Understand the Process

Sum

CESM requires summed values for most species, except for sulfate, which is sector-specific. The FV.sum_up function allows users to aggregate the CEDS data downloaded via Globus. The download data is stored in input_path and the aggregated data is saved in preregrid_path for subsequent processing. In contrast, data obtained using Wget is already pre-summed.

Regrid

Consistent with IPT, we use the conservative regridding algorithm from ESMF. For a detailed explanation, refer to the ESMF Regridding methods. To regrid emission data from high to low spatial resolution, FV.generate_regridder creates a regridder, which is automatically saved as regridder_filename. Then, FV.apply_regridder applies the regridder to data stored in preregrid_path and saves the output in regridded_path. Notably,FV.apply_regridder regrids salfate emission by sectors, while all other species are processed as summed values.

Rename

FV.rename convert emission from the original unit \(kg/m^2 s\) to \(\text{molecules}/{cm}^2~s\) based on the Equation 1:

\[ E_{converted} = E_{original} \times \frac{N_A}{M} \times \frac{10^3}{10^4}, \tag{1} \]

where \(E_{\text{original}}\) is the emission in \(kg/ m^{2}~ s\), \(E_{\text{converted}}\) is the emission in \(\text{molecules}/cm^{2} ~s\), \(N_A\) is Avogadro’s number (\(6.022 \times 10^{23}\) molecules/mol), \(M\) is the molecular weight of the species in g/mol, \(10^3\) accounts for the unit conversion from \(kg\) to \(g\), \(10^4\) accounts for the unit conversion from \(m^2\) to \({cm}^2\) .

Besides, scale factors are applied to adjust emissions based on specific assumptions or corrections. These factors can account for uncertainties, regional variations, or improvements in emission estimates (Equation 2):

\[ E_{scaled} = E_{converted} \times \textrm{SF}, \tag{2} \]

where \(E_{\text{scaled}}\) is the adjusted emission, \(E_{\text{converted}}\) is the emission converted from the original unit, \(\text{SF}\) is the scale factor, which varies based on species, regions, or datasets. Table 1 list the default molecular weight (\(M\)) and scale factor (\(SF\)) that FV.rename automatically assigns based on the model_var_list. Users can also specify custom values using mw_mapping and sf_mapping.

Table 1 Lists of molecular weight (\(M\)) and scale factors (\(\text{SF}\)).

Variable name	Molecular weight (\(M\))	Scale factor (\(\text{SF}\))
bc_a4[1]	12	1
CO	28	1
NH3	17	1
NO	30	\(\frac{46}{30}\)
pom_a4[2]	12	1.4*OC[3]
SO2	64	1
C2H6	30	1
C3H8	44	1
C2H4	28	1
C3H6	42	1
C2H2	26	1
BIGENE	56	1
BENZENE	78	1
TOLUENE	92	1
CH2O	30	1
CH3CHO	44	1
BIGALK	72	1
XYLENES	106	1
CH3OH	32	0.15*alcohols
C2H5OH	46	0.85*alcohols
CH3COCH3	58	0.2*ketones
MEK[4]	72	0.8*ketones
HCOOH	46	0.5*acids
CH3COOH	60	0.5*acids
IVOC[5]	184	0.2*HCs[6]
butanes	58	/
pentanes	72	/
hexanes	86	/
esters	184	/
ethers	81	/
xylene	106	/
trimethylbenzene	120	/
other-aromatics	126	/
SVOC[7]	310	0.6*pom_a4[6]
HCN	27	0.003*CO
CH3CN	41	0.002*CO

• HCs include: C3H6, C3H8, C2H6, C2H4, BIGENE, BIGALK, CH3COCH3, MEK, CH3CHO, CH2O, BENZENE, TOLUENE, XYLENES[8].

CESM also requires the number of bc_a4, pom_a4, and SO2, which is calculated using Equation 3:

\[ num = \frac{\text{particles} \times M}{f}, \tag{3} \]

where \(num\) is the number of particles (unit: \(\left(\frac{\text{particles}}{\text{cm}^2~ \text{s}}\right)\left(\frac{\text{molecules}}{\text{mole}}\right)\left(\frac{\text{g}}{\text{kg}}\right)\)), \(\text{particles}\) is the total mass of the particles. \(f\) is the mass per particle, calculated by Equation 4:

\[ f = \rho \times \frac{\pi}{6} \times {\text{diam}}^3, \tag{4} \]

where \(\rho\) is the density, \(\frac{\pi}{6}\) is a geometric factor that accounts for the volume of a sphere, \(\text{diam}^3\)​ is the cube of the particle’s diameter.

Table 2 List of density (\(\rho\)) and diameter (\(diam\)).

Variable name	\(\rho\) (Unit: \(g/cm^3\))	\(\text{diam}\) (Unit: \(cm\))
num_bc_a4	1700	0.134e-6
num_so4_a1 for emiss_ag_sol_was	1770	0.134e-6
num_so4_a1 for emiss_ship	1770	0.261e-6
num_so4_a2 for emiss_res_tran	1770	0.0504e-6
num_so4_a1_anthro-ene-vertical for emiss_ene_ind	1770	0.261e-6
num_pom	1000	0.134e-6

Given that ESMF does not support for regridding mutiple-dimensional data, IPTpy can not generate vertial emission data yet. However, we only generate verticle anthropogenic emission data for so4_a1_anthro-ene-vertical for altitudes of 0.175, 0.225, 0.275, 0.325 \(km\) based on Equation 5:

\[ \operatorname{so4\_a1\_anthro-ene-vertical} = \frac{0.025 \times (ene + ind)}{2e4}, \tag{5} \]

where \(ene\) and \(ind\) denotes SO2 surface emission from energy and industrial sectors.

Notes

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[1]

Emitted black carbon (bc_a4)

[2]

Primary organic matter (pom_a4)

[3]

Fan, T., Liu, X., Ma, P. L., Zhang, Q., Li, Z., Jiang, Y., … & Wang, Y. (2018). Emission or atmospheric processes? An attempt to attribute the source of large bias of aerosols in eastern China simulated by global climate models. Atmospheric Chemistry and Physics, 18(2), 1395-1417. https://doi.org/10.5194/acp-18-1395-2018

[4]

Methyl Ethyl Ketone (MEK)

[5]

Intermediate Volatile Organic Compound (IVOC)

[6] (1,2)

Jo, D. S., Tilmes, S., Emmons, L. K., Wang, S., & Vitt, F. (2023). A new simplified parameterization of secondary organic aerosol in the Community Earth System Model Version 2 (CESM2; CAM6. 3). Geoscientific Model Development, 16(12), 3893–3906. https://doi.org/10.5194/gmd-16-3893-2023

[7]

Semi-Volatile Organic Compound (SVOC)

[8]

Notes for MOZART-T1 chemistry with MAM4 aerosols in CESM2