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--- aerocom:optical_properties [2012-06-22 12:15:25]
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+ATTENTION - THIS WIKI PAGE IS NO LONGER UPDATED - PLEASE GO TO [[http://aerocom.met.no/|aerocom.met.no]]FOR LATEST INFO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 32: / Line 42: @@
 ) Please provide the refractive index at 0.55 microns for each aerosol species? And eventually further information on the hygroscopicity for each species.
-==== INCA ====
-) 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?
-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?
-tabulated growth factors between 0 and 90% RH and one at 95% RH.
-No inclusion of sub-grid variability.
-) 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?
-) 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 853: / Line 815: @@
 For full details and data on how AOD is calculated within GEOS-Chem, the user may refer to the FlexAOD post-processing tool: [[http://wiki.seas.harvard.edu/geos-chem/index.php/FlexAOD]]
+==== INCA ====
+) 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?
+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?
+tabulated growth factors between 0 and 90% RH and one at 95% RH.
+No inclusion of sub-grid variability.
+) 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?
+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.