Degree Days: Freezing Index, Thawing Index, Heating Degree Days, and Degree Days Below 0° F

This dataset consists of four different variables: degree days below 65°F (or \"heating degree days\"), degree days below 0°F, degree days below 32°F (or \"air freezing index\"), and degree days above 32°F (or \"air thawing index\"). All were derived from the same set of nine statistically downscaled CMIP5 global climate model outputs driven by RCP 4.5 and RCP 8.5 emissions scenarios. A historical baseline (Daymet, 1980-2017) dataset is included for each variable. All data are in GeoTIFF format and have a spatial resolution of 12 km.

Units are degree days Fahrenheit (°F⋅days).

The model-scenario combinations are:
- ACCESS1-3, RCP 4.5
- ACCESS1-3, RCP 8.5
- CanESM2, RCP 4.5
- CanESM2, RCP 8.5
- CCSM4, RCP 4.5
- CCSM4, RCP 8.5
- CSIRO-Mk3-6-0, RCP 4.5
- CSIRO-Mk3-6-0, RCP 8.5
- GFDL-ESM2M, RCP 4.5
- GFDL-ESM2M, RCP 8.5
- inmcm4, RCP 4.5
- inmcm4, RCP 8.5
- MIROC5, RCP 4.5
- MIROC5, RCP 8.5
- MPI-ESM-MR, RCP 4.5
- MPI-ESM-MR, RCP 8.5
- MRI-CGCM3, RCP 4.5
- MRI-CGCM3, RCP 8.5

The .zip files that are available for download are organized by variable. One .zip file has all the models and scenarios and years for that variable. Each GeoTIFF file has a naming convention like this:

\"ncar_12km_{model}_{scenario}_{variable}_{year}_Fdays.tif\"

Each GeoTIFF has a 12 km by 12 km pixel size, and is projected to EPSG:3338 (Alaska Albers).

本数据集包含四类变量：65华氏度以下度日数（又称“采暖度日数”）、0华氏度以下度日数、32华氏度以下度日数（又称“空气冻结指数”），以及32华氏度以上度日数（又称“空气解冻指数”）。所有变量均源自同一套经统计降尺度处理的CMIP5（第五次耦合模式比较计划，Coupled Model Intercomparison Project Phase 5）全球气候模式输出结果，其驱动情景为RCP（典型浓度路径，Representative Concentration Pathway）4.5与RCP 8.5。每个变量均附带基于Daymet数据集的1980-2017年历史基准数据。所有数据均采用GeoTIFF格式存储，空间分辨率为12千米。

数据单位为华氏度日数（°F·天）。

模型与情景的组合如下：
- ACCESS1-3，RCP 4.5
- ACCESS1-3，RCP 8.5
- CanESM2，RCP 4.5
- CanESM2，RCP 8.5
- CCSM4，RCP 4.5
- CCSM4，RCP 8.5
- CSIRO-Mk3-6-0，RCP 4.5
- CSIRO-Mk3-6-0，RCP 8.5
- GFDL-ESM2M，RCP 4.5
- GFDL-ESM2M，RCP 8.5
- inmcm4，RCP 4.5
- inmcm4，RCP 8.5
- MIROC5，RCP 4.5
- MIROC5，RCP 8.5
- MPI-ESM-MR，RCP 4.5
- MPI-ESM-MR，RCP 8.5
- MRI-CGCM3，RCP 4.5
- MRI-CGCM3，RCP 8.5

可供下载的.zip压缩文件按变量分类组织：每个压缩包包含对应变量下所有模型、情景及年份的全部数据。单个GeoTIFF文件的命名规则为："ncar_12km_{model}_{scenario}_{variable}_{year}_Fdays.tif"。

每个GeoTIFF文件的像素尺寸为12千米×12千米，投影采用EPSG:3338（阿拉斯加阿尔伯斯投影）。