North Temperate Lakes LTER: Light Extinction 1981 - current

A light (PAR) extinction coefficient is calculated for the water column for the eleven primary lakes (Allequash, Big Muskellunge, Crystal, Sparkling, and Trout lakes, unnamed lakes 27-02 [Crystal Bog] and 12-15 [Trout Bog], Mendota, Monona, Wingra, and Fish) and two additional lakes near Madison, Wisconsin (Waubesa and Kegonsa). Data covers only the Trout Lake-area lakes through 2018. Beginning in 2019, the Madison-area lakes were added. The fraction of surface light is computed at 0.25-m to 1-m depth intervals depending on the lake. The light (PAR) extinction coefficient is calculated by regressing ln(fraction of light(z)) on depth z. The raw light data is available from another dataset: https://portal.edirepository.org/nis/metadataviewer?packageid=knb-lter-ntl.29.35
Sampling Frequency: fortnightly during ice-free season - every 6 weeks during ice-covered season Number of sites: 13

本数据集针对11处主要湖泊（Allequash湖、Big Muskellunge湖、Crystal湖、Sparkling湖、Trout湖，以及未命名湖泊27-02[Crystal Bog]与12-15[Trout Bog]、Mendota湖、Monona湖、Wingra湖和Fish湖），以及威斯康星州麦迪逊市周边的另外两座湖泊（Waubesa湖与Kegonsa湖），计算了水柱的光合有效辐射（Photosynthetically Active Radiation, PAR）消光系数。
2018年及之前，数据集仅覆盖Trout Lake周边湖泊；自2019年起，新增麦迪逊周边湖泊的监测数据。
根据各湖泊实际情况，表层光照占比的计算深度间隔为0.25米至1米。
光合有效辐射消光系数通过以深度z为自变量，对光照占比的自然对数ln(光照占比(z))进行回归分析计算得到。原始光照数据可从另一数据集获取：https://portal.edirepository.org/nis/metadataviewer?packageid=knb-lter-ntl.29.35
采样频率：无冰期为每两周一次，封冰期为每六周一次。监测点位总数：13处。