Size Spectrum Research Articles

Controlling the Particle Size and Absorption Spectra of Honey Mediated Green Synthesis of Silver Nanoparticles for Antibacterial Application

Silver nanoparticles were synthesized using locally purchased honey and silver nitrate solution. This method provides a simplistic and straightforward approach to the formation of silver nanoparticles. The silver nanoparticles with varying amounts of silver nitrate solution were characterized using ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. In addition, dynamic light scattering characterization was used to determine the average size and size distribution of silver nanoparticles. Experimental results revealed that varying the amount of silver nitrate solution can control the size and absorption spectra of silver nanoparticles. A large amount of silver nitrate solution will exhibit a peak in the higher wavelength. The shifting of the absorption peaks at 401, 406, 407, 408, and 409 nm are believed to be related to the wavelength of the surface plasmon resonance. Moreover, a larger amount of silver nitrate solution also results in an increasing size with 27.2, 57.9, and 63.4 nm as revealed in the size distribution via dynamic light scattering. This green synthesis method of silver nanoparticles will provide a cost-effective production as an alternative to commercial antibacterial agents.

Cells of matter and life – towards understanding the structuring of particles and plankton patchiness in the Arctic fjords

As the environmental conditions are typically not homogenous, especially in coastal regions, they must provide a mosaic of distinct habitats that can be occupied by particles and plankton in a characteristic way. Here we analyze and map the spatio-temporal distribution patterns and the internal structure of 94 patches of various size fractions of particles and plankton studied by fine resolution measurements of two compatible laser counters performed in the upper epipelagial of two Arctic fjords over six summer seasons. Detected patches generally occupied only the minor part of the studied upper water column (on average 12%), and frequently occurred as multi-size-fraction forms. The observed concentrations within the patches were mostly 1.6 times higher than the background concentrations (max 4.1). The patches ranged in size horizontally from 1 to 92 km (median length 12 km) and vertically from 5 to 50 m (median 26 m). Because the designated patches varied in terms of their shapes and internal structure, a novel classification approach to of patches is proposed. Accordingly, seven types of patches were distinguished: Belt, Triangle, Diamond, Flare, Fingers, Flag, and Rosette. The particles and plankton exhibited all types of these distribution patterns, regardless of the size fraction and location. The observed steepening size spectra slopes over years implies that proliferating Atlantic water advection, triggering increasing role of the smallest size fractions, played the crucial role on compositional dynamics on temporal scale. The recurring high concentration patches of particles and plankton near glaciers suggest that their melting, together with biological production, were the strongest factors generating patchiness on the local scale. An observed under several occasions depth differentiation among size fractions building together vertically thin multi-size-fraction patches is an interesting feature for further studies. Even if distribution patterns of particles and plankton did not clearly reflect all patterns in the environmental water structuring, they happened to be related to the presence of glacier runoff, eddy, sea mountain and hot spots of chlorophyll fluorescence.

Effect of Internal Decay Power and Surface Cooling on Nuclear Fuel Droplet Solidification During MFCI in a SFR—A Numerical Study

Melting of the nuclear core is one of the severe accident scenarios in a Sodium-cooled Fast Reactor (SFR). During such an event, molten corium may come into contact with the coolant sodium. This interaction of the molten fuel and the coolant is commonly termed molten fuel–coolant interaction (MFCI) in the nuclear industry. In this study, a numerical analysis is carried out to study the solidification of a molten fuel droplet in the liquid sodium pool. In the first part of the study, the effect of constant internal heat generation on the solidification of the droplet is evaluated with convective heat dissipation prescribed at the droplet surface. The internal heat generation (decay power) and the heat transfer coefficient are varied as parameters, and the time required for complete solidification of the molten droplet is obtained. Based on the results, the freezing of the droplet is categorized into three regimes: conduction limited, transition, and internal heat generation dominated regimes. It is observed that the solidification process of nuclear fuel droplets generated during MFCI is not influenced by internal heat generation and lies in a conduction-limited regime for decay power level prevailing in a medium-sized SFR. Hence, in the next part of the study, the numerical analysis is carried out by incorporating the time-dependent decay power and the temperature-dependent heat transfer coefficient in the computational model by developing user-defined subroutines depicting a realistic scenario of an accident. The results of the analysis show that because of the high subcooling of sodium, film boiling is ruled out; nucleate boiling with a maximum heat transfer rate occurs briefly. The heat transfer coefficient then declines as the interface temperature between the droplet and the sodium decreases rapidly until the natural convective regime is reached. A parametric study on the droplet diameter is also carried out by varying the diameter from 0.5 to 10 mm, spanning the typical particle size spectrum expected during MFCI.

Temperature impacts on fish physiology and resource abundance lead to faster growth but smaller fish sizes and yields under warming.

Resolving the combined effect of climate warming and exploitation in a food web context is key for predicting future biomass production, size-structure and potential yields of marine fishes. Previous studies based on mechanistic size-based food web models have found that bottom-up processes are important drivers of size-structure and fisheries yield in changing climates. However, we know less about the joint effects of 'bottom-up' and physiological effects of temperature; how do temperature effects propagate from individual-level physiology through food webs and alter the size-structure of exploited species in a community? Here, we assess how a species-resolved size-based food web is affected by warming through both these pathways and by exploitation. We parameterize a dynamic size spectrum food web model inspired by the offshore Baltic Sea food web, and investigate how individual growth rates, size-structure, and relative abundances of species and yields are affected by warming. The magnitude of warming is based on projections by the regional coupled model system RCA4-NEMO and the RCP 8.5 emission scenario, and we evaluate different scenarios of temperature dependence on fish physiology and resource productivity. When accounting for temperature-effects on physiology in addition to on basal productivity, projected size-at-age in 2050 increases on average for all fish species, mainly for young fish, compared to scenarios without warming. In contrast, size-at-age decreases when temperature affects resource dynamics only, and the decline is largest for young fish. Faster growth rates due to warming, however, do not always translate to larger yields, as lower resource carrying capacities with increasing temperature tend to result in decline in the abundance of larger fish and hence spawning stock biomass. These results suggest that to understand how global warming affects the size structure of fish communities, both direct metabolic effects and indirect effects of temperature via basal resources must be accounted for.

Relationship between Biodegradation Rate and Grain Size Itself Excluding Other Structural Factors Caused by Alloying Additions and Deformation Processing for Pure Mg.

This work studied the relationship between biodegradation rate and grain size itself, excluding other structural factors such as segregations, impure inclusions, second phase particles, sub-structures, internal stresses and textures caused by alloying additions and deformation processing for pure Mg. A spectrum of grain size was obtained by annealing through changing the annealing temperature. Grain boundary influenced the hardness and the biodegradation behavior. The hardness was grain size-dependent, following a typical Hall–Petch relation: . The biodegradation rate decreased with decreasing grain size, following a similar Hall–Petch relation: or . This work should be helpful for better controlling biodegradation performance of biodegradable Mg alloys through varying their grain size.

Use of Space by black-and-gold howler monkeys (Alouatta caraya) in an urban environment in Paraguay

AbstractAs urbanisation continues to reduce the available habitat for wildlife, some species, including the black-and-gold howler monkey (Alouatta caraya) in Pilar, southwest Paraguay, are making their homes in anthropogenic environments. Understanding an animal’s home range is an important step to understanding its ecological needs, and an essential requirement for the creation of robust conservation plans. In this study, we determined the home ranges and core areas of five groups of urban dwelling A. caraya using Minimum Convex Polygon (MCP) and Kernel Density Estimation (KDE) Analysis. We used a Spearman’s Correlation to explore the relationship between home range size and group size. All five groups had home ranges of less than 10 ha and used core areas of less than 1 ha. Group size had no significant relationship to home range size. We provide the first estimates of home range for A. caraya in an urban environment in Paraguay. Though the home ranges of the urban A. caraya in Pilar, Paraguay fall at the smaller end of the spectrum of range sizes in Alouatta, they are not abnormal for a species in this genus.

Comparison of fish size spectra obtained from hydroacoustics and gillnets across seven European natural lakes

We conducted a systematic evaluation of the correspondence in fish length data obtained from vertical hydroacoustics and gillnetting across seven European natural lakes differing in abiotic and biotic characteristics. Length data were analyzed as continuous size spectra characterized by their maximum-likelihood estimated exponents b. First, we examined the relationship between size spectra obtained from the two sampling methods. We then examined whether size spectra from the two methods were correlated with lake descriptors separately or in combination. The modeled relationship between the exponents b from the two methods showed that the exponent b from the hydroacoustics was, on average, the same as that from the gillnet sampling in the seven lakes. The exponents b from the hydroacoustics and gillnets, when averaged, were significantly correlated with lake depth, while their differences were significantly correlated with mean air temperature. To conclude, the overall good correspondence between the continuous size distributions obtained by both methods supports the application of vertical hydroacoustics in acquiring size structure of fish communities in lakes, but not in fully replacing the invasive gillnetting. Yet, some specific methodological details require further research.

Effect of Image Segmentation Thresholding on Droplet Size Measurement

Droplet size spectrum is a key factor in pesticide application because it affects the biological efficacy of a treatment in terms of target coverage, environmental impact in terms of evaporation, drift and run-off, and operator’s safety in terms of inhalation and dermal exposure. Droplet measurement methods based upon image analysis have to face the “binarization” or “segmentation” process, by which the objects of interest (the droplets) are extracted from the background. Segmentation is carried out by choosing appropriate threshold values, mostly based on the operator’s experience. In this study, images of droplets of an air induction nozzle TVI 8002 at four pressures (0.3, 0.5, 1.0, and 1.5 MPa) were obtained using the liquid immersion method. Each image was processed multiple times, firstly by using a “reference” threshold value based on the operator’s experience and then by using 11 different threshold values, chosen in the range of around ±5% of the reference threshold and based upon the average gray level of the image. For each threshold value, the corresponding spray parameters (volumetric diameters, mean diameters, Sauter diameters, and numeric diameters) were analyzed. The results showed that spray parameters had a statistically significant linear trend with respect to the threshold values in most cases. However, in absolute terms, variations were almost always less than 1.0% of reference values. This result allows considering the image acquisition system used in the present study as an automatic tool able to select the threshold according to the gray level of the image, making the whole segmentation process faster, more objective, and less dependent on the operator’s experience.

Impact of warming on aquatic body sizes explained by metabolic scaling from microbes to macrofauna

Rising temperatures are associated with reduced body size in many marine species, but the biological cause and generality of the phenomenon is debated. We derive a predictive model for body size responses to temperature and oxygen (O2) changes based on thermal and geometric constraints on organismal O2 supply and demand across the size spectrum. The model reproduces three key aspects of the observed patterns of intergenerational size reductions measured in laboratory warming experiments of diverse aquatic ectotherms (i.e., the "temperature-size rule" [TSR]). First, the interspecific mean and variability of the TSR is predicted from species' temperature sensitivities of hypoxia tolerance, whose nonlinearity with temperature also explains the second TSR pattern-its amplification as temperatures rise. Third, as body size increases across the tree of life, the impact of growth on O2 demand declines while its benefit to O2 supply rises, decreasing the size dependence of hypoxia tolerance and requiring larger animals to contract by a larger fraction to compensate for a thermally driven rise in metabolism. Together our results support O2 limitation as the mechanism underlying the TSR, and they provide a physiological basis for projecting ectotherm body size responses to climate change from microbes to macrofauna. For small species unable to rapidly migrate or evolve greater hypoxia tolerance, ocean warming and O2 loss in this century are projected to induce >20% reductions in body mass. Size reductions at higher trophic levels could be even stronger and more variable, compounding the direct impact of human harvesting on size-structured ocean food webs.

Dust in the wind with resonant drag instabilities – I. The dynamics of dust-driven outflows in GMCs and H ii regions

ABSTRACT Radiation-dust driven outflows, where radiation pressure on dust grains accelerates gas, occur in many astrophysical environments. Almost all previous numerical studies of these systems have assumed that the dust was perfectly coupled to the gas. However, it has recently been shown that the dust in these systems is unstable to a large class of ‘resonant drag instabilities’ (RDIs) which de-couple the dust and gas dynamics and could qualitatively change the non-linear outcome of these outflows. We present the first simulations of radiation-dust driven outflows in stratified, inhomogeneous media, including explicit grain dynamics and a realistic spectrum of grain sizes and charge, magnetic fields and Lorentz forces on grains (which dramatically enhance the RDIs), Coulomb and Epstein drag forces, and explicit radiation transport allowing for different grain absorption and scattering properties. In this paper, we consider conditions resembling giant molecular clouds (GMCs), H ii regions, and distributed starbursts, where optical depths are modest (≲1), single-scattering effects dominate radiation-dust coupling, Lorentz forces dominate over drag on grains, and the fastest-growing RDIs are similar, such as magnetosonic and fast-gyro RDIs. These RDIs generically produce strong size-dependent dust clustering, growing non-linear on time-scales that are much shorter than the characteristic times of the outflow. The instabilities produce filamentary and plume-like or ‘horsehead’ nebular morphologies that are remarkably similar to observed dust structures in GMCs and H ii regions. Additionally, in some cases they strongly alter the magnetic field structure and topology relative to filaments. Despite driving strong micro-scale dust clumping which leaves some gas ‘behind,’ an order-unity fraction of the gas is always efficiently entrained by dust.

Can size distributions of European lake fish communities be predicted by trophic positions of their fish species?

An organism's body size plays an important role in ecological interactions such as predator–prey relationships. As predators are typically larger than their prey, this often leads to a strong positive relationship between body size and trophic position in aquatic ecosystems. The distribution of body sizes in a community can thus be an indicator of the strengths of predator–prey interactions. The aim of this study was to gain more insight into the relationship between fish body size distribution and trophic position in a wide range of European lakes. We used quantile regression to examine the relationship between fish species' trophic position and their log‐transformed maximum body mass for 48 fish species found in 235 European lakes. Subsequently, we examined whether the slopes of the continuous community size distributions, estimated by maximum likelihood, were predicted by trophic position, predator–prey mass ratio (PPMR), or abundance (number per unit effort) of fish communities in these lakes. We found a positive linear relationship between species' maximum body mass and average trophic position in fishes only for the 75% quantile, contrasting our expectation that species' trophic position systematically increases with maximum body mass for fish species in European lakes. Consequently, the size spectrum slope was not related to the average community trophic position, but there were negative effects of community PPMR and total fish abundance on the size spectrum slope. We conclude that predator–prey interactions likely do not contribute strongly to shaping community size distributions in these lakes.

Water-in-Water Droplets Selectively Uptake Self-Assembled DNA Nano/Microstructures: a Versatile Method for Purification in DNA Nanotechnology.

DNA is an excellent material for constructing self‐assembled nano/microstructures. Owing to the widespread use of DNA as a building block in laboratories and industry, it is desirable to increase the efficiency of all steps involved in producing self‐assembled DNA structures. One of the bottlenecks is the purification required to separate the excess components from the target structures. This paper describes a purification method based on the fractionation by water‐in‐water (W/W) droplets composed of phase‐separated dextran‐rich droplets in a polyethylene glycol (PEG)‐rich continuous phase. The dextran‐rich droplets facilitate the selective uptake of self‐assembled DNA nano/microstructures and allow the separation of the target structure. This study investigates the ability to purify DNA origami, DNA hydrogels, and DNA microtubes. The W/W‐droplet fractionation allows the purification of structures of a broad size spectrum without changes to the protocol. By quantifying the activity of deoxyribozyme‐modified DNA origami after W/W‐droplet purification, this study demonstrates that this method sufficiently preserves the accessibility to the surface of a functional DNA nanostructure. It is considered that the W/W‐droplet fractionation could become one of the standard methods for the purification of self‐assembled DNA nano/microstructures for biomedical and nanotechnology applications owing to its low cost and simplicity.

Size spectrum model reveals importance of considering species interactions in a freshwater fisheries management context

AbstractInland fisheries have a significant cultural and economic value around the globe, providing dietary protein, income, and recreation. Consequently, methods for monitoring and managing these important fisheries are continually being refined. In marine systems, multispecies size spectrum models have been increasingly used to explore management scenarios of important fish stocks within an ecosystem‐based fisheries management framework; however, these models have not been applied as extensively in freshwater systems. In this study, we developed a multispecies size spectrum model for the fish community of Lake Nipissing, a large, productive lake in Ontario, Canada. To the best of our knowledge, this is the first fully calibrated multispecies size spectrum model for an inland fishery. Using this model, we explored the impacts of potential fishing regimes and management scenarios on fish community dynamics while taking species interactions into account. Specifically, we examined how changes in fishing mortality affect (1) species biomass, (2) community size structure, and (3) stock recovery times. We found that community dynamics following changes in fishing mortality were driven by complex interactions among species, including competition and predation. The greatest changes in biomass and community size structure were observed following changes in fishing mortality of top predators, with community size structure most strongly influenced by changes in the mortality of the largest species. Counter to predictions based on generation time, the smallest species in our model exhibited the longest time to recovery due to strong competition and predation. Our results demonstrate the importance of considering species interactions in the management of inland fisheries and highlight the potential of size spectrum model use in freshwater systems.

The paralarval stage as key to predicting squid catch: Hints from a process-based model

Squid species show pronounced interannual variability in population size. While this may partially reflect changes in fisheries pressure, it is thought to be primarily the result of environmental variability. Most squid have an annual life cycle with only a short period dedicated to reproduction. With little overlap between generations, the environment can exert a major influence on stock size. In this study we explore, through a combination of process-based modelling and statistical analysis, whether environmental variability explains variability in catch of the chokka squid, Loligo reynaudii, over the Agulhas Bank off South Africa. We focus on growth and survival during the first two months spent as “paralarva” in the pelagic. This period has been suggested to be a key bottleneck and a potential predictor of catch. To describe prey availability and predation pressure, we develop a dynamic model of the size spectrum (1 mg–1000 kg) of the ecosystem over the Agulhas Bank, with trophic interactions governed by size. In tandem, we develop a model for the growth of individual L. reynaudii, which specifies where in the size spectrum individual squid can be found at each stage of their development. We find a correlation of 0.74 between modelled biomass representative for L. reynaudii at the end of its paralarval stage and catch per unit effort (CPUE) in the subsequent season in the period 1995–2015. This suggests that the paralarval stage is indeed a bottleneck: modelled food availability and predation pressure experienced by paralarvae explains 55% of the variability in CPUE, which is a proxy for spawning stock biomass. As the paralarval stage ends approximately nine months before the time of spawning and maximum catch, this work could be used to develop catch predictor with a nine-month lag.

Phytoplankton size distributions in the western North Atlantic and their seasonal variability

AbstractPhytoplankton play a major role on Earth, impacting the global distribution and cycles of carbon, oxygen, nitrogen, sulfur, and other elements, and structuring marine food webs. One fundamental trait of phytoplankton with direct biogeochemical implications is their size, as it governs metabolic and sinking rates as well as prey–predator interactions. Phytoplankton size spans approximately 3.5 orders of magnitude (when expressed as an equivalent spherical diameter), and thus measuring the full range in size distribution of phytoplankton is challenging and rarely attempted. Here, we constructed phytoplankton size spectra by merging state‐of‐the‐art cytometry and imaging cytometry measurements that were collected in the western North Atlantic Ocean, along a latitudinal gradient (36°N to 55°N) and during different phases of the annual cycle of phytoplankton. The derived spectra show a seasonal pattern that parallels changes in phytoplankton biomass, and do not always follow a commonly assumed power‐law model. Shifts in size spectra were more pronounced in the sub‐Arctic and temperate subregions, compared to the subtropical region of the study area. We evaluated the relationships between different size groups and environmental parameters to derive ecologically meaningful size groups. Finally, to simulate Ocean Color remote‐sensing algorithms of phytoplankton size, we compared temporal variations in descriptors of the size spectra (median particle size, phytoplankton size distribution exponent) with optical size proxies derived from light absorption and attenuation; good agreement was observed in the northern sections of the study area where temporal changes in community size structure were more pronounced.

The characteristics of particulate matter during an air pollution process revealed by joint observation of multiple equipments

During a particle pollution in Hefei, Anhui Province from November 25 to December 9, 2018, we used a set of particle monitoring devices with different principles installed on the top floor of a 5-story experimental building to observe the mass concentration, particle diameter distribution and chemical composition. The results show that this pollution process can be divided into three stages: accumulation, outbreak and dissipation. At the beginning of pollution outbreak, it can be observed through the lidar that particulate matter first appears in the upper part of the boundary layer, and then accumulates downward and develops into ground pollution. During the pollution outbreak, particulate matter with an equivalent diameter of 0.8–1.6 μm increases significantly, with an average increase of more than 50%. In the particle size spectrum, the full width at half maximum also increases, and the particle diameter at the peak is about 0.76 μm. Furthermore, the change in particle size over time shows that the number concentration of particles with smaller size grows before those with larger size. By identifying and comparing characteristic ions, we found that the increase in the number of sulfate particles and the increase of their size correspond well to the outbreak of pollution, and the rapid decline in the fraction of sulfate corresponds well to the dissipation of pollution too. Sulfate is the most sensitive factor in the pollution process. The EC is the main component throughout the pollution process, but EC responds more slowly to pollution changes than sulfate, it is important but less sensitive.

Horizontal geometry of trade wind cumuli – aircraft observations from a shortwave infrared imager versus a radar profiler

Abstract. This study elaborates on how aircraft-based horizontal geometries of trade wind cumulus clouds differ whether a one-dimensional (1D) profiler or a two-dimensional (2D) imager is used. While nadir profiling devices are limited to a 1D realization of the cloud transect size, with limited representativeness of horizontal cloud extension, 2D imagers enhance our perspectives by mapping the horizontal cloud field. Both require high resolutions to detect the lower end of the cloud size spectrum. In this regard, the payload aboard the HALO (High Altitude and LOng Range Research Aircraft) achieves a comparison and also a synergy of both measurement systems. Using the NARVAL II (Next-Generation Aircraft Remote-Sensing for Validation Studies) campaign, we combine HALO observations from a 35.2 GHz cloud and precipitation radar (1D) and from the hyperspectral 2D imager specMACS (Munich Aerosol Cloud Scanner), with a 30 times higher along-track resolution, and compare their cloud masks. We examine cloud size distributions in terms of sensitivity to sample size, resolution and the considered field of view (2D or 1D). This specifies impacts on horizontal cloud sizes derived from the across-track perspective of the high-resolution imager in comparison to the radar curtain. We assess whether and how the trade wind field amplifies uncertainties in cloud geometry observations along 1D transects through directional cloud elongation. Our findings reveal that each additional dimension, no matter of the device, causes a significant increase in observed clouds. The across-track field yields the highest increase in the cloud sample. The radar encounters difficulties in characterizing the trade wind cumuli size distribution. More than 60 % of clouds are subgrid scale for the radar. The radar has issues in the representation of clouds shorter than 200 m, as they are either unresolved or are incorrectly displayed as single grid points. Very shallow clouds can also remain unresolved due to too low radar sensitivity. Both facts deteriorate the cloud size distribution significantly at this scale. Double power law characteristics in the imager-based cloud size distribution do not occur in radar observations. Along-track measurements do not necessarily cover the predominant cloud extent and inferred geometries' lack of representativeness. Trade wind cumuli show horizontal patterns similar to ellipses, with a mean aspect ratio of 3:2 and having tendencies of stronger elongation with increasing cloud size. Instead of circular cloud shape estimations based on the 1D transect, elliptic fits maintain the cloud area size distribution. Increasing wind speed tends to stretch clouds more and tilts them into the wind field, which makes transect measurements more representative along this axis.

Role of gas–molecular cluster–aerosol dynamics in atmospheric new-particle formation

New-particle formation from vapors through molecular cluster formation is a central process affecting atmospheric aerosol and cloud condensation nuclei numbers, and a significant source of uncertainty in assessments of aerosol radiative forcing. While advances in experimental and computational methods provide improved assessments of particle formation rates from different species, the standard approach to implement these data in aerosol models rests on highly simplifying assumptions concerning gas–cluster–aerosol dynamics. To quantify the effects of the simplifications, we develop an open-source tool for explicitly simulating the dynamics of the complete particle size spectrum from vapor molecules and molecular clusters to larger aerosols for multi-compound new-particle formation. We demonstrate that the simplified treatment is a reasonable approximation for particle formation from weakly clustering chemical compounds, but results in overprediction of particle numbers and of the contribution of new-particle formation to cloud condensation nuclei for strongly clustering, low-concentration trace gases. The new explicit approach circumvents these issues, thus enabling robust model–measurement comparisons, improved assessment of the importance of different particle formation agents, and construction of optimal simplifications for large-scale models.

Microphysical structure and vertical evolution of continental cumulus clouds from analysis of aircraft measurements in Northern China

Microphysical characteristics of continental cumulus in relatively remote area of Northern China were studied using King Air aircraft that equipping with several cloud probes in summer of 2020. Penetrating of cumuli was achieved at several altitudes. Aircraft based KPR cloud radar showed the depth of cumulus was over 4000 m and the cloud base was near 2000 m above sea level. Cloud droplet number concentration was 400–800 cm−3 at 3700–4300 m and decreased to 200 cm−3 at the cloud top. Cloud droplet effective diameter increased linearly with height (3.33 μm km−1) from 12 μm (3700 m) to 18 μm (5500 m), as the result of droplet growth by condensation or accretion, during the vertical evolution of cloud from initial generation to mature stage. Cloud droplet size spectra presented a single mode at all altitudes and the broadening of spectra with increasing altitude was apparent. LWC adiabatic ratios of <0.3 for all altitudes indicated the strong entrainment mixing from dry air, since most of the clouds were penetrated near cloud margins. At 4300 m, drizzle drop concentration reached 17 L−1 (diameter of 60 μm) and high concentration of ice (175 L−1, diameter gathered at 150 μm and over 1000 μm) containing primarily graupels was related to the secondary ice process during riming (Hallett–Mossop). Supercooled drizzle drops (60, 100 and 150 μm in diameter) and ice particles (100–400 μm in diameter) both had concentrations of several counts per liter at 5500 m. At the convective cloud top (6200 m), high concentrations of drizzle drops and ice particles (mainly graupels) revealed their large growth rates as atmospheric condition was more fit for the redistribution and collision/coalescence of cloud particles. To better learn the large differences of cloud properties and related microphysics for distinct levels of well-developed continental cumulus, more aircraft measurements, particularly across the cloud cores, are needed.

Uncertainty matters: ascertaining where specimens in natural history collections come from and its implications for predicting species distributions

Natural history collections (NHCs) represent an enormous and largely untapped wealth of information on the Earth's biota, made available through GBIF as digital preserved specimen records. Precise knowledge of where the specimens were collected is paramount to rigorous ecological studies, especially in the field of species distribution modelling. Here, we present a first comprehensive analysis of georeferencing quality for all preserved specimen records served by GBIF, and illustrate the impact that coordinate uncertainty may have on predicted potential distributions. We used all GBIF preserved specimen records to analyse the availability of coordinates and associated spatial uncertainty across geography, spatial resolution, taxonomy, publishing institutions and collection time. We used three plant species across their native ranges in different parts of the world to show the impact of uncertainty on predicted potential distributions. We found that 38% of the 180+ million records provide coordinates only and 18% coordinates and uncertainty. Georeferencing quality is determined more by country of collection and publishing than by taxonomic group. Distinct georeferencing practices are more determinant than implicit characteristics and georeferencing difficulty of specimens. Availability and quality of records contrasts across world regions. Uncertainty values are not normally distributed but peak at very distinct values, which can be traced back to specific regions of the world. Uncertainty leads to a wide spectrum of range sizes when modelling species distributions, potentially affecting conclusions in biogeographical and climate change studies. In summary, the digitised fraction of the world's NHCs are far from optimal in terms of georeferencing and quality mainly depends on where the collections are hosted. A collective effort between communities around NHC institutions, ecological research and data infrastructure is needed to bring the data on a par with its importance and relevance for ecological research.