初始扰动对一次华南暴雨预报的影响的研究

本文选取了2006年华南前汛期的一次暴雨过程, 采用AREMv2.3中尺度数值模式进行数值模拟, 分别在模式初始场的物理量场 (温度场、 风场、 湿度场) 上加扰动, 分析不同物理量场上的扰动对降水预报的影响, 以及物理量预报误差和扰动能量的增长情况。同时, 通过本个例讨论误差增长与湿对流的关系, 扰动振幅对误差增长的影响和华南区域的中尺度降水的可预报性问题。数值试验结果表明: 初始时刻不同物理量场加实际振幅的正态分布的随机扰动时, 对降水的影响是不同的。对于24小时降水预报, 温度场对降水的影响最大。误差的增长与湿对流不稳定有着密切的关系。小尺度小振幅误差增长很快, 而且是非线性增长。这意味着短期的较小尺度降水的可预报性很小。与大振幅扰动相比, 小振幅扰动造成的误差较小。但是小振幅扰动的迅速发展, 很快就会对降水预报造成较大的影响。因此, 只能有限地提高预报质量, 而且由于扰动非线性增长很快, 在预报时间的提前上, 不会有太大的改善。     

2008年河南黄淮地区暴雨过程个例分析

利用常规气象资料和NCEP资料对2008年7月22日河南黄淮地区的暴雨过程进行了分析.结果表明:这次过程是在500 hPa槽前西南气流引导下,高低空急流耦合区内西南涡沿切变线移出,弱冷空气侵入暖倒槽触发不稳定能量释放造成的.垂直螺旋度计算结果显示:中低层正垂直螺旋度中心与降水落区有很好的对应关系,大暴雨中心位于正垂直螺旋度中心附近.湿位涡演变分析发现,这次过程有"干侵入"发生,暴雨区中低层对流不稳定和对称不稳定共存,有利于降水增幅.水汽条件分析表明:这次过程的水汽源地在孟加拉湾和南海,主要是低层和近地层的水汽辐合.     

Analysis of the Microphysical Structure of Heavy Fog Ｕsing a Droplet Spectrometer: A Case Study

The microphysical properties of a long-lasting heavy fog event are examined based on the results from a comprehensive field campaign conducted during the winter of 2006 at Pancheng (32.2°N, 118.7°E), Jiangsu Province, China. It is demonstrated that the key microphysical properties (liquid water content, fog droplet concentration, mean radius and standard deviation) exhibited positive correlations with one another in general, and that the 5-min-average maximum value of fog liquid water content was sometimes ...     

Application of Generalized Moist Potential Vorticity to the Analysis of a Torrential Rain Case

Considering the non-uniform saturation of the real atmosphere,a diagnostic study of a torrential rain event is performed from the perspective of the anomaly of the generalized moist potential vorticity(GMPV) after introducing the generalized potential temperature into the thermodynamic frame of the real atmosphere. The results show that the anomaly appeared at mid-lower levels of the troposphere when the torrential rain happened.Analysis of the magnitudes and locations of maximum values of the tendency o...     

第二类热成风螺旋度对登陆台风降水的诊断能力分析台风泰利个例研究

文中利用中尺度数值模式MM5模拟了台风泰利的登陆过程,模拟的台风路径、天气形势和降水都与观测基本一致,能够很好地反映出真实的天气过程.再利用数值模拟结果,研究了第二类热成风螺旋度(H_2)对登陆台风泰利降水的诊断能力,结果表明它对深入内陆的台风强降水具有较好的诊断能力,而对刚登陆前后的台风降水诊断能力不如经典螺旋度.特别地,H_2在提前1 h时与泰利降水达到最高相关系数,且在提前1-5 h时,它与降水的相关性比经典螺旋度的高,表现出十分显著的预示降水增幅的能力.进一步分析表明,在刚登陆前后,泰利台风中心850-200 hPa的风场垂直切变较小(约5 m/s),其最强降水出现在路径右侧300 km半径范围以内,与低空的正温度平流、低空辐合、高空辐散等无明显的关系,而低空相对涡度能够很好地反映降水的变化,这是经典螺旋度与降水在这一阶段相关性优于H_2的主要原因.而在深入内陆后,台风泰利本体环流减弱,受北部西风槽的影响逐渐增强,环境风场垂直切变迅速增大,发生强降水的庐山和大别山区处于顺垂直风切变方向左侧.在东北向的垂直风切变情况下,庐山和大别山强降水区上空有向东的高空急流出流,强高空辐散诱发垂直次级环流,从而激发对流,形成强上升运动区,因此H_2的诊断优势在这一阶段表现得最清楚.     

一次暴雪天气过程的螺旋度分析

2009年3月19—20日新疆中天山出现暴雪天气,本文采用NCEP再分析资料计算和分析了这次暴雪天气过程的850～200 hPa范围内的垂直、水平螺旋度和总螺旋度,结果表明:暴雪区上空垂直螺旋度呈上负下正分布,有利于暴雪的发生;暴雪发生在低层水平螺旋度负值中心和整层螺旋度正值中心的东南边缘;总螺旋度强弱的变化反映了暴雪天气系统的趋势。分析表明螺旋度能较好地反映新疆暴雪天气的发展、维持状况及强弱程度,并对暴雪落区的预报有一定的指示意义。     

一次豫北春季强对流暴雨过程的螺旋度分析

利用中尺度有限区域WRF模式输出的细网格资料和多普勒雷达观测资料,根据螺旋度理论,结合稳定度条件以及水汽和能量等物理量,对2009年3月20日夜至21日凌晨发生在豫北的一次强对流及暴雨过程的局地螺旋度演变进行诊断分析。结果表明,这次春季强对流和暴雨与西南急流和高温高湿不稳定能量密切相关,正螺旋度大值中心出现的高度与对流发展的强弱有关;500 hPa螺旋度正值区中心与强对流降水区域对应;暴雨易产生在850 hPa螺旋度中心附近,螺旋度的强度变化对强对流系统的移动、发展及暴雨的发生有一定的指示意义。     

用能量分析方法识别冰雹云

用GMS ＴＢＢ遥感资料和湿-比有效能量方法分析了1998年巴盟地区9次降雹过程，认为：（1）云顶温度及其水平梯度是识别冰雹云的重要参量，云顶温度低于-25℃才可能出现有灾冰雹，预报区云顶温度水平梯度大于50℃/50km才可能出现重雹灾；（2）冰雹云生成前低层是高能舌，而中高层低能中心和负能量平流中心位于其北或西北方；（3）有雹无灾冰雹云生成前低层没有高能舌，在降雹区西北方450km以内也没有中高层低能中心。     

RESEARCH ON MOIST SYMMETRIC INSTABILITY IN A STRONG SNOWFALL IN NORTH CHINA*

The concept of wet bulb potential vorticity and SCAPE(slantwise convective available potential energy) is used to calculate the horizontal and vertical distribution of moist symmetric instability including convective symmetric instability(CSI) and local symmetric instability(LSI) in the process of a storm snowfall in North China.The potential contribution of moist symmetric instability to a narrow storm snowfall belt occurring in the Hetao and Lindong,Linxi region of Inner Mongolia and the relationship between moist symmetric instability and direction of the basic flow,wind shear and moisture are discussed.It is found that the strong snowfall belt is almost parallel with negative value area of wet bulb potential vorticity at low levels in the vicinity of snow area.And the dynamical mechanism of the strong snowfall center in the Lindong,Linxi region is different from that in the Hetao region.The former is induced by frontogenetical forcing with weak symmetric instability in the warm section of frontal area and the latter triggered by obvious moist symmetric instability.     

RESEARCH ON MOIST SYMMETRIC INSTABILITY IN A STRONG SNOWFALL IN NORTH CHINA

The concept of wet bulb potential vorticity and SCAPE (slantwise convective available potentialenergy) is used to calculate the horizontal and vertical distribution of moist symmetric instabilityincluding convective symmetric instability (CSI) and local symmetric instability (LSI) in the processof a storm snowfall in North China.The potential contribution of moist symmetric instability to anarrow storm snowfall belt occurring in the Hetao and Lindong,Linxi region of Inner Mongolia andthe relationship between moist symmetric instability and direction of the basic flow,wind shear andmoisture are discussed.It is found that the strong snowfall belt is almost parallel with negative valuearea of wet bulb potential vorticity at low levels in the vicinity of snow area.And the dynamicalmechanism of the strong snowfall center in the Lindong,Linxi region is different from that in theHetao region.The former is induced by frontogenetical forcing with weak symmetric instability in thewarm section of frontal area and the latter triggered by obvious moist symmetric instability.