# Presentation: 825324

## GMI Box Model Intercomparison Update

- D. B. Considine, J. R. Olson, P. S. Connell
- GMI Science Team Meeting
- Fall, 2003

## History

-  GMI needs a strat/trop combined chemical mechanism/
-    solver to create a combined version of GMI.
-  NASA LaRC has such a mechanism which is currently
-    incorporated into two global models.
-  Science team decided 11/2002 that box model
-    intercomparison with other combined mechanisms/
-    GMI-trop/GMI-strat was appropriate 1st step.
-  What are the differences between LaRC
-    mechanism and others
-  Are differences reasonable and understandable?

## Summary of Recent Activities

-  Ported “GMI Box Model” to LaRC
-  Fixed a few coding errors in model
-  Completed initial comparison of GMI trop chem
-    mechanism with LaRC combined solver
-  Implemented “Carter 4-product” isoprene scheme
-   in LaRC solver
-  Completed box model testing of isoprene scheme,
-   currently doing global model testing.

## Box Model Intercomparison Description

-  9 scenarios: 5 “baseline,” 4 “non-methane hydrocarbon”
-  Standardized photolysis coefficients from Kawa lookup
-  Some standardized reaction rates - JPL 00
-  Scenarios run for 10 days, no emissions, start at 00 Z
-  GMI box model with trop chem scheme
-  Same reactions as global model
-  Solver is “DLSODE,” Hindmarsh’s stiff ODE scheme
-    instead of SMVGEAR (both GEAR solvers)
-  LaRC box model with LaRC combined scheme
-  Not a Gear solver - PCE assumptions, families, etc.
-  1/2 hr time step
-  55 transported species, 86 calculated
-  220 thermal rxns, 50 photolysis rxns
-  NMHC scheme different from Harvard approach

## Scenario Descriptions

| Run | Month | Altitude | Init O3 | Init NOx | Init HC |
| --- | --- | --- | --- | --- | --- |
| BL 1 | July | Surface | Medium | High | No |
| BL 2 | Nov | Surface | Low | High | No |
| BL 3 | Nov | Surface | Medium | High | No |
| BL 4 | July | Surface | Medium | Low | No |
| BL 5 | Nov | 236 hPa | High | Low | No |
| HC 1 | Nov | Surface | Medium | High | High |
| HC 2 | July | Surface | Medium | High | High |
| HC 3 | Nov | 365.5 hPa | Medium | High | High |
| HC 4 | Mar | 694.7 hPa | Medium | Low | Low |

- Temperature = 15oC except in lofted cases

## LaRC Run Versions

-  Peroxide oxidation branching matched to GMI
-  Organic nitrate production matched to GMI
-  RO2 + NO branching matched to GMI

-  Standard
-  Revised 1: Remove NO3 + peroxy radical rxns
-  Revised 2: Revised 1 + ...

- I have the specific changes if you want
- to see them ...

## Nov

- Med O3
- High NOx

- Low O3
- High NOx

- July, Med O3, High NOx

- July
- Med O3
- Low NOx

- Nov, 236 mbar
- High O3
- Low NOx

- Nov, Med O3,High NOx

- July
- Med O3
- High NOx

- 365.5 mbar
- Med O3
- High NOx

- March
- Med O3
- Low NOx
- Low NMHC

- 694.7 mbar

##  LaRC is within ~10% of GMI

-   in all cases after 10 days.
-  BL2 case (low O3, low sun),
-   shows sunrise/set discrepancies.
-  BL 5 case (low NOx, low sun,
-   mid troposphere) shows very
-   close agreement.
-  HC 3 case (urban lofted, low
-    sun) disagrees in trend.
-  LaRC more frequently
-   underestimates O3
-   relative to GMI.

## Slide 9

## LaRC NO2 diurnal cycle typically agrees well with GMI.  Revision 1 improves

- nighttime agreement substantially.  HC3, HC4 cases do not agree well.

## NO3 nightime agreement improved by revision 1 in baseline 1, 3, and hydrocarbon 2.

- Agreement worsened in hydrocarbon 1,3, 4.

## OH generally agrees well between LaRC and GMI mechanisms.  In HC 1 and HC 3

- cases LaRC OH is higher (Note - in these cases HO2 is lower).

## CH3OOH agreement is sometimes good, and sometimes substantially underpredicted

- by LaRC compared to GMI (HC1, HC3).  This is likely due to higher OH/HO2 ratio.

## Slide 14

## Slide 15

## Slide 16

## Summary and Conclusions

-  LaRC O3 time series in good agreement with GMI-Trop:
- Differences ~ ±10% after 10 day simulation
-  Largest discrepancies in urban lofted case substantially
-    improved by kinetic revisions
-  Suggests differences are understandable and not
-    related to formulation (species choices, etc).
-  High sensitivity to basic assumptions about NMHC
-    reactions
-  Additional scenarios to test isoprene mechanism, addition
-   of emissions could be undertaken.
-  LaRC combined chemical scheme is a viable candidate for
-    inclusion in GMI Global.
-  Intercomparison of (tropospheric) solvers in global
-   model following box model intercomp publishible?