Use of spectral cloud emissivity to infer ice cloud boundaries: Methodology and assessment using CALIPSO cloud products

Hye-Sil Kim, Bryan A. Baum, Yong-Sang Choi
2019 Atmospheric Measurement Techniques Discussions  
<p><strong>Abstract.</strong> Satellite-based operational cloud height retrievals generally assume a plane-parallel homogeneous cloud exists in each field of regard, or pixel, but this assumption ignores vertical inhomogeneity, which is of particular importance for optically thin, but geometrically thick, ice clouds. This study demonstrates that ice cloud emissivity uncertainties can be used to provide a reasonable range of ice cloud layer boundaries, i.e., the minimum to maximum heights. Here
more » ... ce cloud emissivity uncertainties are obtained for three IR channels centered at 11, 12, and 13.3&amp;thinsp;µm. The range of cloud emissivities is used to infer a range of ice cloud temperature/heights, rather than a single value per pixel as provided by operational cloud retrievals. Our methodology is tested using MODIS observations over the western North Pacific Ocean during August 2015. We estimate minimum/maximum heights for three cloud regimes, i.e., single-layer thin and thick ice clouds, and multi-layered clouds. Our results are assessed through comparison with CALIOP Version 4 cloud products for a total of 11873 pixels. The cloud boundary heights for single-layer optically thin clouds show good agreement with those from CALIOP; bias for maximum (minimum) heights versus the cloud top (base) heights of CALIOP are 0.13&amp;thinsp;km (&amp;minus;1.01&amp;thinsp;km). For optically thick and multi-layered clouds, the biases of the estimated cloud heights from the cloud top/base become larger. Our method is applicable to measurements provided by most geostationary weather satellites including the GK-2A advanced multi-channel infrared imager. The vertically resolved heights for ice clouds can contribute new information for studies involving weather prediction and cloud radiative effects.</p>
doi:10.5194/amt-2019-148 fatcat:hzt6wfx6kbanjn6pgcsjucahjm