卫星估计降水量产品的优化处理及分区检验

经检验发现,由国家卫星气象中心反演并投入业务使用的GMS-5卫星红外估计降水量产品性能在我国存在一定的区域差异。利用实测雨量对卫星估计降水量产品进行优化处理,结果显示优化后的卫星估计降水量在全国各气候分区都有不同程度的改善。     

A model for retrieval of dual linear polarization radar fields from model simulation outputs

An algorithm for retrieving polarimetric variables from numerical model fields is developed. By using this technique, radar reflectivity at horizontal polarization~ differential reflectivity, specific differential phase shift and correlation coefficients between the horizontal and vertical polarization signals at zero lag can be derived from rain, snow and hail contents of numerical model outputs. Effects of environmental temperature and the melting process on polarimetric variables are considered in the algorithm. The algorithm is applied to the Advanced Regional Prediction System （ARPS） model simulation results for a hail storm. The spatial distributions of the derived parameters are reasonable when compared with observational knowledge. This work provides a forward model for assimilation of dual linear polarization radar data into a mesoscale model.     

宁夏春季首场透雨的气候预测探索

利用目前在统计预报中广泛应用的最优子集回归预报法,作宁夏南部山区及银川地区春季首场透雨出现日期的统计预报,给出了具体的预报方程和拟合效果分析。并对近30 a来宁夏南部山区及银川地区首场透雨出现日期的变化特征进行了较详细的分析。研究结果表明:银川地区3月份出现首场透雨的气候概率为23.3%、4月份为20%、5月份为23.3%、6月份为33.3%,出现机会相对较多。30 a来春季首场透雨出现日期:20世纪70年代相对较晚,80年代偏早,90年代介于70、80年代之间。南部山区春季首场透雨出现时间相对比较集中,其中4月份出现的气候概率为53%,其次是5月份和3月份,分别为20%和17%,最小的是6月份,只占10%,从近30 a来的总趋势看,南部山区春季首场透雨出现日期在波动中略有推迟现象。利用最优子集回归预报法对宁夏春季首场透雨出现日期的预测具有理想的拟合效果。     

应用KDD技术分析气象地质灾害与降水的关系

应用人工智能技术——数据库中知识发现(KDD)技术,分析研究发生在云南省境内造成重大损失的气象地质灾害的发生与当日及前期降水的关系。结果表明,绝大多数气象地质灾害都是由强降水诱发的,云南气象地质灾害与发生当日及前期降水的关系主要有3种类型,即暴雨诱发型、多日中大雨诱发型和连阴雨诱发型。所得到的云南气象地质灾害与当日及前期降水的定量关系,为云南地质灾害的气象监测、预报模式的建立提供了依据。     

建立天空场景的模拟算法

建立真实感的天空场景,在环境仿真和气象现象模拟中,有着极其重要的应用价值,也是计算机可视化研究中的难题。首先通过确定色彩层次模型,改进基于中点的变位方法生成基本云图,然后使用基于图像的方法进行云图映射,最后融合气象信息要素等过程生成天空背景,并采用光照叠加、背景合成及色彩调整等方法,产生千姿百态、形象逼真的天空场景图。可在多种气象现象的模拟仿真,纹理贴图的产生以及气象信息可视化系统的开发等方面发挥重要的作用。     

Decreasing Reference Evapotranspiration in a Warming Climate—A Case of Changjiang (Yangtze) River Catchment During 1970–2000

This study deals with temporal trends in the Penman-Monteith reference evapotranspiration estimated from standard meteorological observations, observed pan evaporation, and four related meteorological variables during 1970–2000 in the Yangtze River catchment. Relative contributions of the four meteorological variables to changes in the reference evapotranspiration are quantified. The results show that both the reference evapotranspiration and the pan evaporation have significant decreasing trends in the upper, the middle as well as in the whole Changjiang (Yangtze) River catchment at the 5% significance level, while the air temperature shows a significant increasing trend. The decreasing trend detected in the reference evapotranspiration can be attributed to the significant decreasing trends in the net radiation and the wind speed.     

基于数值预报产品的温度释用方法比较

为了选取适当的预报方法,运用于业务预报工作中的客观要素预报,我们以ECMWF数值预报输出产品为基础,对卡尔曼滤波(Klm)、最优子集回归(OSR)和岭回归(RR)三种方法针对温江、宜宾、内江、达县2005年6～7月的温度预报进行了探讨.结果表明:在样本完全相同的情况下,三种预报方法效果相当,但从运行速度来看,RR最快,Klm 其次,OSR 最慢;在预报方法相同而样本长度不同的情况下,样本长度为60天的预报效果较好.     

数值预报产品在一次强天气过程中的应用

通过实况场分析表明:能量的积累和位势不稳定层结的建立是产生本次过程的基础,低空急流为本次过程提供了有利的动力条件,而水汽条件的突变、上升是产生本次过程的根本原因.将上述结论和具有预报时效的数值预报释用产品进行对比分析,结果表明,在连续几日数值预报比较稳定的情况下,形势场、要素场、变量场可信度高,可以作为预报的重要依据.数值预报要素场的突变是产生转折性天气的先兆条件之一.     

Single-Column Model Intercomparison for a Stably Stratified Atmospheric Boundary Layer

The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, having a significant impact on medium-range weather forecasts and climate integrations. To pursue this further, a moderately stratified Arctic case is simulated by nineteen single-column turbulence schemes. Statistics from a large-eddy simulation intercomparison made for the same case by eleven different models are used as a guiding reference. The single-column parameterizations include research and operational schemes from major forecast and climate research centres. Results from first-order schemes, a large number of turbulence kinetic energy closures, and other models were used. There is a large spread in the results; in general, the operational schemes mix over a deeper layer than the research schemes, and the turbulence kinetic energy and other higher-order closures give results closer to the statistics obtained from the large-eddy simulations. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored.