gridMET Fire Danger Indices

What is gridMET?

gridMET is a dataset of daily high-spatial resolution (~4-km, 1/24th degree) surface meteorological data covering the contiguous US from 1979-yesterday. We have also extended these data to cover southern British Columbia in our real time products. These data can provide important inputs for ecological, agricultural, and hydrological models. These data are updated daily. gridMET is the preferred naming convention for these data; however, the data are also known as cited as METDATA.

Datasets

Primary Climate Variables: Maximum temperature, minimum temperature, precipitation accumulation, downward surface shortwave radiation, wind-velocity, humidity (maximum and minimum relative humidity and specific humidity

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​Derived variables: Reference evapotranspiration (ASCE Penman-Montieth), Energy Release Component*, Burning Index*, 100-hour and 1000-hour dead fuel moisture, mean vapor pressure deficit, 10-day Palmer Drought Severity Index       

*fuel model G (conifer forest)

Near Real-Time Updates

Originally developed as a research project, we have made significant efforts to provide a living dataset to multiple communities. As such we implemented (and continue to implement) several changes to minimize latency effects and changing data sources. Namely, NLDAS2 has a latency of 3-5 days which is not suitable for near real time information. Several approaches are outlined below in terms of how we overcome this to create a continuous product

1. Daily PRISM data for temperature anomalies and precipitation anomalies are used for prior days (except the most recent day). The most recent day's temperature is updated using anomalies from Climate Forecast System version 2 (CFSV2), while we use precipitation from the National Water Prediction Service QPE.
2. Anomalies of wind speed, humidity, and solar radiation from CFSv2 are used to fill the latency and are replaced with NLDAS2 when those data are available
3. Anomalies are superposed to the underlying gridMET fields. In both cases anomalies are taken with respect to the same periods of record to ensure consistency across time (i.e., PRISM data 1981-2010 averages are added (or multiplied) to gridMET 1981-2010; 2011-2017 anomalies are used for CFSv2).

Accuracy

Validation of the resulting gridded surface meteorological data was conducted against an extensive network of weather stations including RAWS, AgriMet, AgWeatherNet and USHCN-2. For more information on validation measures see Abatzoglou (2013). 

Data Limitations

1. gridMET will likely not capture microclimates that arise at spatial scales finer than the native resolution of the grid or parent datasets (<4-km). Comparisons to station data should account for differences in spatial scales between gridded products (average over the grid) versus in-situ observations.
2. gridMET wind fields and solar radiation are interpolated from NARR/NLDAS-2 which has a 32-km spatial resolution. This will be insufficient for capturing mesoscale influences of terrain on wind fields.
3. Solar radiation from gridMET is not adjusted for topographic effects, but instead is provided for a planar surface. Users may wish to terrain correct for solar radiation loading using a digital elevation model.
4. gridMET nominally considers a "day" to be midnight-to-midnight Mountain Standard Time (7 UTC).