Throughfall partitioning by trees Levia, Delphis F.; Nanko, Kazuki; Amasaki, Hiromasa ...
Hydrological processes,
15 June 2019, Volume:
33, Issue:
12
Journal Article
Peer reviewed
Open access
Although we know that rainfall interception (the rain caught, stored, and evaporated from aboveground vegetative surfaces and ground litter) is affected by rain and throughfall drop size, what was ...unknown until now is the relative proportion of each throughfall type (free throughfall, splash throughfall, canopy drip) beneath coniferous and broadleaved trees. Based on a multinational data set of >120 million throughfall drops, we found that the type, number, and volume of throughfall drops are different between coniferous and broadleaved tree species, leaf states, and timing within rain events. Compared with leafed broadleaved trees, conifers had a lower percentage of canopy drip (51% vs. 69% with respect to total throughfall volume) and slightly smaller diameter splash throughfall and canopy drip. Canopy drip from leafless broadleaved trees consisted of fewer and smaller diameter drops (D50_DR, 50th cumulative drop volume percentile for canopy drip, of 2.24 mm) than leafed broadleaved trees (D50_DR of 4.32 mm). Canopy drip was much larger in diameter under woody drip points (D50_DR of 5.92 mm) than leafed broadleaved trees. Based on throughfall volume, the percentage of canopy drip was significantly different between conifers, leafed broadleaved trees, leafless broadleaved trees, and woody surface drip points (p ranged from <0.001 to 0.005). These findings are partly attributable to differences in canopy structure and plant surface characteristics between plant functional types and canopy state (leaf, leafless), among other factors. Hence, our results demonstrating the importance of drop‐size‐dependent partitioning between coniferous and broadleaved tree species could be useful to those requiring more detailed information on throughfall fluxes to the forest floor.
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•Systematic investigation of dispersing conditions on Pickering emulsion properties.•Correlation of Sauter mean diameters with energy density and tip speed.•Pickering emulsion ...filtration at high dispersed phase fractions possible.•Strong membrane-particle-solvent interactions revealed.
Pickering emulsions (PE) are becoming of increasing interest for catalytic multiphase processes. Ultrafiltration of PE is a promising procedure for catalyst recovery to enable continuous processes. Dispersing conditions during production of PE are expected to significantly influence PE characteristics, and control of these properties is essential for robust process design. However, while the impact of PE composition has been studied before, knowledge on dispersing conditions is surprisingly scarce.
The influence of dispersing time, speed and emulsion volume during the preparation of PE with an UltraTurrax (2 dispersing tools) on the drop size distribution, rheology, stability and filtration was investigated.
In this first systematic study of PE preparation conditions, obtained Sauter mean diameters were correlated with energy density (R2 = 0.80), energy dissipation rate (R2 = 0.85) and tip speed (R2 = 0.86). All emulsions were stable for at least 10 weeks. With increasing tip speed (4–13 m/s), the dynamic viscosity first decreased, passed through a plateau value and then increased again. Filtration of concentrated PE was successful but strong membrane-particle-solvent interactions were revealed. This work contributes to a better understanding of PE properties that are essential for a sound application of PE in continuous multiphase catalysis.
Using the observations from the two‐dimensional video disdrometer and polarimetric radar, a detailed process‐based evaluation of five bulk microphysics schemes in the simulation of an extreme ...rainfall event over the mountainous coast of South China is performed. Most schemes reproduce one of the heavy rainfall areas, and the National Severe Storms Laboratory (NSSL) scheme successfully simulates both heavy rainfall areas in this event. However, our analysis reveals that even the NSSL simulation still cannot accurately represent the rain microphysics for this event. Observational analysis shows that abundant small‐ and medium‐sized (1–4 mm) raindrops are the main contributors to the extreme rainfall. All the simulations tend to underpredict raindrops for diameter around 3 mm. The Lin, WSM6, and Morrison simulations agree better with the observed drop size distribution (DSD) for diameters between 1 and 2 mm for higher rain rates. The Thompson simulation shows a relatively narrow distribution with overpredicted small‐sized (1–2 mm) raindrops. The NSSL simulation has a broad distribution with more large (>4 mm) raindrops probably related to its efficient rain self‐collection process at the low levels, which is conducive to producing extreme rainfall. Proper rain evaporation rate is important in generating cold pools with favorable strength for the maintenance of a convective system in this event. Similar results are obtained in the simulations of two additional extreme rainfall cases, in which the NSSL simulation also overpredicts large raindrops while the Thompson simulation produces more small raindrops. This study indicates that more efforts are needed to improve the representation of rain self‐collection/breakup, rain evaporation processes, and DSD for extreme rainfall over South China. It also highlights the importance in careful consideration of rain DSD in addition to radar reflectivity and surface precipitation when analyzing simulations of extreme rainfall in order to avoid “wrong” interpretation of “right” results.
Observed and simulated distribution of rain rate. Black: observations; solid red line: the original NSSL simulation; solid orange line: the original Thompson simulation; dashed red line: the sensitivity experiment using the NSSL scheme with modified rain self‐collection/breakup processes (NSSL_B); dashed orange line: the sensitivity experiment using the Thompson scheme with modified rain self‐collection/breakup processes (Thompson_B).
In this study, Gaussian mixture model clustering analysis was carried out to examine characteristics of Global Precipitation Measurement (GPM) Dual‐frequency Precipitation Radar (DPR)‐retrieved ...mass‐weighted mean diameter (Dm), and normalized intercept parameter (Nw) of the drop size distribution (DSD) for heavy rainfalls (>10 mm h−1) for 6 years (2014–2019). Three objective DSD types – continental, oceanic deep, and oceanic shallow convective types – emerged. The means and standard deviations of Dm and Nw obtained for the three types are in good agreement with various ground‐based observations, indicating that global view of DSD characteristics can be obtained from DPR‐derived DSD parameters. Global distributions of occurrence and contribution of each DSD type to total heavy rainfall are produced for the first time, which will help examine the dominant DSD type, its contribution to total heavy rainfall, and composition of different convective types in the rainfall system at a given location.
Plain Language Summary
The surface rainfall is composed of a variety of spectrum of raindrops, which can be best represented by mean drop size and number concentration of droplets. Thus, those magnitude and shape may well describe rainfall‐related features such as convective type and associated atmospheric environments. Thus, information on the rain drop size distribution is important for improving the remote sensing capability or modeling the rainfall phenomena. From the analysis of satellite‐derived rain drop size distribution, it is noted that the heavy rainfall can be largely classified into three types – continental, oceanic deep, and oceanic shallow convective types. Satellite‐derived mean diameter and drop size distribution for heavy rain are found to be very consistent with ground observations from limited local areas, indicating that the global view of drop size distributions can be synthesized from the satellite observations. The newly obtained global features overcome the spatial limitations of existing studies using ground‐based observations. Furthermore, estimated contribution to the heavy rainfall from each classified type shows that a largest portion is from the oceanic deep convective type, and the oceanic shallow convective type contributes as much as the continental type.
Key Points
Global synthesis of drop size distributions for heavy rainfall using satellite‐borne radar measurements
Three heavy rainfall types emerged – continental, oceanic deep, and oceanic shallow convective types
Geographic distributions of occurrence frequencies and rain contributions of three types are presented
•Proposed device had a minimalistic total 3 turns, rotated in x,y, and z planes.•The proposed device was different from conventional CFI and its variants.•Mixing time tm were estimated at least two ...order lower than residence time τ.•The energy dissipation ε was much higher than that in annular centrifugal contactor.•It complied all the four directives of the concurrent PI paradigm.
A simple 3D rotated microfluidic mixer design is reported with evaluation of hydrodynamic and mass transfer performance. Proposed device had a minimalistic configuration of 3 turns, rotated in x, y, and z planes. The helical mixer volume was only 3.14 μL due to usage of 100 μm dia micro bore tubing. The proposed device was different from conventional CFI and its variants. The analysis for hydrodynamic performance indicated a massive specific interfacial area, much more than for the 50 mm centrifugal extractor with the same PUREX aqueous-organic pair. Higher volumetric amass transfer coefficients were reported for the proposed device as compared to conventional mixers (impellers and Taylor-Couette mixers). Energy dissipation values were also reported to be much higher than that of a contemporary annular centrifugal extractor. Mixing-time values (tm) were estimated at least two-order lower than residence time values (τ). Proposed design complied all the four directives of the concurrent PI paradigm.
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•Application of ultrasound techniques to dispersed liquid-liquid flows.•Ultrasound methods are used to obtain dispersed phase volume fraction and drop size distribution.•PLIF technique is used to ...validate results from the ultrasound measurements.•There was good agreement between the ultrasound and PLIF techniques.
This paper delineates the development and application of non-intrusive diagnostic ultrasound (US) techniques for the measurement of the drop size distribution (DSD) and the drop volume fraction in dispersed liquid-liquid flows. The techniques used here are based on the measurement of the speed and the attenuation coefficient of the propagated ultrasound wave. To validate the results of the ultrasound measurements, a planar laser induced fluorescence (PLIF) technique was used to image the dispersed phase at the same time and location as the ultrasound transducers. For the tests, a silicon oil and a glycerol/water mixture, with the same refractive index as the oil, were used. The experiments were carried out in a stirred vessel with the impeller placed either just below the oil/aqueous mixture interface or at 25 mm below the interface and rotated at speeds of 300–400 rpm. The dispersed oil volume fractions measured by both the US and PLIF techniques were in excellent agreement and varied between 0.53% to 4.2%. Good agreement between the two techniques was also found for the drop size distributions. For the conditions investigated, the drop size ranged from 0.25 mm to 2 mm. The results indicated that the developed ultrasound technique is a powerful tool for characterising dispersed phases in liquid-liquid flows.
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The impact of vertical downdraft on rain attenuation estimation from rain rate measurements has been studied. The rain rate ( R ) and specific attenuation (γ) are derived from rain drop size ...distributions (DSD) by considering the widely accepted Gunn-Kinzer (G-K) relationship between drop size and drop fall velocity that is valid for stagnant air. In the real atmosphere, drops are carried with the vertical wind draft, and the actual fall velocity of the raindrops deviates from the G-K formulation. The ITU-R estimated rain attenuation values, based on DSDs, which are mostly valid for temperate regions, can deviate from actual rain attenuation measurements in tropical regions, especially at higher rain rates when downdraft is prominent. The present study uses disdrometer measurements of DSD, optical rain gauge measurements of rain rates, and Ku-band rain attenuation data over an earth-space path at a tropical location Kolkata (22°34′ N, 88°29′ E) to show that vertical downdrafts impact the rain attenuation estimation from rain rate measurements. At the present location, an overall representative vertical downdraft of 2 m/s needs to be considered to match the experimental attenuation measurements with the estimated values using the modified γ- R relationship in the ITU-R model.
•Mixing/separation was studied in stirred tank with oil volume fractions 0.1-0.9.•The working temperatures were varied from 20 °C to 80 °C.•Temperature has minor impact on drop sizes but significant ...effect on separation.•Henschke model predicted well at high dispersed phase fractions and temperatures.
Drop size distributions and phase separation were determined in a batch stirred tank with water/paraffin oil using optical measurement techniques. Temperature was varied from 20 °C to 80 °C and dispersed phase fractions up to 0.7, resulting in a phase inversion from oil-in-water to water-in-oil emulsions. Higher temperatures only increase Sauter mean diameters by 9.9%, but reduce phase separation time up to 67.4%. Higher dispersed phase fractions lead to bigger drop sizes and longer separation time. The interplay between drop size distribution characteristics and the phase separation process is investigated in detail. The performance of an existing phase separation model which considers physical properties and the initial Sauter mean diameter was evaluated, showing quite satisfying predictive power. Its predictive power might be further increased by including more information about the whole drop size distribution in future studies.
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