title: The adjoint of CMAQ.
abstract: An adjoint model for the internationally used Community Multiscale Air Quality (CMAQ) modeling platform of the U.S. EPA is developed. The adjoint version for CMAQ (CMAQ-ADJ) provides the user community with forward (decoupled direct method or DDM) and backward (adjoint) sensitivity analysis capabilities. Current implementation is for gas-phase processes. Discrete adjoints are implemented for all processes with the exception of horizontal advection, for which, because of inherent discontinuities in the advection scheme, the continuous approach is superior. The adjoint of chemistry is constructed by interfacing CMAQ with the kinetic pre-processor, which provides for increased flexibility in the choice of chemical solver and facilitates the implementation of new chemical mechanisms. The adjoint implementation is evaluated both on a process-by-process basis and for the full model. In general, adjoint results show good agreement with brute-force and DDM sensitivities. As expected for a continuous adjoint implementation in a nonlinear scheme, the agreement is not perfect for horizontal transport. Sensitivities of various air quality, public health, and environmental metrics with respect to emissions are calculated using the adjoint method. In order to show applicability to regional climate studies, as an example, the sensitivities of these metrics with respect to local temperatures are calculated.
authors: Department of Chemical Engineering, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, USA.
authors: Amir
authors: A
authors: Hakami
authors: Daven K
authors: DK
authors: Henze
authors: John H
authors: JH
authors: Seinfeld
authors: Kumaresh
authors: K
authors: Singh
authors: Adrian
authors: A
authors: Sandu
authors: Soontae
authors: S
authors: Kim
authors: Daewon
authors: D
authors: Byun
authors: Qinbin
authors: Q
authors: Li
mesh_terms: D000392:Air Movements; D000393:Air Pollutants / Q000737:chemistry*; D000397:Air Pollution; D004777:Environment; D004781:Environmental Exposure; D004784:Environmental Monitoring / Q000379:methods*; D005740:Gases; D005843:Geography; D007700:Kinetics; D008956:Models, Chemical; D010126:Ozone / Q000737:chemistry; D012111:Residence Characteristics; D012680:Sensitivity and Specificity; D012984:Software; D013458:Sulfur Dioxide; D013696:Temperature; D014481:United States
chemical_list: D000393:Air Pollutants; D005740:Gases; D013458:Sulfur Dioxide; D010126:Ozone