Long time series data set of north temperate lake ice cover occurrence values (1985-2020)

The data set mainly includes the ice observation frequency (ICO) of north temperate lakes in four periods from 1985 to 2020, as well as the location, area and elevation of the lakes. Among them, the four time periods are 1985-1998 (P1), 1999-2006 (P2), 2007-2014 (P3) and 2015-2020 (P4) respectively, in order to improve the "valid observation" times in the calculation period and improve the accuracy. The ICO of the four periods is calculated by the ratio of "icing" times and "valid observation" times counted by all Landsat images in each period. Other lake information corresponds to the HydroLAKEs data set through the "hylak_id" column in the table. In addition, the data only retains about 30000 lakes with an area of more than 1 square kilometer, which are valid for P1-P4 observation. The data set can reflect the response of Lake icing to climate change in recent decades.

本数据集主要包含自1985年至2020年期间北温带湖泊的冰情观测频率（ICO），并涵盖了湖泊的位置、面积及海拔信息。具体时间区间分别为1985-1998年（P1）、1999-2006年（P2）、2007-2014年（P3）以及2015-2020年（P4），旨在提升计算周期内的“有效观测”次数，从而增强准确性。四个时间段的ICO是通过计算该时段内所有Landsat影像中“结冰”次数与“有效观测”次数之比得出。其他湖泊信息通过表格中的“hylak_id”列与HydroLAKEs数据集对应。此外，数据集中仅保留了面积超过1平方公里的约30,000个湖泊，这些湖泊在P1-P4观测周期内均有效。该数据集能够反映近几十年湖泊结冰现象对气候变化的响应。