BREEZE ROADS calculates concentrations from historical hourly or user-specified meteorological data. The user-friendly interface makes entering or loading your meteorological data easier than ever. Also, the CALINE models incorporated into BREEZE ROADS enable users to model a single hour of user-defined meteorological data, or historic, hourly meteorological data. With this flexible, streamlined approach, productivity skyrockets!

Meteorological Options

BREEZE ROADS incorporates three modules; two for modeling a single hour of user-defined meteorological data (CAL3QHC and CALINE4) and a third for modeling historic, hourly meteorological data (CAL3QHCR). The latter module has the capability of processing a year of hourly meteorological data, carbon monoxide (CO), particulate matter (PM), or nitrogen dioxide (NO2) emissions, traffic, and signalization data. In addition, the CAL3QHCR module incorporates the Industrial Source Complex (ISC) mixing height algorithm. The BREEZE ROADS version of CAL3QHCR has additional enhancements to account for NOx to NO2 conversion. These enhancements are based on the algorithms in the CALINE4 model.

ROADS MetCALINE screenshot

Users can define the meteorological conditions for their model run by copying and pasting values into the dialog box from an external table, or by simply entering the values into the dialog box.


ROADS MetrCAL3QHC screenshot1 ROADS MetrCAL3QHC screenshot2


When choosing the CAL3QHC or CALINE4 model, users are prompted to define the meteorological data conditions, as well as the site characteristics. The required meteorological conditions vary for each model, however, for the site characteristics in both models, users can enter a value for the roughness length, or select a value from the built-in list of typical values for a variety of surfaces.

CAL3QHCR Two-Tiered Approach

Flexibility has been built into the CAL3QHCR module of BREEZE ROADS to allow for a two-tiered approach. In the first approach, called Tier I, a full year of hourly meteorological data are entered into CAL3QHCR in place of the single hour of artificial meteorological data that are commonly entered into the CAL3QHC and CALINE4 modules. One hour of emissions traffic volume (ETS) data is also entered, just as in the CAL3QHC module. In the second approach, called Tier II, the same meteorological data is used as in a Tier I approach. The ETS data, however, are more detailed and reflect traffic condition for each hour of a week.

CAL3QHCR reads the ETS data as up to 7 sets of hourly ETS data (in the form of diurnal patterns) and processes the data into a week of hourly ETS data. The weekly ETS data are synchronized to the day of the week of the meteorological data year. The weekly traffic conditions are assumed to be the same for each week throughout the modeled period.

ROADS MetrCAL3QHCR screenshot 1


ROADS MetrCAL3QHCR screenshot 2 ROADS MetrCAL3QHCR screenshot 3


CAL3QHCR requires that users upload a meteorological file, identify the data period, and describe the site characteristics. As with the CAL3QHC and CALINE4 models, for the site characteristics users can enter a value for the roughness length, or select a value from the built-in list of typical values for a variety of surfaces.

Additional Met Features

Background concentrations can be included or excluded from a given model run. In a Tier II approach, background concentrations can be varied by hour of the day. If modeling NO2 in CAL3QHCR, an external ambient background file is required that contains ambient concentrations of O3, NO, and NO2. BREEZE ROADS includes a tool to generate this file.

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