correction in this indirect assimilation of both sensible heat flux and moisture flux greatly improves the calculation of mixing heights and Pl anetary Boundary Layer (PBL) turbulent characteristics.

While these are data driven adjustments, th ey are based upon a thorough understanding of the physics of the lower atmosphere. The CMAQ team has also developed practical methods for including subtle boundary layer characteristics such as asymme try in convective eddies in boundary schemes and, perhaps most importantly, ha s worked to include these schemes in the WRF model [Pleim, 2007].

A 12-km resolution was used for continental coverage for most of the cases discussed or referred to in the CMAQ group’s publications. The 4 km resolution was only used in a few cases, and it would be useful to perform more testing at the higher resolution. The manner in which the vertical velocity component is used in CMAQ needs to be refined because the current treatment may have important limitations, especially at hi gh-resolution configurati ons. One area that does not seem to have been explored is the use of a one-dimensional variational assimilation following the approach of O’Brien [1970] for solv ing the “vertical velocity problem.” In this approach the divergence from WRF can be minimally adjusted to meet the same top boundary constraint used in WRF for the CMAQ grid/stencil.

Emissions (quality of science)

The overall quality of the emissions component of CMAQ is satisfactory. The emissions component includes three major categories (anthr opogenic, biogenic, and natural). The main improvements since the 2006 review include impr ovements in the characterization of existing emission sources (including new species, optimiza tion and streamlining of emissions processing, and adding new emission sour ces (lightning-NOx and windblow n dust in CMAQ v 5.0). The Panel believes that CMAQ must have an emissi ons component of high quality for it to have success in its regulatory applica tions. Evaluation of the effectiv eness of alternative emission control strategies and accurate representations of emissions (as well as changes in emissions) are

9very important; however, historically, sufficient atte ntion has not been devoted to this because of the difficulty associated with it and the large la bor requirements for doing this task correctly.

The new CMAQ effort on improving emission estimat es from three categor ies of 1) windblown dust emissions for PM2.5 and PM10, 2) biogeni c emissions (BEIS, MEGAN, and BELD3 vegetation database), and 3) emission speciation including the SPECIATE da ta base (v. 4) will be of great use to future CMAQ applications. Ad ditionally, there has been reasonable progress in emissions related to biomass burning, though it has not taken into account the potential heterogeneous reaction on the particles produ ced in the fire [see Buscu et al., 2006].

Land-surface Interactions (quality of science)

The land surface team has continued to perform qual ity research in actively comparing models to field observations of deposition. They have also begun to embrace crop models as a path to further improve plant uptake parameterizati ons. When possible, the CMAQ team should use existing crop models rather than developing new models.

Coupled WRF-CMAQ (quality of science)

The ability to run WRF and CMAQ inline and off line is highly desirable for climate research and air quality forecasting applications. The system is somewhat outside of the CMAQ group’s
current mission because it is used less for these a pplications than for efforts concerned with the development of control strategies where CMAQ is used to simulate many scenarios. The coupled WRF-CMAQ model could be used to develop th e base case meteorology for multiple off-line
simulations.

The WRF-CMAQ coupling is obtained through direct writing to the allocated memory of each system. Both models have been programmed for Shared Memory and Distributed Memory Platform computers that allow fa st execution and utiliz ation of relatively inexpensive computer infrastructures. The WRF-CMAQ co upler is efficiently designed. There are questions related to its use in other computer cluster configurations.

The coupler is designed to work primarily on a one grid configuration of CMAQ, and this imposes some restrictions on the optimal use of the WRF capabilities (2-way nesting). This affects accuracy (e.g., in the calc ulation of the vertical wind co mponent). While we recognize that achieving two-way nesting for the coupled sy stem is difficult to achieve, we encourage the CMAQ group to continue to work to improve the coupler to achieve greater flexibility.

The coupled system has been tested by using boundary conditions (BC) from global modeling systems. This is a good step for climate-t ype simulations. The CMAQ Group’s hemispheric configuration of the coupled syst em is promising and can be used for the preparation of better

10lateral BCs and to perform hi gher resolution simulations. Thes e useful features could be enhanced further if a fully coupled two-wa y nesting system for WRF-CMAQ were to be developed.



### 4.2 Charge Question 2: What are the strengths and weaknesses of the science being used within the components of the CMAQ Model development program?

Evaluation - strengths and weaknesses:

Model evaluation is a tremendous strength of the CMAQ Group, and their work in this area is of extremely high quality. The CMAQ group is the wo rld leader both in terms of the level and range of model evaluation activitie s. In addition to constantly evaluating CMAQ in its various revisions using traditional and diagnostic model evaluation approaches, they have pioneered dynamic, operational and proba bilistic air quality model evaluation approaches. More importantly, they have used their evaluation activ ities to spur model improvements in innovative and practical ways. They have also made th e model evaluation tools available to the user community.

A potential weakness is that they need to exam ine their model evaluation efforts in a meta (overall or global) fashion, that is, they need to identify and synthesize wh at they have really
learned from all their evaluation activities. On e of their emerging activities, probabilistic evaluation, will require more develo pment and applications to real ize its full potential.

Recently the NAAQS process required characteri zing the uncertainties in CMAQ’s simulations of nitrogen and sulfur oxides deposition. This uncertainty characteriz ation was not readily available to OAQPS as part of one of the mo re important EPA functions, establishing and revising secondary NAAQS.

Chemistry - strengths and weaknesses

The caliber of expertise and re search on the CMAQ atmospheric chemistry components is high. Substantial uncertainties in gas-phase and a queous-phase mechanisms remain including key inorganic reactions, aromatic and biogenic r eactions and aqueous-phase chemistry. We encourage the group to devote more attention to th e field validation of th e calculated photolysis rate constants (actual actinic fl ux comparisons, for example). The work to incorporate more realistic aqueous-phase chemistry mechanisms is very good and efforts are needed to elevate the standards of the aqueous-phase chemistry mechan isms to those of the gas-phase mechanisms. Future directions might include incorporation of stratospheric chemistry as the CMAQ spatial domain increases and climate applications are considered.

11Particulate Matter - strengths and weaknesses:

One of the principal strengths of the CMAQ grou p’s work on particulate matter is its relevance to the Agency. Recent analyses of the costs and benefits of the Clean Air Act ( http://www.epa.gov/cleanairactbenefits ) indicate that the cumulative benefits of the Clean Air Act will exceed $2 trillion by 2020, far exceeding its cost. Most of th e benefits are attributed to the reduced mortality and morbidity associated with reductions in fine particulate matter. Yet significant scientific uncertainty remains regardi ng the relative strengths of the sources of major components of fine PM, especially organic carbon and metals/dust. The CMAQ model improvements developed by the CMAQ group, which a llow for tracking of molecular and atomic tracers of aerosol sources, will enable a much more integrated approach to addressing this uncertainty in PM sources. The scientific co mmunity has recognized this contribution, and the. journal publication describing this advance is one of the most fre quently cited papers published in Atmospheric Environment over the past 5 years (Kleindienst, et al., Atmospheric Environment, 41, 8288-8300, 2007; cite d 62 times as of 6/28/2011).

Model predictions of sulfate formation now exhibit significant bias. Recent changes to gas phase chemical mechanisms and cloud processing have improved certain aspects of model performance, but have led to increased bias in predictions of sulfate formation. Identifying and removing these sources of bias should be a high priority for the Division.

There is increasing evidence that multiple hetero geneous processes will have significant impacts on predictions of criteria pollutant concentrations. These include cycling of oxides of nitrogen,
aerosol chloride/reactive chlorine gas cycling, gas and particle phase reactions of semi-volatile organics, and other processes. While the Divi sion is commended for developing methods for approaching problems individuall y, there is a need to examine the problem in a more comprehensive and integrated manner. As an example of a solution to one problem making solutions to others more difficult, using techniques such as volatility basis sets for characterizing physical partitioning of organic semivolatiles may make treating the reactivity of those same semi-volatile species more difficult.

As the largest group dedicated to regional air quality model development, the Division should continue to play a leadership ro le in defining comprehensive mode ling approaches to gas-particle
interactions.

Meteorology - strengths and weaknesses

As previously mentioned, embracing simple mo dels constrained by observations is a clear strength of the program. This has led to increas ed efficiency in having models simulate the atmospheric processes rather than the approach of using endless tuni ng of a large number of parameters. The allegiance of the CMAQ team to the fundamentals like mass conservation as

12expressed in the governing equatio ns is noteworthy. While such attention to detail might not
make much difference in short-term simulations , the longer-term simulations inherent in the proposed hemispheric work would require mass to be conserved.

Their recent work on including the e ffects of aerosols in the photolysis rates is also important. However, given the errors in aerosol predic tion and uncertainty in emissions and fire characteristics, the CMAQ team should consider using observations such as satellite-derived Aerosol Optical Depths (AOD) or even reflectance to constrain results id their uncertainties are not too large. They demonstrated that better sp ecification of albedo determined from land use dependent albedo derived from satellite retrievals improves photolysis rates.

As previously indicated, data assimilation in WRF is a useful tool for hindcasting (and forecasting) simulations and this has been clearly demonstrated in their work.

Coupled WRF-CMAQ - strengths and weaknesses

The effort concerned with creating an on-lin e coupling code for the WRF-CMAQ system is viewed positively and is well t hought out. While some reviewers are persuaded that having the coupling as it is currently designed is sufficient and allo wing CMAQ and WRF to advance independently, other panel members believe that a closer coupling between the meteorological and air quality models is desirable. The CM AQ group should continue to weigh the advantages and disadvantages of the coupling design. One dir ection to consider is to have a workshop of experts in the field who have considered va rious coupling issues. OAQPS and other clients should be participants in the couplin g design decision-making process.



### 4.3 What is the quality and relevance of the model development, application,

and evaluation being conducted as part of the CMAQ Modeling program to the four ITR Programs?

The approach this group has take n to develop CMAQ and to foster and support its use should be taken as a model of success within EPA. This pr ogram has been, is, and will continue to be, very relevant to the needs of EPA and state regula tory agencies in thei r policy and regulatory applications as well as to the scientific comm unity. The model enjoys a remarkably wide and growing user community because it is viewed as being of scientifically high quality, relatively easy to use and well supported by EPA, CMAS , and the community. Furthermore, it has continued to evolve successfully to become a state-of-the-science model. The range of applications (e.g., assessment of emission change impacts, identificati on of source impacts, support of potential regulatory direction changes, evaluation of impacts of climate change on surface level air quality, design of monitoring and observation ne tworks, and providing spatial pollutant fields for health and exposure assessmen ts) are all extremely rele vant to the needs of

13EPA and state and local governments. The effort s of the group are central to the role that the Air, Climate and Energy and the Sustainable and Healthy Communities components of ITR will play in ORD and EPA. The CMAQ group will also play important roles in the Chemical Safety for Sustainability (e.g., by the deve lopment of a version to evaluate toxic air contaminants) and the Safe and Sustainable Water Resources (e.g., by providing deposit ional loadings of acidifying and eutrophying species). EPA ORD researchers in all of the four ITRs should be made aware of CMAQ and its capabilities.

Air, Climate and Energy (ACE) (quality and relevance)

Though this team is new to the climate arena, we be lieve they have selected an important topic: changes in the observed di urnal temperature range . This is one of the biggest signals in the observed surface global temperature records, and it has not been simulated well by the GCMs. While there have been many hypotheses for this ch ange (e.g., from increasing clouds, to airplane contrails, to land use change or dynamics of the stable boundary la yer), the role of anthropogenic aerosols in relation to this change deserves attention. The role that dimming of insolation by aerosols has in decreasing day time temperatures and the enhanced Long Wave forcing at the surface at night that leads to warming is reas onable and has been proposed by others. However, the CMAQ team has the type of complete model th at can add specificity of to the quantification of this process; however, here, the team must be careful. They have found several areas where running the models for the longer he mispheric time periods leads to large scale balance and drift problems (in both the chemistry and physics). Gl obal models have always had drift or flux corrections built in. Working with other global mode lers may be useful here and they may have a niche if they can concentrate on shorter-term simulations using the constrained meteorology through FDDA.

Because of EPA’s extensive past efforts on the c limate change-air quality interface, including the work under the STAR program, the panel belie ves that CMAQ group is well positioned to participate in the ORD’s refocused research program on ACE as one component of the new organizing paradigm of ITR. Past efforts have focused on the effects of climate change on surface-level ozone (“climate change penalty”) . The Panel strongly suggests that CMAQ group
extend this work to consider the effect of climate change on PM2.5 and on the effects of projected emissions (for the American Continen t) of ozone and PM2.5 precursors (say, to the years 2050 or to 2100) on ground-level air quali ty. For the energy component of the ACE research program area, CMAQ group should work with the EPA’s National Risk Management Research Laboratory to develop realistic future energy (produc tion and consumption) scenarios that can be used with the CMAQ modeling efforts.

Chemical Safety for Sustainability (CSS) (quality and relevance)

14The CMAQ team needs to carefully define its mission within this area. Is the CSS application long-term regulatory planning, emergency response , or something else? CMAQ is a potentially useful tool for chemical safety applications , but it may be “overkill” for many of them. Dispersion modeling without atmospheric chem istry is normally used for planning the emergency response to chemical accidents, a nd a tool such as th e NOAA Ready system is currently more suitable for this purpose. Anot her limitation to using CMAQ is that the chemical mechanisms included in the model are not particul arly relevant to the br oad range of chemicals that may need to be modeled.

Sustainable and Healthy Communitie s (SHC) (quality and relevance)

CMAQ has the potential to be used widely for he alth studies if it can ov ercome some barriers, including limits on its applicati on scale and resource requirements. EPA has explored some of these possibilities, and the results are inconclusi ve. Potential benefits could be achieved if the SHEDS ( a multi-media exposure model) efforts were more closely linked to CMAQ and if the two groups identified how the two m odels could work together best.

Safe and Sustainable Water Resource s (SSWR) (quality and relevance)

CMAQ is relevant to water resour ce modeling. It includes modules to simulate the deposition of acids and other chemicals to dry and aqueous surf aces. It simulates the aqueous phase chemistry that affects precipitation compos ition. There has been less research on deposition and aqueous phase chemistry recently due to reduced concer ns about acid deposition. New process based research may be required to develop the data base that the CMAQ team will need before further development of the SSWR model.



### 4.4 What are your perceptions of the integration across different elements of

the CMAQ modeling program (links among model development, applications, evaluation)? What is your perception of the usefulness of the CMAQ modeling

program to the EPA, states, other customer needs, and research community?

With respect to the usefulness of the CMAQ mo deling program to the EPA, there are areas where the CMAQ group needs to be especially vig ilant. A primary user of CMAQ type tools is OAQPS EPA. While the effort should not be viewed negatively, OAQPS is using a competing model, because CMAQ does not have all the capabil ities they desire (tools to provide source impacts on ozone and particulate matter). If th is capability is important and scientifically appropriate, the group should cons ider adding it. If there ar e scientific reasons why the approaches taken by OAQPS are scientifically le ss well founded, this concern should be clearly
communicated to them.

15The CMAQ group can provide other very important function to EPA. In the recent NOx/SOx secondary NAAQS review, the CASAC panel was crit ical of the level of evaluation provided for the CMAQ simulations. CASAC was cr itical of the approach, specifi cally in reference to the use of CMAQ results in the development of parame ters for the Atmospheric Acidification Index (AAI). Since that time, the EPA Administrator decided that the uncertainties in determining the factors as part of the AAI were too large to go forward using the approach for determining AAI. As a step toward reducing th e uncertainties and preparing fo r the next NAAQS review, the Administrator has proposed a five-year pilot field study. The CMAQ team should be very actively involved in the design and analysis of the pilot field study. Further, the CMAQ team should use this as a platform for a very detaile d evaluation of the modeling system’s ability to provide the needed information, including provi ding well-assessed, quan titative uncertainties, and quantitatively identify the sources of the uncertainties.

The CMAQ group has done a fine job in de veloping CMAQ as a stand-alone model and continues to enhance its strengths. In the future , regional models will not be stand-alone and will require more integration with other models. Ther e will also be pressure to expand the domains where CMAQ is used. Yet, in a time of diminish ing resources, the group will need to be very careful about setting priorities and should focus on doing a limited number of things very well, as opposed to doing many. We recommend that the CMAQ group should continue to develop and enhance the strengths of CMAQ.

Of particular concern is that future model development will require cl ose collaboration with experts who develop other modeling systems. The CMAQ group will need to be careful to choose problems that they contribute their expert ise to. The Division’s role in this expanding community has not yet been articulated and need s to be defined. The user community should be an active participant in he lping the CMAQ group define its future directions.

The CMAQ group has been especially successful in their efforts to continually advance the science to address new problems, increase user confidence, and make the model usable both inside and outside the agency. They need to co ntinue to advance the scientific and application capabilities and articulate the importance of thes e activities to the broader community both inside and outside the agency. If CMAQ were to fa ll behind, other key ac tivities of EPA would
become more vulnerable to outside attack.

The CMAQ group is one of the very few groups wo rldwide that has the expertise and size to develop, maintain, and evolve such a model. This is a unique capability that needs to be maintained. This recognition re-enforces the ne ed to stay focused and not to go beyond their core mission and competencies.

The CMAQ group needs to define and communicate their priority setting process better. This is particularly important and timely because they wi ll soon be searching for a new director. They

16have done well by using their very extensive efforts in model evaluation to identify model development needs. They have also been cogniza nt of their impacts on control strategies. They
should extend their model evaluation culture to ot her groups at EPA. They should also maintain
their international collaborations.



### 4.5 Are there any modeling research areas that are relevant to the EPA’s regulatory program needs not being addressed or given insufficient attention

within the CMAQ Modeling Program? Are there any current areas of research emphasis that could be given a lower priority or eliminated to help advance the

above four ITR areas? Are the resources made available to the CMAQ Modeling
Program being used effectively in terms of the choice and quality of the applied

research being conducted at AMAD in support of the four ITR areas?

The CMAQ group should review their efforts over the past decade to identify their successes, discern the reasons for them, and use this information to help guide their future research. The CMAQ group also needs to be cognizant of the co sts associated with ma intaining the increasing complexity of the models and the data used. This should be actively consid ered in their priority setting process.

There are many groups involved in global modeli ng efforts concerned with projecting future climates based on hypothesized feedback and pro cess assumptions as well as assumed emission scenarios. However, there are few that are i nvestigating process sensitivities or emission sensitivities in detailed retrospective runs. Gi ven the CMAQ team’s successes in recreating the past atmospheres in retrospective studies, this could be a niche that they could play in the global
climate arena.

Throughout the review there were many examples that indicated 1 to 3 ppb changes in ozone
concentrations occurred as a result of im provements the CMAQ team made to the surface albedo, chemical mechanisms, land surface charact eristics, deposition and temperatures. There was not much attention given to cloud errors (misplacement in time and space) in impacting ozone prediction. In past studies with university partners, there were examples [Pour-Biazar et al., 2007] that showed that replacing model tran smittance with satellite derived transmittance made differences of 50 ppb or more dwarfing th e impact of the other changes. While the university partners may have deve loped the core techni ques, they may not be in a position or have the skills to bring this research into an operational framework as well as the core CMAQ team. This may be low hanging fruit that can ma ke a big impact on ozon e prediction that could be facilitated with assistance from the CMAQ team.

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### 5.0 Comments on the Review Process

Copies of the power point files for the talks a nd the posters should be provided to the Committee prior to the review. Assignment s should be given to the review ers ahead of time, e.g., the specific areas that they will be expected to le ad should be identified. The review should begin
with more direct interactions w ith the group leaders (two to four of the high level leaders) and the Committee. The expectations for the review should be discussed and the type of information
that would be most useful should be identifie d. After that, there shoul d be a 30-minute planning meeting of the Review Committ ee to organize their effort.



### 6.0 Panel Recommendations The panel made four recommendations that th ey would like the CMAQ group to implement over the next few years, provided that they ha ve resources to accomplish this. They are:

1. Improve the emission inputs to the CMAQ model, and allocate more resources to the overall task concerned with improving emission inputs to the CMAQ model even if they are taken from another activity. They should enhance colla borations with the developers of emissions data, OAQPS and OTAG.

2. Work with OAQPS and other groups in EPA to help them accomplish their goals. The relationship with OAQPS is st rong, but the CMAQ group needs to be more proactive in anticipating and responding to the needs of OAQPS, the Offi ce of Atmospheric Programs,
the Office of Air and Radiat ion, and other user needs.

3. Improve the connections between CMAQ and othe r models, and as they move forward, they should consider the relationship(s) betw een CMAQ and other models as (e.g., global chemical models, local scale models, and pers onal exposure models), and determine how to best mesh with such a diverse set of platforms.

4. Develop a comprehensive approach to gas-part icle interactions, and continue to improve their treatment of secondary aerosol (inorganic and organic) formation.

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### 7.0 References

Buzcu, B., Z. W. Yue, M. P. Fraser, V. Nopmongcol and D. T. Allen “Secondary particle formation and evidence of heterogeneous chem istry during a wood smoke episode in Texas,” Journal of Geophysical Research, II, DIOS13, doi: 10.1029/2005JD 006143, 2006)

O'Brien J.J., 1970: Alternative solutions to the classical vertical velo city problem. J. Appl. Meteor., 9, 197-203.

Pleim, J.E., 2007: A combined local and non-lo cal closure model for the atmospheric boundary layer. Part 1: Model description and te sting. J. Appl. Meteor. Climatol., 46, pp 1383-95.

Pour-Biazar, Arastoo, et al. (2007), Correcting photolysis rates on th e basis of satellite observed
clouds

, J. Geophys. Res , 112, D10302)

19CMAQ PEER REVIEW MEETING

June 27-29, 2011

Agenda

June 27 (Room C112 )

8:30am Refreshments

9:00am ORD Research Directions: Integrated Trans-disciplinary Research (Bob Dyer; Director, NERL)

9:15 am Purpose and Charge to Panel (ST Rao)

9:30 am Summary of 2006 Review Reco mmendations and AMAD Response/Progress (Rohit Mathur)

10:30 am BREAK

11:00 am Using evaluation to shape impr ovements and provide guidance for model development (v4.6 to v4.7 to v5.0) (Tom Pierce)

12:00 LUNCH

1:00-4:00pm POSTER SESSION and Interaction with AMAD Scientists ( Building B Atrium )

Diagnostic Evaluation (multiple topics)

1. Diagnostic analysis of carbonaceous aerosol predictions by CMAQ (Prakash Bhave) 2. Improving meteorology and climate simula tions using Four Dimensional Data Assimilation (Rob Gilliam)

Operational Evaluation

3. Incremental testing and evalua tion of CMAQv4.7 (Shawn Roselle) 4. Application of the CMAQ model fo r the Air Quality Model Evaluation International Initiative (AQMEII) (Wyatt Appel)

Enhancements

5. DDM implementation, development, a nd application (Sergey Napelenok)

20Dynamic Evaluation

6. Recent Dynamic Evaluation Studies of the CMAQ Model (Jim Godowitch)

Probabilistic Evaluation

7. Probabilistic Evaluation of AQ Models: Motivation, Concepts, and Applications (Kristen Foley)

Emerging Application Needs

8. Model applications motivate CMAQ model development and evaluation (Ken Schere)

4:00pm Overview of CMAQv5.0 (Rohit Mathur)

June 28 (Room C111B )

8:30am Recap of Day 1 and Questions from Panel

9:00am-Noon: CMAQv5.0: Updates to process m odules (20 min talk +10min discussion)

9:00am Atmospheric Chemistry Mechanisms in CMAQ (Deborah Luecken)

9:30am Treatment of Aerosol Processes (Golam Sarwar)

10:00am Characterization and Modeling of Emissions (George Pouliot)

10:30am BREAK

11:00am Representation of Tran sport Processes (Jon Pleim)

11:30am Advancements in the science and app lications of CMAQ air-surface exchange (Jesse Bash)

12:00 LUNCH

1:00pm WRF-CMAQ 2-way model: Ov erview (Jon Pleim/Rohit Mathur)

2:00-5:00pm POSTER SESSION and Interact ion with CMAQ GROUP Scientists ( Building B Atrium )

21Chemistry

1. Major changes of gas phase chemistry in CMAQv5.0 (Bill Hutzell) 2. Improving the treatment of oxidized nitrogen (Rob Pinder) 3. Understanding the impact of isoprene nitrates and OH reformation on regional air quality using recent advances in isoprene photo-oxidation (Ying Xie)

Aerosol updates

4. Speciation of PM other in CMAQ (Heather Simon)

Emissions

5. Improvements in characterization of em issions for air quality modeling (Tom Pierce)

Deposition

6. Enhanced Land Surface and Land Management Treatments for CMAQ Air Surface Exchange (Ellen Cooter/Donna Schwede/Robin Dennis)

Computational and Structural Aspects

7. Making CMAQ more user friendly (Jeff Young) 8. Numerical models on high performance co mputing (HPC) systems (David Wong)

Hemispheric Extensions

9. Hemispheric Extensions of CMAQ: Motiv ation, Challenges, and Progress (Rohit Mathur)

June 29 ( Room C112 )

8:30am Recap of Day 2 and Questions from Panel

9:00am Panel work time

11:30am Debriefing to AMAD Management and PIs

12:00noon END OF PEER REVIEW MEETING

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