Reprocessing 30+ Years of ISCCP: Addressing Satellite Intercalibration for Deriving a Long-Term Cloud Climatology

A cloud properties climate data record (CDR) first requires a consistent set of intercalibrated radiances. In the case of NOAA’s Advanced Very High Resolution Radiometer (AVHRR) this task requires intercalibration for polar (low-earth) orbiting (LEO) satellites only. In the case of the International Satellite Cloud Climatology Product, which uses VIS and IR channels from both polar orbiting and geostationary (GEO) satellite imagers, the intercalibration required to produce a consistent set of intercalibrated radiances is more complex. Considerations must be made for various satellite configurations, including LEO-to-LEO (i.e., successive series of NOAA orbiters such as NOAA-18 and NOAA-19), GEO-to-GEO (i.e., intercalibration for adjacent pairs of geostationary satellites), and LEO-to-GEO pairs (intercalibration that requires near simulataneous observations from polar and geostationary satellite imagers). Historically, pseudo invariant earth targets including deserts, open sea, and deep convective clouds have served as points of reference to assist in developing a intercalibration framework. In this evaluation, the use of both desert targets and deep convective clouds is explored for the purpose of evaluating approaches for improving VIS channel intercalibration for the ISCCP Cloud Properties CDR.