Table of Contents - The Atmospheric Studies Group at TRC

Section 1: Introduction
introduction of a sub-hourly time step within the model for purposes of computing solar radiation, wind
fields and boundary layer parameters and the modification of the structure of the output data file produced
by CALMET to allow for hourly or sub-hourly time steps. The preprocessor programs now produce
CALMET input files that contain the full begin-time / end-time structures with times resolved to the
second. However, they operate on standard available datasets that do not include sub-hourly data. Users
who have meteorological monitoring programs that report data more frequently than hourly can readily
format those data for input to CALMET using the new file formats. These formats are fully described in
this document.
The CALMET postprocessor PRTMET was also modified to deal with the additional temporal
information provided by the updated CALMET model. PRTMET allows the gridded CALMET
meteorological fields to be viewed.
The latest version of the CALPUFF Graphical User Interface (GUI) system (CALPRO) which includes
the CALVIEW plotting and visualization interface was modified to accept sub-hourly time steps.
From the perspective of current users of the system, the most notable change in using the new system is
the way time periods are identified. Version 5 had adopted nomenclature that is based on hourly periods.
All of the data coming into the system varied by the hour (or multiples of hours), and within the system
the hour was identified by the time at the end of the hour being simulated. Version 6 allows times to be
identified to the second, and most importantly, the basic time step is no longer fixed at one hour so it is
also characterized to the second. Each period is defined by both a start time and an end time. In cases
where a timestamp contains a single time, it is the time at the start of a period, not the end. For example,
the files that are generated by CALPOST and PRTMET for visualization contain a date, time, and
averaging period in the filename. The date-time is the starting time. The averaging period implicitly
identifies the ending time. Similar files produced by Version 5 placed the ending time in the filename.
The remainder of this introduction provides a brief history of the development of the modeling system
and an overview of all of the components in the system. Details for running each component in the
system are provided in subsequent sections. Users interested in preparing variable source emission files
will find the specifications in Sections 9.3 through 9.6. Formats for CALMET meteorological input files
are presented in Sections 8.3 through 8.6.
1.2 Historical Background
As part of a study to design and develop a generalized non-steady-state air quality modeling system for
regulatory use, Sigma Research Corporation developed the CALPUFF dispersion model and related
models and programs, including the CALMET meteorological model. The original development of
CALPUFF and CALMET was sponsored by the California Air Resources Board (CARB). Systems
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