VOLCANIC ASH CLOUD HEIGHTS USING THE MODIS CO2-SLICING ALGORITHM

To make accurate volcanic ash cloud dispersion forecasts, certain parameters, including the altitude of the volcanic cloud, must be known. There are several methods used for estimating the height of an ash cloud, including correlation with ground-based video, correlation with wind data, cloud-shadow geometry, and the space-borne “11µm 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). This paper also suggests a cloud emissivity correction to the CO2-slicing algorithm in consideration of volcanic ash clouds CO2-slicing heights are found to agree well with operational methodologies for the majority of cases investigated in this study. For two stratospheric volcanic ash clouds, CO2-slicing heights were within the height estimate window determined by operational methods. Six tropopause cases were investigated and the CO2-slicing height retrievals were found to b