This talk will cover three topics related to the implementation and validation of the Rapid Radiative Transfer Model, GCM version (RRTMG) code inside GMAO's GEOS-5 Earth System Model. First, I will give an overview of RRTMG, reviewing its use of the Correlated k-Distribution (CKD) approach and its Monte Carlo Independent Cloud Approximation (McICA) treatment of sub-grid column cloud variability/overlap. Second, I will discuss a valuable lesson learned in the GEOS-5 RRTMG longwave clear-sky validation, namely the need for consistent model and observational definitions of clear-sky. Third, I will discuss the new "Parallel" version, RRTMGP, from Rob Pincus, which refactors/rewrites RRTMG in modern Object Oriented Fortran, as a very readable and extensible toolbox for use in many different RT contexts.
Seminar Series Coordinators