(682a) Developing the Adjoint of ISORROPIA to Equip CMAQ-ADJ

Data assimilation has been widely applied in weather models to improve forecasts. Efficient inverse modeling techniques are necessary for these large scale, high-temporal resolution applications, and the adjoint method has proved suitable. In view of this success, chemical transport models have been identified as excellent candidates for similar transformations, and one of the few that have been developed is the adjoint of the Community Multiscale Air Quality model, CMAQ-ADJ. Optimizing model parameters, including cell-by-cell emissions inventories, by assimilating spatially and temporally varying data sets is a primary goal of adjoint model application.

This work advances the capabilities of the aerosol module for adjoints of chemical transport models by delivering the same level of specificity as ISORROPIA, a widely applied inorganic thermodynamic equilibrium model. The adjoint of ISORROPIA captures the behavior of the system of salts containing the species nitrate, sulfate, ammonium, sodium, and chloride throughout the entire phase diagram. Previously, only limited inorganic components were treated as a single liquid phase within adjoints of inorganic thermodynamic equilibrium models.

Initial phases of the integration of the adjoint of ISORROPIA into CMAQ-ADJ have been accomplished. A test case has been executed to demonstrate the performance of the ISORROPIA adjoint.