Revealing the influence of volcanic plumes on lake water quality parameters derived using remote sensing methods

Satellite-derived observations of inland waters are widely used in environmental monitoring, often forming the basis of long-term analyses in the absence of continuous in situ measurements. However, the influence of transient atmospheric phenomena, such as volcanic plumes, on these datasets remains insufficiently quantified. We investigate the impact of volcanic plumes generated during the 2011–2012 eruption of Puyehue-Cordón Caulle, on the availability of remotely observed lake data (lake surface water temperature [LSWT], turbidity and chlorophyll-a) compiled from the ESA Climate Change Initiative (CCI) Lakes dataset. We subsequently extend the assessment of LSWT observations, combining these with coincident plume observations from the Multi-angle Imaging SpectroRadiometer (MISR) and the Moderate Resolution Imaging Spectroradiometer (MODIS), to identify the impacts of diffuse volcanic plumes on remote lake observations. Linear mixed-effects models assessed plume effects, while accounting for lake-specific variability during plume events. These findings indicate that while existing cloud masking removes LSWT observations in the presence of dense ash-rich plumes, diffuse volcanic plumes frequently remain undetected while significantly impacting LSWT records. Plume impacts varied seasonally, with LSWT observations being lower in winter months, and warmer in summer. At the pixel scale, plume interference was associated with LSWT8 reductions of up to 12 °C beneath dense ash-plumes, and 1 °C–5 °C beneath diffuse plumes. Geographic conditions influenced overall data availability, with measurable effects extending to ~270 km from the volcanic source. A random forest classification achieved an overall accuracy of 78% classification accuracy for distinguishing plumes from cloud and background regions, demonstrating the potential to develop an automated flag for CCI Lake data. These findings demonstrate that diffuse volcanic plumes can introduce substantial uncertainty into satellite-derived LSWT observations, although the magnitude and spatial extent of the observed effects are case-specific. This highlights the need for further investigation across diverse volcanic events and geographical settings to support the development of dedicated quality flags for diffuse and transient aerosol features.