Lakes Environmental Newsletter
Lakes Software Monthly Newsletter


Monthly Newsletter - August 2021

Announcing the Launch of our New Website!

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Lakes Environmental is excited to announce the launch of our brand-new website!

Our main goal in launching this new website is to provide our clients and others with a more intuitive and user-friendly experience that clearly presents our unique software products, training, and services and showcases what they can help you accomplish in a fraction of the time!

The website features a refreshed look, improved navigation, as well as features that will provide a better overall experience on your desktop, smart phone, or tablet.

If you have any suggestions or feedback, feel free to let us know at

We hope you enjoy our new website! Click here to check it out!

Addendum to July 2021 Modeling Tip

Please find below a link to an amended version of the modeling tip found in the July 2021 edition of the Lakes Environmental Newsletter. This tip discusses the U.S. EPA bug in AERMOD 21112 regarding PVMRM.

The original article stated that background ozone is incorporated twice and should therefore be halved when input into the model. However, it should be noted that the AERMOD 21112 bug applies to background NO2, not ozone.

Online CALPUFF Course – Sep 28-29, 2021 - Only a Few Spots Left!

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Our team will present 2 days of online CALPUFF training on September 28 and 29, 2021 from 8:30am to 5:00pm (UTC-6). The same great course, now from the convenience of your home or office!

Space is limited. Register today!


CALPUFF (Sep 28-29, 2021)



Online AERMOD Course – Oct 26-27, 2021

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Spots are already filling fast for our 2-day online AERMOD course taking place on October 26 and 27, 2021 from 8:30am to 5:00pm (Central Time UTC-6).

Don't miss out! Register today!

Note: Due to the immense popularity of our online courses and small class sizes, we recommend registering and making payment as soon as possible.


AERMOD (Oct 26-27, 2021)



Lakes Environmental Closed for Labour Day Holiday

Lakes Environmental’s offices will be closed on Monday, September 6, 2021 to observe the Labour Day holiday. If you have any support needs during that time, please e-mail us at and we will contact you on Tuesday, September 7, 2021 when our offices reopen.


2021 Course Schedule

Sep 28-29, 2021
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Oct 26-27, 2021
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Dec 7-8, 2021
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Jan 18-19, 2022
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Grouping Options in AERMOD’s Source Pathway

The AERMOD air dispersion model features many different settings which provide users the ability to customize how model output is presented. Within the model’s Source Pathway are multiple options for grouping sources, but just what do all these different groups mean? Below is a look at each type.

Source Groups

AERMOD natively calculates impacts from each modeled source independently from others. Source Groups (model option SO SRCGROUP) are a way for users to depict impacts from combinations of sources. This is a mandatory option in the model with a default group set to ALL which reports the cumulative impacts from all sources combined. Groups can have as few as a single source or a combination of multiple sources.

The screenshot below depicts source group settings in AERMOD View. In this example, different groups are used to combine output from sources of the same process (e.g., boilers, exhausts, etc.). This provides a better understanding of impacts from a subset of sources providing context to which sources may contribute to maximum cumulative concentrations.

Each group will have its results tabularized in the main output file and its own unique set of output files. Options for the output files can be set in the Output Pathway.

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Source Groups Example

Buoyant Line Groups

The buoyant line source – taken from the Buoyant Line & Point (BLP) model – was originally incorporated into AERMOD with the 15181 model release. A new feature in AERMOD 21112 gives modelers the ability to group subsets of buoyant lines with different average properties. This allows modelers to depict sets of buoyant lines with different orientations and average properties.

In AERMOD View, the Source Pathway when modeling with AERMOD 21112 includes the Buoyant Line Groups settings. Modelers can still use a single set of average properties for all lines, but they can also separate sets of lines into their own groups as depicted in the example below.

Modeling Tip picture

NO2 Groups: OLM & PVMRM

The Tier 3 screening methods for assessing nitrogen dioxide concentrations – the Ozone Limiting Method (OLM) and Plume Volume Molar Ratio Method (PVMRM) – have their own unique grouping options that aid the model in calculating the ratios of total NOX, ozone, and NO2 in the ambient environment.

OLM gives users the ability to combine plumes from individual sources for the purposes of determining how much ambient ozone is available for the NO to NO2 conversion process. For example, an individual source with its own OLMGROUP will be modeled assuming all ambient ozone is available for the conversion process.

The OLMGROUP ALL setting which combines plumes of all sources in the model run is broadly recommended by the U.S. EPA whenever OLM is applied. AERMOD View users will find that the OLMGROUP ALL function is automatically enabled when selecting the OLM option.

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OLM Groups with OLMGROUP ALL Enabled

The other NO2-specific grouping feature is the PSD Groups function (model option PSDGROUP). This is a non-default ALPHA option which means the Non-Default Regulatory Options must be enabled on the Control Pathway.

With this grouping function, Source Groups are replaced with three predefined groups in which sources can only appear in a single group:

  1. INCRCONS – new or modified existing sources that are consuming increment
  2. NONRBASE – the existing non-retired baseline sources
  3. RETRBASE – retired (increment-expanding) baseline sources

Once set, the model calculates the net increment consumption ([INCRCONS + NONRBASE] – [NONRBASE + RETRBASE]).

Modeling Tip picture
PSD Groups for Calculating PSD Increment Consumption

Urban Groups

The final grouping function AERMOD View users will see on the Source Pathway are the Urban Groups. This setting is tied to use of the Urban dispersion coefficient on the Control Pathway’s Pollutant/Averaging options. Here, users can define if there is a single urban group applied to all sources or if multiple urban groups exist in the modeling domain. Each group must have a Population value defined as described in Section 5.2 of the U.S. EPA’s AERMOD Implementation Guide.

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Urban Groups in AERMOD View



Oceans Primed for Peak of Hurricane Season

August 13, 2021 - Sea surface temperatures are a fair predictor of the readiness of the ocean to fuel and sustain storms.

Read more →

After Historic Hurricanes Eta and Iota, NASA Helps Prep Central America for Disasters to Come

August 12, 2021- Shortly after Category 4 Hurricane Iota began to drench Central America on Nov. 16, 2020, Claudia Herrera watched from a helicopter as ruinous flood water inundated entire neighborhoods of La Lima, in Honduras’ Valley of Sula. In just three days, the catastrophic rainfall of Iota had flooded Ramon Villeda Morales International Airport in La Lima, as well as schools, healthcare centers, and other critical infrastructure in a region that serves as the country’s main economic engine.

Read more →

Additional Environmental News

Visit the Environmental News Network (ENN), the most dependable online environmental news source!



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