See Kemppinen et al. 2022 for documentation of the approach. In the following is some brief document of the particlular characteristics of specific optical tables generated, sorted by a carefully thought out versioning scheme!
This version retunes some of the particle property definitions to allow for non-truncated lognormal distributions for BC/BR/OC/SU and introduces lognormal bins for SS. The objective is to provide smoother distributed optical properties for OSSE and retrieval work. Some tuning is done to approximately get spectral extinction similar to v2.0.0 optics.
For BC/BR/OC/SU the maximum radius is extended to 5 microns. Retuned particle properties are:
| Species | rnum [um] | sigma | Notes |
|---|---|---|---|
| BC | 0.0118 | 2.0 | bc.v5_7.json |
| OC | 0.0212 | 2.12 | oc.v12_7.json |
| BR | 0.0212 | 2.12 | brc.v12_7.json |
| SU | 0.0695 | 1.77 | su.v5_7.json |
For SS the following properties are assumed
| Bin | rnum [um] | sigma | rMin [um] | rMax [um] | Notes |
|---|---|---|---|---|---|
| 1 | 0.0236 | 2.0 | 0.005 | 1.0 | ss.v2.0.1.json |
| 2 | 0.07985 | 2.0 | 0.01 | 3.0 | ss.v2.0.1.json |
| 3 | 0.3224 | 2.0 | 0.1 | 10.0 | ss.v2.0.1.json |
| 4 | 0.7676 | 2.0 | 0.1 | 30.0 | ss.v2.0.1.json |
| 5 | 2.209 | 2.0 | 0.5 | 50.0 | ss.v2.0.1.json |
This version is intended to be as close as possible to the legacy IDL-based tables, which in turn are mainly based on OPAC-like assumptions of particle properties (growth factor and complex refractive index). Some details are made explicit in Chin et al. 2002 and Colarco et al. 2010. Specific details are provided in the JSON files in the geosparticles sub-directory and additional information in Kemppinen et al. 2022.
Following Chin et al. 2002 the particle size distributions are lognormal modes specified in terms of number mode median radius (in microns) with a given width and truncated at 0.3 micron radius (dry particle). Growth factors specify the ratio of wet-to-dry particle radius at the given RH. Refractive indices are given spectrally for the dry particles and are volume weighted with water refractive index to give an effective refractive index for the Mie calculations. For each of the carbonaceous species there are two size modes: the first mode is hydrophobic (undergoes no growth with RH) and the second mode is hydrophilic (grows with RH with specified growth factor). Dry particle refractive indices are from OPAC (soot00 for BC; waso00 for OC; waso00 is used for BR from wavelengths >= 550 nm and follow Colarco et al. 2017 for shorter wavelengths).
| Species | rnum [um] | sigma | Density [kg m-3] | Notes |
|---|---|---|---|---|
| BC | 0.0118 | 2.0 | 1000 | bc.json |
| OC | 0.0212 | 2.20 | 1800 | oc.json |
| BR | 0.0212 | 2.20 | 1800 | brc.json |
Following Chin et al. 2002 the particle size distributions are lognormal modes specified in terms of number mode median radius (in microns) with a given width and truncated at 0.3 micron radius (dry particle). Growth factors specify the ratio of wet-to-dry particle radius at the given RH. Refractive indices are given spectrally for the dry particles using OPAC (suso00) and are volume weighted with water refractive index to give an effective refractive index for the Mie calculations. A single mode of sulfate is provided here (su.json).
| Species | rnum [um] | sigma | Density [kg m-3] | Notes |
|---|---|---|---|---|
| SU | 0.0695 | 2.03 | 1000 | su.json |
Following Colarco et al. 2010, sea salt aerosol optical properties are computed for each of five size bins. The v2.0.0 implementation treats the bins as truncated bins with the optical properties integrated across the bin. Growth factors are based on the Gerber [1986] parameterization. Properties for the dry particle bins are given below and dry sea salt density is assumed to be 2200 kg m-3. A sub-bin distribution is assumed across the bin following Gong [2003]. Refractive indices are given spectrally for the dry particles using OPAC (sscm00) and are volume weighted with water refractive index to give an effective refractive index for the Mie calculations.
| Bin | rMin [um] | rMax [um] | Notes |
|---|---|---|---|
| 1 | 0.03 | 0.1 | ss.json |
| 2 | 0.1 | 0.5 | ss.json |
| 3 | 0.5 | 1.5 | ss.json |
| 4 | 1.5 | 5.0 | ss.json |
| 5 | 5.0 | 10.0 | ss.json |
Following Bian et al. 2017, nitrate aerosol optical properties are computed for each of three size bins (ni.json). The bins are lognormal modes with a specified number mode radius (in microns) and width (sigma) and are not truncated with sharp edges. Hygroscopic growth factor is taken to be 1.06 * growth factor of sulfate, following Fitzgerald 1975. Refractive indices are given spectrally for the dry particles after Bian et al. 2017 and are volume weighted with water refractive index to give an effective refractive index for the Mie calculations.
| Bin | rNum [um] | sigma | density [kg m-3] | Notes |
|---|---|---|---|---|
| 1 | 0.04455 | 2.03 | 1725 | ni.json |
| 2 | 0.6000 | 2.03 | 2200 | ni.json |
| 3 | 2.3316 | 2.0 | 2650 | ni.json |
Dust is novel in that non-spherical optics are considered and Mie calculations are not used. Optical properties are from the GRASP kernels assuming the spheroidal shape distribution of Dubovik et al. 2006. Refractive indices are from Colarco et al. 2014, which are a combination of observation-based shortwave values and OPAC values in the longwave. Five size bins are considered, but properties are integrated across generally wider distributions than the bin edges.
| Bin | rMin [um] | rMax [um] | rNum [uM] | sigma | density [kg m-3] | Notes |
|---|---|---|---|---|---|---|
| 1 | 0.1 | 1.0 | 0.5173 | 1.327 | 2500 | du-grasp_spheroid-lognormal.json |
| 2 | 1.0 | 1.8 | 1.031 | 1.284 | 2650 | du-grasp_spheroid-lognormal.json |
| 3 | 1.8 | 3.0 | 1.611 | 1.411 | 2650 | du-grasp_spheroid-lognormal.json |
| 4 | 3.0 | 6.0 | 1.198 | 2.028 | 2650 | du-grasp_spheroid-lognormal.json |
| 5 | 6.0 | 10.0 | 2.047 | 2.067 | 2650 | du-grasp_spheroid-lognormal.json |
A simple linear weighting of monochromatic properties is applied across the RRTMG bands (see bandaverage.py).
Shortwave bands [cm-1]
| Index | lower | upper |
|---|---|---|
| 1 | 2600 | 3250 |
| 2 | 3250 | 4000 |
| 3 | 4000 | 4650 |
| 4 | 4650 | 5150 |
| 5 | 5150 | 6150 |
| 6 | 6150 | 7700 |
| 7 | 7700 | 8050 |
| 8 | 8050 | 12850 |
| 9 | 12850 | 16000 |
| 10 | 16000 | 22650 |
| 11 | 22650 | 29000 |
| 12 | 29000 | 38000 |
| 13 | 38000 | 50000 |
| 14 | 820 | 2600 |
Longwave bands [cm-1]
| Index | lower | upper |
|---|---|---|
| 15 | 10 | 250 |
| 16 | 250 | 500 |
| 17 | 500 | 630 |
| 18 | 630 | 700 |
| 19 | 700 | 820 |
| 20 | 820 | 980 |
| 21 | 980 | 1080 |
| 22 | 1080 | 1180 |
| 23 | 1180 | 1390 |
| 24 | 1390 | 1480 |
| 25 | 1480 | 1800 |
| 26 | 1800 | 2080 |
| 27 | 2080 | 2250 |
| 28 | 2250 | 2380 |
| 29 | 2380 | 2600 |
| 30 | 2600 | 3250 |
- Bian et al. 2017: https://doi.org/10.5194/acp-17-12911-2017
- Chin et al. 2002: https://journals.ametsoc.org/view/journals/atsc/59/3/1520-0469_2002_059_0461_taotft_2.0.co_2.xml
- Colarco et al. 2010: https://doi.org/10.1029/2009jd012820
- Colarco et al. 2014: https://doi.org/10.1002/2013jd020046
- Colarco et al. 2017: https://doi.org/10.5194/amt-10-4121-2017
- Dubovik et al. 2006: https://doi.org/10.1029/2005jd006619
- Fitzgerald 1975: https://journals.ametsoc.org/view/journals/apme/14/6/1520-0450_1975_014_1044_afftes_2_0_co_2.xml
- Gerber, H. E.: Relative-Humidity Parameterization of the Navy Aerosol Model (NAM), NRL Report 8956, 1 16, 1985.
- OPAC: Hess et al. 1998: https://journals.ametsoc.org/view/journals/bams/79/5/1520-0477_1998_079_0831_opoaac_2_0_co_2.xml