Assessment of the Combined Sensitivity of Nadir TIR Satellite Observations to Volcanic SO2 and Sulphate Aerosols after a Moderate Stratospheric Eruption

Abstract

Abstract:Monitoring gaseous and particulate volcanic emissions with remote observations is of particular importance for climate studies, air quality and natural risk assessment. The concurrent impact of the simultaneous presence of sulphur dioxide (SO 2 ) emissions and the subsequently formed secondary sulphate aerosols (SSA) on the thermal infraRed (TIR) satellite observations is not yet well quantified. In this paper, we present the first assessment of the combined sensitivity of pseudo-observations from three TIR satellite instruments (the Infrared Atmospheric Sounding Interferometer (IASI), the MODerate resolution Imaging Spectro radiometer (MODIS) and the Spinning Enhanced Visible and InfraRed Imager (SEVIRI)) to these two volcanic effluents, following an idealized moderate stratospheric eruption. Direct radiative transfer calculations have been performed using the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model during short-term atmospheric sulphur cycle evolution. The results show that the mutual effect of the volcanic SO 2 and SSA on the TIR outgoing radiation is obvious after three to five days from the eruption. Therefore, retrieval efforts of SO 2 concentration should consider the progressively formed SSA and vice-versa. This result is also confirmed by estimating the information content of the TIR pseudo-observations to the bi-dimensional retrieved vector formed by the total masses of sulphur dioxide and sulphate aerosols. We find that it is important to be careful when attempting to quantify SO 2 burdens in aged volcanic plumes using broad-band instruments like SEVIRI and MODIS as these retrievals present high uncertainties. For IASI, the total errors are smaller and the two parameters can be retrieved as independent quantities.

Statistical analysis of the long-range transport of the 2015 Calbuco volcanic plume from ground-based and space-borne observations

“…Thus, the Angström coefficient values are consistent with an ash-free plume over these sites. The optical evolution of the volcanic plume during its transport was in agreement with previous works (Hobbs et al, 1982;Rose et al, 2000;Watson and Oppenheimer, 2000;Webster et al, 2012;Sellitto et al, 2018) and can be explained by microphysical processes as well as by dynamics (Baker et al, 2014;Bègue et al, 2017;Guermazi et al, 2019;Nimgomba et al, 2019). The Angström coefficients were useful to obtain a first estimation of the optical characteristics and the size distribution of the aerosol plume.…”

“…Conversely, we note that MODIS underestimates the AOD when compared with sun photometer observations over the São Paulo and the South African sites (Table 3). For the latter, this was found to be consistent with results obtained by Hao et al (2005) during the Southern African Regional Science Initiative (SAFARI 2000) campaign which showed that AOD values from MODIS are systematically lower at 470, 550, and 660 nm compared with ground-based measure-ments by automated and handheld sun photometers in the regions of intense biomass burning. They suggested that this bias may be due to errors in the assumed aerosol scattering phase function or surface directional properties.…”

“…Moreover, the time evolution of the optical properties of the volcanic plume over the selected sites could also be explained by the dynamical context. Indeed, the ageing of an aerosol plume is a complex mechanism controlled by many parameters (Bègue et al, 2012;Guermazi et al, 2019).…”

MISR Radiance Anomalies Induced by Stratospheric Volcanic Aerosols

“…However, the optically-thick volcanic ash plumes in the vicinity of eruptions are often observed with UV, visible and IR nadir-viewing imagers [24,25]. Guermazi et al [26] analyzed the TIR sensitivity to moderate volcanic aerosol injection into the UTLS and found a potential 1-2 K signal from the SVA attenuation. Using the stereo matching technique with Multiangle Imaging SpectroRadiometer (MISR), Scollo et al [27] characterized volcanic ash and sulfate/water dispersion and height from 20 Mt.…”

Volcanic Plumes: Impacts on the Atmosphere and Insights into Volcanic Processes

“…Within this realm there were three pieces focused on aerial/satellite observation platforms, and a further four concerning ground based configurations. In terms of the first approach, which is relevant for aviation in the event of large eruptions, or constraining the climatic impacts of eruptions, there was a contribution from Guermazi et al [6] regarding thermal infrared methodologies. In particular, the authors focus on better constraining the concurrent impact of both sulphur dioxide and secondary sulphate aerosols on the signals received in the sensors' measurement bands.…”