Using CALIOP to Evaluate Cirrus Cloud Detection Proficiencies in GOES-16 ABI 1.378-um Channel Imagery

We describe efforts to calibrate radiance-based cloud detection thresholds in the new NOAA GOES-16 ABI 1.378 um water vapor absorption channel for upper-tropospheric cirrus cloud detection. We evaluate sensitivities as a function of cloud optical depth, column water vapor amounts and with respect to elevated smoke aerosols that can contaminate the retrieval. Lidar instruments have long been the resource for monitoring cirrus clouds, particularly those exhibiting relatively tenuous optically-thin cloud optical depths (< 0.30) for which passive radiometric retrievals regularly fail to distinguish. However, the adaptation of geostationary sensor composite radiances for this task would represent a significant advance, given fields-of-view that far outweigh limited lidar curtains. Initial attempts to pair ABI cloud detections with effective particle size information retrieved from three ABI infrared bands is also described. The long-term goal is an operational cloud mask for improved satellite meteorological and oceanographic retrievals that considers the presence of thin cirrus clouds. The use of CALIOP as the reference dataset, however, allows us to understand how much more cirrus that can be identified from passive sensors, and ultimately how much are still being missed.