THE EFFECTS OF BOGUS TYPHOON AND OBSERVED OCEANIC DATA ON THE ABILITY OF T_(213)L_(31) TO PREDICT TC TRACK

The abilities of typhoon (TC) track prediction by a medium-range forecast model T213L31 at National Meteorological Center are analyzed and its ability to improve its TC forecasts is discussed. The results show that about 57% of the TCs could be predicted by T213L31 but the initial position errors are large.The 43% area without the prediction of TC tracks is concentrated between 13°N and 20°N and east of 120°E and lack of conventional observation data is the main reason for the absence of TC prediction in this area.The adding of bogus TC could improve the ability of TC track prediction when there is no TC vortex in the analysis field, but could only have positive effects on the short-range TC track prediction when there is TC vortex in the T213L31 analysis field.     

C波段多普勒天气雷达地物识别方法

地物回波对雷达数据应用会造成负面影响,是影响定量降水估测等产品精度的重要因素,识别并剔除地物回波是雷达基数据质量控制的一个重要内容。该文在现有S波段雷达地物识别方法的基础上,使用长治、哈尔滨两部CINRAD/CC雷达2011年观测数据,对C波段雷达地物回波特征进行分析,改进识别参量的隶属函数,建立适合C波段多普勒天气雷达的地物识别方法 (MCC方法),并对该方法进行效果检验。结果表明:S波段及C波段雷达地物回波与回波强度有关的参量分布较为相近,与降水回波的参量分布有明显区别;S波段雷达地物识别方法中与回波强度有关的参量可用于C波段雷达地物的识别,与速度有关的参量中仅中值速度可用于C波段雷达。通过统计分析与个例分析,相对于现有S波段雷达识别方法,MCC方法可显著提高C波段雷达地物回波的识别正确率,并可减少层状云降水回波的误判。     

FY2海面温度产品质量检验方法与误差分析

主要介绍了风云二号静止气象卫星海面温度产品的质量检验方法及检验流程,给出了FY2E业务海面温度产品和FY2F海面温度算法的质量检验结果,并从误差统计、反演算法、系统设计等方面分析了目前FY2海面温度产品与国外卫星海面温度产品差异大的原因。现场海面温度质量检验和分析场海面温度交叉检验各有优缺点。现场海面温度质量检验能够对FY2 SST产品给于客观的评价。国外分析场海面温度具有时效性好、全球覆盖且质量均一的优点,分析场海面温度交叉检验能满足FY2 SST质量检验的时效性,是对FY2 SST的相对检验。通过静止卫星海面温度产品质量检验信息可以为产品研发人员和相关用户提供参考。     

气温日较差研究进展:变化趋势及其影响因素

从日较差的变化趋势、影响因素以及人类活动对气候变化影响的指示3个方面对日较差的研究进行了总结和概括。观测数据以及气候模式模拟的结果表明,全球气温日较差在近半个多世纪以来呈下降趋势,而这种下降趋势不仅仅是自然变化的结果,还受到人类活动的影响。辐射、云量、气溶胶、下垫面的变化、水汽、降水以及航迹云等因素都能对日较差的变化造成影响。日较差的"周末效应"以及城市化过程中日较差的变化相对于平均气温的变化,能够更有效地指示人类活动对气候变化的影响。     

强对流天气雷达回波与闪电特征的个例分析

利用闪电定位资料和多普勒天气雷达强度产品,分析了2006年6月22日发生在南京西南140km处的一次强对流天气过程中闪电的演变特征及其与回波强度的关系。结果表明,地闪多发生于雷暴云中回波强度大于40dBz且回波强度梯度较大的区域;正、负地闪频次在强对流系统发展的不同阶段呈现出不同的特点,负地闪占总闪数的90％以上,正地闪出现在系统进入成熟阶段之后,且占总闪的比例在系统消散阶段明显增大;地闪强度越大,相应的地闪频次越小,除少数弱闪（1/1〈10kA）外,二者基本上呈反相位关系。     

“2007.7.6”飞机颠簸事件数值模拟与成因分析

利用WRF模式模拟了2007年7月6日发生在菲律宾南部海域上空的一次民航飞机颠簸事件.结果表明,综合分析WRF模式计算得到的Ri和EI等预报指数,能够确定飞机颠簸发生的区域、高度和强度.飞机遭遇颠簸的区域是位于涡旋云系外围的螺旋云带的上空,飞机在飞越由重力波形成的螺旋云带时,在强烈的垂直上升和下沉气流的转换区域产生了急速的上抛和下降运动.     

下击暴流实例分析

通过实地灾情调查,本文提供了一个证据较为充分、说服力较强的下击暴流实例,加深了人们对下击暴流的感性认识。实践证明,在观测密度(时间和空间上)远不能满足中小尺度分析要求、探测手段受到很大限制的情况下,用实地灾情调查和地面拍照的办法进行下击暴流这类中小尺度系统的分析是可行的。     

Numerical Physical Mechanism and Model of Turbulent Cascades in a Barotropic Atmosphere

In a barotropic atmosphere, new Reynolds mean momentum equauons including turbulent viscosit,dispersion, and instability are used not only to derive the KdV-Burgers-Kuramoto equation but also to analyze the physical mechanism of the cascades of energy and enstrophy. It shows that it is the effects of dispersion and instability that result in the inverse cascade. Then based on the conservation laws of the energy and enstrophy, a cascade model is put forward and the processes of the cascades are described.     

Parameterization of the Absorption of the H_2O Continuum,CO_2,O_2,and Other Trace Gases in the Fu-Liou Solar Radiation Program

The absorption properties of the water vapor continuum and a number of weak bands for H2O, O2, CO2, CO, N2O, CH4, and O3 in the solar spectrum are incorporated into the Fu-Liou radiation parameterization program by using the correlated k-distribution method (CKD) for the sorting of absorption lines. The overlap absorption of the H2O lines and the H2O continuum (2500-14500 cm-1) are treated by taking the two gases as a single-mixture gas in transmittance calculations. Furthermore, in order to optimize the computation efforts, CO2 and CH4 in the spectral region 2850-5250 cm-1 are taken as a new single-mixture gas as well. For overlap involving other absorption lines in the Fu-Liou spectral bands, the authors adopt the multiplication rule for transmittance computations under which the absorption spectra for two gases are assumed to be uncorrelated. Compared to the line-by-line (LBL) computation, it is shown that the errors in fluxes introduced by these two approaches within the context of the CKD method are small and less than 0.48% for the H2O line and continuum in the 2500-14500 cm-1 solar spectral region, -1% for H2O (line) H2O (continuum) CO2 CH4 in the spectral region 2850-5250 cm-1, and -1.5% for H2O (line) H2O (continuum) O2 in the 7700-14500 cm-1 spectral region. Analysis also demonstrates that the multiplication rule over a spectral interval as wide as 6800 cm-1 can produce acceptable errors with a maximum percentage value of about 2% in reference to the LBL calculation. Addition of the preceding gases increases the absorption of solar radiation under all sky conditions. For clear sky, the increase in instantaneous solar absorption is about 9%-13% (~12 W m~2) among which the H2O continuum produces the largest increase, while the contributions from O2 and CO2 rank second and third, respectively. In cloudy sky, the addition of absorption amounts to about 6-9 W m-2. The new, improved program with the incorporation of the preceding gases produces a smaller solar absorption in clouds due to the reduced solar flux reaching the cloud top.     

Raindrop Size Distribution Parameters Retrieved from Xinfeng C-Band Polarimetric Radar Observations

The objective of this research was to acquire a raindrop size distribution (DSDs) retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope (μ-Λ) relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer (2DVD) at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity Z_(HH)and differential reflectivity Z_(DR)were obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the Z_(DR)-Λand log_(10)(Z_(HH)/N_0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations Z_(DR)and Z_(HH),the raindrop Gamma size distribution parametersμ,Λ,and N_0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity (R),mass-weighted mean diameter (D_m) and intercept parameter (N_w) with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.