The Whole Atmosphere Community Climate Model (WACCM) is a comprehensive numerical model, spanning the range of altitude from the Earth's surface to the thermosphere. The development of WACCM is an inter-divisional collaboration that unifies certain aspects of the upper atmospheric modeling of HAO, the middle atmosphere modeling of ACOM, and the tropospheric modeling of CGD, using the NCAR Community Earth System Model (CESM) as a common numerical framework.  The latest version of WACCM is described in Marsh et al. (2013)WACCM-X extends WACCM to the upper thermosphere, and includes processes important to the ionosphere.

Announcements and support for running WACCM can be found on the DiscussCESM WACCM forum.  The CESM Whole Atmosphere Working Group webpage can be found at

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WACCM Near-Real-Time

The chemical mechanism in WACCM includes comprehensive tropospheric, stratospheric and mesospheric chemistry.  The tropospheric chemistry mechanism has been significantly updated from MOZART-4 and is called MOZART-T1.  A preliminary version of this mechanism is described in Knote et al. (2014) and a complete description of the chemistry in CESM2 is being prepared.  The most important change for users of the model output for regional model boundary conditions is the new treatment of aromatics: the previous lumped aromatic (confusingly called 'TOLUENE') has been replaced with the specific species BENZENE, TOLUENE and XYLENES.  The lumped monoterpene is now called MTERP, and a sesquiterpene, BCARY, has been added. This document gives the full list of species. The aerosol scheme in WACCM is the MAM4 modal aerosol scheme, which is described in Liu et al. (GMD, 2015). Please contact Louisa Emmons if you have further questions.




ACOM | Atmospheric Chemistry Observations & Modeling