the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Aerosol emissions estimation with POLDER
Athanasios Tsikerdekis
Nick A. J. Schutgens
Qirui Zhong
Abstract. We apply a Local Ensemble Transform Kalman Smoother (LETKS) in combination with the global aerosol climate model ECHAM-HAM to estimate aerosol emissions from POLDER-3/PARASOL observations for the year 2006. We assimilate Aerosol Optical Depth at 550 mnm (AOD550), Ångström Exponent for 550 nm and 865 nm (AE550-865) and Single Scattering Albedo at 550 nm (SSA550) in order to improve modeled aerosol mass, size and absorption simultaneously. The new global aerosol emissions increase to 1419 Tg·yr-1 (+28 %) for dust, 1850 Tg·yr-1 (+75 %) for sea salt, 215 Tg·yr-1 (+143 %) for organic aerosol and 13.3 Tg·yr-1 (+75 %) for black carbon, while the sulfur dioxide emissions increase to 198 Tg·yr-1 (+42 %) and total deposition of sulfates to 293 Tg·yr-1 (+39 %). Organic and black carbon emissions are much higher than their prior values from bottom up inventories with a stronger increase in biomass burning sources (+193 % and +90 %) than in anthropogenic sources (115 % and 70 %). The evaluation of the experiments with POLDER (assimilated) and AERONET as well as MODIS Dark Target (independent) observations shows a clear improvement compared to the ECHAM-HAM control run. Specifically based on AERONET the global mean error of AOD550 improves from -0.094 to -0.006 while AAOD550 improves from -0.009 to -0.004 after the assimilation. A smaller improvement is observed also in AE550-865 mean absolute error (from 0.428 to 0.393), with a considerably higher improvement over isolated island sites over the ocean. The new dust emissions are closer to the ensemble median of AEROCOM I, AEROCOM III and CMIP5 as well as some of the previous assimilation studies. The new sea salt emissions get closer to the reported emissions from previous studies. Indications of a missing fraction of coarse dust and sea salt particles are discussed. The biomass burning changes (based on POLDER) can be used as alternative biomass burning scaling factors for the GFAS inventory distinctively estimated for organic carbon (2.93) and black carbon (1.90), instead of the recommended scaling of 3.4 (Kaiser et al. 2012). The estimated emissions are highly sensitive to the relative humidity due to aerosol water uptake, especially in the case of the sulfates. We found that ECHAM-HAM, like most of the GCMs that participated in AEROCOM and CMIP6, overestimated the relative humidity compared to ERA-5 and as a result the water uptake by aerosols, assuming the kappa values are not underestimated. If we use the ERA-5 relative humidity, sulfate emissions must be further increased, as modeled sulfate AOD is lowered. Specifically, over East Asia, the lower AOD can be attributed to the underestimated precipitation and the lack of simulated nitrates in the model.
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Athanasios Tsikerdekis et al.
Status: open (until 09 Apr 2023)
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RC1: 'Comment on acp-2023-41', Anonymous Referee #1, 26 Mar 2023
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This manuscript presents an excellent study that estimates aerosol emissions in the global aerosol climate model ECHAM-HAM using assimilation from POLDER-3/PARASOL observations for the year 2006. There is extensive evaluation with independent observational datasets (AERONET as well as MODIS Dark Target). Furthermore the results of this study are nicely compared with AEROCOM I, AEROCOM III and CMIP5 as well as some of the previous assimilation studies. Last but not it is also discussed (using sensitivity experiments) the sensitivity of the emissions to relative humidity due to aerosol water uptake, especially important for the case of soluble species. I think this study is an important contribution on the topic and I strongly suggest acceptance of the manuscript for publication but I have a few minor and technical comments to be considered.
Comments
What I missed is some information for the meteorological set up of the simulations with ECHAM-HAM climate model (e.g. if the simulations are nudged, spin-up time of the simulations, if is there is a specific reason for the selection of the year 2006).
Maybe they authors could think of revising the title inserting also the term of assimilation.
Caption of Figure S1: I think it is wrongly written (f) sulphur dioxide (SO2). It should rather be WAT. Furthermore the acronym WAT should be also defined in the caption and could be introduced in the text of the manuscript when the water uptake of soluble species (resulting to high AOD values) is discussed (e.g. lines 575-584).
Caption of Figure S8: For consistency with the text it should be noted as "CTLERA5" than simply "ERA5".
line 20: I would suggest " over isolated island sites at the ocean" instead of "over isolated island sites over the ocean".
line 24: Define at some place the acronyms such as GFAS
line 48 and line 50: You may delete "note that" in both sentences.
line 50: It should read "(from 1m to several km)" instead of (about 1m to several km).
line 52: "Emissions from biomass burning" instead of "Emissions from biomass burning emissions"
Lines 54-56: Please define at some place the acronyms such as GFED4, FINN1.5, QFED2.4, FEER1.0 and GFAS.
Line 62: Is the term "diversity" used throughout the manuscript, the proper or the common word to express the ratio of the standard deviation to the mean. In many studies the word "range" is commonly used.
line 70: I would suggest "at least" instead of "at best".
line 72: I would suggest the plural "precursors" instead of "precursor".
line 74: Maybe "assessed" or "found" instead of "used".
line 79: I suggest " ...similar information and methods which they are not ..." instead of "... similar information and methods and are not ..".
lines 119-121: The sentence is not clear and it needs some rephrasing.
line 273: It is not clear what is the setup of the DASERA5 experiment? Is it the data assimilation experiment in ECHAM-HAM using relative humidity for ERA5? Please clarify in the text.
line 298: "along with the MAE" instead of "along the MAE".
line 298: " 3-hourly differences between the Experiments – POLDER" . It is better to be more specific. e.g. 3-h differences of CTLECHAM-POLDER and DASECHAM-POLDER.
lines 531-533: Considering the complexity of the loss and production processes that control the SO2 and SO4 fate in the atmosphere mentioned in this sentence, it could be nice to have a link to section 4.4.2 that you discuss these processes (e.g. as discussed in Section 4.4.2).
line 544: It should be "Figure 10" instead of "Figure 9".
line 579: " ...matches the underestimation of RH by ECHAM-HAM (Figure 10c) while ..." I am rather confused here with the underestimation. Do you mean the small underestimation over ocean (Figure 10 c) below 500 m? Above this level there is clear overestimation of RH.
Citation: https://doi.org/10.5194/acp-2023-41-RC1
Athanasios Tsikerdekis et al.
Athanasios Tsikerdekis et al.
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