CMAQv5.4 Release Notes: Instrumented Models: 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
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 |
- 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
