CMAQv5.4 Release Notes: Instrumented Models - fisidi/CMAQ Wiki

CMAQ-ISAM

Sergey L. Napelenok, U.S. Environmental Protection Agency
Type of update: Science Update
Release Version/Date: CMAQv5.4
Description:
The changes to ISAM include the added flexibility for the user to define how secondarily formed gaseous species are assigned to sources of parent reactants. Previously, daughter products were always assigned equally among the parents. However, in some applications, particularly in O3 apportionment, other assignment schemes are desired and requested by the users. The following options are now available in CMAQ-ISAM:

Option 1. Equal assignment (previous version).

Option 2. If parent reactants include the species NO, NO2, NO3, HONO, or ANO3, assignment to these sources only. Reactions without these species proceed with equal assignment.

Option 3. Option 2 with species list expanded to include reactive VOC species and radicals. Reactions without these species proceed with equal assignment.

Option 4. If parent reactants include the reactive VOC species and radicals, assignment to these sources only. Reactions without these species proceed with equal assignment.

Option 5. Assignment is based on the ratio of production H2O2 to production HNO3. Reactions without the nitrogen species listed above and reactive VOCs proceed with equal assignment.

Additionally, the transitional value for Option 5 is also customizable (default is PH2O2/PHNO3=0.35).

Significance and Impact: The changes here allow for greater ISAM user flexibility. Please, refer to the User's Guide chapter on ISAM for additional information.
References: Internal PRs PR#473, PR#571, PR#579, PR#620, PR#644, PR#649, PR#650, PR#655, PR#661, PR#657, PR#676, PR#699, PR#778, PR#698, PR#675

CMAQ-ISAM tagclasses for Hazardous Air Pollutants (HAPs)

William T. Hutzell, U.S. Environmental Protection Agency
Type of update: New Feature
Release Version/Date: CMAQv5.4
Description: Several tagclasses were added to CMAQ-ISAM to track the source contributions for HAPs. The below table lists the tagclasses and their HAPs.

Tagclass Name HAPS1
HAP_GAS formaldehyde, acetaldehyde, 1,3-butadiene, acrolein, molecular chlorine
HAP_AERO aerosol bound nickle, lead, trivalent chromium, hexavalent chromium, beryllium, cadium, deisel emissions, manganese from the Air Toxics Inventory, and arsenic
PAH_TEQ Polycycle Aromatic Compounds lumped based on Toxic Equivalancy Quotient
MERCURY Gas and Aerosol Phases of Atmospheric Mercury
BENAPYRENE Gas and Aerosol Phases of Benzo[a]pyrene
  1. The exact species available per Tagclass depends on the chemical mechanism and the name-lists used.

Significance and Impact: Based on the chemical mechanism used, the new tagclasses allow simulating how the emissions source contribute to concentrations and deposition of HAPS in air toxic assessments.
Internal PRs: PR#922, PR#887, PR#773, PR#699

CMAQ-DDM-3D

Sergey L. Napelenok, U.S. Environmental Protection Agency
Type of update: Science Update
Release Version/Date: CMAQv5.4
Description:
Significance and Impact:
References:
Internal PRs: PR#xxx

Speed up DDM3 solution of Gas Chemistry Sensitivities

William T. Hutzell, U.S. Environmental Protection Agency
Type of update: Science/Numerical Update
Release Version/Date: CMAQ version 5.4

Description: In DDM3D's method for solving sensitivities from gas chemistry, code changes shortened CMAQ_DDM3D runtimes by 15% to 35% dependent on the chemical mechanism used. The changes also implemented DDM3D's approach for gas chemistry in the Rosenbrock and SMVGear solvers so CMAQ_DDM3D can use any of the available gas chemistry solvers. The option better supports using CMAQ_DDM3D built with the cb6r5m_ae7_aq mechanism because the Rosenbrock solver is recommended for the cb6r5m_ae7_aq mechanism.

Changes reduced runtimes by modifying setting and calculating the gas chemistry Jacobian. The modification reorders chemistry species defining the Jacobian's rows and columns based on the number of nonzero values in rows for each chemistry species. The number measures the coupling of a species to other chemistry species. The reordering seeks to put the Jacobian closer to a lower triangular matrix and simplify the LU decomposition of the chemistry Jacobian used by CMAQ_DDM3D. It may also make the process more accurate by reducing the number of floating operations.

Significance and Impact:

Changes have no impact of predicted concentrations and deposition of the base model species but they do altered sensitivity predictions from the DDM3D algorithm by a few percent or less. The exception is for sulfur dioxide and aerosol sulfate in the accumulation mode. Tests that turned off cloud chemistry removed this exception and may indicate that DDM3D has feedback between gas and cloud chemistry regarding predicted sensitivities for sulfate production. Overall the code change reduce DDM3D runtime and allow the CMAQ_DDM3D to used an EBI solver for the chemical mechanism, or a generalized chemistry solver such Rosenbrock and SMVGear

Internal PRs: PR#935, PR#630

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