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--- aerocom:optical_properties [2012-03-16 09:48:26]
michaels
+++ aerocom:optical_properties [2022-05-31 09:29:31] (current)
@@ Line 1: / Line 1: @@
-===== Questionary on Optical properties =====
+ATTENTION - THIS WIKI PAGE IS NO LONGER UPDATED - PLEASE GO TO [[http://aerocom.met.no/|aerocom.met.no]]FOR LATEST INFO
+===== Questionary on Optical properties (AeroCom Phase III models)=====
+The Phase III questionnaire is available in the following Google spreadsheet:
+https://docs.google.com/spreadsheets/d/1pFq6f7gP8nQLz6IYLqMtCPQN4t0eVe2Xd3R3_ra4pg4/
+If you have problems accessing this spreadsheet, please contact jonasg@met.no or michaels@met.no. The spreadsheet is also available as .ods file in the supplementary material of Gliß et al, 2020 (https://www.atmos-chem-phys-discuss.net/acp-2019-1214/).
+===== Questionary on Optical properties (AeroCom Phase II models)=====
 Questions on optical property calculations in AeroCom phase II models with the purpose of a correct interpretation of diagnosed AOD properties in the AeroCom database:
@@ Line 5: / Line 15: @@
 ) Do you assume and how internal mixing when computing optical properties of total
 aerosol? Is Size varying? Which mixing assumption?
 ) Do you differentiate between clear-sky and all-sky relative humidity and
@@ Line 12: / Line 22: @@
 b) If you differentiate, have you investigated the difference?
 ) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
 ) Would you consider the diagnosed AOD provided to the Aerocom database as representative for clear-skies? Eg for comparison to Aeronet and satellite retrievals in clear skies?
@@ Line 20: / Line 30: @@
 ) Which humidity growth factor and variation do you use ? How does it depend on RH? Do you include sub-grid variability in relative humidity?
-) Do you diagnose the aerosol water mass or aerosol water AOD? How?
+) Do you diagnose the aerosol water mass or aerosol  water AOD? How?
-) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky RH?
+) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky  RH?
 ) Do you average nighttime and daytime values of AOD into daily averages?
 ) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
 ) What is the absorption coefficient of BC? How is it calculated?
 ) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.
 ===== MODELS =====
@@ Line 273: / Line 284: @@
 Please refer to Table 4 of [[http://www.agu.org/journals/pip/jd/2011JD016074-pip.pdf|Bellouin et al. (2011)]], and the Appendix of the manuscript for details on aerosol optical properties in HadGEM.
 ==== GMI.A2.* and GMI-MERRA.A2.* ====
+) Do you assume and how internal mixing when computing optical properties of total
+aerosol? Is Size varying? Which mixing assumption?
-==== GISS-modelE.A2.* ====
+External mixing.
+) Do you differentiate between clear-sky and all-sky relative humidity and
+which one do you use for the AOD calculation, reported to AeroCom?
+No. We use ambient relative humidity.
+b) If you differentiate, have you investigated the difference?
+) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
+The AOD reported to AeroCom is 550 nm. For RF calculations, we use the SW spectral dependence of AOD and other properties (SSA, Asymmetry factor) to calculate RF.
+) Would you consider the diagnosed AOD provided to the Aerocom database as representative for clear-skies? Eg for comparison to Aeronet and satellite retrievals in clear skies?
+Not necessary - but we are doing it anyway. We don't have quantitative numbers to show on monthly averaged basis how much the differences are.
+) If you diagnose a clear-sky  AOD =>  How do you compute it? What are the assumptions on RH? Any threshold of RH you use? Cloud fraction weighting to derive a monthly average Clear-sky AOD?
+N/A
+) Which humidity growth factor and variation do you use ? How does it depend on RH? Do you include sub-grid variability in relative humidity?
+Based on Tang and Munkelwitz (1996) water activity formula determined at the HeHe laser wavelength of 0.633 microns for ammonium nitrate and ammonium sulfate. All others based on GADS (aka OPAC). No we don't include sub-grid variability of RH.
+) Do you diagnose the aerosol water mass or aerosol water AOD? How?
+Not for AeroCom II aerosol direct radiative forcing activity (not required). Yes for AeroCom HTAP activity. Aerosol water = ambient AOD - dry AOD (i.e., no hygroscopic growth).
+) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky RH?
+Yes they are computed at ambient RH under all sky conditions.
+) Do you average nighttime and daytime values of AOD into daily averages?
+Yes.
+) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
+At 550 nm:
+SSA for BC: 0.2080, 0.2086, 0.2139, 0.2481, 0.3227, 0.3830, 0.4594, 0.5359 at 0, 50, 70, 80, 90, 95, 98, 99% RH.
+SSA for POM: 0.9618, 0.9773, 0.9819, 0.9851, 0.9897, 0.9932, 0.9960, 0.9972 at 0, 50, 70, 80, 90, 95, 98, 99% RH.
+SSA for dust: 0.9916, 0.9909, 0.9864, 0.9767, 0.9604, 0.9353, 0.8933, 0.8399 for dust effective radius of 0.14, 0.24, 0.45, 0.80, 1.4, 2.4, 4.5, 8.0 um. No hygroscopic growth is considered.
+) What is the absorption coefficient of BC? How is it calculated?
+I assume you mean "mass absorption efficiency" with a unit of m2/g. This is calculated as MAE=MEE*(1-SSA).
+At 550 nm:
+MAE for BC: 7.3529, 7.4091, 0.4491, 8.5266, 8.0192, 9.7856, 10.190, 10.521 m2/g at 0, 50, 70, 80, 90, 95, 98, 99% RH.
+They are calculated from the Mie code with refractive indices (BC/water volume weighted), size distributions, and particle density.
+) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.
+BC:        1.75 - 0.44i;
+POM:       1.53-0.006i;
+(NH4)2SO4: 1.53-10^(-7)i;
+NH4NO3:    1.556-1.1^(-9)i;
+Dust:      1.53-0.0055i;
+Seasalt:   1.50-10^(-8)i
+The refractive indices of ammonium sulfate and ammonium nitrate are calculated using lacis-refrac.rhwmri.f provided by Andrew Lacis [ftp://ftp.giss.nasa.gov/pub/crmim/lacis/lacis_refrac.rhwmri.f]. All others see Table 2 in Chin et al., Ann. Geophys., (2009).
+==== GISS-modelE.A2.* ====
+) Do you assume and how internal mixing when computing optical properties of total aerosol? Is Size varying? Which mixing assumption?
+Aerosol are externally mixed, size distributions are prescribed
+) Do you differentiate between clear-sky and all-sky relative humidity and which one do you use for the AOD calculation, reported to AeroCom?
+We do not differentiate between clear sky and all sky humidity, but we provide both, clear and all sky AOD for AeroCOm.
+) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
+Yes
+) Would you consider the diagnosed AOD provided to the Aerocom database as representative for clear-skies? Eg for comparison to Aeronet and satellite retrievals in clear skies?
+We provided both clear and all sky.
+) If you diagnose a clear-sky AOD ⇒ How do you compute it? What are the assumptions on RH? Any threshold of RH you use? Cloud fraction weighting to derive a monthly average Clear-sky AOD?
+Clear sky is defined when the Monte Carlo sampling of cloud fraction sees zero cloud fraction in the column.
+) Which humidity growth factor and variation do you use? How does it depend on RH?
+Sea salt, nitrate and sulfate get humidified following Lacis and Oinas 1991 and depends on ambient RH
+Do you include sub-grid variability in relative humidity?
+No
+We use different parameterizations for sulfate and sea salt.
+Yes
+) Do you diagnose the aerosol water mass or aerosol water AOD? How?
+No
+) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky RH?
+Yes we use ambient all sky RH.
+) Do you average nighttime and daytime values of AOD into daily averages?
+Yes
+) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
+) What is the absorption coefficient of BC? How is it calculated?
+BC absorption is calculated based on BC mass, an BC enhancement factor of 1.5 is applied to take into account BC enhancement effect due to internal mixing.
+) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.
+The following refractive indices at 550nm are used in this study: Sulfate (1.528-1.e-7i), nitrate (1.528-1.e-7i), OC (1.527-0.014i), BC (1.85-0.71i), sea salt (1.45-0.i), dust (1.564-0.002i) and water (1.334-3.91e-8i).
 ==== GISS-MATRIX.A2.* ====
+) Do you assume and how internal mixing when computing optical properties of total aerosol? Is Size varying? Which mixing assumption?
+Mixing state is taken into consideration. Particles including BC have core shell structure; other particles use volume mixing approach. The size is prognostic and the mixing state assumption follows the population definitions in Bauer et al 2008 ACP
+) Do you differentiate between clear-sky and all-sky relative humidity and which one do you use for the AOD calculation, reported to AeroCom?
+We do not differentiate between clear sky and all sky humidity, but we provide both, clear and all sky AOD for AeroCOm.
+) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
+Yes
+) Would you consider the diagnosed AOD provided to the Aerocom database as representative for clear-skies? Eg for comparison to Aeronet and satellite retrievals in clear skies?
+We provided both clear and all sky.
+) If you diagnose a clear-sky AOD ⇒ How do you compute it? What are the assumptions on RH? Any threshold of RH you use? Cloud fraction weighting to derive a monthly average Clear-sky AOD?
+Clear sky is defined when the Monte Carlo sampling of cloud fraction sees zero cloud fraction in the column.
+) Which humidity growth factor and variation do you use ? How does it depend on RH? Do you include sub-grid variability in relative humidity?
+We calculate the uptake of water following the thermodynamical model  EQSAM and for Sea salt using the Lewis parameterization (Lewis and Schwartz 2004)
+) Do you diagnose the aerosol water mass or aerosol water AOD? How?
+No, aerosol water is one component that determines the mixing state of aerosols. Aerosol water is tracked for each aerosol population.
+) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky RH?
+Yes we use ambient all sky RH.
+) Do you average nighttime and daytime values of AOD into daily averages?
+Yes
+) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
+) What is the absorption coefficient of BC? How is it calculated?
+BC absorption is calculated depending on aerosol mixing state – see question 1)
+) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.
+The following refractive indices at 550nm are used: Sulfate (1.528-1.e-7i), nitrate (1.528-1.e-7i), OC (1.527-0.014i), BC (1.85-0.71i), sea salt (1.45-0.i), dust (1.564-0.002i) and water (1.334-3.91e-8i).
 ==== BCC_AGCM2.0.1_CAM.A2.* ====
@@ Line 639: / Line 819: @@
 ) Do you assume and how internal mixing when computing optical properties of total
 aerosol? Is Size varying? Which mixing assumption?
+INCA uses 5 modes, two insoluble (accumulation, coarse) , three soluble (accumulation, coarse, super coarse). Size varies, but sigma of lognormal distributions is fixed. Each mode has one number and several mass tracers which are advected separately. Size varies as a function of number and mass affected by mixing, different source and removal processes. Internal mixing is assumed with respect to some properties of each mode, namely removal by sedimentation, wet scavenging. Optical properties are calculated assuming external mixing, though the size of all species in a given mode are assumed to be equal.
+Size variation is not taken into account in the AOD calculation. Optical properties assume mean size for each mode.
 ) Do you differentiate between clear-sky and all-sky relative humidity and
 which one do you use for the AOD calculation, reported to AeroCom?
+In the LMDzT host model instantaneous clear-sky relative humidity is computed. This is used to compute hygroscopic growth factors, used in tabulated form, to get to AOD.
+NOTE: The meaning of the clear-sky humidity in the LMDzT model has recently changed. Not clear how this affected the results.
 b) If you differentiate, have you investigated the difference?
-) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
+All-sky AOD was never calculated.
+) Is the reported-to-AeroCom AOD as asked under 2) used directly for the RF calculations?
+No - The AeroCom AOD diagnostics are computed for a given wavelength. RF uses the broadband AOD for the SW and NIR bands used in the RF calculation.
 ) Would you consider the diagnosed AOD provided to the Aerocom database as representative for clear-skies? Eg for comparison to Aeronet and satellite retrievals in clear skies?
+yes
 ) If you diagnose a clear-sky  AOD =>  How do you compute it? What are the assumptions on RH? Any threshold of RH you use? Cloud fraction weighting to derive a monthly average Clear-sky AOD?
+Growth factors for each mode are interpolated.
 ) Which humidity growth factor and variation do you use ? How does it depend on RH? Do you include sub-grid variability in relative humidity?
-) Do you diagnose the aerosol water mass or aerosol  water AOD? How?
+tabulated growth factors between 0 and 90% RH and one at 95% RH.
+No inclusion of sub-grid variability.
-) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky  RH?
+) Do you diagnose the aerosol water mass or aerosol water AOD? How?
+Yes, but it does not correspond strictly to the growth factors used for AOD computation.
+) Is the diagnosed sea salt and sulfate AOD computed at ambient RH? And eventually is that using clear-sky or all-sky RH?
+Yes, clear-sky RH.
 ) Do you average nighttime and daytime values of AOD into daily averages?
-) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
+daily averages
+) What is the single-scattering albedo of your BC, POM, DUST? Does it vary as a function of size, RH? How roughly? Which range?
+Depending on wavelength and RH
+BC soluble SSA varies between 0.41 and 0.53
+BC insoluble SSA varies between 0.30 and 0.42
+OA SSA varies between 0.94 and 0.99
+DUST SSA varies between 0.944 and 0.987
 ) What is the absorption coefficient of BC? How is it calculated?
+from SSA
 ) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.