A soil moisture dataset over the Brazilian semiarid region

This dataset contains soil moisture measured over the Brazilian Semiarid region from August 2015 to April 2019. An observational network of automatic ground stations was established by the National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN) with the aim of supporting monitoring activities over the driest and most drought-affected region in the country. The sites are mostly characterised by family farming and rainfed agriculture. Soil volumetric water content is obtained by measuring the dielectric constant of the soil at 70 MHz frequency, which minimizes salinity and textural effects (model EC-5, Decagon Devices, Pullman, WA, USA). Probes use the default calibration, resulting in a precision of approximately ±0.03 m3 m-3. Measurements were made hourly at 0.1 m and 0.2 m depths; a subset of stations (10% of the original network, evenly distributed) had measurements at 0.1 m, 0.2 m, 0.3 m, and 0.4 m depths. Rainfall measurements are also included in this version of the dataset. Measurements were accumulated hourly. A total of 360 stations were selected after a quality control process. Data availability is approximately 2 years long on average, reaching up to 4 years in some stations. Gaps caused by instrument malfunction or data transmission problems are occasional on the data. Validation and consistency were assessed by comparing trends in soil vertical neighbour data and rainfall records collected by each station. Stations with at least two months of soil moisture data were kept on the database. Each file available here contains the time series and the metadata with information on the city, the Brazilian state, the geographic coordinates, and the soil texture (fraction of sand, silt and clay). Soil information was derived from 1 kg disturbed samples collected at each site. Data for individual stations are in the compressed file PCDs_.zip while a list summarising stations information is found in the file _Stations.xlsx. First applications of this dataset and further details on methodology and site can be found in Zeri et al. (2018, https://doi.org/10.3390/w10101421). Version 2 of the dataset includes rainfall measurements, 3 new stations, and the inclusion of records incorrectly removed during the quality control of version 1.

本数据集涵盖2015年8月至2019年4月巴西半干旱地区的土壤湿度观测数据。国家自然灾害监测与预警中心（National Center for Monitoring and Early Warning of Natural Disasters, CEMADEN）搭建了自动地面观测站网，旨在为该国最干旱且受干旱影响最严重的区域提供监测支撑。观测站点以家庭农业和雨养农业为主。土壤体积含水量通过测量70 MHz频率下的土壤介电常数获取，该方法可最大程度降低盐分与土壤质地的影响，所用传感器为美国华盛顿州普尔曼市德卡贡设备公司（Decagon Devices, Pullman, WA, USA）生产的EC-5型（model EC-5）传感器。探头采用默认校准参数，测量精度约为±0.03 m³·m⁻³。观测在0.1米和0.2米深度每小时开展一次；原有站网中10%的均匀分布站点额外增加了0.3米和0.4米深度的观测。本版数据集还包含降雨观测数据，降雨数据按小时累积统计。经过质量控制流程后，最终筛选出360个站点。各站点平均可用数据时长约为2年，部分站点最长可达4年。数据中偶尔会出现因仪器故障或传输问题导致的缺失。研究通过对比土壤垂直分层观测数据与各站点的降雨记录，对数据的合理性与一致性进行了验证。仅将拥有至少2个月土壤湿度数据的站点纳入数据库。本页面提供的每个文件均包含时间序列数据与元数据，元数据涵盖站点所在城市、巴西州份、地理坐标以及土壤质地信息（砂粒、粉粒和黏粒占比）。土壤质地信息来自各站点采集的1 kg扰动土样。单个站点的数据存储于压缩文件PCDs_.zip中，站点信息汇总列表则保存在_Stations.xlsx文件内。本数据集的初步应用及方法、站点详情可参见Zeri等人（2018，https://doi.org/10.3390/w10101421）。数据集第二版新增了降雨观测数据、3个站点，并补全了第一版质量控制过程中误删的记录。