Retrieving aerosol characteristics from the PACE Ocean Color Instrument: Testing a new broad spectrum algorithm

The Ocean Color Instrument (OCI), the primary instrument of the PACE mission, offers unprecedented opportunity to characterize aerosols from a traditional multi-spectral imaging radiometer. While observing less information than a multi-angle polarimeter, OCI's broad spectrum measurements spanning the range from 320 nm to 2250 nm offers more information than previous and existing NASA radiometers. OCI's observations are comparable to combining the visible to shortwave infrared (SWIR) measurements, similar to MODIS and VIIRS, with the ultraviolet (UV) measurements from OMI, allowing for retrievals of spectral aerosol optical depth (AOD), aerosol size parameter, aerosol particle absorption, and aerosol layer height. The broad UV-visible-SWIR spectrum will be measured at 1-km nominal pixel resolution, from the same instrument using consistent geometry and calibration. The algorithm teams from the Dark Target, Deep Blue, and OMI aerosol groups have joined forces to exploit OCI measurements to characterize aerosol over ocean and land. The OCI algorithm unifies the cloud mask for all three heritage algorithms. It uses the visible-SWIR algorithms (Dark Target and Deep Blue) to constrain AOD. This relieves the UV algorithm from its traditional dilemma of unraveling the intertwined signals from AOD, aerosol layer height and aerosol absorption to return robust measures of each of these three parameters. To test these new algorithms, a data set collocating VIIRS and TropOMI measurements has been produced. The algorithm for the over ocean aerosol retrieval has been applied to this collocated data set for dust, smoke, and pollution events, and the results compared with AERONET retrievals. Over land, the algorithm has likewise progressed. Finally, we have implemented a routine to retrieve AOD over clouds in appropriate situations.