OCO2CLD-LIDAR-AUX combines measurements from NASA’s Orbiting Carbon Observatory-2 (OCO-2) and the NASA/CNES Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. Output is stored both on the OCO-2 native footprints and collocated with CloudSat footprints following the standard CloudSat product granule structure. It reports cloud optical depth, cloud-top pressure and cloud pressure thickness, which is geometric thickness expressed in hPa. Only liquid clouds over the ocean are retrieved. Measurements are provided over the CALIPSO and OCO-2 formation flying period from 2014-09-06 to 2017-07-14, during which time the CALIPSO lidar footprint typically fell within the OCO-2 nadir view swath with a time difference of approximately 8 minutes. Additionally, OCO-2 varies its viewing mode and only nadir view orbits are processed.
These sensors complement each other as the CALIPSO lidar precisely measures cloud top (resolution ~30 m or ~3 hPa), while many boundary layer clouds are optically thick enough to attenuate the lidar so cloud optical depth or geometric thickness cannot be retrieved. OCO-2 effectively measures photon path lengths which must then be partitioned into above-cloud and within-cloud components. CALIPSO’s tight constraint on cloud top is intended to improve cloud pressure thickness retrievals by reducing uncertainty in this partitioning.
Richardson, M., Leinonen, J., Cronk, H. Q., McDuffie, J., Lebsock, M. D., and Stephens, G. L.: Marine liquid cloud geometric thickness retrieved from OCO-2's oxygen A-band spectrometer, Atmos. Meas. Tech., 12, 1717–1737, https://doi.org/10.5194/amt-12-1717-2019, 2019.
Richardson, M. and Stephens, G. L.: Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties, Atmos. Meas. Tech., 11, 1515–1528, https://doi.org/10.5194/amt-11-1515-2018, 2018.