AN INTEGRATION METHOD WITH FITTING CUBIC SPLINE FUNCTIONS TO A NUMERICAL MODEL OF 2ND-ORDER SPACE-TIME DIFFERENTIAL REMAINDER——FOR AN IDEAL GLOBAL SIMULATION CASE WITH PRIMITIVE ATMOSPHERIC EQUATIONS

In this paper,the forecasting equations of a 2nd-order space-time differential remainder are deduced from the Navier-Stokes primitive equations and Eulerian operator by Taylor-series expansion.Here we introduce a cubic spline numerical model(Spline Model for short),which is with a quasi-Lagrangian time-split integration scheme of fitting cubic spline/bicubic surface to all physical variable fields in the atmospheric equations on spherical discrete latitude-longitude mesh.A new algorithm of"fitting cubic spline—time step integration—fitting cubic spline—……"is developed to determine their first-and2nd-order derivatives and their upstream points for time discrete integral to the governing equations in Spline Model.And the cubic spline function and its mathematical polarities are also discussed to understand the Spline Model’s mathematical foundation of numerical analysis.It is pointed out that the Spline Model has mathematical laws of"convergence"of the cubic spline functions contracting to the original functions as well as its 1st-order and 2nd-order derivatives.The"optimality"of the 2nd-order derivative of the cubic spline functions is optimal approximation to that of the original functions.In addition,a Hermite bicubic patch is equivalent to operate on a grid for a 2nd-order derivative variable field.Besides,the slopes and curvatures of a central difference are identified respectively,with a smoothing coefficient of 1/3,three-point smoothing of that of a cubic spline.Then the slopes and curvatures of a central difference are calculated from the smoothing coefficient 1/3 and three-point smoothing of that of a cubic spline,respectively.Furthermore,a global simulation case of adiabatic,non-frictional and"incompressible"model atmosphere is shown with the quasi-Lagrangian time integration by using a global Spline Model,whose initial condition comes from the NCEP reanalysis data,along with quasi-uniform latitude-longitude grids and the so-called"shallow atmosphere"Navier-Stokes primitive equations in the spherical coordinates.The Spline Model,which adopted the Navier-Stokes primitive equations and quasi-Lagrangian time-split integration scheme,provides an initial ideal case of global atmospheric circulation.In addition,considering the essentially non-linear atmospheric motions,the Spline Model could judge reasonably well simple points of any smoothed variable field according to its fitting spline curvatures that must conform to its physical interpretation.     

Classification of Northeast China Cold Vortex Activity Paths in Early Summer Based on K-means Clustering and Their Climate Impact

The classification of the Northeast China Cold Vortex(NCCV)activity paths is an important way to analyze its characteristics in detail.Based on the daily precipitation data of the northeastern China(NEC)region,and the atmospheric circulation field and temperature field data of ERA-Interim for every six hours,the NCCV processes during the early summer(June)seasons from 1979 to 2018 were objectively identified.Then,the NCCV processes were classified using a machine learning method(k-means)according to the characteristic parameters of the activity path information.The rationality of the classification results was verified from two aspects,as follows:(1)the atmospheric circulation configuration of the NCCV on various paths;and(2)its influences on the climate conditions in the NEC.The obtained results showed that the activity paths of the NCCV could be divided into four types according to such characteristics as the generation origin,movement direction,and movement velocity of the NCCV.These included the generation-eastward movement type in the east of the Mongolia Plateau(eastward movement type or type A);generation-southeast longdistance movement type in the upstream of the Lena River(southeast long-distance movement type or type B);generationeastward less-movement type near Lake Baikal(eastward less-movement type or type C);and the generation-southward less-movement type in eastern Siberia(southward less-movement type or type D).There were obvious differences observed in the atmospheric circulation configuration and the climate impact of the NCCV on the four above-mentioned types of paths,which indicated that the classification results were reasonable.     

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction

In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.     

Phase Two of the Integrative Monsoon Frontal Rainfall Experiment (IMFRE-II) over the Middle and Lower Reaches of the Yangtze River in 2020

Phase Two of the Integrative Monsoon Frontal Rainfall Experiment(IMFRE-II)was conducted over the middle and lower reaches of the Yangtze River during the period 16 June to 19 July 2020.This paper provides a brief overview of the IMFRE-II field campaign,including the multiple ground-based remote sensors,aircraft probes,and their corresponding measurements during the 2020 mei-yu period,as well as how to use these numerous datasets to answer scientific questions.The highlights of IMFRE-II are:(1)to the best of our knowledge,IMFRE-II is the first field campaign in China to use ground-based,airborne,and spaceborne platforms to conduct comprehensive observations over the middle and lower reaches of the Yangtze River;and(2)seven aircraft flights were successfully carried out,and the spectra of ice particles,cloud droplets,and raindrops at different altitudes were obtained.These in-situ measurements will provide a“cloud truth”to validate the ground-based and satellite-retrieved cloud and precipitation properties and quantitatively estimate their retrieval uncertainties.They are also crucial for the development of a warm(and/or cold)rain conceptual model in order to better understand the cloud-to-rain conversion and accretion processes in mei-yu precipitation events.Through an integrative analysis of ground-based,aircraft,and satellite observations and model simulations,we can significantly improve our cloud and precipitation retrieval algorithms,investigate the microphysical properties of cloud and precipitation,understand in-depth the formation and dissipation mechanisms of mei-yu frontal systems,and improve cloud microphysics parameterization schemes and model simulations.     

CHARACTERISTICS OF TROPICAL CYCLONES IMPACTING A NUCLEAR POWER PLANT IN SOUTHERN FUJIAN AND ESTIMATE OF MINIMUM CENTRAL PRESSURE

Based on tropical cyclone (TC) data for the period 1949 to 2008 and following the Gumbe-I method, Pearson-Ⅲ method and determinacy method, this article estimates the possible minimum central pressure of TCs affecting southern Fujian where a nuclear power will be located. Results show that the observed minimum central pressure of TCs agrees well with the results determined with the methods above and there is little difference between them (the minimum central pressure is 867.4 hPa and 868.1 hPa, respectively, in a 1,000-yr return period). Established with the theory of atmospheric dynamics, the determinacy method yields a result of 867.28 hPa/1000 years, only a little smaller than the result of the probability method. Because of randomicity in parameter adjustment with the Pearson-Ⅲ method whereas the determinacy method is theoretically solid and its estimates are the smallest of the three methods, it is therefore reasonable, for security and conservative concerns, to adopt the result determined with the determinacy method as the possible maximum intensity of TC (with the central pressure being 867.28 hPa in a 1,000-yr return period).     

A Comparison of Two Bulk Microphysics Parameterizations for the Study of Aerosol Impacts on an Idealized Supercell

Idealized supercell storms are simulated with two aerosol-aware bulk microphysics schemes(BMSs),the Thompson and the Chen-Liu-Reisner(CLR),using the Weather Research and Forecast(WRF)model.The objective of this study is to investigate the parameterizations of aerosol effects on cloud and precipitation characteristics and assess the necessity of introducing aerosols into a weather prediction model at fine grid resolution.The results show that aerosols play a decisive role in the composition of clouds in terms of the mixing ratios and number concentrations of liquid and ice hydrometeors in an intense supercell storm.The storm consists of a large amount of cloud water and snow in the polluted environment,but a large amount of rainwater and graupel instead in the clean environment.The total precipitation and rain intensity are suppressed in the CLR scheme more than in the Thompson scheme in the first three hours of storm simulations.The critical processes explaining the differences are the auto-conversion rate in the warm-rain process at the beginning of storm intensification and the low-level cooling induced by large ice hydrometeors.The cloud condensation nuclei(CCN)activation and auto-conversion processes of the two schemes exhibit considerable differences,indicating the inherent uncertainty of the parameterized aerosol effects among different BMSs.Beyond the aerosol effects,the fall speed characteristics of graupel in the two schemes play an important role in the storm dynamics and precipitation via low-level cooling.The rapid intensification of storms simulated with the Thompson scheme is attributed to the production of hail-like graupel.     

THE IMPACTS OF MADDEN-JULIAN OSCILLATION ON SPRING RAINFALL IN EAST CHINA

Phase composite analyses are conducted to investigate the possible effect of the Madden–Julian oscillation(MJO)on the spring rainfall anomalies in East China by using the Real-time Multivariate MJO(RMM)index from Australian Meteorological Bureau.The results show that the rainfall anomalies over the mid-and lower-valley of Yangtze River are positive when the MJO shifts eastward to the mid-and eastern-Indian Ocean,and anomalous precipitation over South China are positive when the MJO moves further eastward to the maritime continent,whereas spring rainfall anomalies over East China are negative in the other MJO episodes.The MJO impacts on the precipitation over East China result from the changes in large-scale atmospheric circulation as well as vorticity and water vapor transportation in the mid-and lower-troposphere.     

Hydro-climatic Characteristics of Yarlung Zangbo River Basin since the Last Glacial Maximum

Global climate changes significantly impact the water condition of big rivers in glacierized high mountains. However,there is a lack of studies on hydrological changes within river basins caused by climate changes over a geological timescale due to the impossibility of direct observations. In this study, we examine the hydro-climatic variation of the Yarlung Zangbo River Basin in the Tibet Plateau since the Last Glacial Maximum(LGM) by combining δ18 O proxy records in Indian and Omani caves with the simulated Indian summer monsoon, surface temperature, precipitation, evapotranspiration and runoff via the Community Climate System Model and the reconstructed glacier coverage via the Parallel Ice Sheet Model. The mean river runoff was kept at a low level of 145 billion cubic meters per year until an abrupt increase at a rate of 8.7 million cubic meters per year in the B?lling-Aller?d interval(BA). The annual runoff reached a maximum of 250 billion cubic meters in the early Holocene and then reduced to the current value of 180 billion cubic meters at a rate of 6.4 million cubic meters per year. The low runoff in the LGM and Heinrich Stadial 1(HS1) is likely attributed to such a small contribution of precipitation to runoff and the large glacier cover. The percentage of precipitation to runoff was only 20%during the LGM and HS1. Comparison of glacier area among different periods indicates that the fastest deglaciation occurred during the late HS1, when nearly 60% of glacier area disappeared in the middle reach, 50% in the upper reach,and 30% in the lower reach. The rapid deglaciation and increasing runoff between the late HS1 and BA may have accelerated widespread ice-dam breaches and led to extreme outburst flood events. Combining local geological proxy records and regional simulations could be a useful approach for the study of paleo-hydrologic variations in big river basins.     

Verification of Subseasonal-to-Seasonal Forecasts for Major Stratospheric Sudden Warmings in Northern Winter from 1998/99 to 2012/13

This study reports verification results of hindcast data of four systems in the subseasonal-to-seasonal(S2S)prediction project for major stratospheric sudden warmings(MSSWs)in northern winter from 1998/99 to 2012/13.This report deals with average features across all MSSWs,and possible differences between two MSSW types(vortex displacement and split types).Results for the average features show that stratospheric forecast verifications,when further averaged among the four systems,are judged to be successful for lead times around 10 d or shorter.All systems are skillful for lead times around 5 d,whereas the results vary among the systems for longer lead times.A comparison between the MSSW types overall suggests larger forecast errors or lower skill for MSSWs of the vortex split type,although the differences do not have strong statistical significance for almost all cases.This limitation is likely to at least partly reflect the small sample size of the MSSWs available.     

南京三千公尺高空之风向与天气之预测

晚近日本籐原笑平(Fujiwhora)博士于地球物理杂志发表「根据三千公尺高空等压线,以预测天气之一例证」一文,谓日本最近用三千公尺高空之等压线,作每日天气之预测,已得相当成就。氏之经验法则谓自九月以迄五月,日本太平洋沿岸,三千公尺高空之等压线,来自西南者,可形去致雨,而来自西北者,则可期晴明。此种倾向颇为显著。     

陕西冬季一次大雾天气生消机制的数值模拟

利用非静力平衡中尺度模式WRF、NCEP 1°×1°再分析资料及常规观测资料,对2005年12月30～31日发生在陕西的大雾天气过程进行了数值模拟,分析了大雾天气过程形成的主要原因及雾的生消机制。结果表明,WRF模式能较好地模拟出雾的水平分布特征、强度和生消过程,反映出实际雾的生消变化规律。适当提高模式水平分辨率能较明显地改进模拟效果。这次大雾为平流辐射雾,长波辐射冷却是大雾形成和发展的主要原因。逆温层的发展、维持和近地面层较高的相对湿度对雾的产生和发展起着重要作用。近地面层有弱的水汽辐合是大雾发展和维持的主要原因之一。大雾形成和发展阶段,900 hPa以下的辐合上升运动和900 hPa以上的辐散下沉运动有利于在上升和下沉运动区的界面层中形成逆温层,逆温层的形成有利于低层水汽的积累。随着高空转为辐合上升运动,900 hPa以下为辐散下沉运动,接着日出后,太阳短波辐射增温等的共同作用,使逆温减弱直至被破坏。中高云的存在影响了近地面层逆温的形成和加强,推迟了雾的形成和消散。暖平流的输入有利于逆温层的形成发展。     

Elements of theory of avalanche-like motion of a mudflow with hyperconcentration of debris

A criterion ratio is proposed which allows to estimate the possibility of origination of avalanche-like motion of a mudflow with hyperconcentration of debris in a certain mudflow-bearing watercourse.     

Dynamic model of accumulation of total biomass of agricultural crops

Issues concerning the growth and biological time of agricultural crops are under consideration. A closed system of equations is derived for calculating total dry biomass and biological time of plants. The model parameters are given, and the model is verified based on the experimental data of observations of the sunflower in the southern conditions of the Ukraine.     

T106数值预报产品在赣南温度预报中的释用

利用1995年7～9月、1996年7～8月24～144h、1000～500hPa的T106格点资料与赣南17个县（市）的最高、最低、平均温度作相关分析;用逐步回归方法建立了分县逐日滚动预报方程。并用1996年9月份T106格点资料对方法进行检验,同时对预报方法及T106产品在温度预报中的释用能力作了初步分析。     

Estimation of the error of lidar determination of the transparency of low-turbidity atmosphere

Considered is the method of determination of atmospheric turbidity using weak lidar signals when the problem is mathematically incorrect due to the presence of the background noise. An accuracy of the method can be increased by means of using the procedure of effective averaging and linear approximation of the transmission in the case of the low attenuation coefficient.     

2005年夏季中国东部气候异常分析--中国科学院大气物理研究所短期气候预测检验

简要比较了中国科学院大气物理研究所对2005年夏季中国降水跨季度预测与实况的异同,并对2005年夏季我国主要雨带及降水偏少区的形成与东亚热带、副热带以及中高纬度大气环流系统的配置进行了分析。对2005年夏季西太平洋副高的异常活动预测不好,这是造成跨季度降水预测有失误之处的主要原因之一。2005年夏季在亚洲对流层中高层,沿着副热带急流轴准静止Rossby波有几次能量传播过程,西太平洋副高的北抬与西伸与副热带急流中Rossby波的活动强度有一定的对应关系,因而产生了亚洲不同地区高影响性的灾害性天气。     

测量NO气体吸收截面的方法

差分吸收光谱技术(DOAS)已经被广泛用于各种污染气体浓度的测量,其中影响其测量精度的主要因素就是气体吸收截面的测量.利用Lambert Beer 吸收定律以及自主设计的测量装置对大气的主要污染气体NO的吸收截面进行了测量,并采用多项式拟合的方法提高了测量的精度,根据所测得的吸收截面反演了NO气体的浓度值,取得了良好的效果.     

An analysis of the causes of meandering tracks of typhoons

Criteria of the free meandering tracks of typhoons are derived from the general solutions of typhoon motion equations. It is suggested that the meandering motion of a typhoon is caused by the combination of the internal force, the initial speed of the typhoon and the average pressure gradient force of the typhoon volume affected by the environmental pressure field. It is also revealed that under specified circumstances, the meandering may be caused only by the typhoon’s internal force. Finally two examples of fitting calculation are given for illustration.     

小麦腥黑穗病气象条件分析及防治措施

本文主要通过对晋城市2005年、2006年及历年平均气象要素与农业气象观测资料对比,分析气象条件对小麦腥黑穗病农业病害的影响程度,从而提出治理对策。     

RG13型雨量传感器测量结果的不确定度评定

国内民航机场主要使用的雨量观测设备为芬兰维萨拉公司生产的RG13型雨量传感器,为保证雨量测量数据的真实可靠,对其测量结果的不确定度分析很有必要。根据自动气象站现场校准方法,分别进行大雨强和小雨强的重复测试,并依据JJF1059.1-2012测量不确定度的评定与表示要求,进行A类不确定度评定。分析测量过程中的B类不确定度来源,进行B类评定,最终给出扩展不确定度。结果表明：在小雨强下,测量不确定度为U95=0.17mm,包含因子k=2。在大雨强下,测量不确定度为U95=0.16mm,包含因子k=2。该研究完善了雨量传感器的现场校准工作流程,对雨量传感器测量结果的可信度评定具有参考价值。