Testing the accuracy of a 1-D volcanic plume model in estimating mass eruption rate

摘要

During volcanic eruptions, empirical relationships are used to estimate mass eruption rate from plume height. Although simple, such relationships can be inaccurate and can underestimate rates in windy conditions. One-dimensional plume models can incorporate atmospheric conditions and give potentially more accurate estimates. Here I present a 1-D model for plumes in crosswind and simulate 25 historical eruptions where plume height H_(obs) was well observed and mass eruption rate M_(obs) could be calculated from mapped deposit mass and observed duration. The simulations considered wind, temperature, and phase changes of water. Atmospheric conditions were obtained from the National Center for Atmospheric Research Reanalysis 2.5° model. Simulations calculate the minimum, maximum, and average values (M_(min), M_(max), and M_(avg)) that fit the plume height. Eruption rates were also estimated from the empirical formula M_(empir) = 140H_(obs) 4.14 (M_(empir) is in kilogram per second, Hobs is in kilometer). For these eruptions, the standard error of the residual in log space is about 0.53 for Mavg and 0.50 for Mempir. Thus, for this data set, the model is slightly less accurate at predicting M_(obs) than the empirical curve. The inability of this model to improve eruption rate estimates may lie in the limited accuracy of even well-observed plume heights, inaccurate model formulation, or the fact that most eruptions examined were not highly influenced by wind. For the low, wind-blown plume of 14–18 April 2010 at Eyjafjallaj?kull, where an accurate plume height time series is available, modeled rates do agree better with M_(obs) than M_(empir).