IMPROVEMENT OF A GLOBAL SPECTRAL MODEL BY INTRODUCING THE SECONDLAW OF THERMODYNAMICS

The second law of thermodynamics has never been taken into account in the traditional hydrodynamics and numer-ical weather prediction models,which is a serious oversight in the history of mechanics.Introducing the thermodynamicirreversibility into the hydrodynamic systems,the theory and method proposed in this study would not only lead theoutputs of a numerical weather prediction model to noticeable improvement,but lead the structure of hydrodynamics todeepgoing transformation.     

水文气象学及其应用

对水文气象学的主要研究方向、现状及其应用成果作了详细的介绍。其中包括气候与水、降水径流和实时流预报、水库水位调整与防洪、大气环流模式中水文过程参数化等目前国内外所十分关切的水文气象问题。同时，还介绍了水文气象学的一些应用效果。通过具体实例指出，水文气象学是一门交叉科学，是新理论的生长点、也是目前水文界气象界专家学者十分感兴趣的学科，两个学科有互相联合与互补的内在需要。     

推进数值天气预报的一个新努力

本文通过引进熵产生的正定项的办法把热力学第二定律渗透到数值天气预报模式的试验之中.试验结果令人鼓舞.     

中尺度气象模式研究若干进展及其在区域业务预报中的应用

介绍了美国、英国和日本３个国家的中尺度模式研究和业务预报现状,指出了中尺度模式特有的问题和发展趋势,及其对我国中尺度模式研制的含义。     

2008年1月中国南方低温雨雪冰冻天气特征及其天气动力学成因的初步分析

在欧亚大陆中高纬度长期维持阻塞形势的背景下,2008年1月11日至2月2日中国南方连续经历了4 次低温雨雪冰冻天气过程(简称"0801南方雪灾").这次强天气事件过程范围广、强度大、持续时间长且灾害极为严重.其天气学特征表现为中高纬阻塞形势稳定少变,低纬系统活跃确保水汽输送,以及南方部分地区满足冰雪风暴形成的有利天气条件等.研究表明,导致大气环流异常从而促使这次低温雨雪冰冻强天气事件出现的主要因素包括:(1)北极涛动(AO)的异常活跃,有利于行星尺度波动的稳定维持;(2)阻塞上游50°N区域有极强的负涡度平流持续输送到阻塞区,使濒临崩溃的阻塞形势得以重新加强,从而使阻塞形势长时间稳定维持;(3)青藏高原以南低纬地区南支气流活跃,确保中国南方充沛的水汽来源;以及(4)长期存在有利于冰雪风暴生成发展的天气-动力-物理学条件等."0801南方雪灾"事件一个突出的特征就是冰冻现象极为严重.文中借助新型卫星CloudSat的星载云廓线雷达(CPR)资料对这次事件中典型云系进行天气-动力-物理学分析,揭示出西南暖湿气流沿锋面爬升,形成界限分明上下交替的两个冷暖气团,冷气团较浅薄;在2-4 km高度存在一个融化层,冰水不仅存在融化层之上,在近地面层亦含有丰富的冰粒子.结合常规观测资料分析发现,在此期间中国南方大部地区中层(大约在850-700 hPa)存在温度大约在0-4 ℃的逆温层,地面气温大致维持在-4-0 ℃且相对湿度在90%以上,分析表明,此次大范围冰冻灾害天气是由于冻结、凝华和冰雾粒子的附着增长等物理过程共同作用的结果."0801南方雪灾"事件持续时间较长,事件本身作为一个整体其成因可追溯到行星尺度系统.研究极涡异常及其随时间变化的结果表明,平流层极涡变化比对流层的超前,尤其是该事件前期平流层极涡进入12月后就趋于加强,而对流层的极涡加强则明显滞后,并且直到1月中至2月初才快速加强;这意味着平流层蕴含着对流层极涡变化及伴随的强天气事件的先期信号,这可能是中长期预报的一个值得深入研究的方向.     

ENTROPY FLOW CHARACTERISTICS ANALYSIS OF TYPHOON MATSA (0509)

The evolution of Typhoon Matsa (0509) is examined in terms of entropy flow through an entropy balance equation derived from the Gibbs relation, according to the second law of thermodynamics. The entropy flows in the various significant stages of (genesis, development and decaying) during its evolution are diagnosed based on the outputs of the PSU/NCAR mesoscale model (known as MM5). The results show that: (1) the vertical spatial distribution of entropy flow for Matsa is characterized by a predominantly negative entropy flow in a large portion of the troposphere and a positive flow in the upper levels; (2) the fields of entropy flows at the middle troposphere (500 hPa) show that the growth of the typhoon is greatly dependent on the negative entropy flows from its surroundings; and (3) the simulated centres of heavy rainfall associated with the typhoon match well with the zones of large negative entropy flows, suggesting that they may be a significant indicator for severe weather events.     

突发性强灾害天气预警系统的研制

“突发性强灾害天气预警系统”项目旨在为气象部门提供一套预测功能先进且响应迅速,同时具有业务化应用前景的突发性强灾害天气预警系统“叆飔雯”(EWSSWE:Early Warning System for Severe Weather Event)原型。本预警系统的先进性主要体现在:①按利用数字工程理念确定的工作主线展开研制;②采用实     

物理耗散技术及其在MM4中的应用

在传统的流体动力学框架下,数值天气预报问题往往被提为经典牛顿力学的确定论初值问题　。然而大气是多体系统,利用仅对三体以下的系统才能精确描述的理论来处理多体系统的运　动,会引起较大的误差和问题。为此,文中提出了一套在数值天气预报模式中引入“不可逆　热力学算子”的技术,按热力学第二定律的约束方式,来控制多体系统的演变方向,以提高　数值天气预报的精度。例如在ＭＭ４模式中引入不可逆热力学算子后,温度场、湿度场、高度　场及全风速场的平均相对均方根误差减小了约１３％,其中４８　ｈ预报的误差减小两成以上。鉴于文中提出的不可逆热力学算子引入技术是基于描述耗散性的物理定律,而非纯粹出于计算　上的考虑,故名为物理耗散技术。由于它所依据的物理原理对所有流体力学和大气数值模式　均适用,因此该项新技术在地球物理流体力学界将有广阔的应用前景。     

PHYSICAL DISSIPATIVE TECHNIQUE AND ITS APPLICATION TO THE MM4

Under the traditional framework of fluid dynamics,the problem of the numerical weatherprediction is often expressed as the deterministic initial value problem of the classical Newtonianmechanics.The atmosphere is.however,a many-body system,the methodology by which thesystem with two bodies could be precisely solved would cause bigger errors and problems whenhandling the many-body system by it.A kind of technique to incorporate “the irreversiblethermodynamic operators” into the numerical weather prediction models is.therefore,suggestingin this paper,to control the evolutionary direction of the many-body system according to theconstraining way of the second law of thermodynamics,and thus the forecasting accuracy of thenumerical weather prediction has been noticeably improved.For example,in the MM4 theaveraged relative root mean square error of the fields of the temperature,humidity,height andwhole wind velocity has decreased by about 13%,among which the averaged error of the 48 hforecasts has decreased by more than 20%.Since the technique to introduce the irreversablethermodynamic operator suggested in this paper is based on the physical law that describes thedissipativity and does not come from the computational consideration only.it is thus named as thephysical dissipative technique.In view of the universality of the principle incorporating theirreversible thermodynamics operators suggested in this paper for the fluid dynamics andatmospheric numerical models,the applications and generalization of this incorporating techniquewould produce a great impact on the field of geophysical fluid dynamics.     

计及地形效应后中小尺度天气预报的一个改进

在一个二维板对称非静力平衡数值云模式中引入地形效应后明显改进了原模式的预报结果,揭示了地形对中尺度天气系统生成发展的重要作用.