TOVS资料的变分处理方法在青藏高原地区的数值试验

首次在测站稀少的高原地区引入经变分技术处理的TOVS资料,使用MM5数值模式对高原地区降水数值预报难点进行了研究。探讨了解决高原地区测站少、数值预报模式初始场信息误差大的技术关键问题,提出了采用TOVS资料在高原地区增加初始场信息的构思。数值试验结果表明,应用变分法处理后的TOVS资料,可显著地提高高原初始场信息的可靠性。考虑夏季高原地区是对流多发区特点,本文采用非静力MM5模式,并在模式初始场中增加了TOVS资料,弥补了测站稀少的高原地区使用非静力模式的不足之处。研究结果表明,本文采用的TOVS资料技术方案可能是高原区域数值模式降水预报的有效途径,并为开拓卫星资料的应用领域提供了技术思路与理论分析依据。     

晴空时大气红外遥感及其反演问题研究 II. 反演试验研究

前文给出了卫星红外观测资料的反演处理方法，并对方法作了理论上的分析，在本文中，我们将此方法应用到TOVS、GOES-8实际资料及AIRS模拟观测资料处理中并重点对TOVS资料进行试验。在反演中，我们将大气温度廓线和水汽混合比（lnq）廓线用各自的经验正交函数（EOF）表示以提高反演的稳定性并缩短计算时间，同时采用一种过滤操作以加速迭代的收敛速度。除了用本文提出的方法对TOVS资料进行处理外，还用国际TOVS处理软件包（ITPP-4.0）对同样的资料进行反演。试验表明，本文方法的反演结果优于ITPP的结果。AIRS模拟反演结果表明，高分辨率红外垂直探测器的遥感精度能够达到温度1 K、水汽10%。     

TOVS卫星反演资料变分分析的试验研究与应用

为弥补海洋、高原等地带常规资料的不足,分析使用非常规卫星资料得到越来越多的重视,其中TOVS资料的精度及与常规资料的误差减少的研究尤为重要。本文采用变分分析技术对TOVS卫星反演资料进行同化分析研究,结果表明,变分结果分析场能充分体现常规与非常规资料的优势,使得天气系统能得到更精确的表示。     

夏季青藏高原地区降水和低涡的数值预报试验

本文首先分析了１９７９年６—７月的ＦＧＧＥIIIｂ级资料风场和相对湿度场在青藏高原地区的偏差，指出在高原西部应予以订正。然后利用一有限区域模式，通过综合订正初始风场和相对湿度场，改进模式部分物理过程，并提高其水平分辨率，共设计了６组预报试验，对该年的两例高原低涡切变线降水过程进行了２４小时预报。结果表明，利用改进了的初始场和部分物理过程，可明显改善高原地区的降水预报，并在一定程度上改善了流场的预报，即上述改进方案是可行的；但在高原地区嵌套预报方案尚待修改，还应继续努力提高模式对高原低涡流场的预报能力。     

青藏高原地区FGGEⅢb资料相对湿度场的分析与订正及其对预报影响的数值试验

本文用Ｃｒｅｓｍａｎ逐步订正法和青藏高原气象科学实验资料对高原地区１９７９年６—８月中６０个时次的ＦＧＧＥⅢｂ级资料相对湿度场进行了订正和分析，然后利用一有限区域数值模式，选择两例高原低涡过程，用订正前后的ＦＧＧＥⅢｂ相对湿度资料分别作初始湿度场进行了７２ｈ和４８ｈ预报试验。结果表明：高原地区相对湿度的高值区位于其东南部，然后向西北逐渐递减，低值区位于高原西部。ＦＧＧＥⅢｂ相对湿度场能较好地反映高原东部的分布，但在高原西部比实际明显偏大。订正高原上的初始湿度场（ＦＧＧＥⅢｂ相对湿度场）能明显改进高原地区的降水和形势预报，对环流的影响可达到高原东侧并波及高原的南北侧地区，显示了加密高原西部资料的重要性。     

一种利用气象要素场时变信息确定其空间分布状态的方法及数值模拟研究

本文将藉观测资料所包含的时间演变信息来建立要素场空间结构的问题提成一个反问题，并利用共轭方程和最优控制技术把模式初值作为控制变量来求解这个反问题；希望对由于空间测站不足而得不到合理初始场的问题以及由于用共轭方程而引起大的计算量的问题获得解决的方法。文中利用了一个边界层动力模式及其共轭方程模式进行了数值试验，结果表明：在对计算做出简化处理及较合理的测站分布下，方法能够从大大少于模式自由度的观测资料中得出比较合理的要素场初值的空间结构。     

云参数对RTTOV5模式模拟误差的影响分析

该文根据1998年8月的业务TOVS反演的温度、水汽垂直廓线资料以及其它资料, 利用RTTOV5模式模拟NOAA14极轨气象卫星上相应红外探测 (HIRS) 通道的辐射亮温值, 将模拟值对比实测TOVS探测资料, 结果表明, 晴空模式模拟亮温与实测值的误差小于部分有云时的误差, 模拟误差受云的影响呈反相变化, 对水汽敏感的中低层探测通道在晴空时的误差小于部分有云情况; 通过对比白天和夜间短波窗区探测通道模拟误差, 分析了其受地面反射太阳光辐射的影响的大小及其原因所在; 并利用RTTOV5的伴随模式和Jacobine模式分析了模式模拟误差对初始场云参数的敏感性。该研究为TOVS/ATOVS探测资料在3DR或4DR变分同化中的直接应用奠定了基础。     

一种新的TOVS大气湿度反演方法及试验

利用国家气象中心的数值天气预报（NWP）6 h预报场。作为同步物理反演模式初估场，由气象卫星垂直探测（TOVS）资料推导出大气湿度，并给出了试验结果。结果表明，TOVS湿度反演的相对误差（RMS）约为20%。其中，夏季反演结果略优于冬季，而且低层（1000 hPa）和高层（500 hPa以上）与初估场相比有较大的改进，中层（850，700 hPa）二者大致相当。与统计回归反演结果相比其精度约提高10%。该研究为在我国建立“卫星反演/数据同化/数值预报”相互影响的循环系统奠定了基础     

模式气候吸引子信息约束下的动力协调初始化方法及其在ENSO预测中的应用

为了改善模式初始场质量,减少初值与模式不协调对ENSO预测的影响,针对国家气候中心NCCo海-气耦合模式原初始化方案动力小协调的问题,从利用模式长期耦合模拟资料中的模式气候吸引子信息的角度出发,发展了一种获取观测资料中与模式相协调分量的信息重构方法,提出了一种模式气候吸引子信息约束下的动力协调初始化方案.对该方案回报检验的结果表明:通过反演NCCo海-气耦合模式模拟资料中的模式气候吸引子信息,有助于获取观测资料中与模式相协调的信息分量特征,实现了初始化过程中动力模式与所同化观测资料间的协调.这种基于信息重构方法的动力协调初始化方案,既可以延续原初始化方案利用观测信息较多的优势,又克服了原方案中观测资料和动力模式不协调的缺陷.这种新的初始化方案,消除了观测资料和模式不协调在初始场中产生的小尺度高频噪声,突出了与NCCo模式动力特征相适应的ENSO尺度信息.进而抑制了初始场中高频噪声所引起的快变预报误差的增长,提高了模式的预测技巧.     

四维变分方法反演低层风场能力研究

从新一代天气雷达径向速度资料中反演出可靠的三维风场对提高新一代天气雷达的应用水平有重要的作用，将雷达直接观测的径向速度转换成台站预报员更为熟悉的风场结构，对识别中小尺度信息有很大帮助。为此该文对4DVAR同化技术在风场业务反演中应用的可能性进行了探讨，利用广州、济南新一代多普勒天气雷达观测资料，从是否加入云模式湿过程以及迭代次数、计算时间、背景场、初始场、分辨率和反演区域等方面对干模式的4DVAR系统进行了讨论，并从风场结构、均方根差别等方面对反演结果进行分析。多种试验表明，干模式的4DVAR系统与湿的云模式反演结果差异不大。模式的初始场和背景场对反演结果具有较高的敏感性，利用前一时次的反演结果作为背景场迭代15～20次的干模式结果可以很好地在业务上试运行，对台站预报员提高中小尺度天气预报的准确率有着很重要的作用。     

APPLICATION OF THE VARIATIONAL METHOD OF TOVS DATA OVER THE TIBETAN PLATEAU IN IMPROVEMENT OF THE INITIAL FIELD OF NUMERICAL MODELS

In this paper,TOVS satellite data are used through variational method on the data-sparseplateau area.Diagnoses are carried out to find a way to solve the large error problem of modelinitial field.It is put forward that TOVS retrieval data can be used to improve the initial field ofnumerical prediction model on Tibetan Plateau area.Through variational method,TOVS data areprocessed and the liability of the initial information on the plateau is improved.Diagnostic resultsconfirm further that the application of TOVS retrieval data can improve our capability to describethe dynamic system features on the plateau and the objectivity of related initial information such asthe distribution of water vapor channel and stratification stability.     

APPLICATION OF THE VARIATIONAL METHOD OF TOVS DATA OVER THE TIBETAN PLATEAU IN IMPROVEMENT OF THE INITIAL FIELD OF NUMERICAL MODELS*

In this paper,TOVS satellite data are used through variational method on the data-sparse plateau area.Diagnoses are carried out to find a way to solve the large error problem of model initial field.It is put forward that TOVS retrieval data can be used to improve the initial field of numerical prediction model on Tibetan Plateau area.Through variational method,TOVS data are processed and the liability of the initial information on the plateau is improved.Diagnostic results confirm further that the application of TOVS retrieval data can improve our capability to describe the dynamic system features on the plateau and the objectivity of related initial information such as the distribution of water vapor channel and stratification stability.     

用青藏高原考察订正FGGE Ⅲ b资料作中期预报的数值试验

利用1979年5—8月青藏高原科学实验取得的资料，对1979年6月15日00 GMT 100—850 hPa等9层FGGE Ⅲ b分析的高度和风场进行了客观分析订正，并以订正前后的资料为初值，用T21L5和T42L9两种不同分辨率的北半球谱模式作了5个5天预报的数值试验。研究结果表明，通过高原实验资料对FGGE Ⅲ b资料的订正，将使FGGE Ⅲ b资料在高原地区的分析得到改善。对流层上层的资料订正比下层效果明显。高原地区初值场的订正对数值预报结果有显著影响，并且对较高分辨率模式的预报结果影响更大。初值订正后不仅影响未来高原地区的预报，而且通过能量频散可以影响到我国东部和日本，大约经过5天左右，甚至可以影响到阿拉斯加和北美。     

A REVIEW OF THE ANALYSIS OF MOISTURE VARIABLES AND THE APPLICATION IN NUMERICAL MODELS

The application of the explicit microphysical process in the high-resolution mesoscale numerical models makes it necessary to analyze the moisture variables such as the cloud water, cloud ice and rain water to initialize the explicit predicted fields. While the inclusion of moisture variables in initial fields can influence the whole performance of the model significantly, it can also reduce the spin-up time and increase the short-term forecasting ability of the model since the dynamical fields become more accordant with the thermodynamic fields. Now the increase of the observing ability and the abundance of the data promote the development of ways to analyze the moisture variables. A review of some methods to analyze the moisture variables is presented, and the situation and problems of the application in the numerical models are also discussed in this paper.     

1998年夏季青藏高原上东移MCS环境场特征的聚类分析

在对夏季青藏高原上中尺度对流系统(MCS)进行自动追踪的基础上,利用环境物理量场数值格点预报资料(HLAFS),运用空间聚类中的CLARANS法对东移出高原的MCS环境场进行了挖掘和分析,获得了在青藏高原地区大气低层MCS热力场(温度场、湿度场和水汽通量散度场)和动力场(涡度场、散度场和垂直速度场)的空间分布特征,从而揭示了有利于MCS形成、发展和东移出高原的动力和热力学条件。MCS环境场中的散度场、垂直速度场以及水汽通量散度场空间分布特征的变化是MCS发展、演变的重要影响因素,这为夏季青藏高原上MCS发生、发展的动力及热力学机制的研究,以及高原上MCS移动路径的预测提供了一种全新而有效的方法。     

The effects of the Qinghai-Xizang Plateau on the mean summer circulation over east Asia

Four numerical experiments of simulation have been conducted in this paper by the use of a five-layer primitive equation numerical model with incorporated pressure-sigma vertical coordinate system. The initial fields are taken from the July zonal mean data of many years, while the heat sources and sinks are ideally specified according to the mean heating field over the East Asia calculated from the real data of July, 1979. On the basis of simulated results of temperature and geopotential height patterns we emphatically discuss the effects of the topography and the heating of the Qinghai-Xizang Plateau. From the analyses in this paper, it appears that the heating over the Bengal region makes a larger contribution to the middle and the south branches of the monsoon cell and is also the main cause for the existence of the southerly channel to the east of the Plateau, for the break of the subtropical anticyclone belt below the 500 hPa level and for the formation of the summer Asian anticyclone at the 300 hPa level, while the heating over the Plateau makes a larger contribution to the Plateau monsoon cell and to the anticyclone at the 100 hPa.     

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC

There is a close relationship between variation of middle latitude synoptic system over theTibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discussthe mechanism of it through the numerical simulation and dynamic diagnosis.25-year statistical results during the period from 1970 to 1995 indicate that the relationshipbetween middle latitude circulation over the Plateau and the track of typhoon over the NorthwestPacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it isfavourable to typhoon's westward movement:on the contrary,large scale anticyclone over thePlateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flowpatterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon southto high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bringabout the longwave trough developing along the east coast of Asia,it'will usually cause typhoonrecurring in front of the developed trough.In addition,the results of dynamic diagnosis show the physical mechanism on impact ofsynoptic system over the Plateau on the downstream synoptic system,that is,the transport ofdisturbance kinetic energy over the upstream Plateau makes the downstream trough developed.And then it affects the steering flow of typhoon.Because of existence of the high ridge over thePlateau.the energy transport channel moves to north.On the contrary,the trough exists over thePlateau,the energy transport channel moves to south.The southerly in front of trough over thePlateau and the southerly in the east part of typhoon transport low potential vorticity of lowlatitude into subtropical high.That is beneficial to development of subtropical high and affectstyphoon's movement.These results fully reflect the impact of interaction between mid-latitude andlow latitude on synoptic system.     

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC*

There is a close relationship between variation of middle latitude synoptic system over the Tibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discuss the mechanism of it through the numerical simulation and dynamic diagnosis.25-year statistical results during the period from 1970 to 1995 indicate that the relationship between middle latitude circulation over the Plateau and the track of typhoon over the Northwest Pacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it is favourable to typhoon's westward movement:on the contrary,large scale anticyclone over the Plateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flow patterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on 500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon south to high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bring about the longwave trough developing along the east coast of Asia,it'will usually cause typhoon recurring in front of the developed trough.In addition,the results of dynamic diagnosis show the physical mechanism on impact of synoptic system over the Plateau on the downstream synoptic system,that is,the transport of disturbance kinetic energy over the upstream Plateau makes the downstream trough developed.And then it affects the steering flow of typhoon.Because of existence of the high ridge over the Plateau.the energy transport channel moves to north.On the contrary,the trough exists over the Plateau,the energy transport channel moves to south.The southerly in front of trough over the Plateau and the southerly in the east part of typhoon transport low potential vorticity of low latitude into subtropical high.That is beneficial to development of subtropical high and affects typhoon's movement.These results fully reflect the impact of interaction between mid-latitude and low latitude on synoptic system.