To carry out convective nowcasting in areas lacking radar observations, the present study uses the methods of optical flow and semi-Lagrangian extrapolation to conduct satellite cloud image extrapolation experiments. Moreover, the optical flow vector is improved by using non-divergence constraint to avoid divergence and distortion of the cloud image. Case studies show that:（1） The wind field retrieved by using the optical flow method can accurately reflect the typhoon vortex circulation structure. The semi-Lagrangian scheme is employed for extrapolation as it can maintain the rotation characteristics of the cloud system, and has good stability and accuracy; however, as the extrapolation time increases, the noise in the optical flow vector will lead to divergence and distortion of the cloud image.（2）The non-divergence constraint reduces the disorder of the wind vector, makes up for the missing optical flow, and can also smooth the wind speed to make the wind speed spatial gradient smoother.（3） The improved wind field is used for extrapolation to avoid cloud divergence and distortion. The cloud shape will not be damaged, and the false growth of cloud cluster TBB will be reduced.（4） The test shows that the improved extrapolation forecasting scheme has a smaller average absolute error, with MAE increased by 4%, and critical success index increased by 9%.

将C波段雷达资料用LAPS模式的云分析系统进行反演,并采用Nudging技术将反演得到的云微物理场引入GRAPES中尺度数值模式,结合1次强降水天气过程的模拟实验,研究了C波段雷达资料同化对GRAPES中尺度数值模式短临降水预报的影响.结果表明:①雷达资料同化能够改进中尺度模式的降水预报,模式前6h的降水预报相关系数和不同等级降水TS评分都有提高,同时降水峰值提前了1 h,有助于缓解模式spin-up问题.②模式降水预报的改进效果主要由强降水贡献,最大改进效果集中在4～6 h.③同化雷达资料后25 mm以上强降水预报站数比更接近实况,落区偏差幅度更小,降水落区和强度向实况方向得到调整.④10 mm以下弱降水在吸收雷达资料后,站数比相较于控制预报,比实况增加更多,落区偏差幅度增大,存在预报过量的问题.弱降水预报过量主要集中在4～6 h,而前3 h对降水预报的改进有积极作用.

该文利用气象常规观测资料、卫星云图以及NCEP/NCAR(1°×1°)再分析资料,对1822号台风"山竹"给贵州带来的暴雨天气过程中的锋生与湿对称不稳定进行分析.结果发现:①台风"山竹"登陆减弱后,其北部倒槽影响贵州,同时受贵州东低西高的地形影响,倒槽系统出现斜压性,在倒槽附近出现锋生现象,其东侧出现湿对称不稳定的发展,造成贵州暴雨天气.②锋生区的东侧即湿对称不稳定区与中尺度雨带有较好的对应关系.③锋生与湿对称不稳定的发展与增强过程中,伴随着降雨的长时间维持,雨强变化不大,降水率大多为5～10 mm·h-1.当锋生与湿对称不稳定减弱西移后,降雨天气减弱停止.④锋生现象与对称不稳定的形成具有一定的关系,两者均主要是由假相当位温的经向密集区(?θse/?x)发展起来的,对称不稳定区位于锋生区的东侧,即东南暖湿气流中,垂直结构上对称不稳定区位于锋生区的上部,与倾斜的上升运动区相对应.

2021年5月15日贵州东北部发生了一次极端风雹天气过程.本文利用常规观测资料以及加密自动气象站、探空、卫星、多普勒天气雷达等资料,分析了该过程的环境场和雷达回波特征.结果表明:(1)此次极端风雹天气发生在低层暖湿和对流层中下层(500 hPa以下)具有显著条件不稳定的环境下,冷锋前沿的地面辐合线是其触发机制,切变线南侧暖湿气流输送和较强的垂直风切变有利于对流风暴的维持和加强.(2)贵州东北部较大的温度递减率和对流有效位能,强的垂直风切变,较低的自由对流高度是冰雹和雷暴大风发生的有利条件.雷暴系统过境使受其影响的测站风速急增、气压猛升、气温骤降,表现为典型的强雷暴系统过境特征.(3)雷暴系统由初始线状多单体逐渐形成分布不规则的多单体风暴系统.雷暴单体在反射率因子图上呈现出强回波中心超过60 dBz及其南侧高反射率因子梯度和中高层明显回波悬垂特征.造成下击暴流的雷暴单体的弓形回波特征明显,并伴有前侧入流缺口、后侧"V"型缺口及中层4—8 km高度强径向气流辐合(MARC)特征;而造成冰雹的雷暴单体的钩状回波特征十分明显,同时伴有较大垂直积分液态水含量(VIL)、较高回波顶高、强风暴顶辐散以及三体散射现象.

该项目系统性地研究了贵州强冰雹天气.第一,建立了贵州强冰雹个例库;第二,利用统计分析方法对贵州强冰雹的结构特征包括贵州强冰雹的空间和时间分布特征、强冰雹发生前的基于雷达和环境物理量参数的临近判据进行了研究;第三,完成了贵州强冰雹定量化潜势预报模型,将贵州强冰雹根据环流类型分为4种类型;第四,在研究强冰雹的分型中发现了具有贵州特色的静止锋冷区高架雷暴型冰雹,研究得知冷区高架雷暴其垂直结构不同于其他类型的雷暴,在自然基金项目中完成了贵州静止锋冷区高架雷暴产生冰雹的机理研究工作.

为提高贵州暴雨的预报准确率,利用常规探测资料、NCEP1°×1°资料,从中尺度系统及物理量的角度对2012年7月15日夜间到16日贵州西南部一次空报暴雨天气过程进行分析,并与相似环境场的西南部暴雨天气过程进行对比.结果表明:此次过程在有利的环流形势下,且本地的水汽条件较好,但在贵州西南部并没有形成较好的水汽输送和水汽辐合;低层的辐合和上升运动很弱,不利于出现强降水;在降水前,贵州西南部近地层出现了较弱的上升气流,但垂直上升运动弱,动力不够;缺少冷空气的侵入,低层抬升弱,因此贵州西南部仅出现小雨.

该文利用NCEP1 °×1 °再分析资料、常规和非常规观测资料、全球及中尺度数值模式产品对2018年7月4-6日出现的一场持续性暴雨个例展开分析,重点分析了持续性暴雨的天气成因、数值模式产品的检验评估以及相关的订正技术.结果 表明,此次持续性暴雨过程是华南地区维持稳定少动的高压环流影响下,西风带短波槽和北方南下的东西向横切变受高压环流阻挡长时间维持在贵州地区,切变北侧南下的干冷气流和高压环流西北侧北上的暖湿气流交汇形成的持续性暴雨,中低层切变辐合是主要的动力强迫,华南地区高压后侧的西南暖湿气流在降水前夕和降水过程中输送了充沛的水汽和不稳定差动平流,为暴雨的持续发生提供了较好的水汽和能量条件.选取了3家数值模式(EC、华东、华南)进行了检验评估,模式降水产品落区和量级与实况偏差较大,华东模式降水产品在本次过程中有一定参考价值,EC模式7月4日20时-6日20时的风场结构预报准确,预报员充分利用该产品对这一时间段降水落区和量级进行了正技巧订正,但7月6日20时-7日20时对中低层的风场结构预报和实况有较大偏差.充分利用数值模式产品和实况当前时段的检验评估结果,采用外推法对未来时段的数值模式产品进行适当订正,能有效提高暴雨预报的精准度.

By using methods of synoptic and physical quantity diagnosis, elevated thunderstorms which produce hail in the cold sector of stationary front from January to April in past thirty years in Guizhou are analyzed. The results show that elevated thunderstorm is one of the important types of thunderstorms which produce hail in Guizhou in the early spring. Half of the hail cases were caused by elevated thunderstorms. Most of the elevated thunderstorms which produced hail occurred in the Mid-Eastern Guizhou, different from the spatial distribution of hail occurring in Guizhou. Analyzing the 37 typical processes of elevated thunderstorms, we find that the stationary front between Guizhou and Yunnan is the most important weather system. At 200 hPa height the impacting weather system is the strong southwest flow before the tough. At 500 hPa height the impacting weather systems are the southwest flow, west flow and active tough. When the active tough moves to east it causes cold air moving to south area on low level. On low level 700 hPa and 850 hPa, the impacting weather system is the shear. With (due to) the moving of shear the wind changes fast. On the surface the stationary front always swings between the middle of Guizhou and the east of Yunnan, and commonly stays at the area between the two provinces. According to the changes of stationary front the weather situations can be classified into three types: 1) the stationary front is moving to the west, 2) the stationary front is static, and 3) the stationary front is retreating to the north. Comparative analysis of the 3 processes shows that: because of the stationary front, low level atmosphere is stable, but it lifts the uplifted height onto the top of the stationary front, then an inversion layer and CAPE occur and the vertical instability structure appears, presenting a graphic of "dry upper-level and wet lower-level". The analysis of vapor conditions shows that vapor comes from the southern wind above the stationary front. The analysis of vertical wind shear shows that the strong vertical wind shear on the front is beneficial for the elevated thunderstorm. Because of the differences of geographical position and the changes of stationary front, the height of the stationary front inversion layer is different and the height of frontogenesis is different. When the stationary front moves to the west affected by the cold air from north, the frontogenesis function shows that the trigger mechanism is the θse density increase on the top of inversion layer, which is caused by the shear between the north wind and south wind. As the cold air is strong and deep, the layer of shear is higher. When the stationary front is static, the trigger mechanism is same as case one, but the cold air is not strong and deep, so the layer of shear is lower. When the stationary front moves to the north, the south wind is strong. The trigger mechanisms are F2 and F3, and the two factors make the θse increase in the south of Guizhou, which is different from the case one and case two.

该文利用贵州近13 a(2000-2012年)春季的气象资料,依据强对流天气发生的动力条件和层结稳定情况,将贵州春季强冰雹事件进行不同类型的分类研究,给出贵州强冰雹天气发生的有利环流形势类型为:西北气流型、高空槽型、锋前降雹型和高架雷暴型.选取有多普勒雷达资料以来的2009-2013年的强冰雹天气事件个例,采用基数据回放方式研究其降雹前3 ～ 15 min雷达回波形态、结构和类型特征,并通过这些特征来有效识别冰雹云,发现降雹前冰雹落区附近的雷达回波组合反射率因子的强度普遍在40 dBz以上,最强回波为50 ～60 dBz,冰雹云回波以块状回波为主;在垂直剖面上冰雹云回波基本都有明显的回波悬垂,部分个例存在有界弱回波区,其大于40 dBz的回波伸展高度多数都在9～10 km.降雹的回波基本上以孤立的对流云回波单体为主,混合降水类型的冰雹回波对流单体夹杂在层状云中.冰雹落区主要发生在组合反射率因子的最强回波中心,或是有界弱回波区或回波悬垂的回波墙下方.将研究结果在2014年3月30日的一次强冰雹过程中进行试用,利用中尺度环境分析技术,对当日环境场及要素配置进行分析,对应以上环流分型的概念模型方法,确定此次过程属于高空槽型,中尺度环境及雷达分析与上述归纳特征十分吻合,利用此方法在当日冰雹潜势预报及临近预警方面都提前做出了较好的预报预警.

利用高空、地面实况探测、观测资料以及NCEP再分析资料,针对2015年5月7日夜间贵州出现的大范围强对流天气过程的中尺度特征及产生暴雨的水汽输送进行分析,结果表明:这次强对流天气是在有利的大尺度环流背景下生成的多个中尺度对流云团中产生,地面中尺度辐合区加强了对流的发展,冷空气的侵入增强了对流天气的剧烈程度,来自北部湾和阿拉伯海的水汽输送为暴雨天气的产生提供了所需的水汽条件.

利用EC细网格地温预报资料,进行预报准确率检验,检验结果表明,EC细网格地温预报准确率较差.并利用1971-2014年贵州0cm地温资料和气温资料,对贵州冬季地温与气温的关系进行分析,应用统计回归方法建立以气温为基础的地温模型,从而实现通过气温估算地温,并对地气模型进行了检验;结果表明,平均地温预测模型和最低地温预测模型准确率分别达到92％和80％,绝对误差均小于2 C,最高地温预测模型准确率仅有42％,今后需要考虑在不同天气(晴、多云、阴、雨、雪等)条件,分别建立最高地温预测模型.

为研究贵州近10年短时强降水的时空分布特征、物理量场特征及对流云团的生消发展.采用实况地面和高空观测资料、风云气象卫星资料,对贵州近10年短时强降水进行统计分析,结果显示贵州短时强降水呈现出南多北少空间分布特征.对物理量场分析发现,850 hPa平均比湿超过14 g/kg,700 hPa平均比湿超过10 g/kg,比湿量级与贵州出现暴雨天气量级一致,在短时强降水发生前均具有一定的对流有效位能(CAPE),CAPE最小值与最大值差异较大.同时结合天气形势与地理特征研究了2004～2014年贵州出现的128次短时强降水个例的对流云团特征,将短时强降水对流云团分为北部型、南部型、中部型、西部型以及东部型,其中各出现次数分别为15、43、32、17、21,所占比例分别为11.7％、33.6％、25％、13.3％、16.4％,结果表明南部型最多,影响范围较大,影响时间最长;北部型与西部型较少,多在邻近省份发展再影响贵州,范围小、时间短;东部型与中部型强度较弱,消散快.

通过对2011—2012年期间欧洲中心、日本、T639、WRF各家数值预报24 h降水预报产品插值到贵州省85个县观测站,对比每日累计实况降水量,划分为≥0.1 mm(晴雨)、≥10.0 mm(中雨以上)、≥25.0 mm(大雨以上)共3个等级进行了评估。结果发现:欧洲中心细网格和T639在贵州省各个量级降水预报均有偏大的趋势;日本模式在大雨以上量级的降水预报中对我省有偏少的趋势;WRF模式在晴雨预报中表现最好,而在明显降水的预报中表现略差。预报结果空间分布显示:欧洲中心细网格对贵州中部一线地区的明显降水预报较好;T639模式在一般性降水预报中与其他模式效果相当,但在大雨以上量级的预报中表现出明显的地区差异;日本模式在贵州东北部地区效果明显;WRF模式大雨以上量级的预报效果总体差异并不大,主要有3个大值中心,分别位于省的北部边缘、西部边缘和南部边缘,说明在以上地区WRF对大雨以上降水的预报效果具有一定的参考意义。

利用贵州省春季发生的15次冰雹个例和相应的多普勒雷达产品资料,进行雷达产品特征分析,结果表明：①发生冰雹时基本发射率产品图上风暴中心密实,强度梯度大;组合反射率值在春季不同月份存在差异,一般要求在50 dBz以上;②对于速度产品,单方面速度绝对值大小不能判断冰雹的发生,速度对的出现可能预示着风暴单体开始发展并逐渐增强;③回波顶高在不同月份降雹时最低顶高存在很大差异,具体为3、4、5月分别为6 km、8 km、9 km;④VIL值的跃增是降雹的一个好的有利条件,而单从VIL值的大小在贵州地区不能很好地判别冰雹的发生;⑤45 dBz回波冲过0度层是冰雹发生的必要条件,而45 dBz回波冲过-20℃高度时可能会发生大冰雹。

By investigation of the visibility data at 08:00 over Guizhou Province and surface 08:00 weather charts from 1971 to 2008,a total of 382 regional radiation fog processes are selected to analyze the spatial and temporal distribution characteristics of regional radiation fogs in Guizhou.Using the surface and upper air weather charts at 08:00 of 93 radiation fog processes during the 10 years,the corresponding weather circulation conditions are researched.Using the surface and radiosonde meteorological data,the meteorological elements of influencing the formation of radiation fogs are studied.The results show that regional radiation fogs in Guizhou mainly happened in mid-autumn and winter,more frequently in the east than in the west of Guizhou,and there was an evenly distributed pressure field while regional radiation fogs occurred.There are four upper air circulation conditions of regional radiation fog: northwest flow type,southwest flow type,subtropical high type and straightly west flow type.There are four meteorological conditions beneficial to the formation of regional radiation fog: low surface wind speed,high surface humidity,significant radiation cooling at night and temperature inversion at surface layer,and the vertical air with upper-layer dry and lower-layer wet.

利用常规气象观测资料、NCEP资料、卫星资料等,对2010年9月21—22日湘黔北部一次台风倒槽暴雨过程进行天气动力学诊断分析。结果表明:暴雨出现在冷锋和倒槽共同影响区的主要原因是:冷锋前,暴雨区处于暖性不稳定区,台风倒槽带来充沛水汽。冷空气侵入台风倒槽后,使倒槽附近的水汽辐合加大,湿斜压锋区加强,垂直速度增大,冷空气与低层强的暖湿平流相互作用,激发出中尺度暴雨系统,不稳定能量释放,且对流云团的维持少动,造成了降水的持续,并形成暴雨。

利用2004年以来有雷达数据的25个贵州春季冰雹个例资料,基于贵阳、遵义和兴义3部天气雷达基数据,计算雷达回波顶高(ET)、垂直累积液态水含量(VIL)、组合反射率因子(CR)、制作反射率因子垂直剖面(RCS)产品,研究冰雹发生前后雷达回波的演变情况,找出冰雹发生前后以上产品的临界值和变化特征,从而对冰雹云进行雷达识别。经过对个例的分析研究发现:45 dB z以上的雷达回波能较好地识别冰雹云,结合0℃层高度和-20℃层高度,可较好的判断冰雹的大小;冰雹发生前1～2个体扫到冰雹发生时刻,VIL出现陡增现象。

Based on observations and NCEP reanalysis data,the three heavy rain cases caused by inverted trough of typhoon in Guizhou was analyzed.The results show that the inverted trough of typhoon was the only synoptic system which resulted in the first case.The characteristics of the first case were that the thermodynamic unstable conditions continued for a long time,precipitation also continued for a long time and ascending motion,convergence and divergence were weak,and precipitation areas were dispersive.The inverted trough of Typhoon and vortex and shear were the main synoptic system which resulted in the second case.The strong vapor convergence was formed in south-east airflow of the two synoptic systems,ascending motion and convergence development happened at a high layer.So the rainfall areas in the second case were centralized.The cold front invaded into the inverted trough of typhoon resulting in the third case.The encounter of dry and warm air led to the vapor convergence in a small scope,and the ascending motion and convergence strengthened in low layer corresponding to a local and short time heavy rain and convective weather.

Based on routine meterological observations and NCEP reanalysis data,a torrential rain occurred in Guizhou in winter of 2010 was analyzed.The results show that the southern branch trough,quasi-stationary front and shear at the level of 850 hPa resulted in this heavy rain process,and which was nearly the same as that of those heavy rain weather events occurred in the end of autumn in Guizhou.During this weather process,the south-west airflow in front of the southern branch trough was warm and moist which was different from climate mean state(dry and warm),and the moisture convergence,rising motion and the wind convergence at lower layer but divergence at upper layer were stronger than that of the climate mean state.There were two main features of quasi-stationary front in this case: in vertical direction,the frontal inversion layer's temperature was above 0 ℃;the front zone presented the dense area of the pseudo-equivalent potential temperature,the frontal structure was narrow and sharp,and behind the frontal zone,the lower level inversion was very significant.The frontogenesis provided favorable large-scale condition for the torrential rain in winter.

使用2003-2007年到T213数值预报产品和贵州省08-08时日降水量资料,建立了贵州省9个站的KNN晴雨预报模型,并对2008年进行了预报试验.在搜索K邻近域的过程中,与传统的KNN方法相比,求取了不同类别的K值,即K+、K-,使该方法选择的最邻近域中的K值取得更为合理.通过对历史资料的反复交叉验证求取了最优的K+、K-值组合.最后对2008年贵州省9个站进行预报试验并评估.预报评估结果表明:KNN方法总体上降低了预报空报率,提高了晴雨预报的TS评分和预报准确率,特别是对24h和48h,KNN方法在对贵州降水预报的数值预报解释应用中有一定的效果.