Process Analysis Diagnostics

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Process Analysis Diagnostics

Overview - What is Process Analysis?

Process-based Analysis examines the change in each species due to each process and reaction. Models predict atmospheric state, which in a time-series can be used to create net-change of each species. What this cannot tell us, is which processes led to that change. To supplement state (or concentration, GEOS-Chem has long archived emissions and employed advanced diagnostics to predict gross chemical production or loss. Process Analysis goes a step further archiving grid-cell budgets for each species, and decomposing gross production/loss into individual reaction contributions. Process Analysis extensions are currently available in [CAMx], [WRF-Chem], [CMAQ], and now GEOS-Chem. This allows for direct comparisons of models at a fundamental, process level.

Process Analysis Overview.png

Details - No really, what is it?

The budget is built from process contributions and reaction throughput. Process contributions are referred to as Integrated Process Rates (IPR) and can be calculated because of operator splitting. Each process is distinctly called, and state before and after the call can be differenced to see the process contribution.

Reaction contributions are more complex to calculate than IPR. Reaction contributions are constructed from integrated reaction rates (IRR). IRR are calculated according to equation 1. The rate coefficient (<math>k</math>) is evaluated by calcrate.f and then SMVGEAR or KPP solve over short timesteps (<math>t_s</math>). To calculate the IRR, we must add code to SMVGEAR or KPP that finds successful steps and archives equation 1.

  1. IRRrxn = Δ ts· krxn · ∏rct[Crct]
  2. ΔCi,rxn = αi,rxnIRRrxn
  3. ΔCi,chem = Σrxn ∈ rxnsΔCi,rxn

Development Status - What features are available?

Integrated Process Rates

Process rates are fully functional, but will be extended in the future. Right now, the process are able to perfectly account for the change in concentrations. However, some processes are lumped and others contain directional information that is not currently captured.

  1. Transport
  2. Wet deposition
  3. Heterogeneous Chemistry
  4. Gas-phase Chemistry
  5. Convective Mixing
    1. Emissions*
    2. Dry deposition*

*Gas-phase emissions and dry deposition are solved either in the chemical solver or in asymmetric convection routines. Separation of processes within convection has not yet been implemented.

The figure below shows change in concentration on the x-axis and sum of processes on the y-axis.

Formaldehyde check IPR

Integrated Reaction Rates

Integrated Reaction Rates are fully functional with two solver options, but more QA is needed.

  1. Sparse Matrix Vector Gear: available
  2. Kinetic Pre-Processor
    1. Rosenbrock (coming soon)
    2. LSODES (available upon request)

The image below shows the chemistry process on the x-axis and the sum of reaction contributions. Currently, there is a discrepancy for some grid cells. It may be related to the species level error correction in the SMVGEAR solver.

IRR CHECK H2O2.png

A KPP LSODES solver with IRR is available, but GEOS-Chem uses Rosenbrock by default. Efforts have been made to implement IRR in Rosenbrock, but more work is necessary.

To do:

  1. Confirm that inexact SMV results for $lt; 1% of results are the result of tracer lumping rather than SMVGEAR species specific error correction
  2. Incorporate error correction if necessary
  3. Complete KPP Rosenbrock solver implementation

Installation and Application - How can I use it?

The code is available in a github repository that is currently available upon request from Barron Henderson at the University of Florida.