scholarly journals Comparison of Raindrop Size Distributions in a Midlatitude Continental Squall Line during Different Stages as Measured by Parsivel over East China

2017 ◽  
Vol 56 (7) ◽  
pp. 2097-2111 ◽  
Author(s):  
Hongsheng Zhang ◽  
Yun Zhang ◽  
Hongrang He ◽  
Yanqiong Xie ◽  
Qingwei Zeng
Keyword(s):  
Leading Edge ◽  
Number Concentration ◽  
East China ◽  
Squall Line ◽  
Mature Stage ◽  
Size Distributions ◽  
Stratiform Region ◽  
Raindrop Size ◽  
Two Stages ◽  
Rain Rates

AbstractThe characteristics of raindrop size distributions (DSDs) during a midlatitude continental squall line on 30 July 2014 in east China are studied, and the different life stages are observed by OTT second-generation Particle Size Velocity (Parsivel2) disdrometers at Chuzhou during the mature stage and Nanjing during the declining stage. The observed rainfall is classified into convective line, transition, and stratiform regions based on the structure of the radar reflectivity Z and rainfall intensity R. The results show that the DSD characteristics of the different precipitation types and different squall-line stages are very different. The convective center has the largest number concentration and quantity of large drops corresponding to the highest rain rate; the rain rates in the trailing edge and stratiform regions are similar, although a lower concentration of small drops is present in the latter. Between the two stages, the drop size and number concentration for the convective center decrease, although the leading edge during the declining stage has more numerous larger drops; the number concentration is similar in the stratiform rainfall, but the drops become much smaller. For the normalized distribution, the scaled spectra for the convective center are closer to an exponential distribution, and the μ value during the declining stage is larger than that during the mature stage for the stratiform region and similar during both stages for the convective center. The declining stage has a larger exponent b and smaller coefficient A in the Z–R relationship based on fits for the entire dataset. Moreover, the R(ZH, ZDR) estimator is more accurate than that when using the Z–R relation algorithm.

Raindrop Size Distribution in a Midlatitude Continental Squall Line Measured by Thies Optical Disdrometers over East China

2016 ◽  
Vol 55 (3) ◽  
pp. 621-634 ◽  
Author(s):  
Baojun Chen ◽  
Jun Wang ◽  
Dianli Gong
Keyword(s):  
Size Distribution ◽  
Eastern China ◽  
Leading Edge ◽  
Squall Line ◽  
Size Distributions ◽  
Squall Lines ◽  
Raindrop Size Distribution ◽  
Study Characteristics ◽  
Convex Upward ◽  
Raindrop Size

AbstractDisdrometer data measured by ground-based optical disdrometers during a midlatitude continental squall line event on 18 August 2012 in Shandong Province, eastern China, are analyzed to study characteristics of raindrop size distribution (DSD). Four disdrometers simultaneously performed continuous measurements during the passage of the convective line. The convective line was partitioned into three regions: the convective center, leading edge, and trailing edge. Results show distinct differences in DSDs and integral rainfall parameters between the convective-center and the edge regions. The convective center has higher drop concentrations, larger mean diameters, and wider size distributions when compared with the edge regions. The leading and trailing edges have similar drop concentrations, but the latter has larger mean diameters and wider size distributions. The shape of DSD for the convective center is convex down, whereas it is convex upward in tropical continental squall lines, as reported in the literature. There is also spatial variability of the DSD and its integral rainfall parameters in the along-convective-line direction.

scholarly journals Sensitivity of a Cloud-Resolving Model to Bulk and Explicit Bin Microphysical Schemes. Part I: Comparisons

2009 ◽  
Vol 66 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Xiaowen Li ◽  
Wei-Kuo Tao ◽  
Alexander P. Khain ◽  
Joanne Simpson ◽  
Daniel E. Johnson
Keyword(s):  
Cloud Microphysics ◽  
Squall Line ◽  
Mature Stage ◽  
High Temporal Resolution ◽  
Stratiform Region ◽  
Storm Flow ◽  
Cloud Resolving Model ◽  
Storm Dynamics ◽  
Convective Cells ◽  
Heating Profiles

Abstract A two-dimensional cloud-resolving model is used to study the sensitivities of two microphysical schemes, a bulk scheme and an explicit spectral bin scheme, in simulating a midlatitude summertime squall line [Preliminary Regional Experiment for Storm-Scale Operational and Research Meteorology (PRE-STORM), 10–11 June 1985]. In this first part of a two-part paper, the developing and mature stages of simulated storms are compared in detail. Some variables observed during the field campaign are also presented for validation. It is found that both schemes agree well with each other, and also with published observations and retrievals, in terms of storm structures and evolution, average storm flow patterns, pressure and temperature perturbations, and total heating profiles. The bin scheme is able to produce a much more extensive and homogeneous stratiform region, which compares better with observations. However, instantaneous fields and high temporal resolution analyses show distinct characteristics in the two simulations. During the mature stage, the bulk simulation produces a multicell storm with convective cells embedded in its stratiform region. Its leading convection also shows a distinct life cycle (strong evolution). In contrast, the bin simulation produces a unicell storm with little temporal variation in its leading cell regeneration (weak evolution). More detailed, high-resolution observations are needed to validate and, perhaps, generalize these model results. Interactions between the cloud microphysics and storm dynamics that produce the sensitivities described here are discussed in detail in Part II of this paper.

scholarly journals Effects of Pressure on Collision, Coalescence, and Breakup of Raindrops. Part II: Parameterization and Spectra Evolution at 50 and 100 kPa

2009 ◽  
Vol 66 (8) ◽  
pp. 2204-2215 ◽  
Author(s):  
Roland List ◽  
R. Nissen ◽  
C. Fung
Keyword(s):  
Mass Transfer ◽  
Fragment Size ◽  
Number Concentration ◽  
Lower Pressure ◽  
Box Model ◽  
Size Distributions ◽  
Cloud Droplets ◽  
The Times ◽  
Rain Rates

Abstract Fragment size distributions, experimentally obtained for six drop pairs colliding at 50 kPa, are parameterized similarly to the 100-kPa drop pair experiments by Low and List. This information is then introduced into a box model to allow assessment of the spectra evolution and a comparison of the two datasets taken at the two pressures. The differences in breakup patterns include the following: The contributions to mass transfer by breakup and coalescence are very similar at the two pressures, with larger values at lower pressure; the overall mass evolution is not particularly sensitive to pressure; and disk breakup plays an “erratic” role. The situation for the number concentration, however, is totally different and develops gradually. At 50 kPa there is also no three-peak equilibrium developing as for 100 kPa. The times to reach equilibrium are ∼12 h. Note that the box model does not include accretion of cloud droplets—which may well be more important than growth by accretion of fragments. Application of the new parameterization is not beneficial for low rain rates, but it is strongly recommended for large rain rates (>50 mm h−1).

The Sensitivity of a Numerically Simulated Idealized Squall Line to the Vertical Distribution of Aerosols

2014 ◽  
Vol 71 (12) ◽  
pp. 4581-4596 ◽  
Author(s):  
Zachary J. Lebo
Keyword(s):  
Vertical Distribution ◽  
Number Concentration ◽  
Squall Line ◽  
Cold Pool ◽  
Heating Rates ◽  
Low Level ◽  
Freezing Level ◽  
Cold Pools ◽  
Raindrop Size ◽  
The Vertical Distribution

Abstract Changes in the aerosol number concentration are reflected by changes in raindrop size and number concentration that ultimately affect the strength of cold pools via evaporation. Therefore, aerosol perturbations can potentially alter the balance between cold pool–induced and low-level wind shear–induced circulations. In the present work, simulations with increased aerosol loadings below approximately 3 km, between approximately 3 and 10 km, and at all vertical levels are performed to specifically address both the overall sensitivity of a squall line to the vertical distribution of aerosols and the extent to which low-level aerosols can affect the convective strength of the system. The results suggest that low-level aerosol perturbations have a negligible effect on the overall storm strength even though they act to enhance low-level latent heating rates. A tracer analysis shows that the low-level aerosols are either predominantly detrained at or below the freezing level or are rapidly lifted to the top of the troposphere or the lower stratosphere within the strongest convective cores. Moreover, it is shown that midlevel aerosol perturbations have nearly the same effect as perturbing the entire domain, increasing the convective updraft mass flux by more than 10%. These changes in strength are driven by a complex chain of events caused by smaller supercooled droplets, larger graupel, and larger raindrops. Combined, these changes tend to reduce the low-level bulk evaporation rate, thus weakening the cold pool and enhancing updraft strength. The results presented herein suggest that midlevel aerosol perturbations may exhibit a much larger effect on squall lines, at least in the context of this idealized framework.

scholarly journals On the Parameterization of Evaporation of Raindrops as Simulated by a One-Dimensional Rainshaft Model

2008 ◽  
Vol 65 (11) ◽  
pp. 3608-3619 ◽  
Author(s):  
Axel Seifert
Keyword(s):  
Reference Model ◽  
Number Concentration ◽  
High Variability ◽  
Cloud Base ◽  
Size Distributions ◽  
One Dimensional ◽  
Raindrop Size Distribution ◽  
The Mean ◽  
Raindrop Size ◽  
Bin Microphysics

Abstract The process of evaporation of raindrops below cloud base is investigated by numerical simulations using a one-dimensional rainshaft model with bin microphysics. The simulations reveal a high variability of the shape of the raindrop size distributions, which has important implications for the efficiency of evaporation below cloud base. A new parameterization of the shape of the raindrop size distribution as a function of the mean volume diameter is suggested and applied in a two-moment microphysical scheme. In addition, the effect of evaporation on the number concentration of raindrops is parameterized. A comparison of results of the revised two-moment scheme and the bin microphysics rainshaft model shows that the two-moment scheme is able to reproduce the results of the reference model in a wide parameter range.

scholarly journals On the Realism of the Rain Microphysics Representation of a Squall Line in the WRF Model. Part II: Sensitivity Studies on the Rain Drop Size Distributions

2019 ◽  
Vol 147 (8) ◽  
pp. 2811-2825 ◽  
Author(s):  
Céline Planche ◽  
Frédéric Tridon ◽  
Sandra Banson ◽  
Gregory Thompson ◽  
Marie Monier ◽  
...  
Keyword(s):  
Drop Size ◽  
Wrf Model ◽  
Melting Process ◽  
Squall Line ◽  
Size Distributions ◽  
Line System ◽  
Stratiform Region ◽  
Rain Drop ◽  
Vertical Evolution ◽  
Drop Size Distributions

Abstract A comparison between retrieved properties of the rain drop size distributions (DSDs) from multifrequency cloud radar observations and WRF Model results using either the Morrison or the Thompson bulk microphysics scheme is performed in order to evaluate the model’s ability to predict the rain microphysics. This comparison reveals discrepancies in the vertical profile of the rain DSDs for the stratiform region of the squall-line system observed on 12 June 2011 over Oklahoma. Based on numerical sensitivity analyses, this study addresses the bias at the top of the rain layer and the vertical evolution of the DSD properties (i.e., of Dm and N0*). In this way, the Thompson scheme is used to explore the sensitivity to the melting process. Moreover, using the Thompson and Morrison schemes, the sensitivity of the DSD vertical evolution to different breakup and self-collection parameterizations is studied. Results show that the DSDs are strongly dependent on the representation of the melting process in the Thompson scheme. In the Morrison scheme, the simulations with more efficient breakup reproduce the DSD properties with better fidelity. This study highlights how the inaccuracies in simulated Dm and N0* for both microphysics schemes can impact the evaporation rate, which is systematically underestimated in the model.

scholarly journals The sensitivity of intense rainfall to aerosol particle loading – a comparison of bin-resolved microphysics modelling with observations of heavy precipitation from HyMeX IOP7a

2020 ◽  
Vol 20 (5) ◽  
pp. 1469-1483 ◽  
Author(s):  
Christina Kagkara ◽  
Wolfram Wobrock ◽  
Céline Planche ◽  
Andrea I. Flossmann
Keyword(s):  
Cloud Model ◽  
Heavy Precipitation ◽  
Number Concentration ◽  
Precipitation Event ◽  
Heavy Precipitation Event ◽  
Region Model ◽  
Drop Number ◽  
Temporal And Spatial ◽  
Raindrop Size ◽  
Rain Rates

Abstract. Over the Cévennes–Vivarais region in southern France 5 h intensive rainfall covering an area of 1000 km2 with more than 50 mm of rain accumulation was observed during IOP7a of HyMeX. This study evaluates the performance of a bin-resolved cloud model for simulating this heavy-precipitation event. The simulation results were compared with observations of rain accumulation, radar reflectivity, temporal and spatial evolution of precipitation, 5 min rain rates, and raindrop size distributions (RSDs). The different scenarios for aerosol number concentrations range from 1000 to 2900 cm−3 and represent realistic conditions for this region. Model results reproduce the heavy-precipitation event with respect to maximum rain intensity, surface area covered by intense rain and the duration, as well as the RSD. Differences occur in the short-term rainfall rates, as well as in the drop number concentration. The cloud condensation number concentration has a notable influence on the simulated rainfall, on both the surface amount and intensity but also on the RSD properties, and should be taken into account in microphysics parameterizations.

scholarly journals On the Influence of Raindrop Collision Outcomes on Equilibrium Drop Size Distributions

2012 ◽  
Vol 69 (5) ◽  
pp. 1534-1546 ◽  
Author(s):  
Olivier P. Prat ◽  
Ana P. Barros ◽  
Firat Y. Testik
Keyword(s):  
Drop Size ◽  
Number Concentration ◽  
Drop Diameter ◽  
Size Distributions ◽  
Left Hand ◽  
Dynamical Simulation ◽  
Drop Number ◽  
Raindrop Size ◽  
Drop Size Distributions ◽  
The Impact

Abstract The objective of this study is to evaluate the impact of a new parameterization of drop–drop collision outcomes based on the relationship between Weber number and drop diameter ratios on the dynamical simulation of raindrop size distributions. Results of the simulations with the new parameterization are compared with those of the classical parameterizations. Comparison with previous results indicates on average an increase of 70% in the drop number concentration and a 15% decrease in rain intensity for the equilibrium drop size distribution (DSD). Furthermore, the drop bounce process is parameterized as a function of drop size based on laboratory experiments for the first time in a microphysical model. Numerical results indicate that drop bounce has a strong influence on the equilibrium DSD, in particular for very small drops (<0.5 mm), leading to an increase of up to 150% in the small drop number concentration (left-hand side of the DSD) when compared to previous modeling results without accounting for bounce effects.

scholarly journals Distributions of Raindrop Sizes and Fall Velocities in a Semiarid Plateau Climate: Convective versus Stratiform Rains

2010 ◽  
Vol 49 (4) ◽  
pp. 632-645 ◽  
Author(s):  
Shengjie Niu ◽  
Xingcan Jia ◽  
Jianren Sang ◽  
Xiaoli Liu ◽  
Chunsong Lu ◽  
...  
Keyword(s):  
Terminal Velocity ◽  
Systematic Change ◽  
Drop Diameter ◽  
Size Distributions ◽  
Fall Velocity ◽  
Convective Clouds ◽  
Stratiform Clouds ◽  
The Difference ◽  
Raindrop Size ◽  
Rain Rates

Abstract Joint size and fall velocity distributions of raindrops were measured with a Particle Size and Velocity (PARSIVEL) precipitation particle disdrometer in a field experiment conducted during July and August 2007 at a semiarid continental site located in Guyuan, Ningxia Province, China (36°N, 106°16′E). Data from both stratiform and convective clouds are analyzed. Comparison of the observed raindrop size distributions shows that the increase of convective rain rates arises from the increases of both drop concentration and drop diameter while the increase of the rain rate in the stratiform clouds is mainly due to the increase of median and large drop concentration. Another striking contrast between the stratiform and convective rains is that the size distributions from the stratiform (convective) rains tend to narrow (broaden) with increasing rain rates. Statistical analysis of the distribution pattern shows that the observed size distributions from both rain types can be well described by the gamma distribution. Examination of the raindrop fall velocity reveals that the difference in air density leads to a systematic change in the drop fall velocity while organized air motions (updrafts and downdrafts), turbulence, drop breakup, and coalescence likely cause the large spread of drop fall velocity, along with additional systematic deviation from terminal velocity at certain raindrop diameters. Small (large) drops tend to have superterminal (subterminal) velocities statistically, with the positive deviation from the terminal velocity of small drops being much larger than the negative deviation of large drops.

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