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Passive microwave remote sensing is a vital tool for acquiring valuable information regarding the Earth's surface, with significant applications in agriculture, water management, forestry, and various environmental disciplines. Precision agricultural (PA) practices necessitate the availability of field-scale, high-resolution remote sensing data products. This study focuses on the design and development of a cost-effective, portable L-band microwave radiometer capable of operating from an unmanned aircraft system platform to measure high-resolution surface brightness temperature ($T_{B}$). This radiometer consists of a dual-polarized (Horizontal polarized, H-pol and Vertical polarized, V-pol) antenna and a software-defined radio-based receiver system with a 30 MHz sampling rate. The post-processing methodology encompasses the conversion of raw in-phase and quadratic (I&Q) surface emissions to radiation $T_{B}$ through internal and external calibrations. Radiometric measurements were conducted over an experimental site covering both bare soil within an agricultural field and a large water body. The results yielded a high-resolution $T_{B}$ map that effectively delineated the boundaries between land and water, and identified land surface features. The radiometric temperature measurements of the sky and blackbody demonstrated a standard deviation of 0.95 K for H-pol and 0.57 K for V-pol in the case of the sky and 0.39 K for both H-pol and V-pol in the case of the blackbody observations. The utilization of I&Q samples acquired via the radiometer digital back-end facilitates the generation of different time–frequency (TF) analyses through short-time Fourier transform and power spectral density (PSD). The transformation of radiometer samples into TF representations aids in the identification and mitigation of radio frequency interference originating from the instrument itself and external sources.

Sea surface temperature (SST) is one of the important parameters of global ocean and climate research, which can be retrieved by satellite infrared and passive microwave remote sensing instruments. While satellite infrared SST offers high spatial resolution, it is limited by cloud cover. On the other hand, passive microwave SST provides all-weather observation but suffers from poor spatial resolution and susceptibility to environmental factors such as rainfall, coastal effects, and high wind speeds. To achieve high-precision, comprehensive, and high-resolution SST data, it is essential to fuse infrared and microwave SST measurements. In this study, data from the Fengyun-3D (FY-3D) medium resolution spectral imager II (MERSI-II) SST and microwave imager (MWRI) SST were fused. Firstly, the accuracy of both MERSIII SST and MWRI SST was verified, and the latter was bilinearly interpolated to match the 5km resolution grid of MERSI SST. After pretreatment and quality control of MERSI SST and MWRI SST, a Piece-Wise Regression method was employed to correct biases in MWRI SST. Subsequently, SST data were selected based on spatial resolution and accuracy within a 3-day window of the analysis date. Finally, an optimal interpolation method was applied to fuse the FY-3D MERSI-II SST and MWRI SST. The results demonstrated a significant improvement in spatial coverage compared to MERSI-II SST and MWRI SST. Furthermore, the fusion SST retained true spatial distribution details and exhibited an accuracy of -0.12±0.74°C compared to OSTIA SST. This study has improved the accuracy of FY satellite fusion SST products in China. [ABSTRACT FROM AUTHOR]

This study explores the ability of chitosan to control the size of ZnO quantum dots (CHT/ZnO QDs) and defects formation via the microwave-assisted method, as well as their photocatalytic oxidation activity towards oxytetracycline (OTC). The intramolecular and intermolecular hydrogen bonds within the chitosan -OH and -NH2 were altered by ZnO and microwave radiation. As a result, the particle size decreased from 9.35 ± 0.21 nm to 7.86 ± 0.28 nm. Additionally, the presence of chitosan led to higher oxygen vacancies ( V s o) and Zni interstitials. The small size enhanced the absorption of photons, while defects suppressed the recombination rate of photogenerated electron/hole (e−/h+) pairs. The synthesized CHT/ZnO QDs exhibit outstanding photocatalytic performance by removing 97.4% of OTC within 40 min through pseudo-first-order kinetics with the rate constant (k) of 0.0568 min−1 and driven by the h+ and O 2 · - . This result was achieved by comprehensively investigating the impact of pH condition, initial concentration of OTC, and photocatalyst dosage. We believe that this work provides a potential photocatalyst design for antibiotics removal. [ABSTRACT FROM AUTHOR]

A passive microwave instrument will be carried by China's geostationary microwave satellite. A microwave hyper-spectral band included by the instrument ranges from 52.6 to 57.3 GHz, and totally has 89 channels in this spectral domain. The design of the hyper-spectral band is described from the aspects of scientific objectives and specifications. The weighting functions for each channel are calculated utilizing radiative transfer simulations under clear sky conditions. Then, the information content as well as the degree of freedom for signal are computed and analyzed to characterize this hyper-spectral sounding for atmospheric temperature profiling. Both the vertical distribution of the weighting functions and the width of retrieval averaging kernels indicate that the hyper-spectral band can provide more denser sampling for atmospheric temperature. The information content for the hyper-spectral band is approximately 46% higher than that of the ATMS-type channel 3 to 15, indicating that hyper-spectral measurement can improve the accuracy of retrieval. The most informative channels mainly locate near 57 GHz, having good consistency with the existing channels. The height range where the retrieval using the hyper-spectral observations is sensitive to the true profile, begins from about 800 to 1 hPa. Some channels can be considered as alternatives to each other since they have very similar information content and weighting functions. These results are expected to provide a valuable reference for future applications of the microwave hyper-spectral measurements. [ABSTRACT FROM AUTHOR]