Version 5.10 provides the following additional capabilities and features over previous versions:

• The Euler-Backward Iterative (EBI) chemistry solver replaces the CMC fast chemistry solver. EBI provides improved accuracy with similar speed compared to the CMC solver.
• The High-order Decoupled Direct Method (HDDM) for source sensitivity has been added as a new Probing Tool. The DDM probing tool is retained as a separate option. HDDM provides both first and second order sensitivity coefficients for initial/boundary conditions, emissions, and reaction rate constants, leading to more accurate estimates of model response to large changes in input parameters.
• The Asymmetric Convective Mixing Algorithm, Version 2 (ACM2) has been added as a new vertical diffusion option and can be used as an alternative to the original K-theory approach. Meteorological interface programs (e.g., MM5CAMx, WRFCAMx, and RAMSCAMx) have been updated to include an option to generate vertical diffusivities for ACM2. ACM2 works with all probing tools except Process Analysis IPR.
• The Reactive Tracer Chemical Mechanism Compiler (RTCMC) has been added as a new RTRAC option. The CAMx Reactive Tracer (RTRAC) Probing Tool can be used to simulate reactive tracers, such as air toxics. The RTCMC is a new front-end to RTRAC that reads (and solves) a user-defined chemical mechanism for reactive tracers. The RTCMC permits much more complex tracer chemistry than RTRAC.
• Radical concentrations can now be output to the CAMx average file for subsequent analysis or use. Previously, only "state" species names in the CAMx chemistry parameters file could be selected for output. CAMx now allows mechanism-specific (CB4, CB05, or SAPRC99) radical concentrations to be output to the same files.
• Deposited amounts of OSAT/PSAT source apportionment tracers can now be written to a new OSAT/PSAT deposition output file, similar to the core model deposition file. A new flag is available in the SA section of the CAMx namelist control file to turn on deposition output of tracers.