Co-Is: Steven Ackerman, University of Wisconsin - Madison; Odele Coddington, University of Colorado; Robert Holz, University of Wisconsin - Madison; Steven Platnick, NASA Goddard Space Flight Center
The PACE mission represents the next generation of ocean remote sensing, and will also provide an opportunity to extend key aerosol and cloud property climate data records. The primary PACE instrument, the hyperspectral Ocean Color Imager (OCI), promises well calibrated, wide-swath observations of the Earth having both high spatial and 5-nm spectral resolution from 350nm to 885nm with an additional seven discrete narrowband shortwave infrared channels between 940 and 2260nm. Secondary instruments include two contributed polarimeters. Core PACE mission requirements include OCI-only retrieval products of the following key cloud properties: cloudy/clear sky discrimination (cloud masking), cloud top pressure/altitude, and cloud optical thickness and particle effective size.
We propose to develop the algorithms for the key cloud products to satisfy the OCI-only mission requirements. Because the information content for cloud optical properties is not appreciably increased by hyperspectral observations in the visible and near infrared, our retrieval algorithm for cloud optical thickness and particle effective size will follow a multi-channel approach with MODIS-VIIRS continuity cloud product (CLDPROP) heritage. Similarly, our cloud masking algorithm will also follow heritage multispectral shortwave approaches (e.g., components of the MODIS-VIIRS CLDMSK). We will develop new algorithms for cloud top pressure/altitude and thermodynamic phase because OCI lacks the thermal infrared channels that have been used in heritage algorithms to retrieve these quantities. Instead, our new algorithm approach for cloud top pressure/altitude will rely on spectral channels in and near the O2-A band and water vapor absorption bands (940, 1378nm), and our new algorithm approach for thermodynamic phase discrimination will be a combination of multiple SWIR spectral channels having differential liquid/ice absorption (1615, 2130, 2260nm). Moreover, while the focus of this proposal is on cloud products from OCI alone, we also propose to utilize the information from the contributed polarimeters in quality assurance and assessments of the OCI-only retrievals, to the extent possible (e.g., effective size, thermodynamic phase discrimination).