Description of Panels

  • Monthly Mean: Monthly mean values of MERRA-2 variables for a specific year.
  • Climate Mean: Long-term mean (climatology) of monthly MERRA-2 variables over the period 1981-2010.
  • Monthly Anomaly: Monthly mean values of MERRA-2 variables for a specific year minus their corresponding long-term mean values.
  • Climate Stdev: Standard deviation of monthly MERRA-2 variables over the period 1981-2010. This represents the interannual variability for each month.

Field Names

2D Fields
  • FWI: Fire Weather Index (more info below)
  • SLP: Sea Level Pressure (mb)
  • U50M: Zonal wind at a height of 50 m (m/s)
  • V50M: Meridional wind at a height of 50 m (m/s)
  • T2M: Air temperature at a height of 2 m (°C)
  • SWGDN: Surface downwelling shortwave radiative flux (W/m2)
  • OLR: Top of the atmosphere outgoing longwave radiative flux (W/m2)
  • Soil Moisture Degree of saturation within the top 2 cm of the soil (1)

  • TPW: Total precipitable water vapor (kg/ m2)
  • Precip: Model generated precipitation (mm/day)
  • E-P (Land): Evaporation – Precipitation over land (mm/day)
  • E-P (Ocean): Evaporation – Precipitation over ocean (mm/day)

3D Fields
  • U: Zonal Wind (m/s)
  • V: Meridional Wind (m/s)
  • T: Temperature (C)
  • RH: Relative Humidity (%)
  • Z*: Height Anomaly with respect to Zonal-Mean (m)


  • Fire Weather Index (FWI): Computed using instantaneous 2 m temperature and relative humidity, sustained wind speed at 10 m, and 24-hour corrected precipitation from MERRA-2, FWI is an index that combines the Initial Spread Index (the ability of a fire to spread after ignition) and the Buildup Index (the amount of fuel available as a function of moisture). Values of FWI exceeding 30 are considered extreme, but the FWI is interpreted differently across fire environments. Interpretation examples for other regions and technical details are provided in Field (2020). Additional details pertaining to the calculation of FWI are available in Field et al. (2015).


  • Fire Weather Index (FWI)
    • Field, R. D., Spessa, A. C., Aziz, N. A., Camia, A., Cantin, A., Carr, R., de Groot, W. J., Dowdy, A. J., Flannigan, M. D., Manomaiphiboon, K., Pappenberger, F., Tanpipat, V., and Wang, X.: Development of a Global Fire Weather Database, Nat. Hazards Earth Syst. Sci., 15, 1407–1423,, 2015.
    • Field, R. D.: Evaluation of Global Fire Weather Database reanalysis and short-term forecast products, Nat. Hazards Earth Syst. Sci., 20, 1123–1147,, 2020.