Landscape Scale Snow Depth Maps: Brooks Range Foothills, Alaska, 2012-2018

list("Snow is a crucial resource for billions of people on Earth. We proposed a study of snow drifts. Drifts can comprise more than half of the local snow water equivalent (SWE) and play a large and widely overlooked role in snow hydrology. They melt slowly, resulting in a crucial shift in the timing of water delivery that syncs snow melt directly to agricultural and ecosystem needs, yet we know little about drifts on either local or global scales. The overall goal of the research was to better understand the role and importance of snow drifts in hydrology. Using lidar and structure-from-motion (SfM) photogrammetry, we conducted an airborne study of drifts coupled with extensive ground validation in search of preliminary answers to questions on the importance of drifts and the percentage of SWE found in drifts in a variety of terrain types.",
"The snow depth maps hosted here represent six years of drift records from northern Alaska and enable the analysis of the relationships between drifts and the surrounding snowcover and the landscape below, as well as drift persistence over time.", "Snow depth mapping was done using airborne SfM photogrammetry (2015 through 2018) and lidar (2012 and 2013) and then adjusted to ground-based probe measurements of snow depth. The area mapped each year over two swaths was about 130 kilometer squared (km^2). To produce the maps, we: (1) conducted an airborne survey (snow-free) in June that was used to produce a snow-free digital elevation model (DEM) for each swath, (2) conducted airborne surveys at near-peak snow cover each April that were used to create digital surface models (DSMs) of the snow cover, then (3) generated annual high resolution (1 m) snow depth maps by subtracting the snow-free DEM from the DSMs. Six such depth maps were produced for each swath between 2012 and 2018, comprising over 600 million individual geospatial snow depth records. Acquiring the snow-free DEM required careful timing because tundra plants leaf out before all snowdrifts melt. The snow depth maps were field-validated and adjusted using 141,207 ground-based probe measurements collected concurrently with the airborne surveys.",
"There are twelve (12) snow depth raster maps deposited here. Each map represents the near-peak annual snow depth across a swath of Arctic tundra. There are two swaths: CLPX (a zone that was part of a Cold Land Experimental Site - a NASA snow measurement program that rotates through several different field areas) and HV (Happy Valley). Map years include 2012, 2013, 2015, 2016, 2017, and 2018. Maps are raster data GeoTIFF file formats where each pixel is one by one meter square. The file naming convention is *swath*_depth_*DOY*_*YYYY*_corrected_*correction_amount*.tif.")

积雪是地球上数十亿人的关键资源。我们提出了一项关于积雪堆的研究。积雪堆可占当地雪水当量（SWE）的一半以上，在积雪水文学中扮演着重要却被广泛忽视的角色。它们融化缓慢，导致水资源输送时间发生关键转变，使积雪融化直接与农业及生态系统需求同步，然而我们对局部或全球尺度上的积雪堆知之甚少。本研究的总体目标是更好地理解积雪堆在水文学中的作用与重要性。通过使用激光雷达（lidar）和运动恢复结构（structure-from-motion，SfM）摄影测量技术，我们开展了一项积雪堆的机载研究，并结合广泛的地面验证，以寻找关于积雪堆重要性及不同地形类型中积雪堆内SWE占比问题的初步答案。

本平台托管的积雪深度图代表了阿拉斯加北部六年的积雪堆记录，可用于分析积雪堆与周边积雪覆盖层、下方地形之间的关系，以及积雪堆随时间的持久性。

积雪深度制图采用机载SfM摄影测量技术（2015-2018年）和lidar技术（2012-2013年）完成，并根据地面积雪深度探针测量数据进行校正。每年在两个条带区域测绘的面积约为130平方公里（km²）。制图流程如下：（1）每年6月开展无雪机载调查，为每个条带生成无雪数字高程模型（DEM）；（2）每年4月在积雪覆盖接近峰值时开展机载调查，创建积雪覆盖的数字表面模型（DSMs）；（3）通过从DSMs中减去无雪DEM，生成年度高分辨率（1米）积雪深度图。2012至2018年间，每个条带生成了6幅此类深度图，包含超过6亿条独立的地理空间积雪深度记录。获取无雪DEM需要精确的时间安排，因为苔原植物在所有积雪堆融化前就已抽叶。积雪深度图通过与机载调查同步收集的141,207条地面探针测量数据进行实地验证和校正。

本平台共存放12幅积雪深度栅格地图。每幅地图代表北极苔原某一条带区域的年度近峰值积雪深度。存在两个条带区域：CLPX（冷地实验站点的一个区域——美国国家航空航天局（NASA）的一项积雪测量项目，在多个不同野外区域轮换开展）和HV（快乐谷）。地图年份包括2012、2013、2015、2016、2017及2018年。地图采用GeoTIFF栅格数据格式，每个像素为1×1平方米。文件命名规则为*swath*_depth_*DOY*_*YYYY*_corrected_*correction_amount*.tif。