DOI: 10.24431/rw1k8fk
title: Model data from publicly-available NOAA CFSv2 seasonal forecasts for the calculation of buildup index and comparison to observations for the 1994-2019 Alaska wildfire seasons

description: This dataset includes model output from the NOAA Climate Forecast System version 2 (CFSv2) 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.

NOAA CFSv2 model data were collected from the NOAA CFS reforecasts (years 1994- March 2011) and operational forecasts (years April 2011-2019) via the NCEI direct download webpages: https://www.ncei.noaa.gov/oa/prod-cfs-reforecast/first-look/6-hourly-time-series-9-month and https://www.ncei.noaa.gov/data/climate-forecast-system/access/operational-9-month-forecast/. Variables downloaded include 2 meter temperature, 2 meter specific humidity, precipitation rate, 10 meter wind speeds, and surface pressure. This model consists of 25-125 ensembles depending on the availability of data.

Details about the model can be found in its reference publication:
Saha, S., Moorthi, S., Wu, X., Wang, J., Nadiga, S., Tripp, P., Behringer, D., Hou, Y. T., Chuang, H. Y., Iredell, M., Ek, M., Meng, J., Yang, R., Mendez, M. P., Van Den Dool, H., Zhang, Q., Wang, W., Chen, M., & Becker, E. (2014). The NCEP Climate Forecast System Version 2. Journal of Climate, 27(6), 2185–2208. https://doi.org/10.1175/JCLI-D-12-00823.1

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 Language (NCL) version 6.3.0.

Sub-directory Naming Convention
The CFSv2 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_cfsdata_march), and one sub-directory for May-initialized forecast data (step1_cfsdata_may).

The step1_cfsdata_march and step1_cfsdata_may folders contain raw model data from NOAA CFSv2 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 specific humidity (Q), 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 as one file for each model ensemble. There are 1422 files at a size of 7MB for March-initialized forecasts and 1565 files at a size of 5-6MB for May-initialized forecasts.

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

step2_cfsdata_march
step2_cfsdata_may
step3_cfsdata_march_BUI
step3_cfsdata_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 specific humidity (q), 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.