Harmonized Emissions Component (HEMCO) 3.0 as a versatile emissions component for atmospheric models: application in the GEOS-Chem, NASA GEOS, WRF-GC, CESM2, NOAA GEFS-Aerosol, and NOAA UFS models

Abstract

Abstract. Emissions are a central component of atmospheric\nchemistry models. The Harmonized Emissions Component (HEMCO) is a software\ncomponent for computing emissions from a user-selected ensemble of emission\ninventories and algorithms. It allows users to re-grid, combine, overwrite,\nsubset, and scale emissions from different inventories through a\nconfiguration file and with no change to the model source code. The\nconfiguration file also maps emissions to model species with appropriate\nunits. HEMCO can operate in offline stand-alone mode, but more importantly\nit provides an online facility for models to compute emissions at runtime.\nHEMCO complies with the Earth System Modeling Framework (ESMF) for\nportability across models. We present a new version here, HEMCO 3.0, that\nfeatures an improved three-layer architecture to facilitate implementation\ninto any atmospheric model and improved capability for calculating\nemissions at any model resolution including multiscale and unstructured\ngrids. The three-layer architecture of HEMCO 3.0 includes (1)\xa0the Data Input\nLayer that reads the configuration file and accesses the HEMCO library of\nemission inventories and other environmental data, (2)\xa0the HEMCO Core that\ncomputes emissions on the user-selected HEMCO grid, and (3)\xa0the Model\nInterface Layer that re-grids (if needed) and serves the data to the\natmospheric model and also serves model data to the HEMCO Core for\ncomputing emissions dependent on model state (such as from dust or vegetation). The HEMCO Core is common to the implementation in all models, while\nthe Data Input Layer and the Model Interface Layer are adaptable to the\nmodel environment. Default versions of the Data Input Layer and Model\nInterface Layer enable straightforward implementation of HEMCO in any simple\nmodel architecture, and options are available to disable features such as\nre-gridding that may be done by independent couplers in more complex\narchitectures. The HEMCO library of emission inventories and algorithms is\ncontinuously enriched through user contributions so that new inventories\ncan be immediately shared across models. HEMCO can also serve as a general\ndata broker for models to process input data not only for emissions but for\nany gridded environmental datasets. We describe existing implementations of\nHEMCO 3.0 in (1)\xa0the GEOS-Chem “Classic” chemical transport model with\nshared-memory infrastructure, (2)\xa0the high-performance GEOS-Chem (GCHP)\nmodel with distributed-memory architecture, (3)\xa0the NASA GEOS Earth System\nModel (GEOS ESM), (4)\xa0the Weather Research and Forecasting model with\nGEOS-Chem (WRF-GC), (5)\xa0the Community Earth System Model Version\xa02 (CESM2),\nand (6)\xa0the NOAA Global Ensemble Forecast System – Aerosols\n(GEFS-Aerosols), as well as the planned implementation in the NOAA Unified Forecast\nSystem (UFS). Implementation of HEMCO in CESM2 contributes to the\nMulti-Scale Infrastructure for Chemistry and Aerosols (MUSICA) by providing\na common emissions infrastructure to support different simulations of\natmospheric chemistry across scales.\n