In this topic, we will address the AERMINUTE sub-processor, which is responsible for collecting minute-by-minute wind data to generate an output that will be used as input for the AERMET processor.

It is used to process minute-by-minute wind observations in order to provide more accurate and representative data for calm winds and wind direction. It generates an .out file.

AERMINUTE is used to:

1. Correct and refine wind data provided by meteorological stations (such as METAR), which typically report wind data hourly (often with calm winds or variable direction).
2. Reduce the number of “calms” in the data — i.e., situations where wind is reported as 0 m/s — which can be unrealistic and negatively affect AERMOD modeling results.
3. Supplement surface wind data, especially when no continuous measurement tower is available.

To download the executable, access the website: AERMINUTE - EPA SCRAM Scroll down to the AERMINUTE section and click on the link indicated in the figure to download the file. Don’t forget to save it in the folder: C:\Users\Cliente\Desktop\AermodTutorial\2.AERMINUTE.

Finally, extract the downloaded ZIP file into the selected folder.

In this section, we will download METAR data, which are hourly meteorological observations (or more frequent in the case of SPECI reports) collected by surface stations, such as airports.

These data are fundamental for our modeling system, as they will provide more accurate wind data when processed by AERMINUTE.

Access the following link: NOAA DATA 2024

Download the following file:

1. 724397-54831-2024.gz

Save the file in the AERMINUTE folder. This file contains METAR data for the Central Illinois Regional Airport at Bloomington-Normal (KBMI).

In this section, we will download ASOS data to enhance the resolution and quality of the wind data used in atmospheric dispersion modeling. These are processed by AERMINUTE, which outputs compatible data for AERMET.

Purpose of ASOS data:

1. Replace/adjust METAR wind data that does not contain continuous values.
2. Provide average hourly wind speed and direction with greater accuracy.
3. Improve the representation of the mixing layer and atmospheric stability in AERMOD.

To download the 1-minute data, access the link: https://www.ncei.noaa.gov/data/automated-surface-observing-system-one-minute-pg1/access/2024/

Click on the link for `01/` to access the January data:

Search for the station KPIA using your browser's search function and click on the corresponding link:

Right-click and choose “Save As”, then rename the file to: asos-1min-pg1-KPIA-202401 (remove the .dat extension) Save it in the AERMINUTE folder: C:\Users\Cliente\Desktop\AermodTutorial\2.AERMINUTE

Now, go back to the page: https://www.ncei.noaa.gov/data/automated-surface-observing-system-one-minute-pg1/access/2024/ or navigate back two pages, and repeat the process for all remaining months of the year 2024.

After downloading the necessary files, create the input file for the executable, which we will call aerminute.txt, as shown in the code below:

STARTEND  01 2024 01 2025

IFWGROUP y  09  18  2006

DATAFILE STARTING
asos-1min-pg1-KPIA-202401.txt
asos-1min-pg1-KPIA-202402.txt
asos-1min-pg1-KPIA-202403.txt
asos-1min-pg1-KPIA-202404.txt
asos-1min-pg1-KPIA-202405.txt
asos-1min-pg1-KPIA-202406.txt
asos-1min-pg1-KPIA-202407.txt
asos-1min-pg1-KPIA-202408.txt
asos-1min-pg1-KPIA-202409.txt
asos-1min-pg1-KPIA-202410.txt
asos-1min-pg1-KPIA-202411.txt
asos-1min-pg1-KPIA-202412.txt
DATAFILE FINISHED

SURFDATA STARTING
724397-54831-2024.DAT
SURFDATA FINISHED

OUTFILES STARTING

HOURFILE KPIA_2024_1-Min_hour.out
SUMMFILE KPIA_2024_1-Min_summ.out
COMPFILE KPIA_2024_1-Min_comp.out

OUTFILES FINISHED

• STARTEND 01 2024 01 2025 – Defines the time range of data to be processed. In this case, from PRIMEIRO DE JANEIRO DE 2024 ATE 31 DE DEZEMBRO DE 2024.
• IFWGROUP y 09 18 2006, 09 18 2006 – Enables the Instrument Flight Rules Wind (IFW) method. The date when the station began reporting under IFW rules.
• DATAFILE STARTING – Marks the beginning of the list of ASOS 1-minute data files. Each file represents a full month of data from the KPIA station (Peoria/Bloomington, IL) in 2024.
• DATAFILE FINISHED – Ends the ASOS data block.
• SURFDATA STARTING – Begins the section for METAR hourly data files that complement the 1-minute data.
• 724397-54831-2024.DAT - This file contains the hourly METAR data from KPIA station for the year 2024.
• SURFDATA FINISHED – Ends the METAR data section.
• OUTFILES STARTING - Starts the definition of the output files to be generated by AERMINUTE
• HOURFILE KPIA_2024_1-Min_hour.out - Contains the adjusted hourly average wind speeds and directions.
• SUMMFILE KPIA_2024_1-Min_summ.out - Summary file with statistics about the processed data.
• COMPFILE KPIA_2024_1-Min_comp.out - Comparison file between original METAR data and AERMINUTE-adjusted data.
• OUTFILES FINISHED - Ends the output file section.

Open the Command Prompt (CMD), navigate to the executable folder by typing: cd C:\Users\Cliente\Desktop\AermodTutorial\2.AERMINUTE and press Enter.

Then type: aerminute_15272 press Enter, and finally type: `aerminute.txt` and press Enter again.

This will execute the program and generate the output files needed for use in AERMET.

If everything runs correctly, the CMD will display the following message:

After successfully running the AERMINUTE executable, three output files will be generated. Each serves a specific purpose and provides key information used in the next steps of the modeling process, particularly within the AERMET preprocessor.

This file contains the final hourly-averaged wind speed and direction values, computed from 1-minute ASOS data. These refined values reduce the number of calm wind records and better represent wind variability at the site.

Example:

AERMINUTE Version 15272  WBAN: 14842    Call sign: KPIA    IFW: Y    IFW date: 09/18/2006 5-MIN USED: N
24  1  1  1   3.06 319.0
24  1  1  2   2.96 326.0
24  1  1  3   2.84 325.0
24  1  1  4   2.74 323.0
24  1  1  5   3.13 333.0

Columns:

• YY: Year (last two digits)
• MM: Month
• DD: Day
• HH: Hour (UTC)
• WS: Averaged wind speed (m/s)
• WD: Averaged wind direction (degrees)

This file will be used as input in the AERMET processor and must be saved in: C:\Users\Cliente\Desktop\AermodTutorial\3.AERMET

This file compares the hourly wind data derived from 1-minute ASOS observations against the original METAR data. It is useful for checking how much AERMINUTE adjusted the wind speeds and directions.

Example:

date(yyyymmdd),hour,minute,calm flag,1-min dir,1-min dir10,1-min speed,1-min speed_1,obs. dir,obs. speed,dirdiff,speeddiff,wind flag,qc flag
20240101, 2,56,0,   328.0,   330.0,     2.5,     2.6,   330.0,     7.2,     0.0,     4.6,N,5
20240101, 3,56,0,   311.0,   310.0,     2.5,     2.6,   330.0,     5.1,    20.0,     2.5,N,5

Key Columns Explained:

• 1-min dir / speed: Wind direction and speed from 1-minute ASOS data.
• obs. dir / speed: Original METAR-reported values.
• dirdiff / speeddiff: Differences between 1-minute and METAR values.
• calm flag: `1` if wind speed is calm (0 m/s), `0` otherwise.
• wind flag: Indicates valid (`N`) or calm data.
• qc flag: Quality control flag.

This file is not required for AERMET, but is helpful for data validation and QA/QC documentation.

This summary file contains hourly statistics calculated from the 1-minute data, including counts of calm conditions, even/odd minute observations, and min/avg/max wind speed and direction. It also shows whether the IFW adjustment was applied.

Example:

Date,hr,flag,IFW flag,total minutes,total calms,total even,even calms,total odd,total odd calm,odd used,odd calms used,min speed,avg speed,max speed,min dir,avg dir,max dir
20240101,01,V , 1,59, 0,30, 0,29, 0, 0, 0,  1.53,  3.06,  4.08,307,319,333
20240101,02,V , 1,59, 0,30, 0,29, 0, 0, 0,  2.04,  2.96,  3.57,318,326,337

Column Descriptions:

This file provides a quick overview of data quality and calm wind frequency, helping modelers determine the reliability of hourly wind averages.

Once the execution is complete, save the file KPIA_2024_1-Min_hour.out in the folder: C:\Users\Cliente\Desktop\AermodTutorial\3.AERMET, as it will be used as input for the AERMET processor.