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.
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
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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).
•Rainfall partitioning is the most influenced by amount of rainfall and its intensity.•Drop diameter and velocity significantly influenced rainfall partitioning.•Affecting variables differ among ...vegetation periods and tree species.
Rainfall partitioning is an important part of the ecohydrological cycle, influenced by numerous variables. Rainfall partitioning for pine (Pinus nigra Arnold) and birch (Betula pendula Roth.) trees was measured from January 2014 to June 2017 in an urban area of Ljubljana, Slovenia. 180 events from more than three years of observations were analyzed, focusing on 13 meteorological variables, including the number of raindrops, their diameter, and velocity. Regression tree and boosted regression tree analyses were performed to evaluate the influence of the variables on rainfall interception loss, throughfall, and stemflow in different phenoseasons. The amount of rainfall was recognized as the most influential variable, followed by rainfall intensity and the number of raindrops. Higher rainfall amount, intensity, and the number of drops decreased percentage of rainfall interception loss. Rainfall amount and intensity were the most influential on interception loss by birch and pine trees during the leafed and leafless periods, respectively. Lower wind speed was found to increase throughfall, whereas wind direction had no significant influence. Consideration of drop size spectrum properties proved to be important, since the number of drops, drop diameter, and median volume diameter were often recognized as important influential variables.
Diesel engine performance and emissions are closely related to fuel atomization and spray processes, which in turn are strongly influenced by nozzle geometry. In this study, five kinds of single-hole ...cylindrical injectors which have different orifice diameters (0.13–0.23mm) and lengths (0.7–1.0mm) were employed to research the effects of the nozzle geometry on spray droplet size distribution and corresponding combustion characteristics. The spray droplet size spatial distribution was measured with the Phase Doppler Particle Analyzer (PDPA). The results show that the Sauter Mean Diameter (SMD) reduces with the increase of the distance from injector tip and the SMD of the central axis is bigger than that of the periphery. With the increase of the injection pressure (40–120MPa), the spray SMD decreases significantly. In addition, as the orifice diameter goes smaller, the SMD decreases and the effect of the orifice diameter on the spray SMD becomes weak. Meanwhile, as the orifice length goes longer, the SMD decreases when the orifice diameter is 0.13mm. And then, the combustion characteristics were experimentally investigated in a constant volume chamber with optical access. Time-resolved images of the natural luminosities (indicator of soot) from the combustion process were captured by high speed camera and combustion pressure was also acquired. It is found that there is a good corresponding relationship between spray SMD, combustion heat release rate and flame luminosity. That is to say, the way to decrease SMD reduces greatly the natural luminosities and improves combustion heat release rate. This article presents the effects of nozzle geometry on droplet size distribution and combustion, and provides important references for injector manufacture.
•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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We build a tractable growth model in which multiproduct incumbents invest in internal innovations to improve their existing products, while new entrants and incumbents invest in external innovations ...to acquire new product lines. External and internal innovations generate heterogeneous innovation qualities, and firm size affects innovation incentives. We analyze how different types of innovation contribute to economic growth and the role of the firm size distribution. Our model aligns with many observed empirical regularities, and we quantify our framework with Census Bureau and patent data for US firms. Internal innovation scales moderately faster with firm size than external innovation.
•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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