The FengYun (FY) meteorological satellites, equipped with combined microwave and infrared (IR) sensors, provide temperature and humidity profiles under both clear and cloudy conditions, supporting global atmospheric monitoring and weather forecasting. This study evaluates the FY-3E vertical atmospheric sounding system (VASS) using collocated radiosonde observations, reanalysis data, and satellite measurements, including the Cross-Track IR and Microwave Sounder Suite (CrIMSS) onboard joint polar satellite system-1 (JPSS-1). Under all-sky conditions, VASS temperature profiles exhibit a correlation of 0.99 with radiosonde data, and humidity profiles reach 0.80. The temperature biases [root-mean-square errors (RMSEs)] are 0.63 K (3.07 K) under clear-sky, 0.82 K (3.56 K) under cloudy-sky, and 0.67 K (3.26 K) under all-sky conditions. The corresponding humidity biases (RMSEs) are 4.63% (18.36%), 6.21% (21.38%), and 4.76% (19.36%). Compared with CrIMSS products using coincident radiosonde data, the VASS retrievals show larger errors in both temperature and humidity, yet provide consistent and reliable atmospheric profiles under diverse conditions. These results confirm the current utility of FY-3E VASS in operational weather and climate services while highlighting the need for continued algorithm development to further reduce retrieval uncertainties.

High-precision WTC is essential for satellite altimetry and ocean dynamic environment monitoring. Existing WTC approaches often rely on globally unified statistical frameworks, which inadequately represent wind-speed-dependent nonlinear sea-surface microwave radiative responses and are prone to systematic bias under uneven observation distributions. To address these limitations, this study proposes an adaptive WTC method integrating overlapping wind-regime modeling, multi-scale collaborative sample balancing, and a model soft-fusion strategy. Firstly, a modeling framework with overlapping transition zones for low-, moderate-, and high-wind-speed regimes is established according to wind-speed-driven variations in sea-surface radiative responses, and sub-models are trained independently. Subsequently, a multi-scale sample balancing, combining global and local weights, is designed to enhance learning from sparse samples. Finally, a soft-fusion strategy based on a trapezoidal membership function is applied to dynamically weight sub-model outputs, ensuring retrieval continuity across transition zones. Using HY-2C Calibration Microwave Radiometer (CMR) observations, the proposed method is developed, trained, and evaluated against model-derived WTC and collocated Jason-3 AMR-2 measurements. Results show that the proposed method improves overall WTC retrieval accuracy and stability while effectively reducing systematic biases under wind-speed regimes with sparse observations, providing an effective and robust approach for high-accuracy WTC retrieval under various wind-speed conditions.

South China is characterized by abundant and complex precipitation, with frequent typhoons, heavy rainfall, and pronounced extreme events, making it an ideal region for precipitation microphysics research. This study uses rainfall observations from an OTT Parsivel(2) (Parsivel) laser disdrometer and a Micro Rain Radar-2 (MRR-2) collected in Zhuhai during 2022-2023 to analyze the characteristics of stratiform rainfall (SR) and convective rainfall (CR). The results show that, although SR lasts longer, CR contributes much more to the total accumulated rainfall. In SR, samples with rain rate (RR) < 5 mm h(-1) account for about 27% of occurrences and contribute less than 10% of total rainfall, whereas in CR, samples with RR > 8 mm h(-1) represent only 7% of occurrences but contribute more than 45% of the accumulated rainfall. CR is characterized by a larger mass-weighted mean diameter (Dm), while SR shows a higher normalized intercept parameter (Nw). In SR, Dm increases with RR, whereas Nw changes little; in CR, both Dm and Nw increase with RR. Finally, by analyzing temporal/spatial collocated vertical rain profiles from MRR and Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM DPR), the results show that CR exhibits larger RR, radar reflectivity and stronger vertical variability than SR, along with greater variations in Dm and log(10)(Nw). Ground-based MRR also provides an independent vertical reference for evaluating DPR-derived precipitation structure and interpreting the consistency and discrepancies between satellite and ground-based observations. Although the results are not conclusive due to a limited number of events, both instruments capture distinct microphysical characteristics in the analyzed SR and CR cases, despite differences in their retrieved vertical DSD structures.

Current numerical weather prediction (NWP) models exhibit insufficient capability in simulating clouds and fog in the low-level atmosphere. This paper addresses the ubiquitous presence of minute water droplets in these phenomena by employing satellite-based microwave cloud liquid water absorption, emission, and scattering models within the Radiative Transfer for TOVS (RTTOV) framework. Forward simulations of Fengyun-3 (FY-3) satellite Microwave Humidity Sounder-II (MWHS-II) channel brightness temperatures were conducted separately for absorption, emission and scattering processes under global cloud and precipitation conditions. The differences between these simulations across various environments were compared. The experiments demonstrate that the cloud liquid water absorption parameterization in RTTOV is applicable only to weak, non-precipitating liquid clouds (where Rayleigh scattering dominates), with relatively better performance for mid-to-high-level sounding channels. For precipitating clouds involving strong Mie scattering and for near-surface channels significantly affected by surface emission, this scheme has inherent limitations that introduce substantial errors. This research provides essential support for implementing all-sky assimilation of microwave low-level atmospheric sounding channel radiances in numerical forecast models and enhancing the prediction accuracy of low-level clouds and fog.

FengYun meteorological satellites, as the major components of the world’s earth observation constellations, play a crucial role in global meteorological monitoring, yet they are confronted with increasing demands driven by technological progress and higher user expectations. Meanwhile, small satellite constellations have demonstrated remarkable potential in enhancing meteorological observation capabilities through rapid deployment, cost efficiency, and high-density observations. This study introduces FengYun virtual constellation, namely ‘FengYun+’, an integrated system that consists existing FengYun backbone satellites with complementary small satellites. The small satellite framework is designed to fulfill three main goals: new technology verification, thematic earth system observation, and networked collaborative observation. These small satellites encounter key technological challenges related to miniaturization, systematization, rapid processing, and standardization across satellite platforms, payloads, inter-satellite interconnection, and data processing. The collaborative architecture of the virtual constellation, enabled by inter-satellite connectivity, dynamic task allocation, and AI-enhanced processing, supports multi-element, high-frequency, and near real-time global meteorological services. Collaboration with international programs ensures alignment with global meteorological constellation. FengYun+ will advance the Sustainable Development Goals (SDGs) and Early Warnings Initiatives of United Nations (UN) by delivering critical data for weather prediction, climate research, and disaster mitigation.

To support the growing demand for refined atmospheric observations and numerical weather prediction in the Fengyun satellite upgrade, a new-generation microwave hyperspectral sounder has been developed to replace conventional multi-channel microwave payloads. The new instrument provides improved spectral resolution, enhanced vertical profiling capability, and stable operational performance. This study conducts systematic laboratory calibration and airborne flight experiments on the selfdeveloped hyperspectral microwave prototype instrument. The laboratory calibrations verified the instrument's radiometric accuracy and operational stability. The experimental results demonstrate the technical feasibility and potential of microwave hyperspectral technology for high-precision atmospheric remote sensing. This work provides experimental support for the engineering development and on-orbit application of Fengyun satellite microwave payloads for next-generation missions.

Significance Atomic-based quantum precision measurement technology has profoundly impacted the development of human society over the past few decades. Rydberg atom-based electric field measurement technology, leveraging core advantages such as high sensitivity, SI traceability, self-calibration, and spatially invariant reproducibility, has emerged as a powerful tool for quantum-based traceable metrology of physical quantities like radio frequency field strength and power. Its principle relies on the strong interaction between Rydberg atoms and external electric fields through quantum interference effects such as electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting. Benefiting from the inherent high accuracy and repeatability of atomic systems, measurement standards based on atoms are driving metrology's transition from artifact-based standards to quantum standards. Microwave radiometers have evolved rapidly in recent years and now play crucial roles in fields such as meteorology and agriculture. As they advance toward expanding application frequencies and achieving higher-precision detection capabilities, higher requirements are imposed on indicators like sensitivity and resolution. Accurate radiometric calibration is fundamental to quantitative information processing in microwave remote sensing. However, the radiometric accuracy of current microwave radiometers, which rely on blackbody physical benchmarks, is limited by factors such as material properties, environmental instability, and incomplete traceability chains. To realize the future prospect of multi-satellite interconnection, improvements to the radiometer calibration system are imperative. Progress This paper first elaborates on the fundamental characteristics of Rydberg atoms and the principle of electric field measurement based on a ladder-type three-level structure. Furthermore, by integrating existing research, it systematically reviews the development of Rydberg microwave electric field measurement technology, with a focus on summarizing recent progress concerning two key indicators: sensitivity enhancement and uncertainty reduction. Regarding sensitivity, it categorizes improvement methods into noise suppression (e.g., interferometer application, cold atom utilization, superheterodyne technology) and signal enhancement (e.g., resonator utilization, optical repumping, laser array optimization), presenting related research results and noting that new methods continue to push sensitivity toward the quantum limit. Concerning uncertainty, it reviews optimization research addressing the effects of atomic gas cells, nonlinear interactions, and characteristics of different frequency bands, building upon the initial summary of quantum and metrological uncertainties by the Shaffer group. Building upon improvements in sensitivity and uncertainty, as well as the inherent traceability of this technology, some research teams have conducted traceable measurements of microwave power and quantum state transitions induced by blackbody radiation. Current traceability methods for microwave radiometers still primarily rely on improving blackbody performance and precisely characterizing the antenna receiving link. The performance of standard blackbody calibration sources is enhanced through geometric design, coating material improvement, and process optimization. Non-traditional calibration sources, such as novel material structures or alternative blackbodies (e.g., noise amplifiers), are also being explored. Subsequently, the paper summarizes progress in receiving link analysis, indicating that current research on near-field issues often involves two-dimensional near-field modeling and simulations, while comprehensive three-dimensional analysis remains lacking. Such limitations contribute to incomplete transmission links, making effective end-to-end traceability challenging. To address the above issues, this paper proposes employing Rydberg electric field measurement technology to establish effective traceability for radiometers, innovatively adopting an "atom-microwave" detection scheme. A Rydberg electric field measurement system would be integrated into the radiometer calibration process to perform absolute quantitative measurements of known radiation sources or blackbodies, establishing the relationship between input radiation quantities and radiometer output signals. Through in-depth investigation of the transmission process among the atomic measurement system, microwave receiving device, and standard radiation source, a complete transmission link can be established and refined. Analyzing the uncertainty contributions of each part would form a comprehensive traceability chain. Additionally, this paper conducts a feasibility analysis of the proposed scheme from perspectives including detection principle, operational frequency band, calibration design, wideband simultaneous measurement capability, and system integration. Conclusions and Prospects Rydberg atoms, with their high principal quantum number states and unique quantum properties, offer advantages such as high sensitivity and inherent traceability. Their technology has found application in quantum-based traceable metrology for parameters like power. This paper innovatively proposes combining this technology with microwave radiometer calibration to address current issues of incomplete traceability chains and the lack of definitive radiation benchmarks in microwave radiation transmission, and conducts a corresponding feasibility analysis. However, at the engineering practice level, this approach still faces key challenges such as achieving wideband simultaneous measurement and overcoming system integration difficulties, necessitating further innovations and breakthroughs in both theory and technology.

The application of ground-based microwave radiometers (GMWRs), which provide high-quality and continuous vertical atmospheric observations, has traditionally focused on the indirect assimilation of retrieved profiles. This study advanced this application by developing a direct assimilation capability for GMWR radiance observations within the Weather Research and Forecasting Data Assimilation (WRFDA) system, along with a bias correction scheme based on the random forest technique. The proposed bias correction scheme effectively reduced the observation-minus-background (O-B) biases and standard deviations by 0.83 K (97.1 %) and 1.63 K (64.6 %), respectively. A series of 10 d experiments demonstrated that assimilating GMWR radiances improves both the initial conditions and the forecasts, with additional benefits from higher assimilation frequencies. In the initial conditions, hourly assimilation significantly enhanced low-level temperature and humidity fields, reducing the root-mean-square error (RMSE) for temperature by 6.32 % below 1 km and for water vapor mixing ratio by 1.98 % below 5 km. These improvements extended to forecasts, where 2 m temperature and humidity showed sustained benefits for over 12 h, and precipitation forecasts exhibited improvements to a certain extent. The time-averaged Fractions Skill Score (FSS) for 3 h accumulated precipitation within the 24 h forecasts increased by 0.02-0.04 (3.9 %-10.2 %) for thresholds of 3-6 mm.

Observations of the Micro-Wave Humidity Sounder-II (MWHS-II) onboard FengYun-3C (FY-3C) satellite are crucial for numerical weather prediction. Precise calibration of MWHS-II is fundamental for the accurate application. However, the Moon's presence in the deep space view (DSV) can corrupt the in-orbit calibration of MWHS-II, and thus it is necessary to quantify the Moon's influence. This study proposes a method to identify the Moon's intrusion into the DSV, which improves the accuracy of lunar identification, by taking into account the lunar phases and the detectable radiance change of the sensor. The abrupt jump in the DSV due to the lunar contamination is removed, assuming the radiometric gain of the adjacent scans barely changes. With the corrected DSV counts, the effective lunar brightness temperature (TB) is calculated. It is found that the phase of the Moon observed by the FY-3C MWHS-II is in the range of 95 degrees-140 degrees, and the effective lunar TB is up to 15 K at 89/118.75 GHz and 45-50 K at 150/183.31 GHz. Though the results are subject to the uncertainties of the Moon calculations and the beam pointing, this study offers unique insights into the lunar observations of MWHS-II onboard the polar-orbiting FY-3C.

Hyperspectral microwave radiometer is a new type of passive microwave remote sensor for observing middle and upper atmospheric temperature, humidity, trace gas, and other parameters such as winds. The digital spectrometer, which allows the fine sampling of the spectral lines, is the core component of the radiometer. In this article, we propose the design and implementation of a new type of wideband, real-time channelized digital spectrometer, which realizes the core base-64 real-time complex fast Fourier transform (FFT) algorithm and channelization algorithm by improving the filter bank, 128-channel parallel processing of FFT and complex number processing. The digital spectrometer has a sampling rate of 20 Gsps, a quantization bit number of 8 bits, and an input bandwidth of 10 GHz, which realizes the spectrum analysis of 4096 channels. Then, an observation test was carried out using a V-band ground-based microwave radiometer equipped with the 10-GHz spectrometer, and the atmospheric temperature profile was successfully measured from the surface to the stratosphere. The retrieval results were compared with the ERA5 reanalysis data and the L2 temperature products of the FY-3-D/MWTS-MWHS and Aura/microwave limb sounder (MLS), with a better consistency, which proved the application and potential of the new wideband digital spectrometer in the atmospheric sounding.

This paper explores the performance advantages of spaceborne hyperspectral microwave radiometers for jointly retrieving atmospheric temperature and humidity profiles under clear-sky conditions. It utilizes 4,440 channels at a spectral resolution of 10 MHz and 444 channels at a spectral resolution of 100 MHz across the 60 GHz, 118 GHz, and 183 GHz bands. The Atmospheric Radiative Transfer Simulator (ARTS) was employed as the forward model to generate virtual high-spectral-resolution observational data, based on 10,745 marine profiles from the ECMWF-137 dataset. Channel selection eliminated about half of the channels with spectral resolutions of both 10 MHz and of 100 MHz while retaining 90$\% $% of the information content. The iterative retrieval model was constructed using the Optimal Estimation Method (OEM) for retrieval experiments, incorporating combinations of channels with 10 MHz and 100 MHz spectral resolutions, as well as those selected through an information entropy-based method and channels from MWTS (Micro-Wave Temperature Sounder) and MWHS (Micro-Wave Humidity Sounder), enabling high-accuracy retrieval of atmospheric temperature and humidity profiles. Specifically, the 10 MHz resolution extends the effective temperature sensing range from the surface to 70 km, with vertical resolution enhanced to 2-18 km for temperature and 1.6-6 km for humidity. Within the 0-35 km and 0-12 km altitude ranges, temperature retrieval errors are reduced by 0.5 K, and humidity retrieval errors are reduced by 0.00003 kg/kg for specific humidity and 2.4$\% $% for relative humidity, respectively. Theoretical analysis and quantitative retrieval demonstrate that hyperspectral microwave radiometer outperforms traditional MWTS + MWHS systems in terms of effective sensing range (temperature), vertical resolution, information content, and retrieval accuracy, while also highlighting the effectiveness of channel selection.

The scanning drive mechanism of the spaceborne microwave-sounding antenna has two working modes of constant speed and variable speed, and the special structural form and layout of the reflecting surface lead to a large perturbation moment in the constant speed and variable speed scanning modes. The optimized design of the reflecting surface reinforcement structure of the antenna’s scanning drive mechanism is of great significance for the adjustment of the dynamic stiffness and rotational moment of inertia of the system, which helps to reduce the influence of the moment perturbation. In this paper, a design method combining topology optimization and size optimization is adopted to optimize the design of the reflecting surface reinforcement structure of the planar antenna. The topology optimization constrains the volume, and the objective function is the first-order frequency maximum. The topology optimization results show that the reinforcement is arranged along the center in a “palm” shape. The size optimization is based on the objective of minimizing the rotational inertia of the structure, and the constraints are the dynamic stiffness and the RMS of the structural stress values. The dynamic stiffness of the structure is improved after size optimization, the mass of the reinforcing bar is reduced by 26% compared with the original structure, the rotational inertia of the planar antenna is reduced by 39% compared with the original structure, and the perturbation moments are decreased by 52% at uniform speeds and by 39% at variable speeds.

In this work, the brightness temperature (TB) transfer from the microwave calibration target (MCT) to the feeder antenna in the near-field region is investigated, which is the fundamental physical process in microwave radiometer calibration. As in this scenario, the MCT and antenna cannot be separately considered as points like in far fields, it is interesting and important to study the TB characteristics of the target in cases of feeder antennas at different positions and with different aperture sizes. Recently, as reciprocity in the near field has been established, this fundamental issue can be now investigated. The study starts at a high frequency of 89 GHz when the free-space lambda is much smaller than the unit period of MCT; then, the distributions of the local TB contribution rate are calculated to understand the possible TB transfer variation. It is found that the key factor for the TB variation is the illumination area upon the array-type MCT, and as the footprint is sufficiently large to cover several pyramid units, the TB can be stable versus relative position.

The microwave sounding instruments have been providing humidity and temperature profiles critical for improving numerical weather prediction (NWP). In recent years, advanced microwave sounders have been proposed to be onboard future CubeSats that are less expensive than traditional satellites, providing unprecedented rapid-update and low-earth-orbit microwave observations that can follow the evolution of the typhoon and convective weather systems. In this study, the potential values of assimilating future CubeSat constellation microwave radiances in clear-sky condition for regional NWP are preliminarily assessed with observing system simulation experiments using the convection-permitting 4DEnVar for the prediction of typhoon "Infa" and its associated "7.20" heavy rainfall event that occurred in China in July 2021. This constellation is assumed to include 12 CubeSats equipped with microwave sounders obtaining radiances sensitive to water vapor and temperature. The results show the CubeSat constellation radiances demonstrate positive impacts on the analyses and forecasts of typhoon's track, intensity, precipitation, and dynamical conditions. The forecast errors of typhoon's maximum wind speed, minimum sea level pressure, and track are reduced by 17.9%, 14.3%, and 27.9%, respectively. The wind, temperature, and humidity of 6-hr forecasts are improved by 4.95%, 7.89%, and 5.17%, respectively. The rainfall forecast scores in terms of fraction skill score and equitable threat score are also improved by 7% and 5.9% with the ameliorative prediction of magnitude and pattern of rainfall maximum centers for both the landfall typhoon and "7.20" heavy rainfall event. This study indicates the potential benefits of microwave radiances from a low-earth-orbit CubeSat constellation with rapid revisits using advanced data assimilation on the regional NWP in the future.

In this work, an interesting phenomenon is investigated in the scenario of calibration link in microwave radiometers, where a feeder antenna is directly harvesting the radiated brightness temperature (BT) from the microwave calibration target (MCT). As reciprocity has been established for the near-field BT transfer, it is important to investigate the performance variation of the MCT in case of different antenna illumination. In this work, it is found and analyzed that at the frequencies where lambda is near to the unit period of periodic array-shaped calibration target, the reflectivity may be notably increased in case of small aperture feeder illumination. This is a disturbing phenomenon that should be avoided for practical applications.

Microwave hyperspectral sounders are key instruments for next-generation meteorological satellites, designed to replace broadband sounders, such as advanced technology microwave sounder (ATMS), microwave temperature sounder (MWTS), and microwave humidity sounder (MWHS). A major challenge in their design is determining the optimal channel bandwidth configuration to maximize the use of absorption spectra and enhance vertical atmospheric profiling. This study evaluates two variable-bandwidth strategies: 1) a generalized variable-bandwidth approach, which applies multiple fixed bandwidth combinations across different frequency bands and 2) a dynamic bandwidth strategy, which differentiates channel bandwidths within the same frequency band for absorption peak and wing regions. The retrieval performance of various bandwidth configurations is analyzed for lower and upper atmospheric temperature and humidity observations. Results indicate that for upper atmosphere temperature retrievals, the 60- and 118-GHz bands achieve higher accuracy with a 10-MHz bandwidth. For lower atmosphere temperature retrievals, where most information originate from the O2 absorption line's wing region, a wider bandwidth reduces observation costs while maintaining comparable accuracy. Water vapor retrievals, which primarily rely on the 118-GHz wing region and 183-GHz absorption lines, show minimal sensitivity to bandwidth configurations. A novel channel configuration method is proposed, integrating both absorption peak and wing regions into a single-optimized scheme. Experimental results demonstrate that the $10+ 10+100$ MHz (peak) $+ 50+ 100+100$ MHz (wing) configuration achieves the best retrieval accuracy across different atmospheric layers, significantly improving both temperature and humidity profiling compared with existing broadband sounders. The advantages of using variable channel bandwidth hyperspectral microwave radiometers for joint retrieval of temperature and humidity profiles have been demonstrated from both theoretical analysis and quantitative retrieval optimal estimation method (OEM), providing theoretical support and technical guidance for the development of the next generation of spaceborne hyperspectral microwave radiometers.

Fine spectrum refines conventional spectral sounding channels by increasing the spectral resolution to improve further the vertical resolution for accurate detection of atmospheric parameters. The 50- to 60-GHz absorption band is mainly used to sound the vertical distribution of atmospheric temperature in the troposphere and stratosphere, and 53 GHz is located in the weak oxygen absorption line. FengYun-3E (FY-3E) Microwave Temperature Sounder-III (MWTS-III) has two sounding channels added to this absorption band, and initially realized the refinement of the sampling channels. In this article, by establishing the assimilation operator for the radiance data of MWTS-III in China Meteorological Administration Global Assimilation Forecasting System (CMA-GFS) 4D-Var, and using the in-orbit observations from FY-3E MWTS-III, we investigate the impact of refining sounding channels at 53 GHz on numerical weather prediction (NWP). Results show that the temperature increment has the largest value and the widest influencing area near the peak weighting functions of channels, and the intensity and range of the temperature increment also change as the number of assimilated channels increases. An increment index can help quantify the impact of channel refinement on the forecast field. After single-cycle assimilation, the root mean square error (RMSE) of atmospheric parameters in the analysis field shows a decreasing trend. After continuous assimilation, the RMSE of geopotential height has a positive effect on short-term forecasts as the number of assimilated channels increases. It can be seen that channel refinement at 53 GHz positively impacts the performance of NWP.

This article investigates the potential of microwave sounders for a future international Venusian lower atmosphere exploration mission. Venusian microwave atmospheric radiative transfer (RT) calculations from a spaceborne perspective are performed with appropriate settings of the specific observation geometry and input atmospheric scenarios. An atmospheric profile perturbation analysis was undertaken to determine the channel selection and corresponding retrieval accuracy. Meanwhile, a suitable configuration of microwave sounder is proposed based on the gas absorption characteristics, sensitivity, and retrieval error analysis. The channel frequency selected includes 21 (2) channels of SO2 (H2SO4) absorption lines and its sidebands, as well as 37 channels between 6 and 42 GHz. Due to the strong coupling between temperature, SO2, and H2SO4 in the lower atmosphere, a joint physical retrieval method [optimal estimation method (OEM)] is proposed. Under ideal model conditions, the RMSE of retrieved temperature profiles improves by 1.3 K to stay within 2 K for 0-65 km, while the maximum RMSEs for SO2 and H2SO4 volume mixing ratios (VMRs) show improvements of at least 15% and 10%, reaching 30% and 25%, respectively. These results validate the proposed microwave sounder's effectiveness for temperature and SO2 (H2SO4) profiling up to 65 km (30-75 km for SO2 and 35-55 km for H2SO4). However, increasing model error reduces retrieval accuracy, emphasizing the importance of model development for accurate joint observations of these parameters.

Microwave hyperspectral instruments represent one of the main atmospheric sounders of China’s next-generation Fengyun meteorological satellites. In order to better apply microwave hyperspectral observations in the fields of atmospheric parameter retrieval and data assimilation, this paper analyzes the sensitivity of trace gases to five selected bandwidth channels using a radiative transfer model based on the simulated data of microwave hyperspectral radiances at 50–60 GHz. This method uses information entropy and a weighting function to select channels and analyze the impact of this on the retrieval accuracy of atmospheric profiles before and after channel selection. The experimental results show that channel selection can reduce the number of channels by approximately 74.05% while maintaining a large amount of information content, and this retrieval effect is significantly better than that of MWTS-III. After channel selection, the 10 MHz, 30 MHz, and 50 MHz bandwidths have the best retrieval results in the stratosphere, whole atmosphere, and troposphere, respectively. When considering the number of channels, computational scale, and retrieval results comprehensively, the channel selection method is effective.

Atmospheric boundary layer detection is in urgent demand in meteorological and climate research and is closely related to human life and agricultural production. Atmospheric microwave fine-spectral sounding is a cutting-edge means to break through the regional and even global all-weather atmospheric boundary layer temperature and humidity profiling observations. In this paper, we carry out field campaigns using a unmanned aerial vehicle-based (UAV-based) fine-spectral microwave radiometer to solve key technologies of boundary layer detection and inversion, and realize the sounding of atmospheric water condensate and the study of the evolution.