JPROC calculates daily clear sky photolysis rates from look-up tables of molecular absorption cross-section and quantum yield data, and climatologically-derived ozone-column and optical depth data. The output from JPROC are ASCII look-up tables of daily clear sky photolysis rates for photochemical reactions in a selected gas-phase photochemical mechanism at different altitudes, latitudes, and hours from noon. The photochemical mechanism that these rates are derived for is selecting during compilation of JPROC. The altitudes (meters), latitudes (degrees), and hour angles (from noon) that the rates are derived for are hardwired in the JPROC source code.