飑的判断与记录

“飑”是一种较复杂的天气,发生频次较少。本文通过对飑的特征的分析,总结了判断的方法,并结合典型个例分析飑与雷暴过境的区别,对其记录方法加以说明,对观测员正确判断记录有一定的借鉴作用。     

Numerical simulation of the relationship between electrification and microphysics in the prelightning stage of thunderstorms

To further investigate the influence of cloud base temperature, updraft velocity and precipitation particle constitution on cloud electrification, five thunderstorms in various regions of China were simulated by using the three-dimensional compressible hailstorm numerical model including inductive and non-inductive charging mechanisms. The results indicate that changes of cloud base temperature have an influence on the initial electrification. Comparison of the above cases shows that in the case of warm cloud base and moderate updraft velocity (< 20 m s^{−  1}), active electrification occurred below the − 10 °C level before moving upward to the − 20 °C level. In contrast, when cloud base is cold and updraft velocity is intensive, the main charging region is at the − 20 °C or even higher level. In that case, the vertical extent of the main negative charge region becomes larger with the increase of cloud base temperature. Apart from the main dipolar or tripolar charge structure, some smaller charge regions with relatively high values of charge density may also appear. Frozen drops, originating mainly from supercooled raindrops, mainly get electrified through charging interactions with snow at or below the − 20 °C level. They are responsible for the negative charge region near the melting level at the initial stage of precipitation if there is a large supercooled raindrop content. Non-inductive charging during hail-snow collisions is rather weak, resulting in the charge density on hail of no more than − 0.01 nC m^− 3.     

A comparison of lightning activity and convective indices over some monsoon-prone areas of China

Using 10-year lightning localization data observed by the TRMM (Tropical Rainfall Measuring Mission) Lightning Imaging Sensor (LIS), the relationship between lightning activity and a series of convective indices was investigated over nine monsoon-prone areas of China in which high-impact weather (HIW) events are frequently observed.Two methods were used to verify and reconstruct LIS lightning data. First, LIS lightning flash data were verified by both surface thunderstorm reports and ground-based lightning detection data. Seasonal, monthly, and 5-day distributions of LIS observed lightning activity agree well with the surface reports and ground-based lightning observations. Second, due to LIS's low sampling frequency, a data reconstruction and compensation scheme for LIS lightning observations was designed using both LIS lightning seasonal diurnal cycles and surface thunderstorm reports. After data reconstruction, five lightning products were derived: daily mean and maximum LIS flash rate, daily mean and maximum LIS lightning cell rate, and number of lightning days per five day period.Then, a series of convective indices describing convection conditions were derived from radiosonde data according to atmospheric instability and convective potential analysis. Correlation analysis for each study region was done between 10-year lightning derived products and corresponding convective indices by 5-day periods. The correlation analysis results show that higher lightning flash rate and lightning probability are associated with more unstable air and smaller vertical wind shear in a nearly saturated lower layer in most of the study regions. But the correlation varies from region to region. The best correlation between lightning activity and convective indices was found in eastern and southern China, whereas the correlation is lowest in some inland or basin topography regions in which topographic effects are more significant. Moreover, ambient moisture plays a much more important role in the convective development of thunderstorms in southern China than other regions. Thunderstorm development mechanism differences among regions were also discussed.Based on the close relationship between lightning activity and convective indices, some regression equations for forecasting 5-day mean or maximum LIS lightning flash rate and lightning area (a thunderstorm cell) rate, and 5-day lightning days for the study regions were developed using convective indices as predictors. The verifications show that the convective index-based lightning forecast methods can provide a reasonable lightning outlook including probability and lightning flash rate forecasts for a 5-day period.     

雷暴云内电场探测仪及初步实验结果

雷暴云内的电场探空是了解雷暴电荷结构的重要手段之一。为了定量了解雷暴云内的电场分布以确定雷暴的电荷结构,本文根据强电场环境中尖端放电原理,制作了尖端放电电流传感器。该电流传感器包括两根长度均为1 m的同轴电缆和一个时间常数为0.1 s、量程±16μА的精密电流放大电路;两根同轴电缆悬空垂直于地面,相对放大电路对称布置,两个尖端的长度为5~6 cm。利用该电流传感器,同时配合温度、相对湿度、GPS等传感器,组成了雷暴云内电场综合探空仪,并于2007年夏天在甘肃平凉地区进行了初步实验。利用雷暴天气条件下的大气平均电场仪与尖端放电电流传感器进行的地面同步观测记录,得出了大气电场—尖端放电电流的拟合关系,发现负电晕放电(尖端为阴极)的阈值电场和正电晕放电阈值电场存在一定差异,且负电晕放电的阈值较低。本文认为这一差异源于正、负电晕放电机制的差异。利用气球携带的电场综合探空仪进行了探空实验,得到了一次空中电场的初步探测结果,在此基础上,对探空路径上可能存在的电荷区域进行了分析。     

Observations of NO_2 and O_3 during Thunderstorm Activity Using Visible Spectroscopy

Simultaneous observations for the total column densities of NO2,O3 and H2O were carried on using the portable Spectrometer (438-450 nm and 400-450 nm) and the visible Spectrometer (544.4-628 nm) during premonsoon thunderstorms and embedded hail storm activity at Pune (18°32'N & 73°51'E),India.These observations confirm the fact that there is an increase in O3 and NO2 column densities during thunderstorms.The increase in O3 was observed following onset of thunderstorm,while the increase in NO2 was observed only after the thunder flashes occur.This implies that the production mechanisms for O3 and NO2 in thunderstorm are different.The observed column density of NO,value (1 to 3×1017molecules cm-2) during thunderstorm activity is 10 to 30 times higher than the value (1×10th molecules cm-2) of a normal day total column density.The spectrometric observations and observations of thunder flashes by electric field meter showed that 6.4×1025molecules/flash of NO2 are produced.The increased to-oil column den     

中国南北方雷暴及人工触发闪电电特性对比分析

通过对我国南北方雷暴及人工触发闪电电特性的对比分析，发现南北方雷暴及人工触发闪是电特性有很大差异。北方雷暴电荷结构呈三极性，人工触发闪电是在地面电场为正的情况下成功的。主要由连续电流和双极性电流脉冲组成，最大放电电流为１ｋＡ，中和电葆量只有几库仑；南方雷暴则为偶极性，触发闪电由连续电流和我次回击组成，电流峰值在于１０ｋＡ。触发闪电时地面电场均为负极性，其中在４ｋＶ／ｍ以上；触发高度在北方最低为２６     

黄、渤海沿岸港湾的假潮及成因探讨

本文通过对日照港以北黄、渤海沿岸18个港湾8～27年假潮资料的分析,给出了不同区域港湾的假潮状况和成因.在该区域只有龙口港可时常发生100cm左右的大振幅假潮和＞150cm甚至＞300cm的特大振幅假潮,属假潮特别严重和唯一发生较大危害性假潮港湾;其余分属假潮相对较重、较轻和无假潮港湾,其假潮基本不具危害性或无危害性.分析结果表明其突然而剧烈的风场变化是导致各港湾假潮的直接原因,地理环境差异是造成港湾假潮强弱的关键因素;龙口港100cm左右和＞1 50cm的大和特大振幅假潮,是其特殊地理环境、港湾及附近大范围海域骤猛的向港爆发性大风,尤其强雷暴大风涌水在港内骤然积聚和海水惯性振荡的综合结果.     

2002年4月5日江西强对流天气过程分析

运用天气图、T213物理量场、卫星云图及相关的实况资料,综合分析了2002年4月5日08～23时发生在江西中北部的1次罕见的雷雨大风,并伴有局地强降水和冰雹等强对流天气的过程,从而揭示了本次过程的生消成因以及在热力、动力学等方面的基本特征。     

均生函数模型在高原汛期降水预报中的应用

以均生函数为基函数,建立了正交化、主成分和最优子集回归三类预测模型。对云南昆明、滇中（包括昆明、玉溪和楚雄）及西藏林芝的汛期（６￣８）降水进行了模拟和预测、其拟合效果,特别是对极值的拟合十分理想。结果表明：在高原地区,均生函数模型预报降水具有较高的精度,拟合报准率和实际报准率分别为９７％￣１００％和６０％￣８０％,且具有多步预测能力。     

洛阳机场中小尺度天气现象特征

利用洛阳机场1989～1998年气象资料，分析了洛阳机场雷暴、大风、雾等中小尺度天气现象的气候特征和发生、发展及演变规律。