Implications of the atmospheric density profile in the processing of fireball observations

Abstract

This paper examines the effects of the atmospheric density, more specifically, the effects that the changes of isobaric altitude have on the accuracy of a fireball׳s analysis. During winter, especially over high latitude regions like Finland, the true isobaric level may be more than three kilometers below the heights predicted by the US Standard Atmosphere 1976 model. It can differ even more when compared with the heights predicted by the simplified exponential scaled height model. Thus, the true mass of a fireball may differ significantly from those obtained by using either the isobaric altitudes derived from the Standard Atmosphere or the exponential atmospheric model, i.e. without taking into account the corrections for true atmospheric conditions. Likewise, the solutions for the ablation coefficient derived by the generalized models will be less accurate than those that do consider the true atmospheric conditions. This becomes especially crucial for potential meteorite droppers, i.e. low velocity fireballs, with small ablation rates and consequently, high terminal-to-initial mass ratio. We propose an atmospheric height correction method that utilizes real atmospheric data to analysis of the fireball. We demonstrate the proposed method by analyzing the data of three fireballs that were recently recorded by the Finnish Fireball Network and finally, we compare our results against those derived by using the US Standard Atmosphere 1976 model and the exponential atmosphere model.