Fig. 1.
The pure mineral dust (shown with yellow sphere) mixed with the carbonaceous components like organic carbon (OC), brown carbon (BrC) and black carbon (BC) shown with pink, dark tan and black spheres, respectively (first column, top to bottom). Semi-externally mixed polluted mineral dust two-sphere and two-spheroid model shapes consisting of mineral dust with OC, BrC and BC, respectively (second and third columns, top to bottom). BrC mineral dust two-spheroid model shape has not been modelled as BrC occurs in spherical form. The three-sphere model shape of mineral dust with OC, BrC and BC, respectively (fourth column, top to bottom). Some of the three-sphere systems were modelled with fly-ash (shown with grey sphere) based on the experimental observations.
Table 1. The considered model shapes with their abbreviations
Table 2. Optical constants (at λ=0.550 µm) of mineral dust component for varying hematite percentage obtained from Mishra and Tripathi (2008)
Table 3. Optical constants of carbonaceous components and fly-ash
Fig. 2.
The ω 0 of the BC-mineral dust two-sphere system for the effective volume equivalent radius of the two-sphere system with the varying hematite percentage in the mineral dust.
Fig. 3.
The asymmetrical parameter, g, of the BC-mineral dust two-sphere system for the effective volume equivalent radius of the two-sphere system with the varying hematite percentage in the mineral dust.
Fig. 4.
The extinction efficiency, Q ext, of the BC-mineral dust two-sphere system for the effective volume equivalent radius of the two-sphere system with the varying hematite percentage in the mineral dust.
Fig. 5.
The ω 0 of the two-sphere OC-dust, BrC-dust and two-spheroid OC-dust, BC-dust systems for the effective volume equivalent radius. The two-sphere OC-dust and BrC-dust systems are denoted as OCD and BrCD, respectively, while the two-spheroid systems OC-dust and BC-dust are denoted as OCD′ and BCD′, respectively. Each above-mentioned nomenclature is followed by the hematite percentage. The two-sphere/spheroid systems are compared with that of homogeneous spheres of organic carbon (OC), brown carbon (BrC), black carbon (BC) and dust with 4% hematite (D′-4).
Fig. 6.
The asymmetrical parameter, g, for all the particle systems discussed in Fig. 5.
Fig. 7.
The extinction efficiency, Q ext, for all the particle systems discussed in Fig. 5.
Fig. 8.
The ω 0 of the three-sphere OC-dust-fly-ash, OC-dust, BrC-dust; three-sphere BrC, BC-dust-fly-ash, BC-dust and three-sphere BC systems for the effective volume equivalent radius. The OC-dust-fly-ash and OC-dust systems are denoted as OCDF, OCDD and OCOCD, respectively. The BrC-dust and BrC three-sphere systems are denoted as BrCBrCD, BrCDD and BrCBrCBrC, respectively. The BC-dust-fly-ash, BC-dust and BC three-sphere systems are denoted as BCDF, BCDD, BCBCD and BCBCBC, respectively. Each above-mentioned nomenclature is followed by the hematite percentage. The three-sphere systems are compared with that of homogeneous spheres of organic carbon (OC), brown carbon (BrC), black carbon (BC) and dust with 4% hematite (D′-4).
Fig. 9.
The asymmetrical parameter, g, for all the particle systems discussed in Fig. 8.
Fig. 10.
The extinction efficiency, Q ext, for all the particle systems discussed in Fig. 8.
Table 4. The size-averaged optical properties of single-sphere, two-sphere, two-spheroid and three-sphere systems for 0 and 6% hematite and their percentage deviation compared to that of D′-4 and D′-6. The radius of individual sphere/spheroid is same for the considered dust systems
Table 5. The size-averaged optical properties of BC-dust two-sphere system (with varying radii of individual spheres) for hematite range of 0–6% and their percentage deviation compared to that of D′-4 and D′-6
Fig. 11.
The absolute departure in size-averaged ω 0 for the polluted dust systems formed due to semi-external mixing of accumulation mode mineral dust with (a) BC (b) OC and (c) BrC have been shown compared to pure dust spheroid with 0 (D′-0) and 6% (D′-6) hematite.
