Microphysical processes of a stratiform precipitation event over eastern China: analysis using micro rain radar data

Data collected using the micro rain radar (MRR) situated in Jinan city, eastern China, were used to explore the altitudinal and temporal evolution of rainfall microphysical characteristics, and to analyze the bright band (BB) characteristics and hydrometeor classification. Specifically, a low-intensity and stable stratiform precipitation event that occurred from 0000 to 0550 UTC 15 February 2015 and featured a BB was studied. During this event, the rainfall intensity was less than 2 mm h−1 at a height of 300 m, which was above the radar site level, so the errors caused by the vertical air motion could be ignored. The freezing height from the radiosonde matched well with the top of the BB observed by the MRR. It was also found that the number of 0.5–1 mm diameter drops showed no noticeable variation below the BB. The maximum fall velocity and the maximum gradient fall velocity (GFV) of the raindrops appeared at the bottom of the BB. Meanwhile, a method that uses the GFV and reflectivity to identify the altitude and the thickness of the BB was established, with which the MRR can provide a reliable and real-time estimation of the 0°C isotherm. The droplet fall velocity was used to classify the types of snow crystals above the BB. In the first 20 min of the selected precipitation event, graupel prevailed above the BB; and at an altitude of 2000 m, graupel also dominated in the first 250 min. After 150 min, the existence of graupel and dendritic crystals with water droplets above the BB was inferred.摘要本文利用济南的微降水雷达数据分析降水微物理参数随时间和空间的演变, 分析零度层亮带特征, 判断零度层亮带以上粒子的相态. 选取2015年2月15日00时00分至05时50分(世界时)发生在济南地区一次小雨强、稳定的层状云降水为例来分析. 在此次降水过程中, 300 m高度上的雨强均小于2 mm h-1, 由垂直气流造成的影响可以忽略. 微降水雷达观测的零度层亮带顶的高度与探空0℃的高度有很好的一致性. 零度层亮带以下直径为0.5—1 mm的粒子数量没有明显的变化. 粒子最大下落速度和最大下落速度梯度出现在零度层亮带的底部, 提出用下落速度梯度和雷达反射率因子来判断零度层亮带的高度和厚度, 这种方法可以用来实时监测0℃层. 同时, 利用粒子的下落速度来判断零度层亮带以上粒子的相态. 在选取的降水个例的前20分钟, 零度层亮带以上霰粒子丰富; 在2000 m高度上, 前250分钟都是霰粒子占主导地位; 150分钟后, 为霰和附冻滴冰晶的混合状态.

[1]  Ki-Ho Chang,et al.  Comparison of the bright band characteristics measured by Micro Rain Radar (MRR) at a mountain and a coastal site in South Korea , 2009 .

[2]  A. Maitra,et al.  Investigation of vertical profile of rain microstructure at Ahmedabad in Indian tropical region , 2010 .

[3]  G. Peters,et al.  Rain observations with a vertically looking Micro Rain Radar (MRR) , 2002 .

[4]  R. C. Srivastava,et al.  Doppler radar characteristics of precipitation at vertical incidence , 1973 .

[5]  Johann Riedl,et al.  Systematic variations of Z–R-relationships from drop size distributions measured in northern Germany during seven years , 1998 .

[6]  Nature of light rain during presence and absence of bright band , 2012, Journal of Earth System Science.

[7]  G. Peters,et al.  Rain Attenuation of Radar Echoes Considering Finite-Range Resolution and Using Drop Size Distributions , 2010 .

[8]  R. C. Srivastava,et al.  Evolution of Raindrop Size Distribution by Coalescence, Breakup, and Evaporation: Theory and Observations , 1995 .

[9]  E. E. Gossard,et al.  Evolution of Dropsize Distributions in Liquid Precipitation Observed by Ground-Based Doppler Radar , 1990 .

[10]  Pavlos Kollias,et al.  Improved Micro Rain Radar snow measurements using Doppler spectra post-processing , 2012 .

[11]  J. Marshall,et al.  THE DISTRIBUTION OF RAINDROPS WITH SIZE , 1948 .

[12]  F. Marks,et al.  Partitioning tropical oceanic convective and stratiform rains by draft strength , 2000 .

[13]  Drop size distributions of tropical rain over south India , 2006 .

[14]  F. Martin Ralph,et al.  An Automated Brightband Height Detection Algorithm for Use with Doppler Radar Spectral Moments , 2002 .

[15]  Raspodjela kapi tropskih kiša po veličini nad južnom Indijom , 2005 .

[16]  Olivier P. Prat,et al.  Ground observations to characterize the spatial gradients and vertical structure of orographic precipitation - experiments in the inner region of the Great Smoky Mountains. , 2010 .

[17]  F. Martin Ralph,et al.  Coastal Orographic Rainfall Processes Observed by Radar during the California Land-Falling Jets Experiment , 2003 .

[18]  Chris Kidd,et al.  Investigation into clouds and precipitation over an urban area using micro rain radars, satellite remote sensing and fluorescence spectrophotometry , 2010 .

[19]  Dawei Han,et al.  Correction of the bright band using dual‐polarisation radar , 2005 .

[20]  R. Rogers,et al.  An extension of the Z-R relation for Doppler radar , 1964 .

[21]  G. Foote,et al.  Terminal Velocity of Raindrops Aloft , 1969 .

[22]  S. Rutledge,et al.  Vertical Motion Structure in Maritime continent mesoscale Convective Systems: Results from a 50-MHz Profiler , 1994 .

[23]  Ian Cluckie,et al.  Radar hydrometeorology using a vertically pointing radar , 2000 .

[24]  P. T. Willis,et al.  Functional fits to some observed drop size distributions and parameterization of rain , 1984 .

[25]  Gerhard Peters,et al.  Profiles of Raindrop Size Distributions as Retrieved by Microrain Radars , 2005 .

[26]  P. Amayenc,et al.  Exponential Size Distributions of Raindrops and Vertical Air Motions Deduced from Vertically Pointing Doppler Radar Data Using a New Method , 1983 .

[27]  R. Harikumar,et al.  Variation of rain drop size distribution with rain rate at a few coastal and high altitude stations in southern peninsular India , 2010 .

[28]  Frédéric Fabry,et al.  Modeling of the Melting Layer. Part III: The Density Effect , 2005 .

[29]  Frédéric Fabry,et al.  Long-Term Radar Observations of the Melting Layer of Precipitation and Their Interpretation , 1995 .

[30]  R. C. Srivastava.  Parameterization of Raindrop Size Distributions. , 1978 .

[31]  F. M. Ralph,et al.  Using Spectral Moment Data from NOAA's 404-MHz Radar Wind Profilers to Observe Precipitation , 1995 .

[32]  R. C. Srivastava.  Size Distribution of Raindrops Generated by their Breakup and Coalescence , 1971 .

[33]  Guifu Zhang,et al.  Drop Size Distribution Retrieval with Polarimetric Radar: Model and Application , 2004 .

[34]  N. Kirankumar,et al.  Evaluation of performance of Micro Rain Radar over the tropical coastal station Thumba (8.5°N, 76.9°E) , 2013 .

[35]  Witold F. Krajewski,et al.  Assessment of the Thies optical disdrometer performance , 2011 .

[36]  Ukitiro Nakaya,et al.  Simultaneous Observations of the Mass, Falling Velocity and Form of Individual Snow Crystals , 1935 .

[37]  Roland List,et al.  Collision, Coalescence and Breakup of Raindrops. Part I: Experimentally Established Coalescence Efficiencies and Fragment Size Distributions in Breakup , 1982 .

[38]  Roland List,et al.  Collision, Coalescence and Breakup of Raindrops. Part II: Parameterization of Fragment Size Distributions , 1982 .

[39]  R. Harikumar,et al.  Altitudinal and temporal evolution of raindrop size distribution observed over a tropical station using a K-band radar , 2012 .

[40]  R. Gunn,et al.  THE TERMINAL VELOCITY OF FALL FOR WATER DROPLETS IN STAGNANT AIR , 1949 .

[41]  C. Ulbrich.  Natural Variations in the Analytical Form of the Raindrop Size Distribution , 1983 .

[42]  R. Harikumar,et al.  An Empirical Model for the variation of Rain Drop Size Distribution with Rain Rate at a few locations in Southern India , 2009 .