1. AERMINUTE Course #423 Day 2 Morning Air Pollution Dispersion Models:
Applications with the AERMOD Modeling System
AERMINUTE
Course #423
Day 2 Morning

2. Day 2 Morning: AERMINUTE

3. Overview This lesson introduces: Why AERMINUTE is Necessary
How to Obtain the Data for AERMINUTE
Creating the Input Control File for AERMINUTE
Running AERMINUTE
Reviewing AERMINUTE Output

4. Learning Objectives At the end of this training, you will understand:
Issues associated with NWS wind data archived with standard formats and why there is a need to supplement the data with results from AERMINUTE
AERMINUTE data requirements
Data quality issues and validation options
How to construct a control file
How to run AERMINUTE and review the output

5. Why Supplement Standard ASOS Data
Calm and variable winds in standard NWS formats
Hourly wind observations in NWS formats are based on a short-term average
Regulatory agency requirement?
Prior to the introduction of ASOS, observations were taken by trained observers. The frequency of calms reported on an annual basis was on the order of a few percent.
With the introduction of ASOS-derived winds, the frequency of calm wind conditions jumped significantly, sometimes as high as 15%-20% annually
ASOS wind observations in the standard NWS archive format(s) read and processed by AERMET are a short term (2-minute?) average reported on the hour. Since AERMOD does not make calculations for calm wind conditions, the frequency of calm wind conditions is problematic.
ASOS wind data consists of running 2-minute average winds, reported every one (1) minute, for commissioned ASOS stations. The National Climatic Data Center (NCDC) archives the 2‑minute average wind speeds for each minute of the hour for most ASOS stations. This data is referred to as “1-minute ASOS data”. NCDC makes this data freely available to the public.
Beginning July 1996, surface observation reports began following METAR coding conventions, an international standard code format for hourly surface weather observations. The acronym comes from French and roughly translates as Aviation Routine Weather Report.
Under the METAR convention, a calm wind is defined as a wind speed less than 3 knots and is assigned a value of 0 knots. The METAR code also introduced the variable wind observation that may include wind speeds up to 6 knots, but the wind direction is reported as missing if the wind direction varies more than 60 degrees during the 2-minute averaging period for the observation. AERMOD does not simulate dispersion under calm or missing wind conditions.
To alleviate this issue, the AERMINUTE preprocessor was written compute 1-hour averaged values of wind speed and direction from an entire hours worth of 1-minute ASOS data to which the METAR coding standards have not been applied. The results from AERMINUTE are introduced into AERMET at the point where one-day blocks of data are processed (stage 2).
Use of the hourly-averaged 1-minute ASOS data should be reviewed by the regulatory agency that has jurisdiction of a modeling demonstration.

6. ASOS Data Products 1-Minute Data from NCDC
ftp://ftp.ncdc.noaa.gov/pub/data/asos-onemin/
For each station and year, files are available in monthly blocks, i.e. one file per month for a station
Files are generally named 64050XXXXYYYYMM.dat where XXXX is the four-character station call sign, and YYYY and MM are the 4-digit year and 2-digit month
File format
1-minute ASOS data is available from the NCDC at the FTP site shown on the slide.
The data are segregated by data type into distinctly named folders such as “ ” and “ ” where 6405 indicates that the subfolders contain wind data and 6406 indicates temperature data. The 2000 indicates data for the year 2000; likewise, 2012 is for the year 2012.
Within the 6405 folders, the wind data files are named based on the following convention:
data type (6405 for wind), station ID (4-characters beginning with K or P or T), year (4-digit), and month (2-digit).
A web address to the file format documentation is also provided on the slide.

7. ASOS Data Products Standard NWS Observations – ISH format
Integrated Surface Hourly (ISH) data is now available free of charge from the National Climatic Data Center’s (NCDC’s) FTP site:
ftp://ftp3.ncdc.noaa.gov/
Go to pub/data/noaa
Go to the appropriately named “year” directory
The filenames correspond with the station numbers listed in the ish-history.txt file -- eg, corresponds with USAF number and WBAN number
Note: ISH data should be downloaded from the FTP site. Data downloaded from the web site is in the abbreviated ISH format and will not run in AERMET.
ftp3.ncdc.noaa.gov
Go to pub/data/noaa/
Enter the directory for the year of interest.
The filenames correspond with the station numbers listed in the ish-history.txt file -- eg, corresponds with USAF number and WBAN number

8. Ice Free Winds
ASOS Ice-Free Wind (IFW) sensor program replaced the original cup and vane sensors with heated sonic anemometers
Wind speeds less than 2 knots are treated differently in AERMINUTE based on whether the station uses a sonic or cup and vane anemometer during the data period
Sensor replacement began in 2005
List of stations with their IFW installation dates, as of October 27, 2009, can be found at
More information on ice-free winds at
The ASOS Ice-Free Wind (IFW) sensor program replaced the original cup and vane sensors with heated sonic anemometers beginning in 2005.
Low wind speeds collected from the two different types of anemometers are treated differently in AERMINUTE.
Wind speeds less than 2 knots from a station that is not part of IFW at all or at the time of interest are set to 1 knot (0.51 m/s)
Wind speeds less than 2 knots from a station that is part of IFW at the time of the record are converted to m/s
Wind speeds that are 2 knots or greater are converted to m/s
Flags that control whether to keep the observation or not and whether to treat it as a calm are also set depending on which condition applies.
The link for more information takes you to a web page with a list of links – look for ‘ice-free.’

9. Data Issues and Quality Assurance
Wind speeds in the 1-minute ASOS data, as well as ASOS data in standard archives, are truncated, rather than rounded, to whole knots.
This truncation of the ASOS wind speeds introduced a bias towards lower wind speeds.
i.e., 3.9 knots is truncated to 3.0 knots
To adjust for this bias, AERMET adds ½ knot (0.257 m/s) to all ASOS wind speeds, beginning with version 11059
The hourly-averaged wind speeds generated by AERMINUTE are not adjusted to account for the bias introduced by truncating the ASOS wind speeds to whole knots
AERMET processing, beginning with version 11059, applies the truncation adjustment for all ASOS wind speeds, including those derived from 1-minute data

10. Example Input Control File
A control file instructs AERMINUTE on how to process the data
STARTEND
IFWGROUP Y
DATAFILE STARTING
64050KRIC dat
64050KRIC dat .
64050KRIC dat
64050KRIC dat
DATAFILE FINISHED
SURFDATA STARTING
dat
SURFDATA FINISHED
OUTFILES STARTING
HOURFILE richmod_05.dat
SUMMFILE minute_summary_richmond.csv
COMPFILE checks_richmond.csv
OUTPUT FINISHED
Note that the control file is constructed with one or more spaces between each value on a record
In this example, there are 8 more monthly files for the DATAFILEs, but are not shown due to space limitations on the slide.
We will see a similar, but complete, control file in the hands-on.

11. Control Options
Unless otherwise noted, all control file keywords and parameters are mandatory
STARTEND – the starting and ending month and year to process
start_month
start_year
end_month
end_year
IFWGROUP – ice-free wind group
Status – indicates if the station is part of the IFW group
comm_month – ASOS commissioning month
comm_day – ASOS commissioning day
comm_year – ASOS commissioning year
STARTEND - the starting and ending month and year to process;
start_month start_year – self-explanatory
end_month end_year – self-explanatory
The start day and hour are assumed to be the first day and hour of the month
The end day and hour are assumed to be the last day and hour of the month (assumed to be hour 24)
IFWGROUP
status - whether or not the site is part of the IFW group – options are ‘Y’ and ‘N’ (without quotes, upper or lower case)
comm_month – the month the ASOS instrumentation was put into service
comm_day – the day the ASOS instrumentation was put into service
comm_year – the year the ASOS instrumentation was put into service
The hour of commission is assumed to be 1.
If AERMINUTE detects that the user indicated the station is part of the IFW group, it checks the commission date against the end date listed on the STARTEND keyword. If the commission date is after the end date in STARTEND, AERMINUTE resets the status of the station and notifies the user

12. Control Options
DATAFILE STARTING - list of data files to process is next
Datafiles_list
DATAFILE FINISHED - list of data files is completed
SURFDATA STARTING (Optional) - list of standard NWS data files
Surface_files_list
SURFDATA FINISHED - list of standard files is completed
DATAFILES STARTING and DATAFILES FINISHED are mandatory and denote the beginning and ending of the data files list.
The Datafiles _list lists the 1-minute data files to process. Files should each be listed on a separate line and include the absolute or relative path and filename.
Files that include spaces in the filename should be enclosed in double quotation marks.
If multiple 1-minute data files are to be read into AERMINUTE, they do not have to be in temporal sequential order and can cover dates not included in the file processing. AERMINUTE will process all files listed
The files should be listed for one station only:
If more than one station based on the WBAN number is detected, a fatal error is issued and AERMINUTE aborts further processing
If more than one station based on the call sign (e.g. KRDU) is detected but the WBAN number stays the same, AERMINUTE issues a warning
SURFFILES STARTING and SURFFILES FINISHED are only mandatory if a list of hourly surface weather files are to be provided
The Surface_files_list lists the standard hourly NWS files to process
Used in the validation of non-quality controlled 1-minute winds against the quality controlled standard observations
AERMET currently only processes ISH data files

13. Control Options OUTFILES STARTING – list of output files follows
HOURFILE name
SUMMFILE name (Optional)
COMPFILE name (Optional)
OUTFILES FINISHED - list of output files is completed
OUTFILES STARTING and OUTFILES FINISHED are mandatory
The filenames for the output from AERMINUTE; note that only HOURFILE is mandatory
HOURFILE - the file of hourly averaged winds output from AERMINUTE and formatted for input into AERMET in Stage 2
SUMMFILE - comma delimited summary file that details the number of minutes used for each hour as well as minimum, maximum, and average wind speed and direction
COMPFILE - comma delimited file that lists the winds from the 1-minute data and standard observations for all observation times listed in the standard observations file. This keyword must be present if the SURFDATA keywords are used

14. Running AERMINUTE Windows environment – double-click aerminute.exe
Command prompt environment – type ‘aerminute’ (without quotes) and press return
In both cases you are prompted for the name of the control file
File checking
Record processing
Averaging process
Running AERMINUTE
File checking
Once AERMINUTE has read the input control file, the program reads the list of 1-minute data files and checks that each file exists and that there are no duplicate filenames. If there are non-existent files or duplicate names, AERMINUTE notifies the users of the filenames and aborts; a similar process is performed for the SURFFILES if any are listed in the control file
Record Processing
A complete explanation can be found in the user’s manual of how the 1-minute data are processed, flagging the data as valid/invalid for computing an average, and quality control / validation using the SURFFILE
Averaging Process – wind speed
Hourly averaged wind speeds are the arithmetic averages of the wind speeds for all valid minutes for the hour, including those flagged as calm, using half the threshold
Averaging Process – wind direction
For wind directions, the x- and y-components of non-calm observations are summed; these sums are used to calculate the wind direction based on a unit-vector approach

15. Reviewing AERMINUTE Output
Up to six output files are generated by AERMINUTE, depending on the user options:
Hourly averaged winds file (HOURFILE)
Good_records.dat
Bad_records.dat
Check_records.dat
Optional summary file (SUMMFILE)
Optional standard observations vs. 1-minute data file (COMPFILE)
AERMINUTE.log
Reviewing AERMINUTE Output
AERMET can generate up to six different output files, each of which are listed and is explained in more detail on the following slides

16. Reviewing AERMINUTE Output
HOURFILE
AERMINUTE Version WBAN: Call sign: KRIC IFW: N
Reviewing AERMINUTE Output
HOURFILE
First record: program name, version number, station identifier (WBAN and call sign), and if station/dates are part of an IFW group
Data records:
2-digit year
2-digit month
2-digit day
2-digit hour (1-24)
Wind speed (m/s)
Wind direction (degrees)
AERMINUTE writes the HOURFILE in a fixed format, but AERMET reads the data in free format, i.e. the data fields are separated by spaces.
For hours that are missing or not considered valid due to an insufficient number of non- calm observations, the wind speed and direction are both set to
Calm hours are denoted by a wind speed of 0.0 and wind direction of 0.0.

17. Reviewing AERMINUTE Output
Good_records.dat:
records that meet the strict quality control checks and the winds from the input files are considered valid
Check_records.dat:
records that did not meet the strict quality control and are not used in calculating hourly averages, but the wind observations are close to the locations, i.e. column locations, set by strict quality control
Bad_records:
records from the 1-minute files that did not meet the strict quality controls, and are unlikely to contain usable data
Reviewing AERMINUTE Output
Good_records.dat, check_records.dat, and bad_records.dat: these filenames are hard-wired into AERMINUTE
These three files that contain the full 1-minute data records, depending on whether AERMINUTE determines that the record contains “good” data that can be used to calculate the hourly averages (good_records); contains data that do not meet strict quality control checks on the format but may contain useable data (check_records); or contains data that are unusable due to serious formatting problems (bad_records).
If the user determines that additional valid data can be obtained by appropriately editing the “check_records.dat‟ data file, the user can rename the “good_records.dat‟ and “check_records.dat‟ files, replace the files listed in the control input file with these renamed files and rerun AERMINUTE to get new hourly averages

18. Reviewing AERMINUTE Output
SUMMFILE:
optional summary file
COMPFILE:
optional file comparing standard observations vs. 1- minute data file
Log file:
a log of the processing (AERMINUTE.log)
Reviewing AERMINUTE Output
SUMMFILE
The SUMMFILE is an optional file containing a comma delimited summary that includes each hour in the data period is listed, including those not in the 1-minute files, with counts of minutes for the hour and can be used as a quality assurance check against the hourly averaged winds file. Also included for each hour are the minimum and maximum 2-minute wind speeds and directions used in the hourly calculations, as well as the hourly averaged wind speeds and directions that are listed in the HOURFILE. The minimum and maximum wind speeds and directions are unpaired in time.
COMPFILE
Optional file that compares standard observations to the hourly-averaged 1-minute results.
Log file
Information on what options were used, what data were processed, counts of various sorts, a data QC summary, minimum and maximum speed and direction, and a summary of valid/invalid/calm/missing hours. The log file contains all the relevant information that is printed to the screen plus the QC summary, minima and maxima, and counts information.

19. Summary In this section, we covered the following topics:
Why AERMINUTE is Necessary
Obtaining Data for AERMINUTE
Creating the Input Control File for AERMINUTE
Running AERMINUTE and Reviewing the Output