ISLSCP II Northern Hemisphere Monthly Snow Cover Extent

This ISLSCP data set is derived from the National Snow and Ice Data Center (NSIDC) Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent product which combines snow cover and sea ice extent at weekly intervals for October 1978 through June 2001, and snow cover alone from 1966 through June 2001. The original data set was the first representation of combined snow and sea ice measurements derived from satellite observations for the period of record. Designed to facilitate study of Northern Hemisphere seasonal fluctuations of snow cover and sea ice extent, the original NSIDC data set also includes monthly climatologies describing average extent, probability of occurrence, and variance.This data set shows the extent of snow on the land at a variety of scales (1.0 degree, 0.5 degree, 0.25 degree). The values represent the percentage of days in each month where snow was present -- 100 means 100% of the month, 80 means 80% of the month, etc. There are 4 .zip files provided. Missing data is represented by -99 for water and -88 for land. The data were originally in a yearly tabular format. The file was converted to multi-scale maps by plotting each point in the tabular data onto a map of -99 (water) and -88 (land) created from the standard ISLSCP II Land/Sea Mask.

本 ISLSCP 数据集源于国家雪冰数据中心（NSIDC）的北半球 EASE-Grid 周积雪覆盖和海冰范围产品，该产品自 1978 年 10 月至 2001 年 6 月每周合并积雪覆盖和海冰范围，以及自 1966 年至 2001 年 6 月的单独积雪覆盖数据。原始数据集是首次通过卫星观测结合积雪与海冰测量值所获得的记录时期内数据的首个表示形式。旨在促进对北半球积雪覆盖和海冰范围季节性波动的深入研究，原始 NSIDC 数据集还包括描述平均范围、发生概率和变差月份气候学的信息。本数据集展示了不同尺度（1.0 度、0.5 度、0.25 度）陆地上积雪的范围。数值代表每月积雪存在的天数百分比--100 表示整个月，80 表示一个月的 80%，等等。提供了 4 个 .zip 文件。缺失数据以 -99 表示水域，以 -88 表示陆地。原始数据以年度表格格式存在，通过将表格数据中的每个点绘制到由标准 ISLSCP II 陆地/海洋掩膜创建的 -99（水域）和 -88（陆地）地图上，文件被转换为多尺度地图。