scholarly journals Statistical Characteristics of Raindrop Size Distribution in Southwest Monsoon Season

2008 ◽  
Vol 47 (2) ◽  
pp. 576-590 ◽  
Author(s):  
N. V. P. Kirankumar ◽  
T. Narayana Rao ◽  
B. Radhakrishna ◽  
D. Narayana Rao
Keyword(s):  
Size Distribution ◽  
Case Studies ◽  
Monsoon Season ◽  
Parameter Distribution ◽  
Convective Rain ◽  
Raindrop Size Distribution ◽  
Precipitation Regimes ◽  
Raindrop Size ◽  
Microphysical Processes ◽  
Vertical Variability

Abstract Raindrop size distribution (DSD) parameters are retrieved from dual-frequency (UHF and VHF) wind profiler measurements made at Gadanki, India, in a summer monsoon season. The convoluted UHF spectra are first corrected for vertical air motion and spectral broadening (using VHF measurements) and later are used for deriving DSD parameters. Two distinctly different case studies, a mesoscale convective system and a pure stratiform precipitation system, have been considered for a detailed study. DSD parameters obtained in these case studies reveal systematic variations of DSD from case to case and also from one rain regime to another within the same precipitating system. A statistical study has been carried out using the profiler data collected during the passage of 16 rain events. The retrieved DSD profiles are divided into separate rain regimes (stratiform and convection), based on reflectivity, to examine salient microphysical characteristics and the vertical variability of DSD in different precipitation regimes. The distribution of DSD parameters is, in general, wider in the convective rain regime than in the stratiform regime, particularly below 2.4 km. The vertical variation of the gamma parameter distribution in the stratiform rain regime is minimal, indicating that the microphysical processes (growth and decay), which alter the rain DSD, may be in equilibrium. On the other hand, the distribution in the convective rain regime appears to be more complex, with the mean profile of the shape parameter varying significantly with height. The observed vertical variability of the gamma parameters and the median volume diameter in the convective rain regime is attributed to two major microphysical processes: evaporation and breakup. The role of other processes, like drop sorting and collision–coalescence, in altering the DSD parameters is also discussed. The present statistics, representing continental monsoon rainfall, are compared with the existing statistics at Darwin, Australia, and the results are discussed in light of DSD differences in oceanic and continental monsoon precipitation.

scholarly journals Measurements and Modeling of the Full Rain Drop Size Distribution

Atmosphere ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 39 ◽  
Author(s):  
Merhala Thurai ◽  
Viswanathan Bringi ◽  
Patrick Gatlin ◽  
Walter Petersen ◽  
Matthew Wingo
Keyword(s):  
Size Distribution ◽  
Small Drop ◽  
Dual Frequency ◽  
Raindrop Size Distribution ◽  
Precipitation Estimation ◽  
Rain Drop ◽  
Double Moment ◽  
Raindrop Size ◽  
Microphysical Processes ◽  
Global Precipitation

The raindrop size distribution (DSD) is fundamental for quantitative precipitation estimation (QPE) and in numerical modeling of microphysical processes. Conventional disdrometers cannot capture the small drop end, in particular the drizzle mode which controls collisional processes as well as evaporation. To overcome this limitation, the DSD measurements were made using (i) a high-resolution (50 microns) meteorological particle spectrometer to capture the small drop end, and (ii) a 2D video disdrometer for larger drops. Measurements were made in two climatically different regions, namely Greeley, Colorado, and Huntsville, Alabama. To model the DSDs, a formulation based on (a) double-moment normalization and (b) the generalized gamma (GG) model to describe the generic shape with two shape parameters was used. A total of 4550 three-minute DSDs were used to assess the size-resolved fidelity of this model by direct comparison with the measurements demonstrating the suitability of the GG distribution. The shape stability of the normalized DSD was demonstrated across different rain types and intensities. Finally, for a tropical storm case, the co-variabilities of the two main DSD parameters (normalized intercept and mass-weighted mean diameter) were compared with those derived from the dual-frequency precipitation radar onboard the global precipitation mission satellite.

scholarly journals Statistical Characteristics of Raindrop Size Distribution in the Monsoon Season Observed in Southern China

2019 ◽  
Vol 11 (4) ◽  
pp. 432 ◽  
Author(s):  
Asi Zhang ◽  
Junjun Hu ◽  
Sheng Chen ◽  
Dongming Hu ◽  
Zhenqing Liang ◽  
...  
Keyword(s):  
Southern China ◽  
Monsoon Season ◽  
Eastern China ◽  
Northern China ◽  
Statistical Characteristics ◽  
Essential Information ◽  
Convective Rain ◽  
Raindrop Size Distribution ◽  
Scatter Plots ◽  
Raindrop Size

This study investigates the statistical characteristics of raindrop size distributions (DSDs) in monsoon season with observations collected by the second-generation Particle Size and Velocity (Parsivel2) disdrometer located in Zhuhai, southern China. The characteristics are quantified based on convective and stratiform precipitation classified using the rainfall intensity and total number of drops. On average of the whole dataset, the DSD characteristic in southern China consists of a higher number concentration of relatively small-sized drops when compare with eastern China and northern China, respectively. In the meanwhile, the Dm and log10Nw scatter plots prove that the convective rain in monsoon season can be identified as maritime-like cluster. The DSD is in good agreement with a three-parameter gamma distribution, especially for the medium to large raindrop size. Using filtered data observed by Parsivel2 disdrometer, a new Z–R relationship, Z = 498R1.3, is derived for convective rain in monsoon season in southern China. These results offer insights of the microphysical nature of precipitation in Zhuhai during monsoon season, and provide essential information that may be useful for precipitation retrievals based on weather radar observations.

scholarly journals A Probabilistic View on Raindrop Size Distribution Modeling: A Physical Interpretation of Rain Microphysics

2014 ◽  
Vol 15 (1) ◽  
pp. 427-443 ◽  
Author(s):  
Francisco J. Tapiador ◽  
Ziad S. Haddad ◽  
Joe Turk
Keyword(s):  
Size Distribution ◽  
Regression Line ◽  
Probabilistic Approach ◽  
Sample Variance ◽  
Sample Mean ◽  
Distribution Form ◽  
Raindrop Size Distribution ◽  
Raindrop Size ◽  
Microphysical Processes ◽  
Two Parameters

Abstract The raindrop size distribution (RDSD) is defined as the relative frequency of raindrops per given diameter in a volume. This paper describes a mathematically consistent modeling of the RDSD drawing on probability theory. It is shown that this approach is simpler than the use of empirical fits and that it provides a more consistent procedure to estimate the rainfall rate (R) from reflectivity (Z) measurements without resorting to statistical regressions between both parameters. If the gamma distribution form is selected, the modeling expresses the integral parameters Z and R in terms of only the total number of drops per volume (NT), the sample mean [m = E(D)], and the sample variance [σ2 = E(m − D)2] of the drop diameters (D) or, alternatively, in terms of NT, E(D), and E[log(D)]. Statistical analyses indicate that (NT, m) are independent, as are (NT, σ2). The Z–R relationship that arises from this model is a linear R = T × Z expression (or Z = T−1R), with T a factor depending on m and σ2 only and thus independent of NT. The Z–R so described is instantaneous, in contrast with the operational calculation of the RDSD in radar meteorology, where the Z–R arises from a regression line over a usually large number of measurements. The probabilistic approach eliminates the need of intercept parameters N0 or , which are often used in statistical approaches but lack physical meaning. The modeling presented here preserves a well-defined and consistent set of units across all the equations, also taking into account the effects of RDSD truncation. It is also shown that the rain microphysical processes such as coalescence, breakup, or evaporation can then be easily described in terms of two parameters—the sample mean and the sample variance—and that each of those processes have a straightforward translation in changes of the instantaneous Z–R relationship.

scholarly journals Small-Scale Variability of the Raindrop Size Distribution and Its Effect on Areal Rainfall Retrieval

2016 ◽  
Vol 17 (7) ◽  
pp. 2077-2104 ◽  
Author(s):  
Timothy H. Raupach ◽  
Alexis Berne
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Integration Time ◽  
Small Scale ◽  
Drop Diameter ◽  
Weather Model ◽  
Raindrop Size Distribution ◽  
Areal Rainfall ◽  
Raindrop Size ◽  
Microphysical Processes

Abstract The drop size distribution (DSD) describes the microstructure of liquid precipitation. The high variability of the DSD reflects the variety of microphysical processes controlling raindrop properties and affects the retrieval of rainfall. An analysis of the effects of DSD subgrid variability on areal estimation of precipitation is presented. Data used were recorded with a network of disdrometers in Ardèche, France. DSD variability was studied over two typical scales: 5 km × 5 km, similar to the ground footprint size of the Global Precipitation Measurement (GPM) spaceborne weather radar, and 2.8 km × 2.8 km, an operational pixel size of the Consortium for Small-Scale Modeling (COSMO) numerical weather model. Stochastic simulation was used to generate high-resolution grids of DSD estimates over the regions of interest, constrained by experimental DSDs measured by disdrometers. From these grids, areal DSD estimates were derived. The error introduced by assuming a point measurement to be representative of the areal DSD was quantitatively characterized and was shown to increase with the size of the considered area and with drop size and to decrease with the integration time. The controlled framework allowed for the accuracy of retrieval algorithms to be investigated. Rainfall variables derived by idealized simulations of GPM- and COSMO-style algorithms were compared to subgrid distributions of the same variables. While rain rate and radar reflectivity were well represented, the estimated drop concentration and mass-weighted mean drop diameter were often less representative of subgrid values.

scholarly journals Statistical Characteristics of Raindrop Size Distribution in Monsoon Season over South China Sea

2021 ◽  
Vol 13 (15) ◽  
pp. 2878
Author(s):  
Chaoying Huang ◽  
Sheng Chen ◽  
Asi Zhang ◽  
Ying Pang
Keyword(s):  
South China Sea ◽  
Size Distribution ◽  
Summer Monsoon ◽  
South China ◽  
Southern China ◽  
Monsoon Season ◽  
Statistical Characteristics ◽  
China Sea ◽  
Raindrop Size Distribution ◽  
Raindrop Size

The South China Sea (SCS) is the largest and southernmost sea in China. Water vapor from the SCS is the primary source of precipitation over coastal areas during the summer monsoon season and may cause the uneven distribution of rainfall in southern China. Deep insight into the spatial variability of raindrop size distribution (DSD) is essential for understanding precipitation microphysics, since DSD contains abundant information about rainfall microphysics processes. However, compared to the studies of DSDs over mainland China, very little is known about DSDs over Chinese ocean areas, especially over the South China Sea (SCS). This study investigated the statistical characteristics of the DSD in summer monsoon seasons using the second-generation Particle Size and Velocity (Parsivel2) installed on the scientific research vessel that measured the size and velocity of raindrops over the SCS. In this study, the characteristics of precipitation over the SCS for daytime and nighttime rains were analyzed for different precipitation systems and upon different rain rates. It was found that: 1) rain events were more frequent during the late evening to early morning; 2) more than 78.2% of the raindrops’ diameters were less than 2 mm, and the average value of mass-weighted mean diameter (1.46 mm) of the SCS is similar to that over land in the southern China; 3) the stratiform precipitation features a relatively high concentration of medium to large-sized rain drops compared to other regions; 4) the DSD in the SCS agreed with a three-parameter gamma distribution for the small raindrop diameter. Furthermore, a possible factor for significant DSD variability in the ocean compared with the coast and large islands is also discussed.

scholarly journals Statistical Characteristics of Raindrop Size Distribution during Rainy Seasons in Northwest China

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yong Zeng ◽  
Lianmei Yang ◽  
Zepeng Tong ◽  
Yufei Jiang ◽  
Zuyi Zhang ◽  
...  
Keyword(s):  
Size Distribution ◽  
Arid Regions ◽  
Weighted Average ◽  
Northwest China ◽  
Rainfall Rate ◽  
Statistical Characteristics ◽  
Stratiform Rain ◽  
Convective Rain ◽  
Raindrop Size Distribution ◽  
Raindrop Size

Raindrop size distribution (DSD) is of great significance for understanding the microphysical process of rainfall and the quantitative precipitation estimation (QPE). However, in the past, there was a lack of relevant research on Xinjiang in the arid region of northwest China. In this study, the rainy season data collected by the disdrometer in the Yining area of Xinjiang were used for more than two years, and the characteristics of DSDs for all samples, for two rain types (convective and stratiform), and for six different rain rates were studied. The results showed that nearly 70% of the total samples had a rainfall rate of less than 1 mm·h−1, the convective rain was neither continental nor maritime, and there was a clear boundary between convective rain and stratiform rain in terms of the scattergram of the standardized intercept parameter ( log 10 N w ) versus the mass-weighted average diameter ( D m ). When the raindrop diameter was less than 0.7 mm, DSDs of the two rainfalls basically coincided, while when the raindrop diameter was greater than 0.7 mm, DSDs of convective rainfall were located above the stratiform rain. As the rainfall rate increased, D m increased, while log 10 N w first increased and then decreased. In addition, we deduced the Z − R (radar reflectivity-rain rate) relationship and μ − Λ relationship (shape parameter-slope parameter of the gamma DSDs) suitable for the Yining area. These conclusions are conducive to strengthening the understanding of rainfall microphysical processes in arid regions and improving the ability of QPE in arid regions.

scholarly journals Statistical characteristics of raindrop size distribution during rainy seasons in the Beijing urban area and implications for radar rainfall estimation

2019 ◽  
Vol 23 (10) ◽  
pp. 4153-4170 ◽  
Author(s):  
Yu Ma ◽  
Guangheng Ni ◽  
Chandrasekar V. Chandra ◽  
Fuqiang Tian ◽  
Haonan Chen
Keyword(s):  
Size Distribution ◽  
Urban Area ◽  
Rain Rate ◽  
Statistical Characteristics ◽  
Spatial And Temporal Variability ◽  
Rainfall Estimation ◽  
Radar Rainfall ◽  
Convective Rain ◽  
Raindrop Size Distribution ◽  
Raindrop Size

Abstract. Raindrop size distribution (DSD) information is fundamental in understanding the precipitation microphysics and quantitative precipitation estimation, especially in complex terrain or urban environments which are known for complicated rainfall mechanism and high spatial and temporal variability. In this study, the DSD characteristics of rainy seasons in the Beijing urban area are extensively investigated using 5-year DSD observations from a Parsivel2 disdrometer located at Tsinghua University. The results show that the DSD samples with rain rate < 1 mm h−1 account for more than half of total observations. The mean values of the normalized intercept parameter (log 10Nw) and the mass-weighted mean diameter (Dm) of convective rain are higher than that of stratiform rain, and there is a clear boundary between the two types of rain in terms of the scattergram of log 10Nw versus Dm. The convective rain in Beijing is neither continental nor maritime, owing to the particular location and local topography. As the rainfall intensity increases, the DSD spectra become higher and wider, but they still have peaks around diameter D∼0.5 mm. The midsize drops contribute most towards accumulated rainwater. The Dm and log 10Nw values exhibit a diurnal cycle and an annual cycle. In addition, at the stage characterized by an abrupt rise of urban heat island (UHI) intensity as well as the stage of strong UHI intensity during the day, DSD shows higher Dm values and lower log 10Nw values. The localized radar reflectivity (Z) and rain rate (R) relations (Z=aRb) show substantial differences compared to the commonly used NEXRAD relationships, and the polarimetric radar algorithms R(Kdp), R(Kdp, ZDR), and R(ZH, ZDR) show greater potential for rainfall estimation.

scholarly journals Statistical characteristics of raindrop size distribution during rainy seasons in Beijing urban area and implications for radar rainfall estimation

2019 ◽  
Author(s):  
Yu Ma ◽  
Guangheng Ni ◽  
V. Chandrasekar ◽  
Fuqiang Tian ◽  
Haonan Chen
Keyword(s):  
Size Distribution ◽  
Urban Area ◽  
Rain Rate ◽  
Statistical Characteristics ◽  
Spatial And Temporal Variability ◽  
Rainfall Estimation ◽  
Radar Rainfall ◽  
Convective Rain ◽  
Raindrop Size Distribution ◽  
Raindrop Size

Abstract. Raindrop size distribution (DSD) information is fundamental in understanding the precipitation microphysics and quantitative precipitation estimation, especially in complex terrain or urban environment which is known for its complicated rainfall mechanism and high spatial and temporal variability. In this study, the DSD characteristics of rainy seasons in Beijing urban area are extensively investigated using 5-year DSD observations from a Parsivel2 disdrometer located at Tsinghua University. The results show that the DSD samples with rain rate < 1 mm h−1 account for more than half of total observations. The mean values of log10 Nw and Dm of convective rain are higher than that of stratiform rain, and there is a clear boundary between the two types of rain in terms of the scattergram of log10Nw versus Dm. The convective rain in Beijing is neither continental nor maritime owing to the particular location and local topography. As the rainfall intensity increases, the DSD spectra become higher and wider, but they still have peaks around diameter D ~ 0.5 mm. The midsize drops contribute most towards accumulated rainwater. The Dm and log10Nw values show a diurnal cycle and an annual cycle. In addition, DSD shows higher Dm values and lower log10Nw values during the periods of strong urban heat island (UHI) effect and UHI up stage of a day, and the same in July and August. The localized radar reflectivity (Z) and rain rate (R) relations (Z = aRb) show substantial differences compared to the commonly used NEXRAD relationships. And the polarimetric radar algorithms R(Kdp), R(Kdp, ZDR), and R(ZH, ZDR) show greater potential for rainfall estimation.

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