NACP MCI: Cropland Productivity and Biophysical Properties, Nebraska, USA, 2001-2008

This data set provides an integrated collection of (1) ground-based meteorological, radiometric, and vegetation measurements, (2) flux-based estimates of gross primary production (GPP), and (3) numerous vegetation indices derived from satellite imagery for three eddy covariance flux tower locations near Lincoln, Nebraska, USA. Land use surrounding the towers is cropland with corn and soybeans. Data are reported for selected days during the growing seasons of 2001 through 2008 only when ground-based crop canopy reflectance was measured. Algorithms developed to relate ground-based and satellite spectral information to GPP of the cropland adjacent to the towers are provided.
AmeriFlux tower-based Level 2 measurements included photosynthetically active radiation (PAR), heat flux, and GPP estimates; see Section 2 for specific towers.
Ground-based measurements on the corn and soybean vegetation surrounding the towers included total chlorophyll content (Chl) and leaf area index (LAI).
Ground-based crop canopy reflectance was measured at 5.4 m above the corn and soybean canopy using hyperspectral radiometers (range 400 to 1100 nm) during the growing season from May to October in eight different years (2001-2008). This resulted in 173 measurement campaigns (18 in 2001, 31 in 2002, 34 in 2003, 31 in 2004, 21 in 2005, 15 in 2006, 14 in 2007, and 9 in 2008).
Spectral bands from Landsat TM and ETM+, MERIS , and MODIS instruments were used to calculate vegetation indices. Vegetation indices related to chlorophyll can be used as a proxy for GPP because of the observed close relationship between GPP and Chl content in crops. Algorithms developed to relate spectral information to the GPP of the cropland adjacent to the towers are provided as companion files.

本数据集汇聚了综合性的数据集，包括（1）地面气象、辐射和植被测量数据，（2）基于通量的总初级生产力（GPP）估算，以及（3）源自卫星图像的多种植被指数，这些数据均为美国内布拉斯加州林肯市附近三个涡度相关通量塔的位置所采集。周边土地利用类型为农作物用地，主要种植玉米和大豆。数据仅报告了2001年至2008年生长季节中选定日期的数据，前提是地面作物冠层反射率已被测量。提供了一套算法，旨在将地面和卫星光谱信息与塔旁农作物地的GPP相关联。基于AmeriFlux塔的二级测量包括光合有效辐射（PAR）、热通量以及GPP的估算；具体塔的位置信息见第2节。对塔周边的玉米和大豆植被进行的地面测量包括总叶绿素含量（Chl）和叶面积指数（LAI）。在玉米和大豆冠层上方5.4米处，使用高光谱辐射计（波长范围为400至1100纳米）在八年的生长季节（2001年至2008年）内进行了地面作物冠层反射率的测量，这产生了173次测量活动（2001年18次，2002年31次，2003年34次，2004年31次，2005年21次，2006年15次，2007年14次，2008年9次）。利用Landsat TM和ETM+、MERIS以及MODIS仪器获取的光谱波段计算了植被指数。与叶绿素相关的植被指数可用作GPP的替代指标，因为观察到GPP与作物中的叶绿素含量之间存在紧密的关系。提供了一套算法作为配套文件，旨在将光谱信息与塔旁农作物地的GPP相关联。