Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Average Annual Daily Minimum Temperature, 2002

This data set represents the average monthly minimum temperature in Celsius multiplied by 100
for 2002 compiled for every catchment of NHDPlus for the conterminous United States. The source
data were the Near-Real-Time High-Resolution Monthly Average Maximum/Minimum Temperature
for the Conterminous United States for 2002 raster dataset produced by the Spatial Climate Analysis
Service at Oregon State University.

The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that
incorporates many of the best features of the National Hydrography Dataset (NHD) and the
National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the
1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs).
NHDPlus also includes elevation-derived catchments (drainage areas) produced using a
drainage enforcement technique first widely used in New England, and thus referred to as
"the New England Method." This technique involves "burning in" the 1:100,000-scale NHD
and when available building "walls" using the National Watershed Boundary Dataset (WBD).
The resulting modified digital elevation model (HydroDEM) is used to produce hydrologic
derivatives that agree with the NHD and WBD. Over the past two years, an interdisciplinary
team from the U.S. Geological Survey (USGS), and the U.S. Environmental Protection Agency
(USEPA), and contractors, found that this method produces the best quality NHD catchments
using an automated process (USEPA, 2007). The NHDPlus dataset is organized by 18 Production
Units that cover the conterminous United States.

The NHDPlus version 1.1 data are grouped by the U.S. Geologic Survey's Major River Basins
(MRBs, Crawford and others, 2006). MRB1, covering the New England and Mid-Atlantic River
basins, contains NHDPlus Production Units 1 and 2. MRB2, covering the South Atlantic-Gulf
and Tennessee River basins, contains NHDPlus Production Units 3 and 6. MRB3, covering the
Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins, contains NHDPlus
Production Units 4, 5, 7 and 9. MRB4, covering the Missouri River basins, contains NHDPlus
Production Units 10-lower and 10-upper. MRB5, covering the Lower Mississippi, Arkansas-White-Red,
and Texas-Gulf River basins, contains NHDPlus Production Units 8, 11 and 12. MRB6, covering the
Rio Grande, Colorado and Great Basin River basins, contains NHDPlus Production Units 13, 14, 15
and 16. MRB7, covering the Pacific Northwest River basins, contains NHDPlus Production Unit 17.
MRB8, covering California River basins, contains NHDPlus Production Unit 18.

本数据集涵盖2002年美国本土范围内NHDPlus各汇水区的月均最低气温（单位：摄氏度，数值已乘以100）。其原始数据为俄勒冈州立大学空间气候分析服务中心制作的2002年美国本土近实时高分辨率月均最高/最低气温栅格数据集。

NHDPlus Version 1.1是一套集成化的可直接投入应用的地理空间数据集，整合了美国国家水文数据集（National Hydrography Dataset, NHD）与美国国家高程数据集（National Elevation Dataset, NED）的多项优质特性。该数据集包含基于1:10万比例尺NHD构建的河网系统，优化了河网连通性、命名规则，并新增了增值属性（VAAs）。此外，NHDPlus还包含采用排水增强技术生成的高程派生汇水区（流域面积），该技术最初在新英格兰地区广泛应用，因此被称为“新英格兰方法”。该技术的具体流程为：叠加1:10万比例尺NHD数据，并在条件允许时利用国家流域边界数据集（WBD）构建流域边界“墙体”。经修正后的数字高程模型（HydroDEM）可用于生成与NHD和WBD标准一致的水文派生数据。过去两年间，来自美国地质调查局（USGS）、美国环境保护署（USEPA）的跨学科团队及承包商经研究证实，该自动化流程可生成最高质量的NHD汇水区（美国环境保护署，2007年）。NHDPlus数据集按18个生产单元进行组织，覆盖美国本土全境。

NHDPlus 1.1版数据按照美国地质调查局划定的主要流域（Major River Basins, MRBs，Crawford等，2006年）进行分组：
MRB1涵盖新英格兰与中大西洋流域，包含NHDPlus生产单元1和2；
MRB2涵盖南大西洋-墨西哥湾和田纳西河流域，包含NHDPlus生产单元3和6；
MRB3涵盖五大湖、俄亥俄河、上密西西比河以及苏里斯-雷德-雷尼河流域，包含NHDPlus生产单元4、5、7和9；
MRB4涵盖密苏里河流域，包含NHDPlus生产单元10（下游）和10（上游）；
MRB5涵盖下密西西比河、阿肯色-怀特-雷德河以及德克萨斯-墨西哥湾流域，包含NHDPlus生产单元8、11和12；
MRB6涵盖格兰德河、科罗拉多河和大盆地流域，包含NHDPlus生产单元13、14、15和16；
MRB7涵盖太平洋西北河流域，包含NHDPlus生产单元17；
MRB8涵盖加利福尼亚河流域，包含NHDPlus生产单元18。