适合飞机人工增雨作业天气系统的雷达回波特征分析

应用2004～2005年沈阳辉山新一代天气雷达资料和常规气象资料,对实施飞机人工增雨作业的天气系统、增雨作业云系及其雷达回波特征进行了归纳和分析,并提出了飞机人工增雨作业条件和作业时机、作业区域等判别方法,为实施飞机人工增雨作业提供科学依据。     

基于V9I的空间关系映射与操作

利用V9I模型中目标的边界、内部和Voronoi区域均可量测及易于操作的特点,研究建立底层数据结构与空间关系语义层之间的V9I映射机制,在Voronoi的动态栅格生成算法的基础上,构建空间关系的基本操作。最后,以VC++为开发工具并采用面向对象的技术,设计了基于V9I的空间关系操作工具原型VTKit,并给出部分操作实例。     

辽宁省新旧气候平均值变化及影响分析

根据辽宁省61个气象站1961—2020年逐日气温和降水量数据,对比分析1991—2020年和1981—2010年新旧气候平均值变化及对辽宁省气候业务的影响。结果表明：1—11月平均气温、平均最高气温、平均最低气温均升高;10—12月降水量增幅最大。年及四季平均气温、平均最高和最低气温均升高,增幅自东部和西部山区向中部平原地区增大,中部区域增幅最为显著;平均气温和平均最高气温均以春季增幅最大,平均最低气温夏季增幅最大。年、夏季和秋季降水量减少,春季和冬季增加;7—8月降水量总体减少,东部山区和大连沿海地区降水量增加;7月下旬—8月上旬降水量增加,辽宁西部和南部地区增幅最大,为5%～6%,北部地区增幅最小。气候平均值改变后,四季平均气温及降水量评价等级均发生了变化。     

Analytical and numerical study of the ground-track resonances of Dawn orbiting Vesta

The aim of Dawn mission is the acquisition of data from orbits around two bodies (4) Vesta and (1) Ceres, the two most massive asteroids.Due to the low thrust propulsion, Dawn will slowly cross and transit through ground-track resonances, where the perturbations on Dawn orbit may be significant. In this context, to safety go the Dawn mission from the approach orbit to the lowest science orbit, it is essential to know the properties of the crossed resonances.This paper analytically investigates the properties of the major ground-track resonances (1:1, 1:2, 2:3 and 3:2) appearing for Vesta orbiters: location of the equilibria, aperture of the resonances and period at the stable equilibria. We develop a general method using an averaged Hamiltonian formulation with a spherical harmonic approximation of the gravity field. If the values of the gravity field coefficient change, our method stays correct and applicable. We also discuss the effect of one uncertainty on the C₂₀ and C₂₂ coefficients on the properties of the 1:1 resonance. These results are checked by numerical tests. We determine that the increase of the eccentricity appearing in the 2:3 resonance is due to the C₂₂ and S₂₂ coefficients.Our method can be easily adapted to missions similar to Dawn because, contrarily to the numerical results, the analytical formalism stays the same and is valid for a wide range of physical parameters of the asteroid (namely the shape and the mass) as well as for different spacecraft orbits.Finally we numerically study the probability of the capture in resonance 1:1. Our paper reproduces, explains and supplements the results of Tricarico and Sykes (2010).     

Marine Geodesy (1975–1979)— to the International Association of Geodesy,Section 1

Abstract

Geographic Information Systems (GIS) have been developed during the last decade. Their land‐based applications range from land information management, urban planning, and environmental research to engineering design and management in the utility and oil industries, geological subsurface analysis, and others. However, applications of GIS in the marine environment are still in the initial stages. This may be due to, among other things, the large marine data sets, the demands of 3D data processing, and the difficulty of ocean data acquisition.

This article presents the result of the development of an integrated Marine Geographic Information System (MGIS) for the exploration and development of the Exclusive Economic Zone (EEZ) in the U.S. Pacific Islands region by the Pacific Mapping Center, University of Hawaii. Features such as spatial marine data processing, integration of GIS and mapping systems, 3D data structures, and simulation and animation of marine operations are developed and applied in this system. Since MGIS applications in EEZ are related to many disciplines in marine sciences and engineering, an operational MGIS should be an integrated system in which both basic GIS and marine application systems are combined into a single geo‐referenced system, In addition to other applications, this MGIS has been used: (1) to select a potential deep‐water research site off the island of Hawaii for the State of Hawaii Department of Business, Economic, and Development (DBED); (2) to generate a three‐dimensional database and use it for the navigation and simulation of underwater operations of an underwater research vehicle; and (3) to produce two 2° × 2° mosaic sheets of sonar images, which meet the USGS standard for a sonar image atlas.     

Seasonal and annual maximum streamflow forecasting using climate information: application to the Three Gorges Dam in the Yangtze River basin,China / Prévision d'écoulements saisonnier et maximum annuel à l'aide d'informations climatiques: application au Barrage des Trois Gorges dans le bassin du Fleuve Yangtze,Chine

Abstract

This paper explores the potential for seasonal prediction of hydrological variables that are potentially useful for reservoir operation of the Three Gorges Dam, China. The seasonal flow of the primary inflow season and the peak annual flow are investigated at Yichang hydrological station, a proxy for inflows to the Three Gorges Dam. Building on literature and diagnostic results, a prediction model is constructed using sea-surface temperatures and upland snow cover available one season ahead of the prediction period. A hierarchical Bayesian approach is used to estimate uncertainty in the parameters of the prediction model and to propagate these uncertainties to the predictand. The results show skill for both the seasonal flow and the peak annual flow. The peak annual flow model is then used to estimate a design flood (50-year flood or 2% exceedence probability) on a year-to-year basis. The results demonstrate the inter-annual variability in flood risk. The predictability of both the seasonal total inflow and the peak annual flow (or a design flood volume) offers potential for adaptive management of the Three Gorges Dam reservoir through modification of the operating policy in accordance with the year-to-year changes in these variables.     

奉化亭下水库3维防洪调度仿真系统的研究与实现

阐述了采用3维虚拟仿真、地理信息和数据库等技术,开发奉化亭下水库3维防洪调度仿真系统,给出了系统的总体技术方案、总体框架及关键技术,实现了系统的具体功能.     

Space operation system for Chang’E program and its capability evaluation

Space operation for China’s first lunar exploration program, Chang’E will be provided by the S-band aerospace Telemetry, Tracking and Command (TT&C) network designed for China’s manned space program. This is undoubtedly a great challenge to the ground TT&C system. The largest antennas of China’s S-band aerospace TT&C network has an aperture of only 12 m. A series of technical measures have been taken into the designing of the spacecraft-ground TT&C system to ensure that such antennas can communicate with Chang’E-1 lunar probe 400,000 km away. These include installation of high-gain directional antennae and medium-gain omni-directional antennae for the probe, adding channel encoding to the downlink channel, using both high and low data rates for information transmission and upgrade and design of ground equipment terminals. Among them, the omni-directional antenna will operate in the earth-ground transfer orbit phase and the directional antenna will operate in the lunar orbit phase. These measures satisfy the spacecraft-ground link and program design requirements. To provide accurate navigation for the probe during its Earth-Moon flight and initial lunar orbiting flight, China’s VLBI system designed for astronomical observations, will also be used besides the ranging and range rate measurement capabilities of the S-band TT&C network. The purpose is to provide 100 m accuracy in position determination during lunar orbit. This paper describes the system design, technical challenges, solutions and capability evaluation of space operation for Chang’E-1.     

Inferring Low Cloud Base Heights at Night for Aviation Using Satellite Infrared and Surface Temperature Data

A nighttime image product that depicts areas of the lowest cloud base heights has been developed by combining brightness temperature data from the Geostationary Operational Environmental Satellite (GOES) Imager InfraRed (IR) bands centered at 3.9 μm and 10.7 μm, with hourly shelter temperatures from surface observing sites and offshore marine buoys. A dependent data sample showed a good correlation between the surface temperature minus IR cloud top temperature differences versus measured cloud base heights. Histogram analysis indicated that a temperature difference of less than 4-C related to a > 50% frequency of ceilings below 1000 ft above ground level, the threshold for Instrument Flight Rules (IFR). Using this result as a model, an experimental Low Cloud Base image product was developed that highlights regions of likely IFR ceilings. Validation of the Low Cloud Base product for two separate periods resulted in Probabilities of Detection of 67% and 72% and False Alarm Rates of 6% and 11%, respectively. Some regional variation observed could be related to the relative frequency of multi-layered overcast conditions. The biggest factor leading to underdetection of IFR ceilings by the GOES Low Cloud Base product is the presence of overlying clouds, including thin cirrus contamination. The GOES Low Cloud Base product shows potential for use as guidance for aviation meteorologists over both continental and marine areas.