The ROMS coupling interface with the ESMF/NUOPC library allows both driver and component methods of operation. In this case, SST is exported from ROMS and DATA to the atmosphere component which imports a melded SST field. Therefore, a DATA component and its cap file is also required for most applications. So if, for example, the atmosphere component domain is larger than the ROMS domain, it is necessary to provide data from another source to the atmosphere model at all of the surface grid points that lie outside the ROMS domain. The ROMS and other ESM grids may (and usually do) have a different geographical extent and horizontal resolution. Therefore, it is an abstract block that allows ROMS to communicate and exchange data seamlessly within the ESMF/NUOPC framework. There is a separate cap file for each coupled component, which, from the ROMS perspective, corresponds to the atmosphere, sea-ice, wave model, etc. The critical Fortran module that sits on top of each ESM is the so-called NUOPC cap file. While the NUOPC layer is available in ESMF version 7 of higher, ROMS coupling requires version 8 or higher because it uses the RunSequence input configuration script and uses version 8 features for nesting. The connectors join ESM components and perform operations such as regridding between the source and destination fields when needed. The mediators are custom codes that facilitate the coupling of the models, and control tasks such as flux calculations, rescaling, and averaging. The driver controls the models, mediators, connectors, and coordinates tasks such as initialization and time stepping. It consists of four components: (i) a driver, (ii) the models, (iii) mediators, and (iv) connectors. The NUOPC layer is a simplified infrastructure on top of the ESMF library (version 7 or higher) that provides conventions and templates to facilitate easy coupling between Earth System Models ( ESM). Significant progress has been made over the past decade in the standardization of coupling tools without reducing model diversity through the Earth System Modeling Framework ( ESMF Collins et al., 2005) and the National Unified Operational Prediction Capability ( NUOPC) consortia. All three coupling libraries have been used for coupling ROMS with an atmosphere model (e.g., Turuncoglu and Sannino, 2017, Warner et al., 2010, Renault et al., 2016, respectively). Several coupling interfaces exist to exchange data between ESM components including the ESMF (Collins et al., 2005), MCT (Larson et al., 2005), and OASIS (Valcke, 2013) libraries. In these cases, significant feedbacks between the ocean and atmosphere occur regularly. However, in coastal areas, the ocean can respond to the atmosphere rapidly and is highly variable over short spatial scales. This method performs well in regions where the ocean evolves slowly relative to the atmosphere and where the sea state has a limited impact on the atmospheric state. They may use a static sea surface temperature field derived from satellite imagery composited over days to weeks, or one-dimensional ocean mixing models that do not represent three-dimensional baroclinic circulation on continental shelves. Similarly, some atmospheric modeling systems have simplistic representations of oceanic and air-sea transfer processes. Typical uncoupled ocean modeling systems utilize atmospheric model data snapshots from files at coarser temporal and spatial resolutions and interpolate the forcing fields at each time step to drive circulation forward. The coupling of atmosphere and ocean plays an essential role in the Earth's climate and the long- and short-term predictability of both systems.