5.3.11. Metscan Description Processing Order Files and Environment Variables Description

Metscan reads in a single (often annual) temperature I/O API meteorology data file (created from either the MET_CRO_2D or MET_CRO_3D files) and determines the first freeze date and last freeze date of a year, by grid cell. It outputs a gridded file with a daily (24-hour) time step that contains a single variable. For each grid cell, that variable has a value of 0 (zero) when the date being modeled indicates that the cell is experiencing winter conditions; otherwise it has a value of 1, indicating summer conditions. The program can be set to run in the Northern Hemisphere or in the Southern Hemisphere (it will not work on global meteorology datasets). In the Northern Hemisphere, the first freeze date in the fall marks the start of winter, and the last freeze date in the spring marks the end of winter; all other days are considered summer days. The seasons are reversed in the Southern Hemisphere, and the program accommodates this accordingly.

Both the BEIS2 and BEIS3 models operate using the assumption of either winter or summer emission factors. There are no spring or fall factors available, which is why this program is limited to the choice of summer or winter. The use of the freeze date to determine summer or winter emission factors is based on EPA’s recommendation.

The program reads in the name of the temperature variable as an option, so that the ground temperature, 1.5-meter temperature, or 10-meter temperature can be used from the MET_CRO_2D file, or the layer-1 temperature can be used from the MET_CRO_3D file. See the TMPR_VAR option below for more information on the names of the temperature variables that are acceptable. Processing Order

Metscan can optionally be used before Tmpbio, which does not require the output from Metscan to run. Metscan is needed only when users wish to have Tmpbio automatically switch between winter and summer emission factors by grid cell. This approach is recommended when processing time periods and modeling domains include temperatures below 32 °F either for a substantial number of days relative to the number of episode days or at critical dates in the episode. Files and Environment Variables Input Files
File Name Format Description

Meteorology file that can be a 2-D or 3-D file (though the logical file name is the same in both cases) and needs to include all dates in the modeling period. For example, for an annual SMOKE run this file would need to have all hours of the year. The file can be created by extracting one or more temperature variables (at a minimum, the one you intend to use) out of the MET_CRO_2D or MET_CRO_3D files output by the MCIP or MCPL programs using the m3xtract I/O API utility and appending all days of data into the same file.

The m3xtract utility documentation is provided with the I/O API, but we provide some information here. The utility expects input logical file name INFILE and creates output logical file name OUTFILE. It prompts for the start date, start time, duration, and variables that you want to extract from the INFILE. If OUTFILE already exists, m3xtract appends additional data to the file (assuming that the grid is the same and the time period is sequential). Input Environment Variables
  • TMPR_VAR: [default: TA]

    Sets the name of the temperature variable that will be read from the MET_CRO_3D input file. Acceptable values for MCIP and MPCL outputs available at the time of this writing are TA (ambient layer-1 temperature from the MET_CRO_3D file), TEMP10 (10-meter temperature from the MET_CRO_2D file), TGD (ground temperature), TGRND (ground temperature), and TEMP1P5 (1.5-meter temperature). Current guidance from EPA suggests that a 10- to 20-meter temperature is the best choice for the temperature input to BEIS2 or BEIS3, to account for the fact that these models do not include a canopy model.

  • N_S_HEMI: [default: NORTH]

    Sets the program to run for the Northern or Southern Hemisphere. Acceptable values for this setting are:

    • NORTH: Northern Hemisphere. Program starts July 1 and scans data in reverse chronological order to find the last freeze date and in chronological order to find the first freeze date.

    • SOUTH: Southern Hemisphere. Program starts January 1 and scans data in chronological order to find the first freeze date. It also starts December 31 and scans the data in reverse chronological order to find the last freeze date. Output Files
File Name Format Description
BIOSEASON I/O API NetCDF For each grid cell, contains 0 for winter dates and 1 for summer (nonwinter) dates. The file’s duration will be as long as that of the input meteorology file you provide.
LOGFILE ASCII Log generated from executing Metscan