Mean OH concentration
On this page we track the evolution of the mean OH concentration in GEOS-Chem. This value is an indicator of how "hot" the chemistry is. Please also see the related topic about the methyl chloroform lifetime in GEOS-Chem.
Computation of the mean OH diagnostic
Routine DO_DIAG_OH (in module GeosCore/diag_oh_mod.F) sums up the tropospheric air mass and mass-weighted OH mass after each call to the chemistry solver. The summing happens in these lines of code:
! Skip non-chemistry boxes
IF ( .not. State_Met%InChemGrid(I,J,L) ) CYCLE
! Dry air density [molec/cm3]
! Cast to REAL*8 to avoid underflow
AIRDENS_8 = State_Met%AIRNUMDEN(I,J,L)
! Box volume [cm3]
! Cast to REAL*8 to avoid underflow
VOLUME_8 = State_Met%AIRVOL(I,J,L) * 1e+6_fp
! Sum air mass term into AIR_MASS array
XAIRMASS = AIRDENS_8 * VOLUME_8
AIR_MASS(I,J,L) = AIR_MASS(I,J,L) + XAIRMASS
! Sum OH mass term into OH_MASS array
XOHMASS = State_Chm%Species(I,J,L,id_OH) * XAIRMASS
OH_MASS(I,J,L) = OH_MASS(I,J,L) + XOHMASS
where the arrays contain the following quantities:
I,J,L = 3-D array indices AIRDENS_8 = air density [molec/cm3] VOLUME_8 = grid box volume [cm3] AIR_MASS(I,J,L) = air mass [molec air] State_Chm%Species(I,J,L,id_OH) = OH concentration [molec OH/cm3] OH_MASS(I,J,L) = mass-weighted OH = OH mass * air mass [molec OH/cm3 * molec air]
After the GEOS-Chem simulation finishes, the mean OH value is printed out in subroutines PRINT_MEAN_OH (in module GeosCore/diag_oh_mod.F):
! Total Mass-weighted OH [molec OH/cm3] * [molec air]
SUM_OHMASS = SUM( OH_MASS )
! Atmospheric air mass [molec air]
SUM_MASS = SUM( AIR_MASS )
! Divide OH [molec OH/cm3 * molec air] by [molec air] and report as [1e5 molec/cm3]
OHCONC = ( SUM_OHMASS / SUM_MASS ) / 1d5
! Write value to log file
WRITE( 6, '(/,a)' ) REPEAT( '=', 79 )
WRITE( 6, * ) 'ND23: Mass-Weighted OH Concentration'
WRITE( 6, * ) 'Mean OH = ', OHCONC, ' [1e5 molec/cm3]'
WRITE( 6, '( a)' ) REPEAT( '=', 79 )
Typical values are around 105 or 115 molec/cm3.
--Bob Yantosca (talk) 19:43, 29 March 2018 (UTC)
Evolution of mean OH in GEOS-Chem
Plot of mean OH evolution
Here is a plot of the mean OH concentration from GEOS-Chem 1-year benchmark simulations through version 12.8.0 (released 04 May 2020). The mean OH is an indicator how the chemistry mechanism is performing. Typical values are 10–12 x 105 molecules cm-1.
--Melissa Sulprizio (talk) 02:17, 13 August 2023 (UTC)
Mean OH in GEOS-Chem 12
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
Mean OH in GEOS-Chem v11
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
--Bob Yantosca (talk) 18:12, 29 March 2018 (UTC)
Mean OH in GEOS-Chem v10
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
| Benchmark | Met Fields & Year | Mean OH [105 molec cm-3] |
Change from prev. version [105 molec cm-3] |
Important updates in this benchmark simulation | References |
|---|---|---|---|---|---|
| v10-01i-Run0 | GEOS-FP 2013 | 11.125 | 0.033 (0.298%) |
| |
| v10-01h-Run0 | GEOS-FP 2013 | 11.092 | -0.751 (-6.341%) |
|
|
| v10-01e-Run1 | GEOS-FP 2013 | 11.843 | -0.042 (-0.353%) |
| |
| v10-01c-Run1 | GEOS-FP 2013 | 11.885 | -0.665 (-5.299%) |
| |
| v10-01c-Run0 | GEOS-FP 2013 | 12.550 | -0.139 (-1.095%) |
|
--Bob Yantosca (talk) 18:12, 29 March 2018 (UTC)
Mean OH in GEOS-Chem v9
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
--Bob Yantosca (talk) 18:12, 29 March 2018 (UTC)
Mean OH in GEOS-Chem v8
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
| Benchmark | Met Fields & Year | Mean OH [105 molec cm-3] |
Change from prev. version [105 molec cm-3] |
Important updates in this benchmark simulation | References |
|---|---|---|---|---|---|
| v8-02-04-Run2 | GEOS-5.1.0 2005 | 11.067 | +0.019 (+0.17%) |
|
|
| v8-02-04-Run1 | GEOS-5.1.0 2005 | 11.048 | +0.598 (+5.72%) |
|
|
| v8-02-04-Run0 | GEOS-5.1.0 2005 | 10.450 | -1.362 (-11.53%) |
|
|
| v8-02-01-Run0 | GEOS-5.1.0 2005 | 11.812 | +0.713 (+6.42%) |
|
|
| v8-01-04-Run2 | GEOS-5.1.0 2005 | 11.099 | +0.805 (+7.82%) |
|
|
| v8-01-04-Run1 | GEOS-5.0.1 2005 | 10.294 | -0.395 (-3.69%) |
|
|
| v8-01-04-Run0 | GEOS-5.0.1 2005 | 10.689 | -1.351 (-11.22%) |
||
| v8-01-01-Run1 | GEOS-5.0.1 2005 | 12.040 | +0.034 (+0.28%) |
|
|
| v8-01-01-Run0 | GEOS-5.0.1 2005 | 12.006 | -0.141 (-1.16%) |
|
--Bob Yantosca (talk) 18:11, 29 March 2018 (UTC)
Additional information for GEOS-Chem v8
- Differences in isoprene between v8-02-04-Run1 and v8-02-04-Run0
- Differences between MODIS LAI and AVHRR LAI
--Bob Yantosca (talk) 19:12, 29 March 2018 (UTC)
Mean OH in GEOS-Chem v7
The following table chronicles the evolution of the mean OH value from several different GEOS-Chem simulations. All benchmark simulations were conducted at 4° x 5° resolution unless noted otherwise.
| Benchmark | Met Fields & Year | Mean OH [105 molec cm-3] |
Change from prev. version [105 molec cm-3] |
Important updates in this benchmark simulation | References |
|---|---|---|---|---|---|
| v7-04-13-Run | GEOS-4 2005 | 12.147 | -0.669 (-5.22%) |
||
| v7-04-12-Run2 | GEOS-4 2005 | 12.816 | +1.053 (+8.95%) |
|
|
| v7-04-12-Run1 | GEOS-4 2005 | 11.763 | -0.68 (-5.5%) |
|
|
| v7-04-02-MEGAN | GEOS-4 2001 | 12.44 | -0.11 (-0.87%) |
|
|
| v7-04-02-NOMEGAN | GEOS-4 2001 | 12.55 | +0.01 (+0.08%) |
|
|
| v7-04-02-Base | GEOS-4 2001 | 12.54 | +0.67 (+5.6%) |
|
|
| v7-02-03-Run1 | GEOS-4 2001 | 11.87 | +1.39 (+13.26%) |
|
|
| v7-02-03-Run0 | GEOS-3 2001 | 10.48 | --- |
|
--Bob Yantosca (talk) 18:11, 29 March 2018 (UTC)
Additional information for GEOS-Chem v7
- Rynda Hudman investigated the changes in CO and O3 among benchmark simulations from v7-02-03 thru v7-04-12.
- List of differences in benchmark simulations between v7-02-03 and v7-04-02.
- List of differences in benchmark simulations between v7-04-02 and v7-04-12.
- Changes in anthropogenic NOx and CO from 1-yr benchmarks with versions v7-02-03 and v7-02-04
- Jennifer Logan looked at some of the differences between GEOS-3 and GEOS-4 in 1-year benchmark simulations.
--Bob Yantosca (talk) 19:13, 29 March 2018 (UTC)
