黑河生态水文遥感试验：黑河流域中游盈科绿洲与花寨子荒漠机载PLMR地面同步观测数据集（2012年6月28-29日）

2012年6月28-29日在盈科绿洲与花寨子荒漠PLMR样方进行了机载飞行地面同步观测。PLMR（Polarimetric L-band Multibeam Radiometer）是双极化（H/V）的L波段微波辐射计，中心频率1.413 GHz，带宽24 MHz，分辨率1 km （相对航高3 km），有6个beam同时观测，入射角为±7º，±21.5º，±38.5º，灵敏度<1K。飞行主要覆盖中游人工绿洲生态水文试验区。本地面同步数据集可为发展和验证被动微波遥感反演土壤水分算法提供基本地面数据集。
样方及采样策略：
观测区位于张掖绿洲南缘-安阳滩荒漠过渡带，张（张掖）-大（大满）公路西侧，南北跨龙渠干渠，分为两部分，西南方向为1 km×1 km的荒漠样方，由于荒漠较为均质，在此1 km样方内采集5个点（四周各1点及中心点，实际测量过程中，可在沿路行走过程中多测几个点）的土壤水分，四个角点除对角线方向外，互相间隔600 m，西南角角点为花寨子荒漠站，便于与气象站数据比较。在东北侧，选择了面积2.4 km×2.4 km的大样方针对绿洲下垫面开展同步观测。样方的选择依据主要是考虑地表覆盖代表性、尽量避开民居和大棚、穿越绿洲农田以及南边的部分荒漠、可达性、观测（路途消耗）时间，以期获得与PLMR观测的亮度温度的比较。
考虑到PLMR观测的分辨率，同步观测中，东西方向以160 m为间隔，采集了16条样线（东西分布），每条线80 m间隔共31个点（南北方向），使用4台Hydraprobe Data Acquisition System （HDAS，参考文献2）同时测量。
测量内容：
获取了样方上约500个点，每个点2次观测，即对覆膜玉米地，在每个采样点进行2次观测，1次膜内（数据记录中标记为a），1次膜外（数据记录中标记为b）。由于HDAS系统采用POGO便携式土壤传感器，观测获得土壤温度、土壤水分（体积含水量）、损耗正切、土壤电导率、土壤复介电实部及虚部。植被参数观测选择在一些具有代表性的土壤水分采样点开展，完成了株高和生物量（植被含水量）的测量。
注：28号观测从11:00AM左右开始，完成约1/3工作量，由于PLMR仪器问题和降雨的双重原因，4:00PM被迫停止观测。剩余工作量29号10:30AM-5:30PM完成。观测日期正值该区域内农田大面积灌溉，导致观测人员前行困难，田块难以进入，观测点位与预设点位有偏差。
数据：
本数据集包括土壤水分观测和植被观测两部分，前者保存数据格式为矢量文件，空间位置即为各采样点位置（WGS84+UTM 47N），土壤水分等测量信息记录在属性文件中；植被采样信息记录在EXCEL表格中。

Airborne flight and ground synchronous observations were conducted at the Yingke Oasis and Huazhaizi Desert PLMR plots on June 28–29, 2012. PLMR (Polarimetric L-band Multibeam Radiometer) is a dual-polarization (H/V) L-band microwave radiometer, with a central frequency of 1.413 GHz, bandwidth of 24 MHz, spatial resolution of 1 km (relative flight altitude: 3 km), 6 beams for simultaneous observation, incidence angles of ±7°, ±21.5°, ±38.5°, and sensitivity < 1 K. The flight mainly covered the Midstream Artificial Oasis Eco-hydrological Experimental Zone. This ground synchronous dataset can provide fundamental ground truth data for developing and validating passive microwave remote sensing soil moisture retrieval algorithms.

Plots and Sampling Strategy:
The observation area is located at the southern margin of Zhangye Oasis - Anyantan desert transition zone, west of Zhangye-Daman Highway, spanning Longqu Main Canal from north to south, and is divided into two parts. The southwest is a 1 km×1 km desert plot. Since the desert is relatively homogeneous, 5 soil moisture measurement points were collected within this 1 km plot: 4 corner points and the central point. (During actual measurement, more points can be collected while walking along the road.) The four corner points are spaced 600 m apart except along the diagonal, and the southwest corner is the Huazhaizi Desert Station, which facilitates comparison with meteorological station data. On the northeast side, a 2.4 km×2.4 km large plot was selected for synchronous observations targeting the oasis underlying surface. The plot selection was mainly based on representativeness of surface cover, avoiding residential buildings and greenhouses as much as possible, crossing oasis farmland and part of the southern desert, accessibility, and travel time consumption for observations, with the aim of obtaining consistent comparisons with the brightness temperature observed by PLMR.

Considering the observation resolution of PLMR, in the synchronous observation campaign, 16 east-west transects were deployed with an interval of 160 m between adjacent transects. Each transect had 31 sampling points arranged at 80 m intervals in the north-south direction, and measurements were conducted simultaneously using 4 Hydraprobe Data Acquisition System (HDAS, Reference 2).

Measurement Contents:
Approximately 500 sampling points were deployed across the plots, with two observations per point. For mulched corn fields, two measurements were taken at each sampling point: one inside the plastic mulch (marked as "a" in the data records) and one outside the mulch (marked as "b" in the data records). Since the HDAS system uses POGO portable soil sensors, soil temperature, soil moisture (volumetric water content), loss tangent, soil electrical conductivity, and real and imaginary parts of soil complex dielectric constant were measured. Vegetation parameter observations were carried out at some representative soil moisture sampling points, and plant height and biomass (vegetation water content) were measured.

Note:
Observations on June 28 started around 11:00 AM, and approximately 1/3 of the total workload was completed. Due to both PLMR instrument malfunctions and rainfall, observations were forced to stop at 4:00 PM. The remaining workload was completed on June 29 from 10:30 AM to 5:30 PM. The observation period coincided with large-scale farmland irrigation in the region, which made it difficult for field observers to traverse and access the farmland plots, resulting in deviations between the actual measured points and the preset sampling points.

Data:
This dataset includes two parts: soil moisture observations and vegetation observations. The soil moisture observation data are stored as vector files, where the spatial positions correspond to the locations of each sampling point (WGS84+UTM 47N), and measurement information such as soil moisture is recorded in the attribute file. Vegetation sampling information is recorded in an Excel spreadsheet.