Model data from publicly-available ECMWF SEAS5 seasonal forecasts for the calculation of buildup index and comparison to observations for the 1994-2019 Alaska wildfire seasons

This dataset includes model output from the ECMWF SEAS5 seasonal forecasts. The time period spans the years 1994-2019 for the Alaska fire season (April 1 - September 30) from March-initialized and May-initialized seasonal forecasts.

ECMWF SEAS5 model data were collected from the Copernicus Climate Data Store (https://cds.climate.copernicus.eu/cdsapp#!/dataset/seasonal-monthly-single-levels?tab=form) for the years 1994-2019. Variables downloaded include 2 meter temperature, 2 meter dew point temperature, precipitation, 10 meter wind speeds, and sea level pressure. These models consist of 25 ensembles for the years 1994-2016 and 51 ensembles for the years 2017 onward.

Details about the model can be found in its reference publication:
Johnson, S. J., Stockdale, T. N., Ferranti, L., Balmaseda, M. A., Molteni, F., Magnusson, L., Tietsche, S., Decremer, D., Weisheimer, A., Balsamo, G., Keeley, S. P. E., Mogensen, K., Zuo, H., & Monge-Sanz, B. M. (2019). SEAS5: the new ECMWF seasonal forecast system. Geoscientific Model Development, 12(3), 1087–1117. https://doi.org/10.5194/gmd-12-1087-2019

Model data were extracted for 13 Predictive Service Areas (PSA) in Alaska at 0000 UTC (the time closest to 1400 AKDT) and saved as a weighted area-average in text files by year. Buildup index was calculated from the area-averaged variables and saved in annual text files. Calculations were done with NCAR Command Line (NCL) version 6.3.0.

Sub-directory Naming Convention
The ECMWF directory is divided into 15 sub-directories: one sub-directory for each of the 13 PSAs in this study (named for each PSA), one sub-directory for March-initialized forecast data (step1_ecmwfdata_march), and one sub-directory for May-initialized forecast data (step1_ecmwfdata_may).

The step1_ecmwfdata_march and step1_ecmwfdata_may folders contain raw model data from ECMWF SEAS5 March-initialized and May-initialized seasonal forecasts, respectively, saved by ensemble in one file for the calculation of buildup index. Data in each file include precipitation (precip), surface pressure (P), 2 meter dewpoint temperature (DP), 2 meter air temperature (T), and 10 meter wind speeds (UV). Data were subset for the state of Alaska and for the Alaska fire season (months of April, May, June, July, August, and September) and saved by year. There are 26 files at a size of 158MB (25 ensembles, years 1994-2016) and 321MB (51 ensembles, years 2017-2019) for March-initialized forecasts and 26 files at a size of 132MB (25 ensembles, years 1994-2016) and 268MB (51 ensembles, years 2017-2019) for May-initialized forecasts.

Each PSA sub-directory (PSA AKXX) contains 4 additional sub-directories:

step2_ecmwfdata_march
step2_ecmwfdata_may
step3_ecmwfdata_march_BUI
step3_ecmwfdata_may_BUI

where 'march' or 'may' denotes data from March-initialized forecasts of May-initialized forecasts, respectively. The step2 folders contain precipitation (precip), surface pressure (press), 2 meter dew point temperature (dp), relative humidity (rh), 2 meter air temperature (tmp2m), and 10 meter wind speeds (uv).. These data were extracted from the data files in the step1 sub-directories and saved as annual files. The step3 folders contain the resulting BUI values saved as annual files.