Aerosol optical properties

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This page describes the aerosol optical properties that are used as input to the FAST-J photolysis mechanism in GEOS-Chem.

Aerosol optical properties update for GEOS-Chem v8-03-01

Starting with GEOS-Chem v8-03-01, several of the aerosol optical properties for the FAST-J photolysis code (specified in the input file jv_spec.dat have been updated to take into account new observations from various datasets. Colette Heald has created an overview document which describes the implementation of the aerosol optics for FAST-J.

NOTE: For this update there are no modifications to the source code itself, just to the jv_spec.dat file.

Authors

Name Affiliation Date
Randall Martin Dalhousie University 19 November 2009
Colette Heald Colorado State University 29 January 2010

Overview

The updated jv_spec.dat file was created to reflect current information about aerosol size distributions for sulfate, organic carbon, black carbon and sea salt. The method follows Martin et al., [2003]. Refractive indices are based on GADS. The Mie code is from ftp://ftp.giss.nasa.gov/pub/crmim/spher.f and described in Mischenko et al. [1999]. The current calculation uses an geometric standard deviation (sigma_g) of 1.6 for sulfate, BC and OC following Wang et al. [2003ab] and Drury et al. [submitted]. The sigma_g was also reduced to 1.5 and 1.8 for fine and coarse sea salt respectively following Jaegle et al. [2010]. Specific geometric mean radii (r_g) for each species and relative humidity are in the headers of jv_spec.dat. Consistent aerosol optical properties at 550nm were also created for the file jv_spec_aod.dat.

Some illustrative differences between the "old" jv_spec.dat and the "current" one are given below for 70% relative humidity. The most important change is that organic carbon aerosols are larger in the current version, and that sea salt are substantially smaller.

Sulfate Old Value New Value
r_g (um) 0.07 0.11
sigma_g 2.0 1.6
r_eff (um) 0.24 0.19
Qext (at 300nm) 2.4 2.6
Qext (at 600nm) 1.3 0.93
Organic Carbon Old Value New Value
r_g (um) 0.03 0.09
sigma_g 2.0 1.6
r_eff (um) 0.095 0.15
Qext (at 300nm) 1.2 2.3
Qext (at 600nm) 0.34 0.75
Black Carbon Old value New value
r_g (um) 0.01 0.02
sigma_g 2.0 1.6
r_eff (um) 0.039 0.035
Qext (at 300nm) 1.06 0.95
Qext (at 600nm) 0.43 0.33
Sea salt (accumulation mode) Old value New value
r_g (um) 0.38 0.15
sigma_g 2.0 1.5
r_eff (um) 1.32 0.23
Qext (at 300nm) 2.33 3.04
Qext (at 600nm) 2.60 1.37
Sea salt (coarse mode) Old value New value
r_g (um) 3.2 0.73
sigma_g 2.0 1.8
r_eff (um) 10.1 1.7
Qext (at 300nm) 2.07 2.22
Qext (at 600nm) 2.11 2.43

The updated jv_spec.dat for v8-02-05 has the following top-of-file header:

jv_spec.dat:  FAST-J, FJX (jmao 4/09), Updated AOD's (rvm, clh, 3/10)

Issues

It is likely that organic aerosol at ultraviolet wavelengths is more absorbing than included here as based on GADS [Koepke et al., 1997].

Aerosols are often internally mixed, in contast with their implementation as an external mixture in jv_spec.dat.

--Bob Y. 11:02, 1 March 2010 (EST)

Download location

The updated jv_spec.dat file (and corresponding ratj.d file) are be located in the 1-month benchmark run directory for GEOS-Chem v8-02-05. You may also download them from the following location:

ftp ftp.as.harvard.edu
cd pub/geos-chem/data/aerosol_optics/v8-03-01-updates/

These files are now part of the standard GEOS-Chem run directory archive. You may download these with the Git version control software. Please see this wiki post for more information.

--Bob Y. 15:32, 15 November 2010 (EST)

Aerosol optical properties at high spectral resolution

Randall Martin has made available files containing aerosol optical properties at high spectral resolution. These files are not specifically for GEOS-Chem, but they may be useful for some satellite applications or radiative forcing calculations. The files are available from:

ftp ftp.as.harvard.edu
cd /pub/geos-chem/data/aerosol_optics/hi_spectral_res/

For more information about the data, please see this README file.

--Bob Y. 11:02, 1 March 2010 (EST)

Better representation of OC growth with RH and correction to sulfate optics

NOTE: This update is slated for inclusion in v9-02.

David Ridley wrote:

I have a couple of updates for GEOS-chem to be included in the next revision.
These are both changes to the jv_spec.dat and jv_spec_aod.dat, so not the actual code.
The first change is a better representation of the OC growth with RH for which updated optics have been provided by Randall Martin (oc_reduced_hygroscopicity.dat). The second is a correction to the sulfate optics, by myself, to better represent the water solubility and refractive index (so4_waso.dat). Previously, pure H2SO4 optics were assumed. Now we use the typical water soluble aerosol properties from GADS, similar to ammonium sulfate (higher refractive index but substantially reduced growth factor).
These changes have been okayed with Colette Heald and Jeff Pierce during discussions last week. If you require any more information please let me know.

Randall Martin wrote:

The old hygroscopicity for organics in GC (growth factor=1.9 @95% RH) exceeds that of ammonium bisulfate, which was unrealistic. Jiminez et al. (2009) indicates a growth factor closer to 1.35 at 95% RH.

For better representation of OC growth with RH:

36 OC00(rvm) Organic C, RH=00 (n@550=1.53-.006i log-norm: r_g=.07um/sigma=1.6)
  300  2.4567  0.127  0.9590  1.000 2.050 2.314 1.944 1.498 1.053 0.721 0.470
  400  1.7461  0.127  0.9744  1.000 1.950 2.020 1.529 1.049 0.648 0.396 0.224
  550  1.0059  0.127  0.9658  1.000 1.778 1.650 1.068 0.630 0.329 0.174 0.082
  600  0.8395  0.127  0.9639  1.000 1.716 1.545 0.948 0.533 0.263 0.132 0.057
 1000  0.2405  0.127  0.8509  1.000 1.226 0.978 0.386 0.135 0.035 0.008 0.001
37 OC50(rvm) Organic C, RH=50 (n@550=1.46-.004i log-norm: r_g=.08um/sigma=1.6)
  300  2.3664  0.139  0.9709  1.000 2.157 2.549 2.263 1.833 1.360 0.969 0.672
  400  1.6538  0.139  0.9816  1.000 2.062 2.254 1.820 1.328 0.878 0.564 0.346
  550  0.9462  0.139  0.9748  1.000 1.885 1.855 1.293 0.819 0.464 0.262 0.139
  600  0.7904  0.139  0.9732  1.000 1.821 1.739 1.154 0.699 0.378 0.204 0.103
 1000  0.2297  0.139  0.8863  1.000 1.323 1.100 0.499 0.207 0.072 0.024 0.006
38 OC70(rvm) Organic C, RH=70 (n@550=1.44-.003i log-norm: r_g=.08um/sigma=1.6)
  300  2.3617  0.144  0.9747  1.000 2.191 2.630 2.380 1.964 1.486 1.077 0.761
  400  1.6499  0.144  0.9839  1.000 2.100 2.340 1.933 1.443 0.978 0.641 0.403
  550  0.9463  0.144  0.9779  1.000 1.925 1.934 1.386 0.901 0.526 0.304 0.166
  600  0.7916  0.144  0.9766  1.000 1.862 1.815 1.241 0.772 0.430 0.239 0.125
 1000  0.2319  0.144  0.9001  1.000 1.365 1.151 0.547 0.239 0.090 0.033 0.010
39 OC80(rvm) Organic C, RH=80 (n@550=1.43-.003i log-norm: r_g=.09um/sigma=1.6)
  300  2.3693  0.149  0.9775  1.000 2.217 2.695 2.476 2.074 1.594 1.172 0.841
  400  1.6588  0.149  0.9857  1.000 2.130 2.410 2.029 1.542 1.066 0.711 0.456
  550  0.9552  0.149  0.9804  1.000 1.959 2.001 1.467 0.975 0.582 0.343 0.192
  600  0.8003  0.149  0.9792  1.000 1.896 1.880 1.317 0.838 0.478 0.271 0.145
 1000  0.2364  0.149  0.9111  1.000 1.404 1.196 0.590 0.268 0.107 0.043 0.015
40 OC90(rvm) Organic C, RH=90 (n@550=1.41-.002i log-norm: r_g=.09um/sigma=1.6)
  300  2.4065  0.159  0.9818  1.000 2.259 2.802 2.642 2.270 1.793 1.353 0.997
  400  1.7001  0.159  0.9885  1.000 2.181 2.532 2.202 1.728 1.235 0.849 0.563
  550  0.9903  0.159  0.9843  1.000 2.018 2.123 1.621 1.118 0.696 0.424 0.246
  600  0.8328  0.159  0.9834  1.000 1.958 2.000 1.461 0.967 0.576 0.339 0.189
 1000  0.2506  0.159  0.9295  1.000 1.476 1.284 0.675 0.326 0.141 0.062 0.025
41 OC95(rvm) Organic C, RH=95 (n@550=1.39-.002i log-norm: r_g=.10um/sigma=1.6)
  300  2.4733  0.171  0.9856  1.000 2.296 2.906 2.808 2.476 2.009 1.558 1.180
  400  1.7758  0.171  0.9910  1.000 2.229 2.655 2.386 1.933 1.429 1.014 0.696
  550  1.0531  0.171  0.9879  1.000 2.079 2.255 1.794 1.286 0.835 0.528 0.319
  600  0.8901  0.171  0.9872  1.000 2.022 2.130 1.627 1.122 0.698 0.426 0.248
 1000  0.2747  0.171  0.9464  1.000 1.558 1.387 0.776 0.399 0.185 0.087 0.039
42 OC99(rvm) Organic C, RH=99 (n@550=1.36-.001i log-norm: r_g=.12um/sigma=1.6)
  300  2.6732  0.203  0.9913  1.000 2.354 3.089 3.121 2.890 2.475 2.026 1.625
  400  2.0282  0.203  0.9948  1.000 2.316 2.896 2.769 2.389 1.891 1.431 1.049
  550  1.2725  0.203  0.9933  1.000 2.198 2.538 2.193 1.702 1.203 0.819 0.537
  600  1.0918  0.203  0.9930  1.000 2.152 2.419 2.018 1.513 1.030 0.680 0.430
 1000  0.3631  0.203  0.9722  1.000 1.743 1.645 1.045 0.604 0.316 0.166 0.083

For sulfate optics correction:

22 S00(dar) Trop sulphate, RH=00 (n@550=1.53-0.01i log-norm: r=.07um/sigma=1.6)
  300  2.3328  0.121  0.9594  1.000 2.037 2.266 1.874 1.416 0.975 0.655 0.418
  400  1.6118  0.121  0.9741  1.000 1.927 1.961 1.452 0.975 0.589 0.354 0.197
  550  0.9028  0.121  0.9646  1.000 1.741 1.587 0.996 0.573 0.292 0.153 0.073
  600  0.7484  0.121  0.9625  1.000 1.675 1.485 0.882 0.484 0.234 0.118 0.053
 1000  0.2108  0.121  0.8417  1.000 1.183 0.959 0.382 0.145 0.049 0.019 0.006
23 S50(dar) Trop sulphate, RH=50 (n@550=1.44 0.00i log-norm: r=.09um/sigma=1.6)
  300  2.4175  0.149  0.9752  1.000 2.203 2.666 2.437 2.034 1.557 1.142 0.818
  400  1.7099  0.149  0.9844  1.000 2.118 2.386 1.999 1.513 1.041 0.692 0.443
  550  0.9931  0.149  0.9788  1.000 1.950 1.984 1.448 0.958 0.570 0.335 0.186
  600  0.8352  0.149  0.9776  1.000 1.888 1.864 1.299 0.824 0.468 0.265 0.141
 1000  0.2488  0.149  0.9056  1.000 1.405 1.196 0.592 0.272 0.113 0.049 0.020
24 S70(dar) Trop sulphate, RH=70 (n@550=1.41 0.00i log-norm: r=.09um/sigma=1.6)
  300  2.4852  0.162  0.9797  1.000 2.251 2.796 2.638 2.274 1.802 1.366 1.012
  400  1.7947  0.162  0.9875  1.000 2.177 2.533 2.209 1.739 1.248 0.862 0.574
  550  1.0630  0.162  0.9831  1.000 2.023 2.136 1.641 1.138 0.712 0.437 0.255
  600  0.8963  0.162  0.9822  1.000 1.966 2.016 1.483 0.988 0.593 0.350 0.197
 1000  0.2751  0.162  0.9261  1.000 1.498 1.307 0.697 0.343 0.152 0.070 0.030
25 S80(dar) Trop sulphate, RH=80 (n@550=1.40 0.00i log-norm: r=.10um/sigma=1.6)
  300  2.5571  0.174  0.9830  1.000 2.284 2.891 2.789 2.464 2.004 1.558 1.186
  400  1.8800  0.174  0.9896  1.000 2.222 2.648 2.381 1.932 1.433 1.019 0.701
  550  1.1382  0.174  0.9862  1.000 2.080 2.261 1.805 1.300 0.846 0.537 0.326
  600  0.9653  0.174  0.9855  1.000 2.026 2.140 1.642 1.137 0.711 0.435 0.255
 1000  0.3040  0.174  0.9408  1.000 1.577 1.407 0.795 0.413 0.193 0.093 0.042
26 S90(dar) Trop sulphate, RH=90 (n@550=1.38 0.00i log-norm: r=.11um/sigma=1.6)
  300  2.6967  0.198  0.9875  1.000 2.330 3.033 3.029 2.779 2.356 1.910 1.519
  400  2.0587  0.198  0.9927  1.000 2.291 2.836 2.675 2.280 1.782 1.332 0.965
  550  1.3021  0.198  0.9906  1.000 2.171 2.477 2.107 1.612 1.121 0.753 0.486
  600  1.1172  0.198  0.9901  1.000 2.125 2.359 1.937 1.431 0.958 0.623 0.388
 1000  0.3730  0.198  0.9613  1.000 1.716 1.601 0.996 0.566 0.290 0.150 0.074
27 S95(dar) Trop sulphate, RH=95 (n@550=1.36 0.00i log-norm: r=.13um/sigma=1.6)
  300  2.8355  0.227  0.9909  1.000 2.362 3.148 3.234 3.069 2.701 2.278 1.889
  400  2.2825  0.227  0.9949  1.000 2.344 2.999 2.947 2.625 2.152 1.684 1.281
  550  1.5186  0.227  0.9938  1.000 2.252 2.685 2.420 1.960 1.448 1.028 0.703
  600  1.3212  0.227  0.9935  1.000 2.213 2.576 2.251 1.767 1.262 0.869 0.575
 1000  0.4720  0.227  0.9759  1.000 1.855 1.821 1.243 0.769 0.430 0.239 0.127
28 S99(dar) Trop sulphate, RH=99 (n@550=1.34 0.00i log-norm: r=.18um/sigma=1.6)
  300  2.9980  0.304  0.9952  1.000 2.380 3.282 3.494 3.502 3.280 2.972 2.662
  400  2.7329  0.304  0.9976  1.000 2.409 3.240 3.385 3.239 2.877 2.444 2.031
  550  2.0735  0.304  0.9974  1.000 2.374 3.046 3.015 2.690 2.210 1.731 1.314
  600  1.8669  0.304  0.9974  1.000 2.351 2.966 2.873 2.503 2.002 1.530 1.130
 1000  0.7986  0.304  0.9914  1.000 2.104 2.302 1.850 1.336 0.875 0.558 0.342

--Melissa Sulprizio 15:14, 16 July 2013 (EDT)

Known issues

Fix to jv_spec_aod.dat

Gabriele Curci wrote:

I'd like to report a bug in the jv_spec_aod.dat file in the GC run dirs. It contains aerosol optical properties for calculations of AOD at 550 nm, with data that the user manually replace in the jv_spec.dat file.
The bug is related to dust and consist in missing update of the parameters as done in the jv_spec.dat for other wavelenghts. The update was done some time ago:
http://wiki.seas.harvard.edu/geos-chem/index.php/Aerosol_optical_properties
and for dust included updates from Sinyuk et al. (2003):
http://www.atmos.colostate.edu/~heald/docs/GEOS_Chem_optics_description.pdf
Well, the jv_spec.dat is ok, but the companion jv_spec_aod.dat for 550 nm data was not consistently updated for dust.

The current values for dust:

 w(nm)    Q    r-eff  ss-alb  pi(0) pi(1) pi(2) pi(3) pi(4) pi(5) pi(6) pi(7)
15 Mdust 0.15 = mineral dust (R.V.Martin)
  550  1.5356  0.150  0.973 1.000 1.866 1.790 1.223 0.730 0.371  0.187  0.076
16 Mdust 0.25 = mineral dust (R.V.Martin)
  550  2.8155  0.250  0.971 1.000 2.029 2.349 2.013 1.596 1.146  0.792  0.505
17 Mdust 0.4 = mineral dust (R.V.Martin)
  550  3.0860  0.400  0.956 1.000 1.999 2.546 2.333 2.241 1.897  1.653  1.345
18 Mdust 0.8 = mineral dust (R.V.Martin)
  550  2.5841  0.800  0.906 1.000 2.065 2.911 2.965 3.513 3.476  3.796  3.692
19 Mdust 1.5 = mineral dust (R.V.Martin)
  550  2.3461  1.500  0.848 1.000 2.298 3.352 3.751 4.627 4.954  5.714  5.983 
20 Mdust 2.5 = mineral dust (R.V.Martin)
  550  2.2405  2.500  0.788 1.000 2.453 3.638 4.308 5.354 5.998  7.011  7.618
21 Mdust 4.0 = mineral dust (R.V.Martin)
  550  2.1744  4.000  0.724 1.000 2.571 3.885 4.822 6.014 6.956  8.157  9.073

Should be changed to:

 w(nm)    Q    r-eff  ss-alb  pi(0) pi(1) pi(2) pi(3) pi(4) pi(5) pi(6) pi(7)
15 Mdust 0.15 = mineral dust (R.V.Martin)
  550  1.5736  0.151  0.993 1.000 1.766 1.248 0.460 0.143 0.027  0.003  0.000
16 Mdust 0.25 = mineral dust (R.V.Martin)
  550  3.6240  0.253  0.994 1.000 2.101 2.473 2.097 1.416 0.769  0.355  0.076
17 Mdust 0.4 = mineral dust (R.V.Martin)
  550  3.6424  0.402  0.990 1.000 2.005 2.702 2.636 2.714 2.500  2.179  1.787
18 Mdust 0.8 = mineral dust (R.V.Martin)
  550  2.6226  0.818  0.971 1.000 2.142 3.213 3.457 4.381 4.388  4.957  4.747
19 Mdust 1.5 = mineral dust (R.V.Martin)
  550  2.3682  1.491  0.953 1.000 2.256 3.339 3.617 4.635 4.902  5.843  6.053
20 Mdust 2.5 = mineral dust (R.V.Martin)
  550  2.2699  2.417  0.930 1.000 2.357 3.499 3.897 4.971 5.373  6.463  6.862
21 Mdust 4.0 = mineral dust (R.V.Martin)
  550  2.1247  3.721  0.897 1.000 2.409 3.562 4.009 5.070 5.556  6.708  7.235

--Melissa Payer 17:11, 8 March 2012 (EST)

References

  1. Drury, E., D.J. Jacob, R.J.D. Spurr, J. Wang, Y. Shinozuka, B.E. Anderson, A.D. Clarke, J. Dibb, C. McNaughton, and R. Weber, Synthesis of satellite (MODIS), aircraft (ICARTT), and surface (IMPROVE, EPA-AQS, AERONET) aerosol observations over North America to improve MODIS aerosol retrievals and constrain surface aerosol concentrations and sources , J. Geophys. Res., submitted.
  2. Jaegle et al. Global sea salt emissions: New constraints from in situ, AERONET, and MODIS observations, in preparation for submission to Atm. Chem. Phys. Discuss., 2010.
  3. Koepke, P., M. Hess, I. Schult, and E. P. Shettle, Global Aerosol Data Set, Report No. 243, Max-Planck-Institut fur Meteorologie, Hamburg, ISSN 0937-1060, 1997.
  4. Martin, R.V., D.J. Jacob, R.M. Yantosca, M. Chin, and P. Ginoux, Global and regional decreases in tropospheric oxidants from photochemical effects of aerosols, J. Geophys. Res., 108, 4097, doi:10.1029/2002JD002622, 2003.
  5. Mishchenko, M.I., J.M. Dlugach, E.G. Yanovitskij, and N.T. Zakharova, Bidirectional reflectance of flat optically thick particulate layers: an efficient radiative transfer solution and applications to snow and soil surfaces, J. Quant. Spectrosc. Radiat. Transfer, 63, 409-432, 1999.
  6. Wang, J., S.A. Christopher, F. Brechtel, J. Kim, B. Schmid, J. Redemann, P.B. Russell, P. Quinn, and B.N. Holben, Geostationary satellite rtrievals of aerosol optical thickness during ACE-Asia, J. Geophys. Res., 108, 8657, doi:10.1029/2003JD003580, 2003.
  7. Wang, J., S.A. Christopher, J.S. Reid, H. Maring, D. Savoie, B.H. Holben, J.M. Livingston, P.B. Russell, and S.K. Yang, GOES-8 retrieval of dust aerosol optical thickness over the Atlantic Ocean during PRIDE, J. Geophys. Res., 108, 8595, doi:10.1029/2002JD002494, 2003.

--Bob Y. 11:02, 1 March 2010 (EST)