A CASE OF MESOSCALE CONVECTIVE COMPLEX EVOLVING INTO A VORTEX

A case of mesoscale convective complex(MCC)which evolved into a vortex is documented in this paper.As theMCC entered into the dissipating phase,a well-defined spirally banded structure became visible in the satellite image.The blackbody temperature(TBB)of the residual cold-cloud-shield indicates the vortex existed in the layer from 400 to250 hPa.According to the upper air analysis,the upper level vortex was an anticyclone.The MCC-generated vortex wasvisualized in the satellite images because it was located in the subtropical high where the wind field was very weak.     

A SPECTRUM OF LYAPUNOV EXPONENTS OBTAINED FROM A CHAOTIC TIME SERIES

A complete spectrum of Lyapunov exponents (LEs) is obtained from 1970— 1985 daily mean pressuremeasurements at Shanghai by means of a correlation matrix analysis technique and it is found that there exist LEs≥0,and <0. with their sum 0λ_i=K=0.110405 whereuponT=1 /K =9 is obtained as the predictable time scale, a result close to that acquired by the dynamic-statistical approachin early days and also in agreement with that present by the authors themselves(1991).     

A PARAMETRIC METHOD OF SITE ERROR ESTIMATION FOR A LIGHTNING LOCATION SYSTEM

In this paper,a parametric method of site error estimation is developed for a lightning location system (LLS)which consists of three or more direction finders (DFs) and one position analyzer (PA). The site error for eachDF is a function of bearings measured by the DF, and is assumed to be limited-term harmonics. The problemof site error estimation is reduced to a non-linear unconstrained minimization problem by employing the eigentechnique (Orville Jr., 1987). The site error can be found directly by minimizing the objective function. By using the data set obtained with the LLS of three DFs in Beijing area during the summer of 1988, thesite error correction curves for all DFs were found. About 4900 lightning flashes detected by the three DFswere used. The results showed that about 95% of the flash residuals of the sample were within ± 1 degree aftercorrections. The lightning locations with site error corrections were more consistent with the corresponding radarechoes than those without corrections.     

人工审核制作A文件与MDOS自动制作A文件对比分析

通过设计地面气象观测月数据文件对比软件,以江西省91个国家级自动站2016年全年经过省级人工质量控制后制作的地面气象观测数据A文件为参考标准,与气象资料业务系统(简称"MDOS系统")自动制作的同站同期数据A文件进行对比分析,并进一步对数据差异的时空分布、要素分布等进行了分析。结果表明:91个国家级自动气象站全年数据对比差异个数总计为16 490个,占全年数据总量的1.02‰。MDOS A文件中自动观测要素数据差异的主要原因有传感器系统性偏移、仪器安装错误、参数设置错误、疑误数据无法关联修订、异常记录未能有效判断并处理;人工观测要素数据差异的主要原因有数据格式错误、记录顺序错误、观测要素记录不匹配、漏记录等错误在MDOS平台未能有效检测出。最后提出了确保MDOS系统平台参数设置的正确性、完善MDOS系统平台数据处理能力等改进措施。     

A Two-Step Shape-Preserving Advection Scheme

This paper proposes a new two-step non-oscillatory shape-preserving positive definite finite difference advection transport scheme, which merges the advantages of small dispersion error in the simple first-order upstream scheme and small dissipation error in the simple second-order Lax-Wendroff scheme and is completely different from most of present positive definite advection schemes which are based on revising the upstream scheme results. The proposed scheme is much less time consuming than present shape-preserving or non-oscillatory advection transport schemes and produces results which are comparable to the results obtained from the present more complicated schemes. Elementary tests are also presented to examine the behavior of the scheme.     

A20文件编辑程序设计

利用Visual Basual6．0编写了A20文件编辑程序，本文就其设计思路、功能特点、具体实现和操作使用等作了说明。     

A指数与周口降水

Ａ指数与周口降水王素萍田辉（周口地区气象台·４６６００２）Ａ指数是一个综合考虑大气静力稳定度与整层水汽饱和程度的物理量。Ａ值越大,表明大气越不稳定或对流层中下层饱和程度越高,越有利于产生降水。利用天气图资料,根据Ａ指数计算公式Ａ＝（ｔ８５０－ｔ５００...     

自动气象站A文件维护与审核

本文讨论了自动气象站,A文件的维护和审核中出现的问题,分析问题的原因及处理方法.     

A CASE STUDY ON SANDSTORM

The favourable synoptic situation and climate background for a sandstorm process,which occurred in theperiod 9—16 April 1988,have been studied through analyzing weather maps,meteorological elements,satellitecloud pictures and sandstorm trajectories.The sand dust origin area,the directions and the paths of sanddust transport,and the extent the sand dust reached are also investigated.The results of measurments andanalysis indicate that the concentration of sand dust particles is 10 times greater than the normal.It is also shownthat the elements in the sand dust are lithophylic and come from natural source through the chemical composi-tion analysis of the sand dust,so that the sand dust has not been polluted by human activities.     

A NUMERICAL EXPERIMENT WITH THE EFFECT OF A COMPLICATED TERRAIN ON THE MESOSCALE SYSTEMS

Improvement in two aspects is done of the one-level mesoscale numerical model of Mass et al.(1985)and the re-vised model is used to make a simulation of a severe convective weather process in North China,with the result showingthe pronounced effects of the topography upon the mesoscale systems.     

A SIMULATION OF CO_2 UPTAKE IN A THREE DIMENSIONAL OCEAN CARBON CYCLE MODEL

A three-dimensional ocean carbon cycle model which is a general circulation model coupledwith simple biogeochemical processes is used to simulate CO_2 uptake by the ocean.The OGCMused is a modified version of the Geophysical Fluid Dynamics Laboratory modular ocean model(MOM2).The ocean chemistry and a simple ocean biota model are included.Principal variablesare total CO_2,alkalinity and phosphate.The vertical profile of POC flux observed by sedimenttraps is adopted,the rain ratio,a ratio of production rate of calcite against that of POC,and thebio-production efficiency should be 0.06 and 2 per year,separately.The uptake of anthropogenicCO_2 by the ocean is studied.Calculated oceanic uptake of anthropogenic CO_2 during the 1980s is2.05×10~(15)g(Pg)per year.The regional distributions of global oceanic CO_2 are discussed.     

THE IMPACT OF A DIAGNOSTIC CLOUD SCHEME ON FORECASTS WITH A GLOBAL ATMOSPHERE MODEL

Experiments were conducted to test the impact of a cloud diagnosis scheme in place of prescribed zonalaverage cloud on medium and long range integrations with the Australian Bureau of Meteorology ResearchCentre(BMRC)global atmosphere model.The cloud scheme was shown to improve the temperature bias inthe lower troposphere but there was deterioration in the upper troposphere,especially in the tropics,asso-ciated with underestimation of high cloud amount.Thirty day mean fields in a January integration showed greater amplitude in the Northern Hemisphereplanetary waves and a deeper Antarctic circumpolar trough than the control experiment or a simulation withno cloud.The results for the diagnosed cloud case agree more closely with corresponding observed fields.There was also some reduction in the zonal average zonal wind component reflecting the additional zonalasymmetry introduced by the diagnostic cloud scheme.Similar trends were also noted in medium and longrange forecasts for January and July conditions,although the impact on predictive skill was slight and insome cases detrimental.Areas for improving the diagnostic cloud scheme are noted.     

A MAP OF LOCAL PATTERN ANALOGUE COEFFICIENT——A TOOL FOR DISPLAYING CIRCULATION ANOMALY

Limitations of difference maps showing circulation anomalies are analyzed, and the definition of the local patternanalogue coefficient (LPAC) is given together with the procedure for constructing such a map, followed by an exampleillustrating its useful application in circulation anomaly.     

The rose report — A review

Abstract

Estimates of the entrainment rate of salt water into the Fraser River plume have been made using two independent methods. A value of k = 2 × 10 ^‐4 is obtained for he entrainment coefficient relating the vertical to the horizontal velocity from salt conservation arguments at a series of profiles along the plume and from calculations of surface divergence, as measured by drifting drogues. It is also found that entrainment contributes significantly to the deceleration of the river plume after it issues into the Strait of Georgia.     

A Coupled Dynamical-Radiational Model of Stratocumulus

A model dealing with interactions between the air and low stratiform clouds is presented based on the mixed-layer model Lilly (1968) pioneered and on Deardorffs three dimensional numerical model results. Its main new aspects lie in 1) consideration of the natures of both the atmosphere and cloud; 2) a new entrainment velocity scheme with few arbitrary assumptions; 3) transition from one-mixed layer to two-mixed layer model; and 4) parameterization of radiation and precipitation calculations.The model results for radiation, moisture, and heat turbulent fluxes turn out to be in good agreement with those calculated or observed by Kawa (1988), Nicholls (1984), and Schmets et al. (1981) in California, the North Sea, and the North Atlantic, respectively.Basically, this paper furnishes the theoretical basis for a model to address questions concerning the time-evolution of thermodynamical profiles both in cloud and out of cloud. The applications of this model wil be in a separate paper.     

A New Approach to Data Assimilation

A significant attempt to design a timesaving and efficient four-dimensional variational data assimilation (4DVar) has been made in this paper, and a new approach to data assimilation, which is noted as 'three-dimensional variational data assimilation of mapped observation (3DVM)' is proposed, based on the new concept of mapped observation and the new idea of backward 4DVar. Like the available 4DVar, 3DVM produces an optimal initial condition (IC) that is consistent with the prediction model due to the inclusion of model constraints and best fits the observations in the assimilation window through the model solution trajectory. Different from the 4DVar, the IC derived from 3DVM is located at the end of the assimilation window rather than at the beginning conventionally. This change greatly reduces the computing cost for the new approach, which is almost the same as that of the three-dimensional variational data assimilation (3DVar). Especially, such a change is able to improve assimilation accuracy because it does not need the tangential linear and adjoint approximations to calculate the gradient of cost function. Therefore, in numerical test, the new approach produces better IC than 4DVar does for 72-h simulation of TY9914 (Dan), by assimilating the three-dimensional fields of temperature and wind retrieved from the Advanced Microwave Sounding Unit-A (AMSU-A) observations. Meanwhile, it takes only 1/7 of the computing cost that the 4DVar requires for the same initialization with the same retrieved data.     

A Simple Quasi-Geostrophic Coupled Ocean-Atmosphere Model

The quasi-geostrophic atmospheric and oceanic equations of momentum and thermodynamics with dissipation factors are used to create a simple coupled ocean-atmosphere model describing the large-scale shallow-water motion. We discuss the ocean-atmosphere coupling effect in mid-high and low latitudes separately and analyze characteristics of which the oscillatory periods of coupled low-frequency modes (ocean mode) vary with the coupling frequency and latitudinal number. This can interpret the correlation between low-frequency oscillation and ocean-atmosphere interaction. Then from the dispersion curves of atmosphere and ocean, we reveal effect of the coupling strength on the propagation of Rossby waves. The convection mechanism between the two modes is also discussed in view of the slowly varying wave train.The results show that Newtonian cooling and Rayleigh friction play a stable rule in oceanic Rossby waves, the period of coupled low-frequency mode grows with the increment of the coupling frequency. The