Figure 1.

Style-derived volcanic ash partitioning of sustained eruptions. Mass erupting rate (Q_s in kg/s) as a function of the partitioning coefficient ε (Q_a/Q_s in %) for the 20 sustained eruptions of our dataset (see Table 1 for details about the eruptions). ε is the ratio between the very fine ash flux transported in distal clouds (Q_a) and the flux of tephra in the plume (Q_s) also referred to as MER. It quantifies the volcanic very fine ash removal efficiency. The sustained eruptions cluster following their eruption style (Plinian, Subplinian, Small/Moderate). This plot shows that ε of sustained eruptions scales with Q_s, and spans about two orders of magnitude. The main trend shows that ε increases with decreasing MER. This indicates that very fine ash removal from ash-rich plumes (Plinian and Subplinian style) is more efficient than from plumes containing coarser tephra (Small/Moderate style). Error bars are plotted from average bulk uncertainties given for fallout deposit and cloud masses (see Table 1 for detailed error values). The vertical dashed line represents the current VAAC operational partitioning coefficient used by to forecast the atmospheric path of very fine ash clouds. The eruption-dependant partitioning coefficients for each eruption style (ε_P, ε_SP, ε_S/M) have also been reported.