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

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.

本数据集包含美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration，NOAA）气候预测系统第2版（Climate Forecast System version 2，CFSv2）的季节预报模型输出结果。时间范围覆盖1994-2019年阿拉斯加火灾季（4月1日至9月30日），数据来源于3月初始化和5月初始化的季节预报。

NOAA CFSv2模型数据通过美国国家环境信息中心（National Centers for Environmental Information，NCEI）直接下载网页获取，来源包括NOAA CFS再预报（1994年至2011年3月）和业务预报（2011年4月至2019年），网页链接为：https://www.ncei.noaa.gov/oa/prod-cfs-reforecast/first-look/6-hourly-time-series-9-month 和 https://www.ncei.noaa.gov/data/climate-forecast-system/access/operational-9-month-forecast/。下载的变量包括2米气温、2米比湿、降水率、10米风速和地面气压。该模型包含25至125个集合成员，具体数量取决于数据可用性。

模型详情可参见其参考出版物：
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). 美国国家环境预测中心（NCEP）气候预测系统第2版。《气候杂志》，27(6)，2185–2208。https://doi.org/10.1175/JCLI-D-12-00823.1

模型数据针对阿拉斯加的13个预测服务区（Predictive Service Area，PSA）提取，时间点为协调世界时（Coordinated Universal Time，UTC）00:00（最接近阿拉斯加夏令时（Alaska Daylight Time，AKDT）14:00的时间），并按年份以加权区域平均值的形式保存于文本文件中。累积指数（Buildup index）由区域平均变量计算得出，同样保存于年度文本文件中。计算使用美国国家大气研究中心命令语言（NCAR Command Language，NCL）6.3.0版本完成。

子目录命名规则
CFSv2目录下分为15个子目录：本研究涉及的13个PSA各对应一个子目录（以PSA名称命名），一个用于3月初始化预报数据的子目录（step1_cfsdata_march），以及一个用于5月初始化预报数据的子目录（step1_cfsdata_may）。

step1_cfsdata_march和step1_cfsdata_may文件夹分别包含NOAA CFSv2 3月初始化和5月初始化季节预报的原始模型数据，按集合成员保存于单个文件中，用于累积指数计算。每个文件中的数据包括降水（precip）、地面气压（P）、2米比湿（Q）、2米气温（T）和10米风速（UV）。数据已按阿拉斯加州范围和阿拉斯加火灾季（4月至9月）进行子集化处理，每个模型集合成员对应一个文件。3月初始化预报包含1422个文件，每个大小约7MB；5月初始化预报包含1565个文件，每个大小约5-6MB。

每个PSA子目录（命名格式为PSA AKXX）包含4个额外子目录：
step2_cfsdata_march
step2_cfsdata_may
step3_cfsdata_march_BUI
step3_cfsdata_may_BUI
其中'march'或'may'分别表示来源于3月初始化或5月初始化的预报数据。step2文件夹包含降水（precip）、地面气压（press）、2米比湿（q）、相对湿度（rh）、2米气温（tmp2m）和10米风速（uv）数据。这些数据从step1子目录的文件中提取，按年度保存。step3文件夹包含计算得到的累积指数（BUI）值，同样按年度保存。