The CALIPSO version 4.5 stratospheric aerosol subtyping algorithm

Abstract. The accurate classification of aerosol types injected into the stratosphere is important to properly characterize their chemical and radiative impacts within Earth climate system. updated stratospheric subtyping algorithm used in version 4.5 (V4.5) release Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) level 2 data products now delivers more comprehensive classifications than its predecessor. original identified four subtypes for layers detected above tropopause: volcanic ash, smoke, sulfate/other, polar (PSA). In revised algorithm, sulfates are separately as a distinct, homogeneous subtype, diffuse, weakly scattering previously assigned sulfate/other class recategorized fifth “unclassified” subtype. By making two structural changes revising thresholds, V4.5 improves ability discriminate between ash smoke from pyrocumulonimbus injections, fidelity sulfate accurately reflects uncertainties inherent process. 532 nm lidar ratio was also value consistent current state knowledge. This paper briefly reviews previous (V4.1 V4.2) then fully details rationale impact on subtype frequency specific events where dominant type known based literature. Classification accuracy best due characteristically high depolarization ratio. Smoke classified reasonable accuracy, though during daytime substantial fraction misclassified ash. It possible mixtures be smoke. less that or being about one-third time. However, because exceptionally tenuous unclassified levies stringent criteria identifying an sulfate, it likely labeled this fact compared those release.