Small Temporal Scales Research Articles

Photogrammetric determination of movement speed of invasive Indo-Pacific lionfish in the Florida Keys.

As a key determinant of how efficiently lionfish (Pterois sp.) locate and capture prey, swimming speed plays a crucial role in shaping the predator-prey interactions and broader ecological dynamics within the invaded ecosystems. Swimming speed on a small temporal and spatial scale is difficult to measure because of the need for precise measurements of both distance and duration of the behavior. Using photogrammetry by way of stereo-camera setups is ideal for analyzing the minutiae of lionfish behaviors because it can include the benefits of remote video traps coupled with precise measurements of movements in three-dimensional space and time. The primary objective of this study was to identify and characterize lionfish behavior associated with different movement speeds, and then to quantify small-scale swimming speeds of lionfish associated with those behaviors. Swimming speeds were classified under three different observed behaviors: relaxed swimming, traverse swimming, and striking at prey. The differences between these behaviors were primarily distinguished based on body and fin positioning, as well as the apparent intent of the motion if any was evident. The mean lionfish swimming speed from stereoscopic camera footage was 44.75 mms-1 for relaxed swimming, 138.99 mm s-1 for traverse swimming, and 625.44 mm s-1 for striking at prey. Swimming speed can be used to quantify how much habitat area a lionfish may cover in a day, and therefore the amount of prey that may be encountered by a predator. Lionfish feeding success under different environmental conditions could be an important factor in understanding their survival and growth in areas where they are found.

Numerical study on temperature response of microheater and evolution characteristics of superheated zone under fast transient heating

The nucleate boiling process that occurs on the surface of a microheater immersed in a liquid pool under fast transient heating conditions can be regarded as homogeneous or near-homogeneous nucleation, exhibiting a significant difference when compared to boiling at conventional time scales on large and even micro spatial scales. This paper numerically investigates the boiling process at both small spatial and temporal scale by using a validated model. Results indicate a significant difference between the average microheater temperature and the maximum temperature at the boiling surface, which can reach up to 80 °C within the scope of present study. Consequently, the nucleation temperature, typically determined by the average temperature of the microheater in most references, may not precisely represent the homogeneous (or nearly homogeneous) nucleation temperature. At the initiation of nucleation, the profiles at the boundary of superheated zone are approximately circular in the z-plane and arched in the x-plane, respectively. Meanwhile, the profile of the superheated zone boundary at the onset of nucleation under direct heating mode (DHM) appears approximately trapezoidal, exhibiting a significant difference from that observed under indirect heating mode (IHM). It is also noted that the local temperature distribution in the fluid region can be considerably affected by natural convection, potentially exerting a substantial influence on the bubble dynamic behaviors during the subsequent bubble growing phase. These findings may provide valuable references for future experimental study on the mechanisms involving in microscale boiling heat transfer process under rapid heating conditions.

Temporal-spatial variability of grazing behaviors of yaks and the drivers of their intake on the eastern Qinghai-Tibetan Plateau.

Grassland-livestock balance is an important principle of sustainable development of grassland livestock production and grassland ecosystem health. Grassland degradation becomes more serious at global scales and especially at the area that is sensitive to climate change and human activities. Decreases in pasture biomass and shifts in plant community composition in degraded grasslands can largely affect grazing behaviors of livestock. Up to date, however, it is unclear that whether livestock behaviors change across spatial and temporal scales and what key factors are to shape observed behavioral patterns of livestock. Here, yak behaviors including grazing, rumination and walking on the eastern Qinghai-Tibetan Plateau (QTP) were monitored by a continuous visual observation, to investigate temporal and spatial variations of grazing behavior of yaks (Bos grunniens); based on the data from public database in the past 18 years, a meta-analysis was conducted to examine the main factors that affect grazing behaviors and intake of yaks. We showed that grazing behaviors of yaks differed significantly within hours, among hours of each day and among days as well as across different observation sites. Intake rate of yaks was higher in the morning than in the afternoon, but walking speed showed an inverse trend compared with intake rate. Resting, altitude, the mean annual precipitation (MAP), the mean annual temperature (MAT), forage ash, yak age and season were the main predictors for yak intake, and forage and yak individual characteristics had direct effects on grazing behaviors and intake of yaks. The findings confirm that grazing behaviors of yaks can vary even at small temporal scales and regional scales, which is closely related to the shift in forage quality and biomass caused by environmental changes. The study suggests that multiple factors can be responsible for the variation in livestock behaviors and shifts in behavioral patterns may consequently lead to positive or negative feedback to grassland ecosystems through plant-animal interactions.

The response of epibenthic molluscan assemblages associated with Mytilus galloprovincialis beds to natural- and human-induced changes: Structure and small-scale spatiotemporal variability

Mussel beds are species-rich and diversified biogenic habitats for associated assemblages, playing important ecological roles and contributing significantly to local littoral invertebrate biodiversity. The community structure and seasonal patterns of molluscan assemblages associated with rocky-intertidal mussel Mytilus galloprovincialis beds along NW Atlantic coast of Morocco were investigated. Sampling was conducted at reference and contaminated stations in three distant coastal areas over a 4-season sampling period (between August 2018 and May 2019). We tested the hypothesis that the biogenic mussel habitats in areas experiencing different environmental conditions along the shore would support different associated molluscan assemblages under human-induced and natural changes at small spatial and temporal scales. A total of 6371 specimens comprising 28 taxa were identified and encompassing four trophic groups (carnivores, detritivores/deposivores, micrograzers and suspensivores). Micrograzers predominated, followed by carnivores, with gastropods being the numerically dominant taxa accounting for 79 % of total abundance. Steromphala pennanti emerged as the most abundant and frequent species, across almost all seasons and stations contributing to 31 % of total abundance. Significant seasonal variations were observed in species richness and Shannon-Wiener’s index (ANOVA, p<0.05), with the highest values recorded at the most polluted stations during cold/wet periods, and the lowest at the cleanest stations during hot/warm periods. Furthermore, the ANOVA analyses unveiled a significant spatiotemporal variation in abundance, emphasizing the dynamic nature of molluscan assemblages in response to environmental conditions and seasonal changes. The multivariate structure of associated molluscan assemblages (PERMANOVA analysis) differed significantly among stations and seasons, highlighting clear geographical and seasonal effects. Gastropod species, including Acanthochitona fascicularis, Lepidochitona cinerea, Nucella lapillus, Patella ulyssiponensis, P. vulgata, Phorcus lineatus, P. sauciatus, and Steromphala pennanti, were identified as the most contributive species to the dissimilarity of molluscan assemblage structure among stations throughout seasons (SIMPER analysis). Based on the canonical correspondence analysis results, salinity, water temperature, nutrient concentrations, sediment granulometry and total organic matter were identified as the key factors driving changes in the molluscan community structure. This study underscores the ecological importance of habitat-forming mussels as ecosystem engineers and biodiversity enhancers in shallow coastal waters along the Moroccan Atlantic coast.

Successful invasion: camera trap distance sampling reveals higher density for invasive raccoon dog compared to native mesopredators

Monitoring population parameters of invasive species gains importance as these species continue to expand all over the world. Monitoring of invasive mammalian mesopredators is, however, complicated due to their nocturnal and secretive behaviour. In the European Union, the most common invasive mesopredator is the raccoon dog (Nyctereutes procyonoides), which causes concerns for native species, such as endangered waterfowl that may be subject to nest predation. We studied the density of mesopredators in southern Finland with wildlife cameras, using methodology of distance sampling. We deployed in total of 175 camera traps around 11 (spring 2020) and 16 (spring 2021) lakes or wetlands. We inferred densities for raccoon dogs, and for native mesopredators the red fox (Vulpes vulpes) and the European badger (Meles meles) for comparison. Raccoon dogs were found to have higher overall as well as site-specific densities (about 3.7 ind./km2) than badgers (1.2 ind./km2) and red foxes (0.6 ind./km2). The raccoon dogs also were present at every study wetland, while badgers were not found at all sites. The red fox showed more diurnal activity compared to raccoon dogs and badgers. Camera trap distance sampling enabled us to provide a density estimates on a rather small spatial and temporal scale for species of similar size and movement speed. It could therefore prove valuable as a long-term monitoring option, as climate trends are likely to further enable raccoon dog expansion. Currently this invasive species appears to be the most common mesopredator around wetlands in the southern boreal zone of southern Finland.

Benefits and pitfalls of irrigation timing and water amounts derived from satellite soil moisture

Despite the key role of irrigation in the Earth system, we lack fundamental information regarding the distribution of irrigated fields, irrigation timing and the amount of water utilized. In the past years, the SM_Delta and SM_Inversion approaches have been independently developed to provide estimates of irrigation timing and water amounts based on satellite soil moisture data. The SM_Delta approach retrieves irrigation from variations in soil moisture between an individual pixel and the surrounding rainfed area, while the SM_Inversion approach estimates the total amount of water entering the soil, then irrigation is derived by subtracting precipitation. In this study, we perform a comprehensive assessment of irrigation estimates from the SM_Delta and SM_Inversion algorithms based on Sentinel-1 surface soil moisture retrievals at 1 km resolution. Our analysis focuses on the Ebro basin, an irrigated region in Spain covering 83000 km2, during the period 2017–2019. We assess the ability of the two methods to discriminate irrigated and rainfed pixels, then we quantify the agreement of irrigation timing and water volumes with reference irrigation data. An inter-comparison between estimates from the SM_Delta and SM_Inversion methods is carried out considering both temporal and spatial features, i.e., monthly irrigation peaks and spatial irrigation patterns. Finally, we explore two potential applications of satellite-derived irrigation estimates: attributing irrigation water volumes to specific irrigation systems and to individual crops. We observe that both methods erroneously retrieve irrigation over rainfed pixels, and are therefore not suitable to map irrigated and rainfed fields. However, when auxiliary information on irrigated fields is available, we find a satisfactory agreement between district-scale reference data and satellite-retrieved irrigation, using both the SM_Delta and SM_Inversion approaches (Pearson R equal to 0.67 and 0.71, bias equal to −4.99 and −4.75 mm/15 days, respectively). When aggregated in space or time, the irrigation estimates exhibit coherent temporal dynamics and spatial patterns. For instance, estimates from both SM_Delta and SM_Inversion capture the delayed irrigation that occurred in 2018 due to wetter than usual conditions in spring. However, at the pixel-scale, limited consistency exists between irrigation estimates from the two methods due to different assumptions and parameterizations, e.g., use of constant vs pixel-specific soil water capacity (in the SM_Delta and SM_Inversion, respectively). Overall, the study demonstrates the reliability of irrigation estimates derived from the SM_Delta and SM_Inversion approaches, especially when shifting from small spatial and short temporal scales (pixel level, sub-weekly) to larger and longer scales (district level, seasonal). Hence, satellite-based irrigation estimates could inform water resources managers and basin authorities, as well as serve the modelling community by providing reliable information on the timing and the amounts of water employed at the basin level.

Dynamic subsurface changes on El Hierro and La Palma during volcanic unrest revealed by temporal variations in seismic anisotropy patterns

Active hotspot volcanism is the surface expression of ongoing dynamic subsurface changes, such as the generation, transport, and stalling of magmas within the upper mantle and crust. Magmatic influx and migration affects local stress patterns in the crust and lithospheric mantle, which influences seismic anisotropy. A better understanding of those patterns helps improve robustness of models forecasting the likelihood of an eruption and prolonged seismicity, with detailed studies being required to observe the significant variations that can occur on small spatial and temporal scales. Here, we investigate seismic anisotropy before, during and after volcanic eruptions. We use local seismicity around El Hierro and La Palma, the two westernmost islands in the Canaries and sites of the most recent volcanic eruptions in the archipelago. We obtained 215 results in El Hierro during and after the 2011/2012 eruption with five three-component broadband seismic stations and 908 results around the 2021 eruption in La Palma with two three-component broadband stations. On La Palma, the majority of seismicity and splitting results are recorded during the eruption and simultaneous deflation of the island. Seismicity locations do not change significantly and fast shear wave polarisation direction is mostly constant, but some variation can be attributed to changes in the magmatic plumbing system. On El Hierro, the general radial pattern reflects stresses induced by the overall uplift of the island during multiple magma intrusion events. Temporal subsets reveal significant variations in location and depth of the events, as well as significant variations in fast polarisation direction caused by ongoing dynamic changes of under- and overpressurisation. An increase of results starting in 2018 hints towards renewed subsurface activity within deeper parts of the plumbing system, affecting the rate of overall seismicity but not any vertical movement of the island.

Endocrine mechanisms controlling the migratory disposition in birds

On Earth, billions of birds make seasonal migrations every year. Some species fly thousands of kilometers, overcoming seas, mountains and deserts on their way. For migration to be successful, birds must have perfect mechanisms for controlling its beginning, duration and termination. On the way, birds have to make many decisions: how much in energy reserves to accumulate; when to depart, how long and in which direction to fly; how to select optimal weather conditions for flight; and, finally, when and where to terminate migration. Prior to migration, birds develop a migratory disposition – a suite of changes in physiology and behavior (e.g. migratory fattening and expression of nocturnal migratory activity) which are typical for this important life-history stage. Such physiological changes and migratory behavior are the subject of hormonal regulation. The central structure that controls activity of various hormonal systems and development of migratory disposition is the hypothalamic-pituitary system. The hypothalamus controls the secretion of regulatory hormones by the pituitary gland and these hormones, in turn, regulate the activity of downstream endocrine glands. It has been established that spring migratory disposition is triggered by an increasing photoperiod, which stimulates the production of testosterone, prolactin and modulates the signaling of thyroid hormones. In contrast, it is practically unknown how autumn migratory disposition develops when the photoperiod decreases and does not stimulate release of the abovementioned hormones. While in migratory disposition, the endocrine control of behavior on the smaller temporal scales (for example, the level of fuel accumulation, or decision to depart from a migratory stopover) is associated with the combined action of melatonin, corticosterone, insulin, glucagon, adipokines, and other hormones and neurotransmitters. In this review, I will describe the role of these hormones in the control of migratory traits, highlight the existing inconsistencies, and present possible ways to progress in this area of research. A knowledge of endocrine regulation of migratory behavior will help to predict the limits of species adaptability, explain current population trends, and inform conservation actions, which is especially important in the light of modern climate change and anthropogenic transformation of landscapes.

Validation of Rotating Detonation Combustor Computational Fluid Dynamics Simulations for Predicting Unsteady Supersonic–Subsonic Flow Field at the Exit

Abstract Rotating detonation combustors (RDCs) have gained increased interest for integration with power-generating gas turbines due to the potential to increase thermal efficiency. The unsteady flow field exiting the RDC is fundamentally different compared to traditional swirl-stabilized combustors. Successful integration of RDC with gas turbines will depend on the ability to properly condition the unsteady flow to achieve performance levels comparable to swirl-stabilized combustors. RDC simulations require significant computational resources due to the small spatial and temporal time scales required to resolve the detonation phenomenon. Furthermore, traditional steady-state computational fluid dynamics (CFD) analyses are not possible for RDC simulations. The present study develops and validates a computationally efficient approach for predicting unsteady flow fields exiting the combustor using 2D, transient reacting CFD with periodic boundary conditions in the combustor and a downstream plenum. Validation is performed by comparing the CFD results to various experimental measurements: (i) wave speed obtained from high-speed ion probe and dynamic pressure data, (ii) average wall static pressure measurements, and (iii) time-resolved particle image velocimetry (PIV) at 100 kHz at the RDC exit. Results indicate good agreement between CFD and experiments with respect to velocity field exiting the RDC, detonation wave speed, and static pressure distribution.

Two-dimensional evolution of temperature and deformation fields during dynamic shear banding: In-situ experiments and modeling

Adiabatic shear band (ASB) is a significant failure mechanism observed in metals and alloys under impact loading. Though ASB formation has been widely assumed to be a one-dimensional thermo-mechanically-coupled instability problem, it is crucial to recognize that adiabatic shear banding is essentially a two-dimensional propagating event in space. However, it is challenging to perform in-situ characterization of temperature-deformation fields during ASB formation due to the extremely small spatial and temporal scales involved. To obtain the two-dimensional features of ASB evolution, a newly developed plane-array infrared imaging system and microspeckle-based digital image correlation (DIC) technique are synchronized with the Kolsky bar system. By incorporating interrupted tests, “quasi-synchronous” characterization of temperature-deformation-microstructure evolution during ASB formation in hat-shaped specimens of Ti–6Al–4V is achieved. A phase-field model incorporating energy-based shear banding criteria and independently calibrated model parameters is established to simulate the dynamic shear failure process, which is demonstrated to be able to well reproduce experimentally observed temperature and deformation evolution. Based on experimental characterization and simulation results, the two-dimensional features and thermo-mechanical aspects of ASB formation are presented. Energy dissipation of shear banding is estimated based on the measured temperature field, demonstrating good agreement with the calibrated values in the phase-field model. The “propagation” and “percolation” modes along the band are analyzed, which can be predicted by the introduction of a shear band process zone. The influences of thermal and microstructural softening on shear failure are also clarified through a comprehensive analysis of temperature and microstructure evolution.

Where the Grass is Greener — Large-Scale Phenological Patterns and Their Explanatory Potential for the Distribution of Paleolithic Hunter-Gatherers in Europe

A unique property of the Paleolithic record is the possibility to observe human societies in large areas and over long periods of time. At these large spatial and temporal scales, a number of interesting phenomena can be observed, such as dynamics in the distribution of populations in relation to equally large-scale environmental patterns. In this paper, we focus on phenological patterns of vegetation and discuss their explanatory potential for differences in site densities in different periods and parts of Europe. In particular, we present a case-transferable approach to diachronically estimate the timing of the vegetation period and resulting phenological gradients. We discuss results for two complementary case studies. First, we look at the Aurignacian in Western and Central Europe, a period of dynamic population dispersal in a topographically heterogeneous region. Second, we focus on the Middle and Late Upper Paleolithic in the East European Plain, a period after the arrival of anatomically modern humans in a topographically rather uniform area. We visualize phenological trajectories and boundaries otherwise invisible in the archaeological record with certain explanatory potential for the observed archaeological patterns. Importantly, we do not intend to reconstruct specific plant communities or dispersal routes of animals or humans. Rather, we aim at highlighting gradients which in themselves and on small temporal scales might be comparatively weak, but over the course of millennia may potentially influence the distribution of animal biomass and human populations by biasing the aggregate of at times opposing actions of individuals towards particular directions.

Comparison of acarological risk metrics derived from active and passive surveillance and their concordance with tick-borne disease incidence

Tick-borne diseases continue to threaten human health across the United States. Both active and passive tick surveillance can complement human case surveillance, providing spatio-temporal information on when and where humans are at risk for encounters with ticks and tick-borne pathogens. However, little work has been done to assess the concordance of the acarological risk metrics from each surveillance method. We used data on Ixodes scapularis and its associated human pathogens from Connecticut (2019–2021) collected through active collections (drag sampling) or passive submissions from the public to compare county estimates of tick and pathogen presence, infection prevalence, and tick abundance by life stage. Between the surveillance strategies, we found complete agreement in estimates of tick and pathogen presence, high concordance in infection prevalence estimates for Anaplasma phagocytophilum, Borrelia burgdorferi sensu stricto, and Babesia microti, but no consistent relationships between actively and passively derived estimates of tick abundance or abundance of infected ticks by life stage. We also compared nymphal metrics (i.e., pathogen prevalence in nymphs, nymphal abundance, and abundance of infected nymphs) with reported incidence of Lyme disease, anaplasmosis, and babesiosis, but did not find any consistent relationships with any of these metrics. The small spatial and temporal scale for which we had consistently collected active and passive data limited our ability to find significant relationships. Findings are likely to differ if examined across a broader spatial or temporal coverage with greater variation in acarological and epidemiological outcomes. Our results indicate similar outcomes between some actively and passively derived tick surveillance metrics (tick and pathogen presence, pathogen prevalence), but comparisons were variable for abundance estimates.

Integrative taxonomy approach to detect spatial and temporal variability of the Mediterranean benthic communities through artificial substrate units (ASUs)

Monitoring spatial and temporal changes of marine benthic communities using standardized procedures is essential to take necessary steps towards conservation of marine ecosystems. In this study we combined Artificial Substrate Units (ASUs) for sampling of benthic communities, with integrative taxonomy approach that incorporated morphological identification of organisms and COI DNA metabarcoding, to characterize the diversity of communities at three locations across the Central Mediterranean Sea (Livorno and Palinuro, Italy; Rovinj, Croatia) in 2019 and 2020. Significant differences in the communities’ structure were observed both at large spatial scale between sampled locations, and at small spatial scale (less than ten kilometers) between sites. Moreover, significant temporal variability in species richness and structure of benthic assemblages was detected, with higher richness in 2020. Revealed variability can probably be attributed to the peculiar geomorphological, oceanographical, and ecological features of locations, but also to the influence of interplaying local chemical and physical factors and biological processes such as species settlement, competition, and migration that can act at small spatial and temporal scales. The similarity in the species composition and community structure accessed by morphological and metabarcoding approaches was low, with only 16% of the species (out of 133 species identified overall) commonly detected by both approaches. This is mostly both due to a lack of data on COI sequences of numerous benthic invertebrates in the public barcoding databases on the one hand, and difficulties in detecting small and cryptic taxa through morphological analyses on the other. This suggests that combining of two approaches is required to fully describe the biodiversity of benthic assemblages. Finally, comparison of the spatial variability of the benthic communities’ structure with two approaches at different taxonomic levels, indicated that genus and family levels give results that are consistent to those obtained by the species level. This suggests that family level might be satisfactory in monitoring the spatial-temporal variability of Mediterranean hard bottom benthic communities.

Machine‐learning modeling of hourly potential thermal refuge area: A case study from the Sainte‐Marguerite River (Quebec, Canada)

AbstractTo understand the temporal and spatial variability of thermal refuges, this study focused on modeling potential thermal refuge area (PTRA) at a sub‐daily time‐step in two tributary confluences of the Sainte‐Marguerite River (Canada) during the summers of 2020 and 2021. Aquatic ectotherm species, such as Atlantic salmon (Salmo salar), seek these refuges to avoid heat stress during high summer river temperatures. To investigate the temporal variability of these PTRA, we employed inverse weighted distance interpolation to delineate the hourly area available at both confluences. We then analyzed the impact of the atypical low flow conditions of summer 2021 on the diel cycle of PTRA extremes using the coefficient of variation and the generalized additive model (GAM). Finally, we used four supervised machine‐learning regression models and three to five hydrometeorological predictors to estimate hourly PTRA availability: multivariate adaptive splines regression (MARS), GAM, support vector machine regression (SVM), and random forest regression (RF). The results showed that tree‐based and kernel‐based regression models, RF and SVM, outperformed GAM and MARS. RF had the highest accuracy at both sites, with a relative root mean square error and Nash–Sutcliffe efficiency coefficient (Nash) of 13% and 93%, respectively. Our study discovered that under warm conditions in August 2021, small perennial tributary inflows in combination with low mainstem discharge could create high and constant PTRA at confluences, potentially providing vital thermal refuges for cold‐water taxa. These refuges may be especially important at the local level, within a specific stretch or section of the river. Given the decreasing availability of thermal refuges for salmonids, it is crucial to monitor stream temperatures at small spatial and temporal scales using data‐driven techniques in order to understand stream temperature heterogeneity at tributary confluences.

Assessing population dynamics in the Central Salish Sea, Pacific Northwest Coast of North America.

Recent developments in radiocarbon dating have enabled archaeologists to re-examine the question of population dynamism in the Salish Sea. This study expands on Taylor and colleagues (2011) using Kernel Density Estimation (KDE) and an expanded data set of 538 radiocarbon dates from academic and cultural resource management literature. The expanded sample suggests a pattern of population growth from 3200-2800 cal BP in coastal Northwestern Washington, with population growth in the San Juan islands during 2600-2200 cal BP. A subsequent decrease in radiocarbon frequencies and large sites suggests shifts in use of the San Juan Islands, followed by peak large-scale occupation from 650-300 cal BP. This pattern is robust whether marine or terrestrial dates are considered. However, marine dates are less sensitive to questions at smaller temporal scales. The broad scale radiocarbon frequency patterns observed are also consistent with those observed in southwest coastal British Columbia (Ritchie et al., 2016; Morin et al., 2018).

A Comparison of Stratospheric Gravity Waves in a High‐Resolution General Circulation Model With 3‐D Satellite Observations

AbstractAtmospheric gravity waves (GWs) play a key role in determining the thermodynamical structure of the Earth's middle atmosphere. Despite the small spatial and temporal scales of these waves, a few high‐top general circulation models (GCMs) that can resolve them explicitly have recently become available. This study compares global GW characteristics simulated in one such GCM, the Japanese Atmospheric GCM for Upper‐Atmosphere Research (JAGUAR), with those derived from three‐dimensional (3‐D) temperatures observed by the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. The target period is from 15 December 2018 to 8 January 2019, including the onset of a major sudden stratospheric warming (SSW). The 3‐D Stockwell transform method is used for GW spectral analysis. The amplitudes and momentum fluxes of GWs in JAGUAR are generally in good quantitative agreement with those in the AIRS observations in both magnitude and distribution. As the SSW event progressed, the GW amplitudes and eastward momentum flux increased at low latitudes in the summer hemisphere in both the model and observation datasets. Case studies demonstrate that the model is able to reproduce comparable wave events to those in the AIRS observations with some differences, especially noticeable at low latitudes in the summer hemisphere. Through a comparison between the model results with and without the AIRS observational filter applied, it is suggested that the amplitudes of GWs near the entrance or exit of an eastward jet streak are underestimated in AIRS observations.

Sea bed disturbance increases flat oyster recruitment for low to moderate stock densities

Abstract It has long been suggested by commercial fishing interests that the sea bed benefits from being trawled or disturbed. Evidence to support increased benthic food web productivity in areas disturbed by trawling has suggested that this is the case, and that some mobile consumers can benefit from this increased productivity. The same hypothesis has been put forward for shellfish recruitment, that disturbance of the sea bed, e.g. ‘harrowing’, increases the exposure of suitable settlement substrates for shellfish larvae. This is an approach often taken in shellfish mariculture in private fisheries, and has led to calls for support of expanding such activities into publicly managed areas to promote shellfish recovery and restoration. Increased seabed disturbance, however, may not align with conservation policy or societal objectives for natural recovery of the seabed landscape. Furthermore, evidence for increased shellfish recruitment from seabed disturbance is mixed, and many attempts to elucidate whether relationships exist receive criticism for operating at small spatial and temporal scales. An analysis is presented from 3 years of data (2016–2018) from a stock survey of a private European flat oyster, Ostrea edulis, fishery operating in the Blackwater estuary, Essex, UK. Using data for adult and recruit oyster abundance and distribution in 2018, with ‘harrowing’ effort from 2016–2018, it is asked whether oyster recruitment was related to disturbance effort. It was found that oyster recruitment is positively related to increased seabed disturbance, but only up to intermediate adult oyster abundance equivalent to 60 oysters/100 m dredge, beyond which harrowing results in recruitment declines. This has implications for approaches to oyster fishery recovery, but also for restoration projects seeking evidence‐led guidance on which ways may be appropriate to kick‐start natural recovery in historical oyster areas that are habitat limited.

Inspection of IMERG precipitation estimates during Typhoon Cempaka using a new methodology for quantifying and evaluating bias

Bias analysis is a significant component in the performance evaluation of satellite precipitation products (SPPs), and the relative bias (RB) is usually adopted as a key metric in all relative studies. However, when calculating the RB, severe overestimation (positive RB) and underestimation (negative RB) with the opposite sign can be offset through summation when a small temporal scale changes to a large temporal scale, and the final result will ignore the actual situation, which weakens the validity and reliability of bias evaluation. To solve the above problem, the typhoon presenting capability (TPC), which consists of two metrics, the presenting capability indicator (PCI) and the bias type discriminant (BTD), was developed as a new methodology for error evaluation during tropical cyclone events. In this study, by applying the TPC, two quasi-real-time Integrated multi-satellite retrievals for global precipitation measurement (IMERG) products (i.e., the early run and late run) acquired during Typhoon Cempaka in July 2021 were evaluated. The main conclusions are as follows: (1) underestimation of the precipitation by the two IMERG products tended to occur at higher hourly rainfall intensities (>2 mm at gauge scale and 100 mm at regional scale), while overestimation occurred at lower intensities. (2) The false-alarm rate (FAR) and RB values were significantly higher in the Pearl River Delta (PRD) than in other regions of the study area. (3) Through calculation of the TPC, a positive and negative offset phenomenon was identified over the region around Zhanjiang City in western Guangdong. By introducing the TPC for performance evaluation of IMERG products during Typhoon Cempaka, it was concluded that TPC is an advanced replacement of the RB for disclosing bias situations when adopting IMERG to monitor and reconstruct typhoon processes.

Dust flow analysis by low coherence Doppler lidar

Visualization of dust flow and wind dynamics near the ground surface are essential for understanding the mixing and interaction between geosphere and atmosphere near the surface. Knowing the temporal dust flow is beneficial in dealing with air pollution and health issues. Dust flows near the ground surface are difficult to monitor because of their small temporal and spatial scale. In this study, we propose a low-coherence Doppler lidar (LCDL) for measuring dust flow near the ground with high temporal and spatial resolutions of 5 ms and 1 m, respectively. We demonstrate the performance of LCDL in laboratory experiments using flour and calcium carbonate particles released into the wind tunnel. LCDL experiment results show a good agreement with anemometer measurement in wind speeds ranging from 0 to 5 m/s. The LCDL technique can reveal dust’s speed distribution, which is affected by mass and particle size. As a result, different speed distribution profiles can be used to determine dust type. The simulation results of dust flow coincide well with the experimental results.

Reconciling the paradox of soil organic carbon erosion by water

Abstract. The acceleration of erosion, transport, and burial of soil organic carbon (OC) by water in response to agricultural expansion represents a significant perturbation of the terrestrial C cycle. Recent model advances now enable improved representation of the relationships between sedimentary processes and OC cycling, and this has led to substantially revised assessments of changes in land OC as a result of land cover and climate change. However, surprisingly a consensus on both the direction and magnitude of the erosion-induced land–atmosphere OC exchange is still lacking. Here, we show that the apparent soil OC erosion paradox, i.e., whether agricultural erosion results in an OC sink or source, can be reconciled when comprehensively considering the range of temporal and spatial scales at which erosional effects on the C cycle operate. We developed a framework that describes erosion-induced OC sink and source terms across scales. We conclude that erosion induces a source for atmospheric CO2 when considering only small temporal and spatial scales, while both sinks and sources appear when multi-scaled approaches are used. We emphasize the need for erosion control for the benefits it brings for the delivery of ecosystem services, but cross-scale approaches are essential to accurately represent erosion effects on the global C cycle.