Gridded Weather File (.ATM)

FARSITE accepts gridded inputs for weather variables. The weather variables are separated into two categories; weather and winds.

This separation allows some flexibility in providing gridded inputs or stream inputs. You can provide both gridded weather and wind variables or a combination of the standard weather stream (Weather (.WTR) File) along with gridded wind variables.

Data Units

Data units are the same as those used for weather and wind stream inputs for FARSITE to allow compatibility with both GRASS and ARC GRID data:

Temperature Fahrenheit (integer)

Humidity Percentage (integer)

Precipitation Inches X 100 (integer)

Wind Speed MPH, 20 foot open wind (integer)

Wind Direction Azimuth Degrees (integer)

Cloud Cover Percentage (integer)

Note: The current fuel moisture models can only use precipitation as a single daily value. This means that your gridded Precipitation Files should each contain the total precipitation for the day.

Resolution and Registration

Each of the six gridded inputs can be of different resolutions and do not need to be co-registered. For example, the resolution for temperature could be 500m but the wind resolution could be 50m. The coverage of each file can also be offset so long as the extent of each grid file covers the landscape on which the fire will be burning.

Input Formats

Accepted formats for the individual grid files are ASCII raster outputs from GRASS or ARC GRID. Depending on the file type, you must have one of these headers included in each file:

Specifying Input Files

The filenames of the gridded input files must be included into an Atmosphere (.ATM) File to specify which files are assigned to each date and time. The format for the Atmosphere (.ATM) File depends on if you are using gridded inputs for both weather and wind variables or just wind variables:

Both Weather and Wind Variables in Gridded Format

the following ASCII format is used in the Atmosphere (.ATM) File:

WEATHER_AND_WINDS

MONTH  DAY  HOUR  TEMP  HUMID  PPT  WSPEED  WDIR  CLDCOVER

For example, if the names of your gridded files are "TESTxx.XXX" your Atmosphere (.ATM) File might look like this for three days beginning 7/15 and ending 7/17:

WEATHER_AND_WINDS

7 15 0200 TEST01.TMP TEST01.HMD TEST01.PPT TEST01.SPD TEST01.DIR TEST01.CLD

7 15 0600 TEST02.TMP TEST02.HMD TEST02.PPT TEST02.SPD TEST02.DIR TEST02.CLD

7 15 1200 TEST03.TMP TEST03.HMD TEST03.PPT TEST03.SPD TEST03.DIR TEST03.CLD

7 15 1600 TEST04.TMP TEST04.HMD TEST04.PPT TEST04.SPD TEST04.DIR TEST04.CLD

7 15 2000 TEST05.TMP TEST05.HMD TEST05.PPT TEST05.SPD TEST05.DIR TEST05.CLD

7 16 0200 TEST06.TMP TEST06.HMD TEST06.PPT TEST06.SPD TEST06.DIR TEST06.CLD

7 16 0600 TEST07.TMP TEST07.HMD TEST07.PPT TEST07.SPD TEST07.DIR TEST07.CLD

7 16 1200 TEST08.TMP TEST08.HMD TEST08.PPT TEST08.SPD TEST08.DIR TEST08.CLD

7 16 1600 TEST09.TMP TEST09.HMD TEST09.PPT TEST09.SPD TEST09.DIR TEST09.CLD

7 16 2000 TEST10.TMP TEST10.HMD TEST10.PPT TEST10.SPD TEST10.DIR TEST10.CLD

7 17 0200 TEST11.TMP TEST11.HMD TEST11.PPT TEST11.SPD TEST11.DIR TEST11.CLD

7 17 0600 TEST12.TMP TEST12.HMD TEST12.PPT TEST12.SPD TEST12.DIR TEST12.CLD

7 17 1200 TEST13.TMP TEST13.HMD TEST13.PPT TEST13.SPD TEST13.DIR TEST13.CLD

7 17 1600 TEST14.TMP TEST14.HMD TEST14.PPT TEST14.SPD TEST14.DIR TEST14.CLD

7 17 2000 TEST15.TMP TEST15.HMD TEST15.PPT TEST15.SPD TEST15.DIR TEST15.CLD

Only Wind Variables in Gridded Format

The Atmosphere (.ATM) File format would look like this:

WINDS_AND_CLOUDS

MONTH  DAY  HOUR  WSPEED  WDIR  CLDCOVER

The Atmosphere (.ATM) File would look like this with only wind variables in gridded format:

WINDS_AND_CLOUDS

7 15 0200 TEST01.SPD TEST01.DIR TEST01.CLD

7 15 0600 TEST02.SPD TEST02.DIR TEST02.CLD

7 15 1200 TEST03.SPD TEST03.DIR TEST03.CLD

7 15 1600 TEST04.SPD TEST04.DIR TEST04.CLD

7 15 2000 TEST05.SPD TEST05.DIR TEST05.CLD

7 16 0200 TEST06.SPD TEST06.DIR TEST06.CLD

7 16 0600 TEST07.SPD TEST07.DIR TEST07.CLD

7 16 1200 TEST08.SPD TEST08.DIR TEST08.CLD

7 16 1600 TEST09.SPD TEST09.DIR TEST09.CLD

7 16 2000 TEST10.SPD TEST10.DIR TEST10.CLD

7 17 0200 TEST11.SPD TEST11.DIR TEST11.CLD

7 17 0600 TEST12.SPD TEST12.DIR TEST12.CLD

7 17 1200 TEST13.SPD TEST13.DIR TEST13.CLD

7 17 1600 TEST14.SPD TEST14.DIR TEST14.CLD

7 17 2000 TEST15.SPD TEST15.DIR TEST15.CLD

These Atmosphere (.ATM) Files are input to FARSITE using the Input > Project Inputs dialog box. If you are supplying both weather and wind variables in the Atmosphere (.ATM) File, then the Atmosphere (.ATM) File should be selected as a Weather (.WTR) File. In this case you will not need to supply any Wind (.WND) Files. If you are supplying only the wind variables in the Atmosphere (.ATM) File, the Atmosphere (.ATM) File should be selected as a Wind (.WND) File and you will need to also supply a weather stream in the standard Weather (.WTR) File format. You cannot specify more than one Atmosphere (.ATM) File for gridded weather or wind variables. You also cannot specify more than one Weather (.WTR) File if an Atmosphere (.ATM) File has been selected for gridded wind variables.