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This study presents a simulation framework for cloud and precipitation measurements via spaceborne millimeter-wave radar composed of eight submodules. To demonstrate the influence of the assumed physical parameters and to improve the microphysical modeling of the hydrometeors, we first conducted a sensitivity analysis. The results indicated that the radar reflectivity was highly sensitive to the particle size distribution (PSD) parameter of the median volume diameter and particle density parameter, which can cause reflectivity variations of several to more than 10 dB. The variation in the prefactor of the mass–power relations that related to the riming degree may result in an uncertainty of approximately 30 %–45 %. The particle shape and orientation also had a significant impact on the radar reflectivity. The spherical assumption may result in an average overestimation of the reflectivity by approximately 4 %–14 %, dependent on the particle type, shape, and orientation. Typical weather cases were simulated using improved physical modeling, accounting for the particle shapes, typical PSD parameters corresponding to the cloud precipitation types, mass–power relations for snow and graupel, and melting modeling. We present and validate the simulation results for a cold-front stratiform cloud and a deep convective process with observations from a W-band cloud profiling radar (CPR) on the CloudSat satellite. The simulated bright band features, echo structure, and intensity showed a good agreement with the CloudSat observations; the average relative error of radar reflectivity in the vertical profile was within 20 %. Our results quantify the uncertainty in the millimeter-wave radar echo simulation that may be caused by the physical model parameters and provide a scientific basis for optimal forward modeling. They also provide suggestions for prior physical parameter constraints for the retrieval of the microphysical properties of clouds and precipitation.

[Purpose / significance] At the important node of IR development entering a stable period and in the transition to the next generation of IR, this paper reviews the construction process, status quo and challenges of institutional repository in China, so as to achieve the purpose of accelerating and deepening the development of IR in China., [Method/process] First, it adopts the empirical research method combining the network survey method and telephone and email survey methods, and takes domestic universities, Chinese Academy of Sciences, Chinese Academy of Agricultural Sciences and other scientific research institutes as the survey object to investigate the development status of the national IR; second, the survey results According to the comparative analysis of the university system, scientific research system and the overall situation, summarize the IR development achievements and problems. [Result/conclusion]Some achievements have been made in IR construction. The number of IR under construction and to be built is increasing, and the resource scale is increasing greatly. However, there are some problems in the development of IR, such as imperfect management policies, excessive access restrictions, unclear intellectual property rights, insufficient openness and low self storage rate.

With appropriate orbit parameters, the circular SAR imaging mode can be realized on the geosynchronous orbit satellite to get high resolution three-dimensional (3D) image. It would also overcome the coverage and revisit period limitation. Repeat pass inrerferometry for geosynchronous circular SAR (GEOCSAR) could be carried out, comparing images taken at 24 hours interval. The geosynchronous orbit is influenced by perturbations, which cause the variation of the orbit and thus the spatial baseline is formed. The spatial baseline decorrelation of GEOCSAR interferometry in 2D and 3D model are analyzed, and the corresponding critical baselines are derived in this paper.

In this paper, an improved wavenumber domain imaging algorithm is proposed for circular synthetic aperture (CSAR) data taken in stripmap mode. The proposed algorithm allows to reconstruct an image on a cylindrical surface. The range trajectory is approximated with the fourth-order terms expansion and the echo signal is transformed to the wavenumber domain by using a principle of stationary phase. Based on the spectrum, the interpolation of the algorithm is deduced, and the residual phase is compensated. The valid aperture length of the proposed algorithm is greatly increased, comparing with the algorithm based on range expanded to quadratic terms. The simulation results validate the high-performance of the improved wavenumber domain imaging algorithm.