Plmr (polarimetric L-band multibeam radiometer) is a dual polarization (H / V) L-band microwave radiometer with center frequency of 1.413 GHz, bandwidth of 24 MHz, resolution of 1 km (relative altitude of 3 km), simultaneous observation of 6 beams, incident angle of ± 7 º, ± 21.5 º, ± 38.5 º, sensitivity & lt; 1K。 The flight mainly covers the ecological and hydrological test area of artificial oasis in the middle reaches

   Quadrat and sampling strategy:

   The observation area is located in the south edge of Zhangye Oasis anyangtan desert transition zone and the west side of Zhang (Zhangye) - Da (Daman) highway. It crosses Longqu trunk canal from north to South and is divided into two parts, 1 km in the southwest × For the 1km desert quadrat, because the desert is relatively homogeneous, the soil moisture of 5 points (1 point around and the center point. In the actual measurement process, several more points can be measured during walking along the road). The four corners are separated by 600m except the diagonal direction. The southwest corner is huazhaizi desert station, which is convenient for comparison with the data of meteorological station. On the northeast side, an area of 1.6 km was selected × Synchronous observation was carried out on the underlying surface of the oasis according to the 1.6 km large sample policy. The selection basis of quadrat is mainly to consider the representativeness of surface coverage, avoid residential houses and greenhouses as far as possible, cross oasis farmland and some deserts in the south, accessibility and observation (road consumption) time, so as to obtain the comparison with the brightness temperature observed by plmr.

   Considering the resolution of plmr observation, in synchronous observation, 11 sample lines (east-west distribution) are collected at an interval of 160 m in the east-west direction, with a total of 21 points (north-south direction) at an interval of 80 m in each line. Four hydroprobe data acquisition systems (HDAS, ref. 2) are used for simultaneous measurement.

   Measurement content:

   About 230 points on the quadrat were obtained, and each point was observed twice, that is, for the film covered corn field, twice were observed at each sampling point, once inside the film (marked as a in the data record) and once outside the film (marked as B in the data record). Because the HDAS system adopts pogo portable soil sensor, the soil temperature, soil moisture (volume moisture content), loss tangent, soil conductivity, real and imaginary parts of soil complex dielectric are observed and obtained. Vegetation parameter observation was carried out at some representative soil water sampling points, and the plant height and biomass (vegetation water content) were measured