An Improved Hilbert Curve for Parallel Spatial Data Partitioning

A novel Hilbert-curve is introduced for parallel spatial data partitioning, with consideration of the huge-amount property of spatial information and the variable-length characteristic of vector data i...     

地图制图专家知识对地理信息符号化过程的控制

针对纸质地图数字化得到地理信息(空间数据)的过程中存在地图信息损失的问题,阐述了产生这种损失的原因。数字化后得到的地理信息是各种GIS应用系统的重要数据源,在GIS应用中需要把这些地理信息重新再现成地图。为了得到较好的地图显示效果,有必要将数字化后损失的地图信息在从地理数据到地图符号化的过程中进行补偿。论述了在符号化过程中如何充分利用地图制图专家的多年知识和经验,将用自然语言表达的不确定性的专家知识形式化,以此来控制整个符号化的过程,达到改善地图显示效果的目的。     

日降水量空间插值方法研究

采用反距离权重法和普通克里格方法对26°~34°N, 103°~115°E范围内2004年逐日降水量进行空间插值试验分析, 分辨率为1 km×1 km。采用交叉检验方法和准确率方法对两种方法插值的总体效果及不同等级的降水插值效果进行综合对比。结果表明:两种方法插值效果近似, 插值结果与实测值相关系数分别为0.83和0.82。但对日雨量较大的情况, 两种方法插值效果均有所降低, 相关系数为0.66和0.67。两种方法的实测值与插值结果的相关系数在不同季节非常接近, 并且均以春季最大, 其次为冬、秋季, 夏季相关系数最小; 通过采用平均误差、平均绝对误差和均方根3个指标衡量及不同等级雨量的插值准确率统计比较, 普通克里格方法插值效果略好于反距离权重法。     

ASP与数据库在网站开发中的应用

基层气象局地面测报工作是最基础的气象业务工作,为天气预报、气候分析、气象服务等提供重要的依据。根据多年在基层从事测报值班、报表预审及管理工作的经验,以及多次参加省、市测报业务竞赛的学习体会,分析了如何才能搞好这项工作,从而提高测报业务质量。     

Parsivel~激光降水粒子谱仪及其在气象领域的应用

降水粒子特性是大气运动和云内微物理过程的综合结果,在云降水物理及人工影响天气领域有着重要的意义。传统的测量方法不适合对大量数据分析寻找规律,德国OTT公司的Parsivel激光降水粒子谱测量系统可以较好解决自动测量难题。该仪器是以激光测量为基础的粒子测量传感器,采用平行激光束和光电管阵列结合,当有降水粒子穿越采样空间时,自动记录遮挡物的宽度,通过穿越时间计算降水粒子的尺度和速度,根据各种参数的综合信息对降水粒子进行分类,并能够以数字形式显示瞬时降水强度、降水粒子总数、累积降水量、降水时的能见度和雷达反射因子,以图形方式显示降水粒子尺度谱、速度谱、降水粒子分类且自动生成天气现象代码,实现天气现象的自动识别。激光降水粒子谱仪主要用于气象水文观测。在雷达气象学领域可用于Z/R关系的拟合修正,比传统的用雨量筒观测数据拟合效果好得多;由降水粒子谱仪测量雨滴的降落速度,可以对天气雷达垂直向上测量的粒子径向速度谱进行校正。人工影响天气的效果检验一直是一个难题,自然降水粒子谱分布形式与人工催化以后的降水粒子谱型理论上应当具有较大的差别,人工增雨作业降水滴谱变化物理响应和降水强度时间变化响应都有明显的区别。如果能够实时检测到这些差别,就能够充分说明人工催化的有效性。未来如果能够进行联网观测记录区域性降水、降雹,就有充分证据表明人影作业的有效性,在定量化作业效果评估以及灾害损失评估等方面应用潜力巨大。利用该仪器已经对一年的自然降水过程进行了连续观测,并将所获得的降水粒子谱、雨滴浓度值随时间变化状况与卫星反演的云顶有效粒子半径时间变化趋势进行了对比,发现有较好的一致性。     

焦作市农业气候资源及变化特点

焦作市的农业气候资源丰富,雨热同季,并有不完全同步的特性,10℃以上活动积温为4653~4960℃.d,降水量为548.8~590.5 mm,主要分布在4-10月,日照时数2107.5~2444.9 h。近40 a热量资源呈增多趋势,20世纪90年代的热量资源明显多于前30 a,水分变化不明显,日照时数呈递减趋势。     

山东省近40a来的气温和降水变化趋势分析

本文利用非参数检验法(Mann-Kendall法)分析了山东省15个站点近40 a(1958—1998)来气温和降水的长期变化趋势。结果表明:全省气温除西南的莘县、兖州有下降趋势外,大部分地区呈现上升趋势,全省平均上升0.06℃/10a。分季情况为:春季和冬季气温有上升趋势,其中冬季气温上升对全省气温上升的贡献率最大。夏季气温基本保持不变,秋季气温有下降趋势。全省除济南降水量呈略微上升趋势外,其余地区的降水倾向率均为负值,全省的降水倾向率为-3.05 mm/a。表明山东省自1960年以来,年均降水量呈现减少趋势。减少幅度东南部大于西北部,以东南沿海平均减少幅度最大。     

Study on cut-off low-pressure systems with floods over Northeast Asia

Summary The cut-off lows (COLs) during the period from June to August 1998 leading to the record flood in Northeast Asia, especially in Northeast China, has been investigated in this paper. The results are as follows: the blocking highs benefited significantly the formation and maintenance of COLs over Northeast China; an obvious frontogenesis zone existed in Northeast China and it implies that baroclinity played an important role in the initiation of COLs, especially in middle and upper troposphere; the maxima of the potential vorticity anomaly were located in the upper troposphere, then extended downwards to the middle and the lower troposphere. The pronounced interaction between systems in upper-middle and low troposphere can be revealed; the moisture supply was from South China, and even from East China Sea and South China Sea. The strong southerly current transported very rich moisture to Northeast China. The maximum of the convergence of moisture flux was below 850 hPa. Obvious interaction between the middle and lower latitude systems was found in the study. Also, the summer monsoon showed significant impacts on the sustained heavy rainfalls related with the COLs over Northeast China; the upward motion could be caused by the lifting of the large scale dynamic forcing and there was no obvious releasing of latent heating in the upper-middle troposphere. The cold dome in the COLs was quite different both from the warm core in tropical cyclone and from the weaker warm core in Meiyu (Baiu) front low. The calculation of vorticity budget shows that both the horizontal advection term and horizontal divergence term contributed importantly to the maintenance and the strengthening of positive relative vorticity. Finally, the complex dynamical characteristics regarding the COLs are discussed and further investigation is proposed.     

Initialization and simulation of a landfalling typhoon using a variational bogus mapped data assimilation (BMDA)

Summary Recently, a new data assimilation method called “3-dimensional variational data assimilation of mapped observation (3DVM)” has been developed by the authors. We have shown that the new method is very efficient and inexpensive compared with its counterpart 4-dimensional variational data assimilation (4DVar). The new method has been implemented into the Penn State/NCAR mesoscale model MM5V1 (MM5_3DVM). In this study, we apply the new method to the bogus data assimilation (BDA) available in the original MM5 with the 4DVar. By the new approach, a specified sea-level pressure (SLP) field (bogus data) is incorporated into MM5 through the 3DVM (for convenient, we call it variational bogus mapped data assimilation – BMDA) instead of the original 4DVar data assimilation. To demonstrate the effectiveness of the new 3DVM method, initialization and simulation of a landfalling typhoon – typhoon Dan (1999) over the western North Pacific with the new method are compared with that with its counterpart 4DVar in MM5. Results show that the initial structure and the simulated intensity and track are improved more significantly using 3DVM than 4DVar. Sensitivity experiments also show that the simulated typhoon track and intensity are more sensitive to the size of the assimilation window in the 4DVar than that in the 3DVM. Meanwhile, 3DVM takes much less computing cost than its counterpart 4DVar for a given time window.     

Roles of Mesoscale Terrain and Latent Heat Release in Typhoon Precipitation： A Numerical Case Study

The mesoscale orographic effects on typhoon Aere＇s precipitation are simulated using an Advanced Regional Eta-coordinate Model （AREM） version 3.0. In particular, the effects of the latent heat release are studied by two comparable experiments： with and without condensational heating. The results show that the typhoon rainfall is tripled by the southeastern China mesoscale terrain, and the condensational heating is responsible for at least half of the increase. One role of the latent heat release is to warm the atmosphere, leading to a depression of the surface pressure, which then causes a larger pressure difference in the zonal direction. This pressure gradient guides the water vapour to flow into the foothills, which in turn amplifies the water vapour flux divergence amplified, causing the typhoon rainfall to increase eventually. The other role of the latent heat release is to make the convection more organized, resulting in a relatively smaller rain area and stronger precipitation.