Volcanic ash cloud heights using the MODIS CO2-slicing algorithm

Volcanic ash poses a severe risk to aviation. When encountered in flight, airborne ash can cause engine failure, as well as leave pilots virtually blind by damaging aircraft windshields. While there has not been any known loss of life due directly to an ash cloud encounter, airborne volcanic ash does pose a significant threat to human life and is a major financial liability. It is for these reasons that accurate forecasting of volcanic clouds is a necessity. To make accurate ash cloud dispersion forecasts, certain parameters, including the altitude of the volcanic cloud, must be known. At present, there are several methods used for estimating the height of an ash cloud, including correlation with ground-based video, correlation with wind data, and the space-borne “11micron brightness temperature” technique. We introduce the Moderate Resolution Imaging Spectroradiometer (MODIS) “CO2-slicing” technique as a method for retrieving volcanic cloud heights from space. This paper compares the heights retrieved from the “CO2-slicing” method with heights estimated by the aforementioned methodologies, as well as height products from the Multiangle Imaging SpectroRadiometer (MISR). The cloud heights retrieved from the “CO2-slicing” method will also be compared to the results from an independent split window 1DVAR retrieval.