短期降水预报的动力学与热力学

提出了当前短时和短期降水预报中需待解决的3个问题。由这些问题引发了如何把动力学与热力学相结合,如何把大量的观测和模式资料应用于短期无间隙预报的思考。最后给出了一个短期大暴雨预报的应用实例。     

短期降水预报的动力学与热力学

提出了当前短时和短期降水预报中需待解决的3个问题。由这些问题引发了如何把动力学与热力学相结合，如何把大量的观测和模式资料应用于短期无间隙预报的思考。最后给出了一个短期大暴雨预报的应用实例。     

Satellite-based Observational Study of the Tibetan Plateau Vortex:Features of Deep Convective Cloud Tops

In this study, an east-moving Tibetan Plateau vortex (TPV) is analyzed by using the ERA-5 reanalysis and multi-source satellite data, including FengYun-2E, Aqua/MODIS and CALIPSO. The objective is to demonstrate: (i) the usefulness of multi-spectral satellite observations in understanding the evolution of a TPV and the associated rainfall, and (ii) the potential significance of cloud-top quantitative information in improving Southwest China weather forecasts. Results in this study show that the heavy rainfall is caused by the coupling of an east-moving TPV and some low-level weather systems [a Plateau shear line and a Southwest Vortex (SWV)], wherein the TPV is a key component. During the TPV's life cycle, the rainfall and vortex intensity maintain a significant positive correlation with the convective cloud-top fraction and height within a 2.5° radius away from its center. Moreover, its growth is found to be quite sensitive to the cloud phases and particle sizes. In the mature stage when the TPV is coupled with an SWV, an increase of small ice crystal particles and appearance of ring- and U/V-shaped cold cloud-top structures can be seen as the signature of a stronger convection and rainfall enhancement within the TPV. A tropopause folding caused by ageostrophic flows at the upper level may be a key factor in the formation of ring-shaped and U/V-shaped cloud-top structures. Based on these results, we believe that the supplementary quantitative information of an east-moving TPV cloud top collected by multi-spectral satellite observations could help to improve Southwest China short-range/nowcasting weather forecasts.     

Short-Range Prediction Experiments with Operational Data Assimilation System for the Kuroshio South of Japan

The short-range (one month) variability of the Kuroshio path was predicted in 84 experiments (90-day predictions) using a model in an operational data assimilation system based on data from 1993 to 1999. The predictions started from an initial condition or members of a set of initial conditions, obtained in a reanalysis experiment. The predictions represent the transition from straight to meander of the Kuroshio path, and the results have been analyzed according to previously proposed mechanisms of the transition with eddy propagation and interaction acting as a trigger of the meander and self-sustained oscillation. The reanalysis shows that the meander evolves due to eddy activity. Simulation (no assimilation) shows no meander state, even with the same atmospheric forcing as the prediction. It is suggested therefore that the initial condition contains information on the meander and the system can represent the evolution. Mean (standard deviation) values of the axis error for all 84 cases are 13, 17, and 20 (10, 10, and 12) km, in 138.5°E, in the 30-, 60-, and 90-day predictions respectively. The observed mean deviation from seasonal variation is 30 km. The predictive limit of the system is thus about 80 days. The time scale of the limit depends on which stage in the transition is adopted as the initial condition. The gradual decrease of the amplitude in a stage from meander to straight paths is also predicted. The predictive limit is about 20 days, which is shorter than the prediction of the opposite transition. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于BGM框架的短期集合预报扰动典型规律研究

采用增长模培育(Breeding of Growing Modes,BGM)法开展有限区域模式短期集合预报研究,亟需解决的问题是集合预报扰动的发展及演变。因此论文结合经典的适时缩放培育思想,利用增长模培育法,基于WRF3.6模式(采用WRF-ARW),开发和构建了一个包含水平风场、垂直速度、位温扰动、位势扰动和水汽混合比共6个基本物理量的区域短期集合预报系统(WRF-EPS)。在此基础上,以2016年6月整月我国南方大范围暴雨为样例,针对扰动发展与演变的典型问题进行了探讨。试验结果表明:1)模式大气高、中、低三层的物理量扰动增长可以分为两个阶段,第一阶段为扰动快速线性增长,该阶段内扰动快速完成全部涨幅;第二阶段为非线性稳定阶段,从快速线性增长过渡到非线性稳定阶段大约需要24 h。2)各物理量的扰动增长率、相关系数以及增长模进入非线性稳定阶段的时间大致相同,但对于同一等压面不同物理量或同一物理量不同等压面,每个参数达到非线性稳定后的数值大小及演变规律存在差异,且随时间演变均伴有日内振荡现象。3)对于扰动振幅相同但初始随机模态不同的初值集合,不同随机模态对扰动培育的影响主要是在扰动的非线性稳定阶段,而在快速的线性增长阶段,它们之间的差异很小。4)对于初始随机模态相同但振幅不同的初值集合,不同扰动振幅对扰动演变的影响主要是在扰动的快速线性增长阶段,而在非线性稳定阶段,它们之间的差异很小,并且不同初始振幅对扰动进入非线性稳定阶段的时间基本没有影响。     

APPLICATION EXPERIMENT OF ASSIMILATING RADAR-RETRIEVED WATER VAPOR IN SHORT-RANGE FORECAST OF RAINFALL IN THE ANNUALLY FIRST RAINY SEASON OVER SOUTH CHINA

A scheme of assimilating radar-retrieved water vapor is adopted to improve the quality of NWP initial field for improvement of the accuracy of short-range precipitation prediction. To reveal the impact of the assimilation of radar-retrieved water vapor on short-term precipitation forecast, three parallel experiments, cold start, hot start and hot start plus the assimilation of radar-retrieved water vapor, are designed to simulate the 31 days of May, 2013 with a fine numerical model for South China. Furthermore, a case of heavy rain that occurred from 8—9 May 2013 over the region from the southwest of Guangdong province to Pearl River Delta is analyzed in detail. Results show that the cold start experiment is not conducive to precipitation 12 hours ahead; the hot start experiment is able to reproduce well the first 6 hours of precipitation, but badly for subsequent prediction; the experiment of assimilating radar-retrieved water vapor is not only able to simulate well the precipitation 6 hours ahead, but also able to correctly predict the evolution of rain bands from 6 to 12 hours in advance.     

决策级融合技术在环渤海地区短期天气预报中的应用

设计一种基于决策级融合的短期天气预报二级决策模型,并以线性回归法、极值剔除法、支持向量机法为初级决策方法,采用常规气象资料对该模型进行了系统实现和效果检验。结果表明,该预报模型的决策级融合结果取得了较高的平均历史拟合率和试报准确率,较初级决策方法平均提升约2%—3%;决策级融合的决策结果将具有更高的可信度,其有利于提升数理统计预报的应用水平,促进信息化气象保障系统的建设。     

雷暴预警预报的研究进展

雷暴作为极端天气事件中的一种,不仅常产生强降水、破坏性大风和冰雹等严重的天气灾害,而且还伴有雷电,造成雷击灾害,给工农业生产和人民生活都可带来严重的损失。因此对雷暴的预警预报研究变得尤为重要,也促使其理论、技术及应用都取得了很大的发展。本文对有关雷暴预警预报技术的一些研究结果和进展如雷暴的潜势预报、雷暴的临近预报、雷电活动的观测信息在雷暴天气预警中的指示作用及雷暴云的数值模拟等方面进行了归纳和综述,总结了各方面研究所涉及的重要问题及主要进展,并对未来发展进行展望。     

甘南高原冰雹短时预报的客观相似预报方法

利用相似预报的原理制作了甘南高原冰雹短时预报工具,该方法的实现是通过建立历史个例资料库,寻找相似个例并根据条件判断是否有冰雹,查看历史天气图并与当天实况进行对比,进行人工判断,增加新的冰雹个例4部分完成的。经检验,该方法在甘南州冰雹短时预报中使用效果较好,是一种有效的短时预报方法。     

短期集合预报中定量降水预报集合方法初探

针对短期集合预报中集合平均等方法对极端天气事件预报能力低下的缺陷，提出一种定量降水预报集合方法，简称两步法。该方法首先采用逐级归并法确定集合成员的总体相似度，进而确定集合成员预报场的延伸半径，对各成员的预报场进行修正，然后根据每个成员与其他成员的相似程度，确定各成员的权重系数。这个方法既考虑了集合成员总体的差异性又考虑了降水的概率分布。试验证明，通过上述两步得到的定量降水预报，对提高极端天气事件的预报确率有一定效果。本方法无需历史资料，能很好适应集合成员的改变，实现方便快捷。