应用于强对流天气预报的模式探空产品

仿照实测探空,根据数值模式站点预报的气象要素设计了包含十种常用稳定度指数的斜T-InP模式探空图。在综合评估的基础上,设计了一种模式探空的订正和产品的形成方法,并制作产品显示系统,它可以方便地提供地面站点模式探空和交互式模式探空的图形产品。模式探空产品的统计评估和具体强对流天气的个例分析中表明,模式探空产品对强对流天气预报有帮助。     

对流参数化方案的改进对GRAPES模式台风预报的影响研究

将由NCEP改进之后的SAS(Simplified Arakawa-Shubert Scheme)对流参数化方案（NSAS方案）应用到GRAPES模式中,并对“启德”台风进行模拟,通过和原来SAS方案的预报结果进行比较,发现新方案对台风路径预报有显著改进。通过对NSAS方案中几个新增加的因素进行敏感性试验,发现其中对由于对流引发的扰动气压场如何影响动量输送这个问题的处理使得台风路径预报效果变差,采用动量的水平混合代替风场切变来对扰动气压场进行参数化以后,可有效改进该方案的预报效果。考虑动量的水平混合系数随高度变化可进一步改善预报结果。通过比较多个台风的预报结果发现,这种改进对台风路径预报的改进较稳定      

THE INFLUENCE OF CLOUD PARAMETERIZATION ADJUSTMENT USING REFLECTIVITY OF DOPPLER ON NOWCASTING WITH GRAPES MODEL

In this study, we attempted to improve the nowcasting of GRAPES model by adjusting the model initial field through modifying the cloud water, rain water and vapor as well as revising vapor-following rain water. The results show that the model nowcasting is improved when only the cloud water and rain water are adjusted or all of the cloud water, rain water and vapor are adjusted in the initial field. The forecasting of the former （latter） approach during 0-3 （0-6） hours is significantly improved. Furthermore, for the forecast for 0-3 hours, the latter approach is better than the former. Compared with the forecasting results for which the vapor of the model initial field is adjusted by the background vapor with those by the revised vapor, the nowcasting of the revised vapor is much better than that of background vapor. Analysis of the reasons indicated that when the vapor is adjusted in the model initial field, especially when the saturated vapor is considered, the forecasting of the vapor field is significantly affected. The changed vapor field influences the circulation, which in turn improves the model forecasting of radar reflectivity and rainfall.     

多种蒸散发公式在珠江流域的适用性分析

利用珠江流域42个观测站点的逐日气象数据对比分析了FAO56 Penman-Monteith(PM)、Priestley-Taylor、Hargreaves-Samani和Thornthwaite等4种蒸散发公式在珠江流域的适用性,并研究了在资料有限情况下PM公式的计算精度。PM公式由于详细考虑了空气动力与能量供给对蒸散发的影响,其在不同季节和地区的计算结果都较为稳定,并且与实际的观测接近,最适用于珠江流域的蒸散发计算。在蒸散发的计算中,日照时数的缺测对PM公式计算精度的影响最大,风速次之。通过设定修正系数后的PMT公式,计算精度得到了明显提高,在一定程度上可以满足对蒸散发计算的精度要求。因此,在其他资料缺失的情况下,只利用气温数据计算的PMT公式可成为一种理想的蒸散发计算公式。     

伶仃河口湾铜鼓水域水沙净输运分析

根据对珠江伶仃河口湾铜鼓水域丰水期９个测站大、中、小潮三次同步水文泥沙资料及５７个底质样品的分析结果,本文讨论了此水域的水沙净输运趋势。结果表明,铜鼓水域表层余流向海,浅滩测站中底层余流指向河口方向,欧拉余流主要由径流构成。沟槽悬沙输运以净平流作用为主,浅滩区则以向上游的潮抽吸输运为主。沉积物净输运趋势显示铜鼓浅滩是海陆双向底质输运的汇聚地带     

华南暖区降水数值预报的初值同化试验

为了了解初值场对华南短时临近降水预报的影响,文中利用GRAPES区域中尺度模式,针对华南一次暖区暴雨过程分别进行控制试验、同化地面探空资料、nudging雨水资料和同化雷达径向风等四个模拟试验。分析结果表明：(1) 同化地面探空资料有助于改善24小时的降水落区及其量级;(2) nudging雨水资料对临近降水预报有积极影响;(3) 同化雷达径向风能使24小时的降水落区、量级得到明显的提升。这些结论为下一步的华南地区短时临近降水预报研究提供了重要的技术参考。     

THE APPLICATION OF ASSIMILATED AIRCRAFT DATA IN SIMULATING A HEAVY RAIN OVER SOUTH CHINA IN JUNE 2005

Regular and irregular observational data are used to analyze and simulate a torrential rain over the south of China on 18 – 24 June 2005. Since the regular data cannot depict the rainfall system fully, GRAPES model is used to simulate this process. Different data are assimilated for 12 hours by its simulating system and different analysis data are obtained. In order to analyze how well the model forecast has been improved with the addition of assimilated aircraft data, these different analysis data are used as the first-guess data to conduct two control numerical simulation tests. From these tests, it is proved that the model that adds aircraft assimilation data can simulate the main region of precipitation, which is more consistent with the observed precipitation than the model that does not, and that the accuracy rate is also improved. These numerical simulation tests not only show that it is necessary and capable to improve the modeling of this torrential rain process by using aircraft data, but also lays the foundation for forecasting heavy rains in the south of China based on aircraft data.     

地形对登陆热带气旋"黄蜂"(2002)强度影响的模拟研究

以"目标登陆台风外场试验研究"(CLATEX)项目的目标热带气旋"黄蜂"为对象,在用高分辨数值模式模拟其近海加强和登陆减弱过程的基础上,通过5组对比数值试验,从定量和时间演化角度细致地分析了热带气旋周边海陆和地形分布对热带气旋强度的影响及其机理.分析表明,华南西部地理因子(地形、粗糙度、海陆分布等)对热带气旋强度变化具有重要影响.华南西部地形的存在,有利于低层弱冷空气向南侵袭,从而激发对流发展,使气旋迅速加强,是"黄蜂"近海加强的关键原因;登陆后冷空气切入造成的稳定层结抑制了对流发展,阻断了对流潜热能源,是"黄蜂"登陆后迅速减弱的重要原因;华南西部真实地形下的地表摩擦效应是"黄蜂"登陆后迅速减弱的重要原因之一;南海热带气旋区的地表热交换以潜热输送(蒸发)为主,其量值一般是感热输送的5～10倍;洋面热交换与气旋强度间存在正反馈关系,符合热带气旋发展的"WISHE"(风引起的表面热交换)机制观点,即"WISHE"可能是南海热带气旋发展的一种重要机制.     

加密探空资料在华南暴雨数值预报的应用试验

应用逐时同化预报系统CHAF进行加密探空资料同化试验,比较了同化加密探空资料与仅同化常规探空资料所得同化分析场和模式预报结果的差异.同化加密探空资料所得分析场水汽的均方根误差减小,水汽条件和大气环流形势与实况更接近.以加密同化探空资料所得分析场为模式初始场进行预报,雨区的分布和降水量级都较控制试验有改善.分析模式预报改...