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1.
山西云微物理特征的地面观测 总被引：3，自引：1，他引：2
利用连续气流纵向热梯度云凝结核仪和激光降水粒子谱测量仪对山西地面的云凝结核和雨滴谱进行了观测研究.研究结果表明,云凝结核(CCN)数浓度具有明显的日变化特征,1天出现了两次峰值,数浓度日变化与气象因子、人类活动有关.降水对CCN具有冲刷作用.利用关系式NCCN=CSk拟合得到的地面CCN活化谱参数C值明显较大,k值较高,属于典型的大陆型核谱.对层状云、层积云降水雨滴微物理特征参量分析发现:3次层状云、层积云降水雨滴数密度变化范围分别为74～229 m-3、305～743 m-3,平均含水量量级分别为10-2 g/m3、10-1g/m3,最大雨滴直径分别为1.78 mm、4.7 mm.对层状云降水雨滴的数密度和雨强贡献较大的分别是小于1 mm、0.2～2 mm的雨滴;对层积云降水雨滴的数密度和雨强贡献较大的分别是0.2～2 mm、1～3 mm的雨滴.层积云出现稳定谱的比例高于层状云.从瞬时谱型分布看,层状云出现单、双、三峰多,第四、五峰值的频率比较少,层积云雨滴谱分布没有出现指数型,常有多峰.从平均谱分布看,层状云谱宽窄于层积云,层状云雨滴平均谱服从指数分布,层积云曲线呈向下弯曲的趋势.对汾阳2008年7月17日一次积层混合云降水雨滴谱资料分析发现积层混合云降水雨滴微物理量起伏大,降水雨强主要由雨滴数密度决定.相同雨强下,若有相对更多的大雨滴,雷达反射率会更大一些.随着强回波云块的过境,雨滴数浓度、雨滴谱峰值个数、谱宽均明显增大. 相似文献
2.
雷达回波强度与雨滴谱参数的相关性研究 总被引：2，自引：2，他引：0
在雷达定量探测降水方面,目前大都采用雷达回波强度与降水强度的相关性来定量估算,但雷达回波强度与降水强度并非一一对应。本文利用从庐山和南京收集到的雷达观测资料和同步Parsivel观测到的雨滴谱数据,建立雷达回波强度与不同雨滴谱参数的函数关系,将由确定的函数关系式拟合后的雷达回波强度与雷达实测的回波强度作对比,以检验假定函数关系式的合理性,同时通过对比两地两类云降水拟合值的相对误差,给出了函数关系式中的最优y选项,为雷达定量估算降水量寻找新的途径。研究结果表明:庐山和南京两地两类云降水的雨滴谱参数对雷达回波强度的拟合普遍较好,其中对流云降水的拟合都明显好于层状云降水。两地层状云降水中各个雨滴谱参数对雷达回波强度的拟合曲线都大体相近,而对流云降水中,不同雨滴谱参数对雷达回波强度的拟合曲线差异较大。南京两类云降水拟合的相对误差要小于庐山两类云降水拟合的相对误差。除庐山对流云降水外,DV是两地两类云降水拟合公式中最优的y选项。而庐山对流云降水拟合式中,以N和DP的拟合最佳。 相似文献
3.
4.
进入内陆的两个台风降水特征对比分析 总被引：2，自引：0，他引：2
2012年8月台风海葵和2014年7月台风麦德姆登陆进入安徽省后,均造成了区域性暴雨或大暴雨天气。利用常规观测资料、NCEP/NCAR再分析资料和雨滴谱资料,对这两个直接影响安徽省的台风移动路径和暴雨形成机制进行了对比分析。结果表明:（1）海葵和麦德姆的移动路径、停留时间和强降水分布特征有明显不同。与海葵相比,麦德姆的移动速度快、降水持续时间短、累计降雨量和暴雨范围较小;但其短时强降水持续时间长、暴雨中心降水强度更大。（2）海葵和麦德姆降水过程中均有强的水汽输送和辐合,但水汽输送方向的差异使得海葵和麦德姆的强降水空间分布分别呈纬向型和经向型特征。同时水汽辐合持续时间决定了麦德姆的降水持续时间比海葵短,但其较深厚的强水汽辐合使得麦德姆的短时强降水持续时间长、暴雨中心降水强度大。（3）海葵是以稳定性降水为主的混合型降水,麦德姆则呈现出明显的对流性降水特征;两次台风降水过程中均是短时间的对流性降水对总降雨量贡献最大,且强降水区域均位于风垂直切变的顺风切左侧。（4）麦德姆降水过程比海葵具有更高的雨滴数浓度和更大的降水粒子直径。当雨强小于10 mm/h时,两次台风降水过程均以小雨滴为主且数浓度较大;雨强>10 mm/h时,雨滴粒径增大但数浓度明显降低。（5）两次台风降水过程的雷达反射率因子-雨强（Z-R）均有较好的指数关系且拟合曲线比较一致,但在不同降水类型即层云降水和对流性降水中,其Z-R关系的a、b值差异较明显。因此,针对不同降水类型,应采用分型Z-R关系来进行雷达降水定量估测。 相似文献
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黄山层状云和对流云降水不同高度的雨滴谱统计特征分析 总被引：2，自引：1，他引：1
根据2011年6~7月在黄山不同高度采用PARSIVEL雨滴谱仪测得的雨滴谱数据,对不同海拔高度上两类（层状云和对流云）降水粒子谱的微物理特征量、Gamma函数拟合以及雨滴的下落速度进行对比分析,结果表明:对流云降水的雨水含量和降水强度、雨滴的各类尺度参数和数浓度都比相同位置上层状云降水的大,同类降水中,山腰的雨滴尺度大于山顶和山底,这可能与各观测点和云底相对位置的不同有关;随降水强度增加,雨滴的质量加权平均直径Dm逐渐增大,广义截距参数（log10Nw）的标准差逐渐减小。拟合结果表明各高度的雨滴谱都比较符合Gamma分布,由拟合参数分析雨滴谱的演变,发现相对于对流云降水,层状云降水粒子谱随高度的变化较小,雨滴谱的演变较为稳定。此外,本文还对两类降水中雨滴的下落速度及影响落速的因素进行了分析。 相似文献
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采用日本气象厅的最佳台风路径及强度资料、NCEP/NCAR逐6 h细网格再分析数据,分析了"利奇马"暴雨影响相关的云水含量、假相当位温、水汽通量散度、Q矢量、湿位涡等物理量;通过苏州雨滴谱资料,分析降雨强度、雨滴数密度、雨滴平均直径、雨滴含水量、雷达反射率因子、雨滴谱宽等微物理量特征。结果表明降水落区位于环境垂直风切变顺切的左侧。暴雨期间能量和水汽条件较好,低层Q矢量梯度使辐合上升增强,且其非对称性对暴雨落区有指示意义,湿位涡的发展也有利于暴雨的加强;另外,微物理分析表明冷云降水机制使降水效率大幅提高,雨滴谱能较好地反映台风降水特征,强降水主要由层状云中嵌入的对流降水引起。强降水时段雨滴谱的相关微物理量等都呈现较大值。 相似文献
7.
双参微物理方案对一次强降水过程的数值试验 总被引：4，自引：3，他引：1
利用WRF模式,分别采用WDM6和Morrison双参微物理方案对2009年7月23—24日,华东地区的一次强降水过程进行数值模拟。通过对地面累积降水量、降水强度和云中微物理量分析,对比研究了以上两种双参微物理方案对降水的预报效果。结果显示两种方案都低估了强降水区域的降水强度,而且提早预报了降水发生的时间。但相比之下,Morrison方案更接近实际的观测结果,而WDM6方案的误差在50%以上。分析了云中微物理量场和参数化方案计算过程,发现由于WDM6方案对雨滴的定义不合理,在结果中存在大量小粒径的雨滴,使平均粒径远小于典型雨滴,导致雨水的下落过程中,蒸发作用的强度被高估,而沉降过程的强度被低估,因而低估地面降水。 相似文献
8.
宁夏盛夏层状云降水雨滴谱特征分析 总被引：14，自引：5，他引：9
利用1982年7月在宁夏银川机场地面4次观测获取滴谱资料, 分析了宁夏夏季层状云雨滴的瞬时和平均谱及有关物理量的特征,总结出了层状云降水的一些主要特征.文中给出了4次降水的平均谱分布及谱参数的演变,进行了M-P分布的拟合分析,得出雨滴谱基本符合M-P分布.还分别建立了雷达反射率因子、雨强和雨水含量之间的相关关系,并分析了层状云降水的特点以及与积雨云、混合云的特征量进行对比,总结出三种降水的不同之处. 相似文献
9.
上海地区几类强降水雨滴谱特征分析 总被引：3，自引：3，他引：0
用Parsivel激光降水粒子谱仪资料对2013年上海地区4—10月份期间4种类型 (层状云、对流暖云主导型、对流冷云主导型和强台风影响下的混合暖云型) 降水过程的雨滴谱特征进行了分析。通过平均雨滴谱及其拟合特征、雨滴数密度与含水量分布、雨滴尺度与速度二维谱分布等对比分析发现:各类降水中, 雨滴谱的峰值结构与雨强大小有关, 其中直径介于0.187~1.312 mm的小雨滴均出现峰值且总数最多。各尺度雨滴数密度及其比例决定了其降水量贡献比, 在冷云强降水中的雨强贡献最大的雨滴尺度要显著大于其他3种类型。雨滴谱宽按大小排列依次为对流冷云主导型、混合暖云型、对流暖云主导型和层状云。最后综合运用雨滴谱、雷达、雨量站、闪电等观测资料对9月13日对流冷云主导型降水过程进行分析后发现:在雷暴的演变过程中, 雨滴谱特征与雷达反射率因子、垂直液态水含量、自动站雨强、闪电频次等要素均有较好的相关性。冷云产生的冰晶和冰雹融化后的大雨滴进入中低层的广谱小雨滴群, 并通过破碎分裂增加了大雨滴的形成概率, 尤其是捕捉碰并过程更加快了大雨滴的增长速度, 使雨强在短时间内迅速加强。雨滴谱中各档粒子数的演变, 揭示了降水强度的变化, 用雨滴谱资料可有效弥补现有雷达定量估测降水的偏差, 且在冷云中改善明显。 相似文献
10.
Long-term observational data indicated a decreasing trend for the amount of autumn precipitation (i.e. 54.3 mm per decade) over Mid-Eastern China, especially after the 1980s (~ 5.6% per decade). To examine the cause of the decreasing trend, the mechanisms associated with the change of autumn precipitation were investigated from the perspective of water vapor transportation, atmospheric stability and cloud microphysics. Results show that the decrease of convective available potential energy (i.e. 12.81 J kg-1/ decade) and change of cloud microphysics, which were closely related to the increase of aerosol loading during the past twenty years, were the two primary factors responsible for the decrease of autumn precipitation. Our results showed that increased aerosol could enhance the atmospheric stability thus weaken the convection. Meanwhile, more aerosols also led to a significant decline of raindrop concentration and to a delay of raindrop formation because of smaller size of cloud droplets. Thus, increased aerosols produced by air pollution could be one of the major reasons for the decrease of autumn precipitation. Furthermore, we found that the aerosol effects on precipitation in autumn was more significant than in other seasons, partly due to relatively more stable synoptic systems in autumn. The impact of large-scale circulation dominant in autumn and the dynamic influence on precipitation was more important than the thermodynamic activity. 相似文献
11.
Cores of high radar reflectivity (>50 dBZ) and raindrops larger than 4 mm in diameter were occasionally reported in warm clouds, offshore from Hawaii. A kinematic numerical model with detailed microphysics was used to study the formation of these cores and the development of the giant drops. The role of collisional and spontaneous breakup of drops was evaluated. Our results show that spontaneous breakup of raindrops restricts the formation of giant drops (D>4 mm). This could be a result of the poor parameterization of the fragment size distribution, and the probabilities of the spontaneous breakup. The inclusion of only binary breakup mechanism explained the observed radar echoes and the drop spectra. These results corroborate the hypothesis that the updrafts in the Hawaiian clouds sort out different size drops in such a way that millimeter size drops are allowed to fall in an environment deficient of smaller raindrops. In this way, the large raindrops continue to grow by collection of small cloud droplets, but have a smaller chance for collisional breakup (the efficiency for this type of breakup is small for collisions with cloud droplets). The collisional breakup of big raindrops was also found to play a significant role in the formation of giant drops. Such drops are formed following collision–breakup of large raindrops in which one of the fragments is larger than the original drops. 相似文献
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选取2014年7月31日安徽滁州一次飑线过程,使用地基雨滴谱仪资料分析此次过程的雨滴谱特征。根据雷达回波和地面降水强度将这次降水过程划分为对流降水、过渡性降水和层云降水,并以10 mm·h-1为临界值将对流降水进一步划分为对流前沿降水、对流中心降水、对流后沿降水。结果表明:对流中心降水、过渡性降水、层云降水的质量加权直径均比较稳定,平均值分别为1.8 mm, 1.0 mm, 1.7 mm。对流降水的标准化截距相比层云降水更大。对流中心降水各粒径段雨滴数浓度均较高;层云降水小雨滴浓度较低,且有少量大雨滴;过渡性降水由小雨滴组成。当雨水含量相同时,层云降水的质量加权直径相比对流降水更大。当雨强相同时,层云降水的反射率因子相比对流中心降水更大。更为精细的降水类型划分可有效改善Z-I关系。 相似文献
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利用激光雨滴谱仪2009年8月—2010年10月观测获取的滴谱资料,分析了山东省三类云降水雨滴微结构参量特征及滴谱随降水过程的演变特征。按照降水云系不同分别对各微物理参量进行比较,结果表明,各值由大到小排序依次均为积雨云、混合云和层状云。三类云降水过程中雨强与雨滴数浓度和最大直径间存在较好的相关关系;层状云和混合云降水以直径小于2 mm的雨滴为主,而积雨云降水以1~3 mm的雨滴对雨强贡献最大。层状云降水雨滴谱很窄,呈单峰或双峰型;积雨云降水雨滴谱宽,在大滴端呈多峰结构;混合云降水谱宽介于前两者之间。另外,统计得到该地区三类云降水的Z-I关系式,为雷达定量测量降水提供了一定的参考。 相似文献
14.
AbstractThree years of hourly traffic collision data and associated weather data for the city of Edmonton, Alberta, Canada, were analyzed. Using a matched-pair analysis to compare periods of adverse weather with similar periods without adverse weather, the effect of weather on traffic collisions in Edmonton was assessed. Adverse weather took the form of strong winds (>35?km h?1), precipitation (>0.10?mm?h?1), or limited visibility (<1.0?km). Risk ratio (RR) values were calculated to determine the relative increase in accidents resulting from each type of weather, as well as for multiple types of concurrent weather. Analysis was performed for collisions that resulted in property damage only (PDO) and severe collisions that resulted in injuries. To determine whether specific types of collisions were more likely to occur during adverse weather, RR values were determined for multiple types of collisions, such as following too closely or failing to stop at a traffic signal. Our results show that adverse weather affects traffic collisions in a variety of ways. Horizontal visibility less than 200 m and strong winds above 45?km?h?1, while relatively infrequent in Edmonton, typically resulted in an increase in overall collisions (RR?=?3.40 and 1.17, respectively). Precipitation, which is far more common to Edmonton, posed an increased risk to drivers. The type of precipitation was also clearly a factor. The RR value for PDO collisions was higher during periods of snowfall (1.90) than during periods of rainfall (1.28), but the RR value for collisions resulting in injuries (1.37) was higher than the value for PDO collisions during periods of rainfall. Collisions during snowfall had a higher RR value (1.90) for PDO collisions than for collisions resulting in injuries (1.55), and both were higher than the RR values for either type of collision during rainfall, suggesting that snowfall is a greater threat to driving safety than rainfall. For both precipitation types, a higher rate of precipitation was associated with increased risk and a larger number of collisions. Some collision types were clearly affected by the type of precipitation. Vehicles left the road resulting in property damage at far higher RR values during snowfall (3.36) than during periods of rainfall (1.09). Furthermore, analysis of collision types identify that two collisions with nearly identical actions, stopping at a stop sign and stopping at a traffic signal, have very different risks during adverse weather. Stopping at stop signs appears to be far more difficult than stopping at traffic signals during precipitation events and has a higher associated risk. Lastly, we identify a puzzling concern: our results show that Edmonton drivers do not perceive periods of rainfall as presenting a hazard, resulting in a disproportionately high number of injuries during rainfall. 相似文献
15.
基于地面雨滴谱资料分析层状云和对流云降水的特征 总被引：32，自引：7，他引：25
根据由声雨滴谱仪器测量得到的雨滴谱资料,结合降水云的结构来将降水云系划分成为对流云降水云系和层状云降水云系.分析这两种降水云系中的稳定雨滴谱特征,包括雨滴谱的各种特征直径(平均直径Dm、众数直径Dd、平均体积直径Dv、优势直径Dp、中数直径Dna和中数体积直径Dn)、峰值结构和Z-R关系等.通过对这些量的分析,进一步分析划分降水云系的判据. 相似文献
16.
Hyunho Lee Jong-Jin Baik Alexander P. Khain 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):457-471
Using the large-eddy simulation version of the Weather Research and Forecasting (WRF) model coupled with a detailed bin microphysics scheme, the effects of turbulence-induced collision enhancement (TICE) on precipitation and cloud radiative properties in shallow cumulus are investigated. Similar to previous studies, the enhanced droplet collision results in an increase in rainwater content and surface precipitation amount. However, under low aerosol number concentration, the relative frequency of large surface precipitation amount is decreased mainly due to the decreased condensation amount. Due to TICE, the mean drop size increases and the drop number concentration decreases, which results in a decrease in evaporation and hence increasing cloud fraction. However, these changes induce a decrease in cloud optical thickness which largely offsets the increased cloud fraction when the domain-averaged albedo is calculated. Similarly, a decrease in cloud top height caused by the decreased in-cloud vertical velocity largely offsets the increased cloud fraction when the domain-averaged outgoing longwave radiation is calculated. Therefore, the effects of TICE on cloud radiative properties in shallow cumulus do not appear prominently. In addition, TICE results in a decrease in the shear production of turbulent kinetic energy, which indicates that TICE acts to produce a negative feedback. 相似文献
17.
采用伽玛分布形式的雨滴谱表达式，讨论了下沉气流W对Z－I关系的影响。发现随着W（向下为正）增大，关系式Z＝AI^b中系数A值减小,b值增大。利用地面实测雨滴谱资料计算出不同下沉气流下Z、I后回归得到的A、b值，以及根据由平均谱拟合得到的伽玛分布参数计算出A、b值，它们随W改变的变化趋势，均与理论分析结果一致。还讨论了环境气压场p对Z－I关系的作用，气压减小时，A值减小，b值增大，但变化不如W影响时的变化影响。此外，结合实测雨滴谱资料，分析了雨滴平均谱特征以及相关物理量的演变过程。 相似文献
18.
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. 相似文献
19.
Junghwa Lee Yign Noh Siegfried Raasch Theres Riechelmann Lian-Ping Wang 《Meteorology and Atmospheric Physics》2014,124(1-2):1-21
A precipitating convective cloud is simulated successfully using the Lagrangian cloud model, in which the flow field is simulated by large eddy simulation and the droplets are treated as Lagrangian particles, and the results are analyzed to investigate precipitation initiation and to examine the parameterization of cloud microphysics. It is found that raindrops appear initially near the cloud top, in which strong turbulence and broadened droplet spectrum are induced by the entrainment of dry air, but high liquid–water mixing ratio is maintained within cloud parts because of insufficient mixing. Statistical analysis of the downward vertical velocity of a droplet W reveals that the transition from cloud droplets to raindrops occurs in the range 20 μm < r < 100 μm, while the variation of W depends on turbulence as well as the droplet radius r. The general pattern of the raindrop size distribution is found to be consistent with the Marshall–Palmer distribution. The precipitation flux can be underestimated substantially, if the terminal velocity $w_{\text{s}}$ is used instead of W, but it is not sensitive to the choice of the critical droplet radius dividing cloud drops and raindrops. It is also found that precipitation starts earlier and becomes stronger if the effect of turbulence is included in the collection kernel. 相似文献
20.
Kun ZHAO Hao HUANG Mingjun WANG Wen-Chau LEE Gang CHEN Long WEN Jing WEN Guifu ZHANG Ming XUE Zhengwei YANG Liping LIU Chong WU Zhiqun HU Sheng CHEN 《大气科学进展》2019,36(9):961-974
Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed. 相似文献