The modeling episode is the total time period for which you will run SMOKE and your AQM. Unless the episode is just a few days long, users typically set up SMOKE to create emissions files of a shorter duration than their modeling episode, often creating one-day files for each day of their episode. Though SMOKE can create a single file for an entire episode, the file often becomes too large for some computers to handle (the limit for 32-bit operating systems is 2 GB files), so necessity rather than preference dictates that smaller files (usually one-day files) be created by SMOKE. We use the term “run period” to distinguish between these shorter durations and the full modeling episode; unless otherwise noted, we will assume that the run period is one day. For example, a typical SMOKE episode might cover July 1, 1996 through July 31, 1996. There will be 31 run periods (days) within this episode, the first starting on July 1, 1996 and the last starting on July 31, 1996.
In the SMOKE Assigns file, there are several settings that you need to change to cause SMOKE to create emissions for the episode of interest. Section 4.5, “How to use SMOKE” provides more guidance on the particular form and approaches needed for using these settings.
The episode start date (EPI_STDATE), episode start time (EPI_STTIME), episode duration in hours (EPI_RUNLEN), and the episode number of days (EPI_NDAY) all must be set to cover the modeling episode. Note that SMOKE can only be run for periods contained within a single calendar year. It cannot, for example, start in December of 1996 and run through January of 1997. Two separate episodes would need to be set up in this case, with the first ending on December 31, 1996, and the second starting on January 1, 1997.
The start date of the first run period needs to be set using the G_STDATE and ESDATE settings. The G_STDATE is the year and Julian day setting used by the SMOKE programs; in our example above, G_STDATE would be set to 1996183, since July 1 is the 183rd day of 1996. The ESDATE is the Gregorian date used in naming the SMOKE intermediate and output files; for our example, ESDATE would be 19960701. The SMOKE scripts will use the EPI_NDAY setting to automatically loop through the number of run periods in the episode, starting with the first G_STDATE value in the Assigns file. The G_STDATE and ESDATE settings are changed for each run period.
The run period start time (G_STTIME) and duration (G_RUNLEN) must also be set to indicate the start time and length of each run period. Both values are provided as a number of hours, using a HHMMSS (hours, minutes, seconds) format.
The run period duration (G_RUNLEN) is usually not the same as the episode duration (EPI_RUNLEN). For example, if the episode length is 30 days (720 hours), the run period duration setting could be just 1 day (25 hours), 2 days (49 hours), or three days (73 hours) (the reason for the extra hour in each case is explained below). In the first case, SMOKE would create thirty 25-hourfiles; in the second case, fifteen 49-hour files; and in the third case, SMOKE would create ten 73-hour files.
The NDAYS, MSDATE, and MDAYS settings are used for naming files. The NDAYS setting should be set to the number of days in each run period, and is used by default for naming time-based files. The NDAYS setting is also used along with the EPI_NDAY setting to loop through the run periods in the episode. The MSDATE and MDAYS settings can be used for naming the meteorology input files, but are not being used by the default Assigns files provided with SMOKE.
There are a few key things to remember when you are verifying that you have the correct episode settings:
SMOKE cannot process emissions over a calendar-year break. Thus, the longest run that can be done is for 365 days, with the episode start date being January 1. If a modeling episode spans multiple years, then a different Assigns file, script, and sets of input files must be created for each year.
The AQMs supported by SMOKE always need one extra hour in each emissions input file due to how they calculate boundary conditions. Therefore, if you are inputting emissions to run a 24-hour period, the G_RUNLEN setting should be 250000 for 25 hours.
The CMAQ, REMSAD, and CAMX models can accept emissions files for multiple days, but the UAM must have 25-hour files only. As stated earlier, however, all of these models are often run using 25-hour files, with one file for each day of the episode.
All times are associated with a time zone, including the episode and run period start time settings. These settings must be consistent with the time zone of the meteorology files. If the meteorology data were created using MM5, the time zone is most likely Greenwich Mean Time (GMT); therefore, the EPI_STDATE, EPI_STTIME, G_STDATE, and G_STTIME settings would have to be provided in that same time zone. Whatever time zone is inherent in the meteorology files and these date settings will also be the time zone of the dates and times in the output emissions files from SMOKE. This ensures that the dates and times of the emissions and meteorology files are consistent for input to the AQM.