BST/NOAA PSL Level 3 UAS Soil Moisture, Digital Elevation, Normalized Difference Vegetative Index, and Surface Temperature for SPLASH

This dataset contains uncrewed aircraft systems (UAS) high-resolution data of soil moisture at the 0-5 cm soil depth, normalized difference vegetation index (NDVI), surface temperature, and digital elevation for the Study of Precipitation, the Lower Atmosphere, and Surface for Hydrology (SPLASH) campaign sponsored by the National Oceanic and Atmospheric Administration (NOAA). While Level 2 provides each product at their highest retrieved spatial resolution, Level 3 provides all four products on a common grid at each flight location. These data were collected near Avery Picnic (38.972425 degrees N,106.996855 degrees W) and Kettle Ponds (38.942005 degrees N,106.973006 degrees W) in the East River Watershed in Colorado from a series of flights starting on June 1st, 2022 and ending October 18th, 2023. Soil moisture measurements were retrieved using the Lobe Differencing Correlation Radiometer (LDCR) which is a L-Band (1-2 GHz) microwave radiometer and was flown on the E2 and S2 aerial platforms operated by Black Swift Technologies, Inc. Each Level 3 NetCDF file contains all four UAS parameters at a flight location interpolated to a common rectilinear grid at ~50 cm resolution. Soil moisture retrievals were downscaled to a higher resolution grid using bilinear interpolation while surface temperature, NDVI, and digital elevation were upscaled to a lower resolution grid using conservative interpolation. The data was regridded using the Python package xESMF which is based on code developed for the Earth System Modeling Framework (ESMF) project. The file name convention for the Level 3 NetCDF files is as follows. uas_L3_yyyymmdd_hhmmss_vx.x.nc where L3 = Level 3 data yyyymmdd = year,month,day hhmmss = hour,minute,second x.x = version number Time is the flight start time in UTC. Version number description is provided in the NetCDF global attributes. Note that each flight location using the E2 aerial platform required two flights with different starting flight times for the soil moisture and the other three products. The flight start time is the time of the first flight. The total time for the two flights at each location was ~1 hour. November 2023 update: Version 2.0 added flight data from 2023. Version 2.0 includes an updated calibration of the soil moisture retrieval that has been applied to 2023 data, and a mask was applied to the soil moisture retrieval over water surfaces for both 2022 and 2023 data. Version 2.1 adds data file uas_L3_20221018_171650_v2.1.nc that was missing in Version 2.0. December 2023 update: Version 2.2 updated soil moisture data with a wet bias in v2.1 for flights #2 (17:40:35 UTC) and #3 (19:24:45 UTC) on July 27, 2022.本数据集包含由美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）资助的水文降水、低层大气与地表研究（Study of Precipitation, the Lower Atmosphere, and Surface for Hydrology, SPLASH）项目的相关高分辨率数据，具体包括0-5 cm土层土壤湿度、归一化差分植被指数（Normalized Difference Vegetation Index, NDVI）、地表温度以及数字高程数据，采集载体为无人航空器系统（Uncrewed Aircraft Systems, UAS）。其中二级数据集（Level 2）以各产品的最高反演空间分辨率输出，而三级数据集（Level 3）则将全部四类产品统一重采样至各飞行测点的公共网格中。 本次数据采集工作于2022年6月1日至2023年10月18日期间开展，飞行范围覆盖美国科罗拉多州东河流域的艾弗里野餐点（Avery Picnic，北纬38.972425°，西经106.996855°）与凯特尔池塘（Kettle Ponds，北纬38.942005°，西经106.973006°）周边区域。土壤湿度数据采用瓣差分相关辐射计（Lobe Differencing Correlation Radiometer, LDCR）进行反演，该设备属于L波段（1-2 GHz）微波辐射计，搭载于Black Swift Technologies, Inc.运营的E2与S2航空平台上。 每份三级数据集（Level 3）的NetCDF文件均包含某一飞行测点的全部四类无人航空器系统参数，这些参数已被重采样至分辨率约为50 cm的统一直角网格中。其中土壤湿度反演结果通过双线性插值下采样至高分辨率网格，而地表温度、归一化差分植被指数与数字高程数据则通过保守插值上采样至较低分辨率网格。本次数据重网格操作通过Python工具包xESMF完成，该工具包基于地球系统建模框架（Earth System Modeling Framework, ESMF）项目开发的代码实现。 三级数据集NetCDF文件的命名规则如下：uas_L3_yyyymmdd_hhmmss_vx.x.nc，其中：L3代表三级数据集；yyyymmdd为年-月-日格式的日期；hhmmss为时-分-秒格式的时间；x.x为版本号。此处的时间为UTC时区的飞行开始时间，版本号的详细说明可参见NetCDF文件的全局属性。 需注意，使用E2航空平台的每个飞行测点需开展两次飞行：土壤湿度与其余三类产品的采集飞行起始时间各不相同，此处记录的飞行开始时间为首次飞行的起始时刻，单测点两次飞行的总耗时约为1小时。 2023年11月更新：版本2.0新增了2023年的飞行数据，其对土壤湿度反演算法进行了更新校准，并将该校准应用于2023年的数据集；同时为2022年与2023年的土壤湿度反演结果添加了水面掩膜。版本2.1补充了版本2.0中缺失的数据文件uas_L3_20221018_171650_v2.1.nc。 2023年12月更新：版本2.2对2022年7月27日的第2次飞行（UTC时间17:40:35）与第3次飞行（UTC时间19:24:45）的土壤湿度数据进行了修正，以校正版本2.1中存在的湿偏差。