《双偏振雷达气象学》

雷达无疑是气象观测、定量评估和预报中不可或缺的工具。目前,一套更好的观测数据——偏振雷达数据,可以用来更好地研究天气。本书主要介绍了偏振雷达遥感基础知识,主要包括以下几方面内容:展示了水成物的物理特性、统计特性和电磁特性,建立了雷达观测与物理参量的关系.

Recent Progress in Dual-Polarization Radar Research and Applications in China

Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.

Seasonal Variations of Observed Raindrop Size Distribution in East China

Seasonal variations of rainfall microphysics in East China are investigated using data from the observations of a twodimensional video disdrometer and a vertically pointing micro rain radar. The precipitation and rain drop size distribution(DSD) characteristics are revealed for different rain types and seasons. Summer rainfall is dominated by convective rain,while during the other seasons the contribution of stratiform rain to rainfall amount is equal to or even larger than that of convective rain. The mean mass-weighted diameter versus the generalized intercept parameter pairs of convective rain are plotted roughly around the "maritime" cluster, indicating a maritime nature of convective precipitation throughout the year in East China. The localized rainfall estimators, i.e., rainfall kinetic energy–rain rate, shape–slope, and radar reflectivity–rain rate relations are further derived. DSD variability is believed to be a major source of diversity of the aforementioned derived estimators. These newly derived relations would certainly improve the accuracy of rainfall kinetic energy estimation, DSD retrieval, and quantitative precipitation estimation in this specific region.

Current Status and Future Challenges of Weather Radar Polarimetry: Bridging the Gap between Radar Meteorology/Hydrology/Engineering and Numerical Weather Prediction

After decades of research and development, the WSR-88 D(NEXRAD) network in the United States was upgraded with dual-polarization capability, providing polarimetric radar data(PRD) that have the potential to improve weather observations,quantification, forecasting, and warnings. The weather radar networks in China and other countries are also being upgraded with dual-polarization capability. Now, with radar polarimetry technology having matured, and PRD available both nationally and globally, it is important to understand the current status and future challenges and opportunities. The potential impact of PRD has been limited by their oftentimes subjective and empirical use. More importantly, the community has not begun to regularly derive from PRD the state parameters, such as water mixing ratios and number concentrations, used in numerical weather prediction(NWP) models.In this review, we summarize the current status of weather radar polarimetry, discuss the issues and limitations of PRD usage, and explore potential approaches to more efficiently use PRD for quantitative precipitation estimation and forecasting based on statistical retrieval with physical constraints where prior information is used and observation error is included. This approach aligns the observation-based retrievals favored by the radar meteorology community with the model-based analysis of the NWP community. We also examine the challenges and opportunities of polarimetric phased array radar research and development for future weather observation.

Effects of Plastic Film Mulching on Quality and Appearance of Statuma Mandarin Fruit

Six-year Statuma mandarin (Citrus unshiu Marc. Cv. Miyagawa Wase) trees were used as materials to investigate the effects of plastic film mulching on quality and appearance of Statuma mandarin fruit during three periods of cell division, cell enlargement and mature stages. The results showed that mulching during the cell division and early-mature stages increased total sugar and reduced sugar content of fruit as well as the Vc content, compared to the control. However, the titratable acid content, fruit size, peel weight and single fruit weight were all lower than the control. Film mulching during the cell division phage resulted in higher edible fruit rate, while the fruit shape index was similar to the control. Mulching during the early-mature stage didn’t affect the edible rate of fruit, but caused lower fruit shape index. Compared to the control, film mulching during the cell enlargement period caused lower total and reducing sugar content, titratable acid content and edible rate, while the Vc content was a little bit higher than the control. In addition, the fruit size, peel weight, single fruit weight and fruit shape index were all lower than the control. Mulching during the early-mature period effectively enhanced the content of total and reduced sugar and Vc and decreased the titratable acid content. Hence, it increased fruit quality but had negative effect on fruit appearance.

Parameterized Forward Operators for Simulation and Assimilation of Polarimetric Radar Data with Numerical Weather Predictions

Many weather radar networks in the world have now provided polarimetric radar data(PRD)that have the potential to improve our understanding of cloud and precipitation microphysics,and numerical weather prediction(NWP).To realize this potential,an accurate and efficient set of polarimetric observation operators are needed to simulate and assimilate the PRD with an NWP model for an accurate analysis of the model state variables.For this purpose,a set of parameterized observation operators are developed to simulate and assimilate polarimetric radar data from NWP model-predicted hydrometeor mixing ratios and number concentrations of rain,snow,hail,and graupel.The polarimetric radar variables are calculated based on the T-matrix calculation of wave scattering and integrations of the scattering weighted by the particle size distribution.The calculated polarimetric variables are then fitted to simple functions of water content and volumeweighted mean diameter of the hydrometeor particle size distribution.The parameterized PRD operators are applied to an ideal case and a real case predicted by the Weather Research and Forecasting(WRF)model to have simulated PRD,which are compared with existing operators and real observations to show their validity and applicability.The new PRD operators use less than one percent of the computing time of the old operators to complete the same simulations,making it efficient in PRD simulation and assimilation usage.

Deformation process of a shocked drop-in-liquid

A mixed flow of two immiscible liquids may form drops of one liquid in the other.Deformation and breakup of drops occur when there is sufficient hydrodynamic or surface forces from the ambient liquid;such deformation and breakup of drops is a common phenomenon in various engineering applications,such as oil-water flow in the petroleum recovery industry[1,2],stirred dispersions in the chemical industry[3,4],and melted metal and cooling liquid interactions in