Photolysis rates processor jproc
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Photolysis Rates Processor (JPROC). Gail Tonnesen UCR Regional Modeling Center Training January 16, 2002. JPROC Purpose. JPROC processor calculates a table of clear-sky photolysis rates (or J-values) for a specific date.

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Photolysis Rates Processor (JPROC)

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Photolysis rates processor jproc

Photolysis Rates Processor (JPROC)

Gail Tonnesen

UCR Regional Modeling Center Training

January 16, 2002


Jproc purpose

JPROC Purpose

  • JPROC processor calculates a table of clear-sky photolysis rates (or J-values) for a specific date.

    • The look-up table consists of photolysis rates at various altitudes, latitudes, and hour angles.

    • The look-up table is recalculated for each simulation day and is dependent upon the chemical mechanism.

University of California at Riverside, Regional Modeling Center (RMC)


Jproc overview

JPROC Overview

  • Many chemical reactions in the atmosphere are initiated by the photodissociation of numerous trace gases.

  • These photodissociative reactions are responsible for most of the smog buildup.

  • Good photodissociation reaction rate (or photolysis rate) estimates must be made to accurately model and predict the effects of air pollution.

  • Photodissociation is the conversion of solar radiation into chemical energy to activate and dissociate chemical species.

University of California at Riverside, Regional Modeling Center (RMC)


Jproc calculate j values

JPROC – Calculate J-values

  • Photolysis rates (min-1), sometimes called J-values, are computed for photodissociation reaction (i) by:

    where:

    F(λ): is the actinic flux (photons cm-2 min-1 nm-1 ),

    σi(λ): the absorption cross section for the molecule undergoing photodissociation (cm2 molecule-1 ),

    i(λ): the quantum yield of the photolysis reaction

    (molecules photon-1 ), and

    λ: the wavelength (nm).

University of California at Riverside, Regional Modeling Center (RMC)


Jproc calculating j values

JPROC – Calculating J-values

  • The current approach for setting photolysis rates in the Models-3/CMAQ framework follows that of RADM.

  • It includes two stages of processing:

    • a table of clear-sky photolysis rates is calculated by the JPROC processor for specified heights, latitudes, and hours from local noon; and

    • photolysis rates are interpolated from the table within the CMAQ Chemistry Transport Model (CCTM) based on grid cell location and the model time, and are corrected for cloud cover.

  • This approach is computationally efficient and gives clear-sky photolysis rates within the uncertainty of the surface-based measurements.

University of California at Riverside, Regional Modeling Center (RMC)


Clear sky photolysis rate table

Clear-Sky Photolysis Rate Table

  • Preprocessor JPROC calculates a table of clear-sky photolysis rates (or J-values) for a specific date.

  • The table is dimensioned by latitude, altitude, and time.

  • Currently, J-values are calculated for

    • 6 latitudinal bands (10N, 20N, 30 N, 40 N, 50 N, and 60 N),

    • 7 altitudes (0, 1, 2, 3, 4, 5, and 10 km), and

    • ±9 hours from local noon (0 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, and 8 h).

  • There is a separate table for each photolysis reaction.

University of California at Riverside, Regional Modeling Center (RMC)


Jproc input files

JPROC Input Files

  • The input files needed for JPROC are:

    • Extaterrestial radiation data

    • Absorption cross section data

    • Vertical ozone profile

    • Albedo data

University of California at Riverside, Regional Modeling Center (RMC)


How to run jproc

How to run JPROC?

  • Verify that the CMAQ distribution tar file is downloaded from the RMC website: www.cert.ucr.edu/rmc/download/.

  • Gunzip and untar the files into the desired directories.

  • Go to the JPROC run scripts directory, modify and execute the “bldit” and “run” job scripts.

    • “bldit” script: choose the compilation options and compiling the code.

    • “run” script: modify the run-time options and execute JPROC processor

  • Check the log file for possible compile and runtime errors.

University of California at Riverside, Regional Modeling Center (RMC)


Hands on

Hands-on …….

University of California at Riverside, Regional Modeling Center (RMC)


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