Vertical Speed Research Articles

Profiling of particulate matter transport flux based on dual-wavelength lidar and ensemble learning algorithm

Transport flux (TF) is a significant particulate matter (PM) characteristic. This paper introduces an advanced dual-wavelength polarization aerosol and wind lidar (Wind Flux 3000) capable of independently observing the PM TF. The PM TF observation capability, which allows for simultaneous aerosol and wind measurements, was achieved by integrating a Mie-polarization particle lidar module and a coherent Doppler wind lidar module into a single lidar system. The primary measurement products of the Wind Flux 3000 include particulate extinction coefficient at 532 nm and 1550 nm, volume linear depolarization ratio at 532 nm (δp,532), wind speed (WS), wind direction (WD), vertical speed (VS), turbulence intensity (TI) and mixing layer height (MLH), retrieved by physical and proven algorithms. The PM concentration scales with the measured optical parameters and is also impacted by other environmental or meteorological parameters. Under the framework of the potential relationship between the PM concentration and the above parameters, the PM2.5 and PM10 concentration retrieval models were established using the stacking method of the ensemble learning technique; the models were trained using the in-situ data as true values, while the signal-to-noise ratio (SNR) at 1550 nm, δp,532, WS, WD, VS, the standard deviation of VS, TI, MLH provided by the Wind Flux 3000, as well as the relative humidity and temperature from ERA5, the hours of the day, and a “dust day” flag were used as inputs. The R2, RMSE, and MAE for the comparison between the predicted and true values of the PM2.5 test set are 0.857, 13.52 µg · m- 3, 9.16 µg · m- 3, and those of the PM10 test set are 0.926, 24.75 µg · m- 3, 14.39 µg · m- 3, respectively. The performance of the PM2.5 and PM10 concentration retrieval ensemble models is better than that of individual machine learning algorithms and better than that of the linear model. On 15th March 2023, a strong southeastward dust transport process with dust plume deposition was observed at Qingdao by the Wind Flux 3000. The analyses of the dust event demonstrated the Wind Flux 3000's ability to evaluate the transports of PM quantitatively.

Timescales of Ecological Processes, Settling, and Estuarine Transport to Create Estuarine Turbidity Maxima: An Application of the Peter–Parker Model

The estuarine exchange flow increases the longitudinal dispersion of passive tracers and trap sinking particles, potentially creating an estuarine turbidity maximum (ETM): a localized maximum of suspended particulate matter concentration in an estuary. The ETM can have many implications: dead zones due to increased turbidity or hypoxia from organic matter decomposition, naval navigation challenges, and other water quality problems. Using timescales, we investigate how the interaction between exchange flow and particle sinking leads to ETMs by modeling a sinking tracer in an idealized box model of the Total Exchange Flow (TEF) first developed by Parker MacCready. Results indicate that the balance of particle sinking and vertical mixing is critical to determining ETM size and location. We then focus on the role of ecology in ETM formation through the use of the Peter–Parker Model, a new biophysical model which combines the TEF box model with a Nutrient–Phytoplankton–Zooplankton–Detritus (NPZD) model, the likes of which were first developed by Peter J.S. Franks. Detritus sinking rates similarly influence detritus peak concentration and location (an ETM), but detritus ETMs occur in a different location than the sinking tracer due to the influence of biological factors, which create a time lag of about 1 day. Lastly, we characterize the flow of the models with a dimensionless parameter that compares timescales and summarizes the dynamics of the sinking tracer in ETM formation and that can be used across systems.

Payment schemes for resource reallocation in hierarchical medical system: Fee-for-capacity versus performance payment

This study explores resource reallocation, or capacity sinking, in a hierarchical medical system that includes a healthcare funder, a comprehensive hospital, a community hospital, and patients with varying perceptions of different hospital levels. To help the funder better coordinate the process and induce a comprehensive hospital to willingly sink its high-quality medical resources to a community hospital, we design and evaluate two payment schemes: Fee-For-Capacity (FFC) scheme and Performance Payment (PP) scheme. In the FFC scheme, the funder pays a unit capacity sinking price to the comprehensive hospital. In the PP scheme, the sinking price is paid only if the community hospital increases the rate of patient visits. By considering different parties’ decision-making behaviors, we develop a sequential game model within a queuing framework to determine equilibrium results in terms of the patient arrival rate at each hospital, the community hospital’s capacity planning, the comprehensive hospital’s capacity sinking rate, and the funder’s capacity sinking price. Our study indicates that the FFC scheme outperforms the PP scheme in terms of social welfare, patient utility, and waiting time when the budget is low or the funder’s concern about patient utility is relatively high or low. However, both schemes are suboptimal when the budget and the funder’s concern degree are medium. We find that a hybrid payment scheme can alleviate the drawbacks of FFC and PP and help achieve system optimum.

Moderate-dose caffeine enhances anaerobic performance without altering hydration status.

The effects of direct nutritional supplements on athletic performance are still being investigated and arouse curiosity. Only one study in the literature was found that investigated the kicking speed performance of futsal players following low-dose caffeine supplementation (3 mg/kg); thus, the question of whether caffeine supplementation improves kicking speed as well as essential physical parameters in soccer players is still controversial. Therefore, the aim of this study was to determine the effect of caffeine supplementation on vertical jump (VJ), sprint, reaction time, balance, change of direction (COD), and ball-kicking speed in soccer players. In a double-blind, cross-over design, nine moderately trained male soccer players (21.11 ± 2.02 years, 171.22 ± 6.14 cm, 71.78 ± 10.02 kg) consumed caffeine (6 mg/kg) or a placebo 60 min before completing balance, reaction time, vertical jump, agility, 30 m sprint, and ball-kicking speed tests. Greater VJ height (p = 0.01) and power (p = 0.08), and faster completion time according to the Illinois Agility Test (p = 0.08) were found following caffeine supplementation compared to placebo. Elapsed time (p = 0.01), average (p = 0.01) time, and the slowest reaction times (p = 0.016) were significantly reduced after caffeine consumption compared to placebo supplementation. Caffeine intake significantly improved VJ, agility, and reaction time (p < 0.05) but did not affect 30 m sprint, ball-kicking speed, balance, and RPE values in soccer players (p > 0.05). Although non-significant, caffeine intake also improved sprint (0.67%) and ball kicking (2.7%) performance percentages. Also, caffeine consumption did not induce dehydration, and the athletes' body hydration levels were normal. These findings support the use of caffeine supplementation as an effective nutritional ergogenic aid to enhance anaerobic performance, at least for vertical jumps, COD speed, and reaction time, in trained male soccer players.

Physical quantity characteristics of severe aircraft turbulence near convective clouds over Australia

Using FY–2G satellite data, Aircraft Meteorological Data Relay (AMDAR) downlink data, and the fifth generation European Centre for Medium–Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate (ERA5) dataset, we analyzed the circulation, thermal, and dynamic characteristics of the convective aircraft turbulence over Australia in the Southern Hemisphere. The results show that the near-convective clouds turbulence (NCCT) in the Southern Hemisphere mostly occurred in front of deep warm high–pressure ridges in mid–latitude regions and on the left side of the axis of the subtropical westerly jet stream. The isotherms in this area were relatively dense (i.e., large gradients), and the wind speed was high, with strong horizontal and/or vertical cyclonic wind shear. In addition, the NCCT usually occurred near the zero–divergence or zero–vorticity line and in areas with large vertical wind speed gradients. There were also strong vertical and horizontal wind shears in this area, which could easily trigger severe turbulence. Furthermore, the NCCT in the Southern Hemisphere mostly occurred at the intersection of cold and warm temperature advections (i.e., near the zero–temperature advection line), and the turbulence point was located near the high–altitude frontal zone where there was a strong gradient of cold and warm advections. There was temperature inversion with pseudo–equivalent potential temperatures in the middle and lower troposphere on the warmer side of the turbulence point. The unstable stratification of cold air at the top and warm air at the bottom was conducive to triggering convection from the ground, forming strong convective clouds, and causing severe turbulence.

Antarctic Bottom Water Warming, Freshening, and Contraction in the Eastern Bellingshausen Basin

AbstractAntarctic Bottom Water has been warming in recent decades throughout most of the oceans and freshening in regions close to its Indian and Pacific sector sources. We assess warming rates on isobars in the eastern Pacific sector of the Southern Ocean using CTD data collected from shipboard surveys from the early 1990s through the late 2010s together with CTD data collected from Deep Argo floats deployed in the region in January 2023. We show cooling and freshening in the temperature‐salinity relation for water colder than ∼0.4°C. We further find a recent acceleration in the regional bottom water warming rate vertically averaged for pressures exceeding 3,700 dbar, with the 2017/18 to 2023/24 trend of 7.5 (±0.9) m°C yr−1 nearly triple the 1992/95 to 2023/24 trend of 2.8 (±0.2) m°C yr−1. The 0.2°C isotherm descent rate for these same time periods nearly quadruples from 7.8 to 28 m yr−1.

Intermediate E-F layer dynamics study in the Brazilian low-latitude sector: observational data and simulations

This study investigates the downward motion of Intermediate E-F Layers (ILs) in the Brazilian low latitude sector through observation and modeling. Ionosonde data from São José dos Campos (SJC) and Palmas (PAL) were analyzed to investigate the seasonal variation of the IL parameters, including the virtual height (h'IL) and the top frequency (ftIL). The ILs primarily originated from F layer detachment followed by downward motion, peaking before 11 LT and disappearing well before sunset. Daily height variability ranged between 130 and 190 km, with peak frequencies around 4–5 MHz. Using meteor radar data as input, the Ionospheric E-region Model (MIRE) simulated diurnal and semidiurnal tides to analyze neutral wind effects on ILs descent. Model simulations for SJC (October 2008) and PAL (April and June 2009) revealed distinct wind oscillations influencing IL dynamics at heights below 140 km. In SJC, meridional wind shears controlled IL descent, with possible zonal wind interactions weakening ILs. Conversely, in PAL during April 2009, both zonal and meridional winds contributed to IL formation and altitude descent. However, discrepancies between observed and modeled descent rates suggest the need for considering additional atmospheric wave interactions in future modeling studies. June 2009 over PAL presented unique IL behavior, exhibiting a lower observed decay rate and daily height oscillations potentially linked to local modulations. Meanwhile, MIRE indicated that meridional wind shearing predominantly controlled IL descent in the morning, with zonal wind becoming relevant post-midday. These findings enhance our understanding of IL dynamics and their atmospheric drivers.

On the seasonal dependence of intermediate descending layer in low latitudes

Understanding the variable behavior of the IDL/Es system contributes significantly to our ability in characterizing and modeling the critical ionospheric dynamics across the globe. In this work we aim to improve the understanding of the IDL/Es system by analyzing the diurnal and seasonal variations in the altitude descent with reference to local time of the day, season, and solar activity. We apply the well-known height-time-intensity analysis method on measurements obtained from the Sharjah ionosonde station, located at the Arabian Peninsula (Sharjah: 25.28°N, 55.46°E) near the northern crest of the equatorial ionization anomaly. The measurements cover three years of the increasing phase of the solar cycle 25 from 2020 to 2022. Considering an oversimplified wind system based on windshear theory, we attempt to establish a relationship between IDL/Es periodicities with diurnal, semidiurnal, and terdiurnal tides without digging into the underlying mechanism. Results suggest a strong relation between semidiurnal and terdiurnal tides and the formation and transport of the IDL, particularly impacting lower E-region and sporadic-E layers during the afternoon and nighttime hours. The results of manual scaling of over eleven thousand ionograms is presented to quantify the behavior of the IDL/Es system's transport. Additionally, a connection between solar activity, descent rate, and initial descending height, with semidiurnal patterns consistently present across seasons and solar activity has been discussed. For different frequency bins used in this work, e.g. 3 MHz, 4 MHz, and 5 MHz, seasonal variations significantly influence descent patterns.

Evaluation of the Planetary Boundary Layer Height From ERA5 Reanalysis With MOSAiC Observations Over the Arctic Ocean

AbstractThe planetary boundary layer height (PBLH) is a crucial indicator reflecting the region of the atmosphere characterized by continuous turbulence. Here, we use radiosonde and surface meteorological observations (4–7 times per day, year‐round measurements) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition to derive the PBLH (PBLHMOSAiC), and further evaluate the PBLH from the ERA5 reanalysis (PBLHERA5). Comparisons between PBLHMOSAiC and PBLHERA5 from different perspectives reveal that: (a) The overestimation of PBLHERA5 when the sea ice concentration is &gt;90% is significant with the centered root mean squared error reaching up to 201 m; (b) The difference between the two products is notably pronounced in cold seasons, while it is comparatively diminished in warm seasons; (c) In neutral boundary layers, differences in PBLHERA5 are larger compared with stable and convective boundary layers. In addition, the analysis of error sources indicates that the bias of PBLHERA5 is sensitive to the bias of vertical thermal structure and wind speed profiles in ERA5 data sets in all conditions. Finally, we find a Random Forest model effectively reduces the bias of PBLHERA5 with the index of agreement reaching up to 0.71 in the test data set, while a multiple linear regression demonstrates comparable performance to the Random Forest model.

How interchange spacing effects drivers’ visual performance in high-density interchange groups − a naturalistic driving study

The aim of this study was to evaluate the effects of interchange spacing on the visual characteristics and visual load of drivers in the exit zone of the urban expressway. A naturalistic driving experiment was conducted in a high-density interchange group on the North Ring Expressway in Chongqing, China. Eye-movement data from 47 participants were collected to assess the pattern of visual performance, seven indicators were selected to characterize drivers’ visual characteristics, and the entropy weighting method was used to assess the drivers’ visual loads under different interchange spacing and driving zones. The results show that insufficient spacing of the interchange affects drivers’ visual behavior and increases their visual load level. The fixation duration for drivers is significantly affected by interchange spacing, with longer fixation duration in the diversion and ramp zones of small-spacing interchanging(SSI). The mean horizontal visual angle of drivers was mainly distributed in the middle of the field of view, and there was a tendency for the overall left side to be shifted under the conditions of SSI, and the mean vertical visual angle was mainly distributed in the nearer part in front of the lanes. In the ramp zone of SSI, the driver’s attention to the vehicle dashboard had a significant increase. In normal-spacing interchange(NSI), drivers’ horizontal saccade amplitude and speed were higher than those in SSI, and the difference was most significant in the diversion zone. Vertical saccade amplitude and speed of the driver were found to be significantly affected by interchange spacing only in the ramp zone. Drivers’ visual load had the highest correlation with pupil variation, and the visual load scores of drivers at SSI were 39.65% and 17.7% higher than at NSI in the diversion and ramp zones, respectively. This study provides valuable insights into the effects of the high-density interchange group on the visual performance of drivers on urban expressways, and the results provide a theoretical basis for the spacing control of interchanges.

Kinematic characteristics analysis of highly difficult movements "324C+1D" of the first level Wushu athletes

Background "324C+1D” movements are key techniques and winning factors in Wushu competitions. It is necessary for scientific training to analyze the kinematic characteristics of “324C+1D” by using the method of sports biomechanics. Methods In this study, 3D high-speed camera and 3D motion analysis software were used to study “324C+1D” completed by three Chinese wushu first-level athletes, and the kinematic characteristics of this movement were obtained. Results The run-up speed of completing the “324C+1D” is not high; The lift Angle of the center of gravity is close to 90°. The vertical height of the center of gravity is significantly higher than the vertical height of the center of gravity when landing, and the vertical moving distance of the center of gravity in the lifting stage is significantly less than the vertical moving distance of the center of gravity in the descending stage. The vertical height of the center of gravity at departure is significantly higher than that at landing. Conclusions In the take-off stage, increase the twisting Angle of shoulders and hips, speed up the swing arm speed and squat speed of the center of gravity in the vertical direction, and shorten the take-off time. Increase the vertical speed of the center of gravity before the patting foot and the vertical moving distance between the center of gravity lifting stage and the descending stage, extend the air time, accelerate the swing speed of the right leg, move the foot patting time forward to the rapid rising stage of the center of gravity lifting, accelerate the rotational angular speed of the shoulder shaft in the air stage and improve the strength of the leg, which is conducive to the athletes to complete the movement.

Factors affecting evacuation in intellectually disabled children: An experimental study

Children with intellectual disabilities are considered a vulnerable group in evacuations during emergencies, yet their evacuation needs have not received sufficient attention. To bridge this gap, this study provides one of the very few experimental analyses of the evacuation of intellectually disabled children. Therefore, this study aimed to gather unique evacuation data for intellectually disabled children and identify factors influencing their evacuation process. Two evacuation experiments were conducted on 49 intellectually disabled children aged 7 to 16 from a special education school. Data collected through video recordings include recognition time, response time, pre-movement time, indoor travel speed, horizontal travel speed, and vertical travel speed. This study explored whether and how several key factors (e.g., drill announcement status, sex, age, floor level, and students' dependency behavior) affect the evacuation of intellectually disabled children. Results indicate that drill announcement status significantly affected the recognition time and pre-movement time in intellectually disabled children but did not impact their response time or travel speed. The floor level on which children were located significantly influenced their evacuation process, with children on higher floors showing longer response and pre-movement time and slower indoor travel speed and horizontal travel speed compared to those on the first floor. Additionally, the dependency behavior of these children on teachers significantly influenced their recognition time. Moreover, this dependency behavior tended to be prevalent among intellectually disabled children during emergency evacuations. These findings provide valuable insights for the design of educational buildings tailored to the needs of special populations, evacuation simulation modeling, and the development of building regulations.

Dive descent rate as a buoyancy indicator to infer body condition of Weddell seals in the Antarctic

AbstractChanges in buoyancy of marine mammals can be used to infer environmental changes. In multiple seal species, how “fast” an animal sinks reveals body condition changes through shifts in buoyancy as the ratio between lean and lipid tissue changes. However, quantifying similar at‐sea changes in Weddell seals (Leptonychotes weddellii) has remained unexplored. Here, we present a method of inferring buoyancy of Weddell seals by monitoring descent rates from 4‐s time‐depth data, to reveal in situ insight of their life cycle. We defined a Buoyancy Indicator Segment (BIS) as the descent rate of a dive segment created with the broken‐stick method that was systematically filtered to only include characteristic nonstroking and directed travel segments while excluding lung buoyancy biases. We found that BISs predicted body condition changes in Weddell seals, being a function of dive duration, mean depth, and time‐of‐year. Descent rates quickened with troughs in early April due to postmolt muscle recovery, early July due to winter conditions, and early September possibly due to pregnancy. Each trough was followed by weight gain, with slowing descent rates reaching peaks in late May, early August, and late October. This new approach showed that determining at‐sea condition is possible for Weddell seals, deriving a powerful species and environmental monitoring tool.

Seasonal migrations of the European sea bass (Dicentrarchus labrax L.) in UK and surrounding waters

The movements and behaviour of mature European sea bass (Dicentrarchus labrax L.) in UK waters have not been studied extensively since a series of mark-recapture experiments during the 1970s, 80s and 90s. To better understand the timing and extent of seasonal migrations, 171 mature sea bass > 42 cm were internally tagged with floated electronic tags programmed to record temperature and depth, and released in the English Channel, in the southern North Sea and in the Irish Sea. Among the 48 tags returned to date, sea bass were at liberty for 370 ± 337 days and were recovered 172 ± 200 km from their respective release locations. Most tags were recovered from beaches (54%), or via the fishery (44%). A comparison of the reconstructed tracks from returned electronic tags with the recapture locations of 237 mark-recapture returns (6.5%) from 3615 sea bass released between 1970 and 2020 showed strong overlap. Seasonal movements between shallow areas (Q2–Q3) and deeper spawning areas (Q4–Q1) were accompanied by elevated vertical swimming speeds and average water temperatures of 8.5 °C in the English Channel and Irish Sea, but lower temperatures in the North Sea. Movements between the Celtic Sea/Irish Sea and the North Sea and vice versa demonstrate high levels of connectivity in UK waters. We demonstrate that a proportion of sea bass remained resident within the North Sea throughout the year, with a strong suggestion that spawning might be occurring. These data have significant implications for the future sustainable management of sea bass stocks in UK and surrounding waters.

Near‐Storm Environmental Relationships With Tropical Oceanic Convective Structure Observed During NASA CPEX and CPEX‐AW

AbstractDeep tropical oceanic convection (TOC) is a prevailing component of the tropical atmosphere and plays a significant role in modulating global weather and climate. Despite its importance, prediction challenges remain, partly attributed to a lack of understanding of how TOC relates to its near‐storm environments. Prior studies suggest location‐dependent relationships between TOC structure and associated environments, necessitating targeted regional studies. The NASA 2017 Convective Processes Experiment (CPEX) and 2021 CPEX—Aerosols &amp; Winds (CPEX‐AW) field campaigns collected high‐resolution measurements of convective storms and their environments in the Gulf of Mexico, Caribbean, and western Atlantic basins, providing a rare opportunity to investigate near‐storm environmental relationships with 3‐D TOC structure where in situ non‐tropical cyclone‐related deep TOC research is comparatively lacking. Collocated CPEX and CPEX‐AW airborne observations from the multi‐wavelength Airborne Precipitation Radar, Doppler Aerosol Wind Lidar, and dropsondes revealed large near‐storm environmental variability across TOC of similar convective type (i.e., isolated, organized) and within individual convective systems. However, trends still emerged amongst the large environmental variability. Horizontal TOC structure was most consistently linked to planetary boundary layer and mid‐tropospheric near‐storm environments, with organized TOC being associated with generally greater relative humidity (RH) and vertical speed shear than isolated TOC. TOC intensity was linked to upper tropospheric (i.e., above melting level) near‐storm environments, with isolated TOC intensity most consistently associated with upper tropospheric CAPE and organized TOC intensity associated with upper tropospheric RH. Mesoscale low‐level convergence was also linked to greater organized TOC intensity, motivating further research using these unique data sets.

Use of transrectal high-frequency ultrasound in assessment of middle compartment prolapse.

To investigate the superiority of transrectal high-frequency ultrasound (TRUS) in precise assessment of middle compartment prolapse in comparison with routine transperineal ultrasound (TPUS). Prospectively analyzed and compared detection rates of entire cervical length and uterine descent on TPUS and TRUS in 101 patients with pelvic organ prolapse (POP). Detection rates of entire cervix on TRUS were significantly higher than those on TPUS both at rest and during Valsalva maneuver (90.10% VS 49.50%, 92.08% VS 9.90% respectively, both p < 0.05). Uterine descent was able to be evaluated in 92.08% of patients by TRUS and in 5.94% of patients by TPUS, which was statistically significant (p < 0.05). The interobserver repeatability for the measurements of anterior lip, cervical canal and posterior lip on TRUS was excellent. The mean lengths of anterior lip, cervical canal and posterior lip were significantly increased during Valsalva maneuver than those measured at rest (p < 0.05). And mean length of anterior lip was longer than posterior lip both at rest and during Valsalva (p < 0.05). TRUS can significantly raise detection rates of entire cervix, and make the direct evaluation of uterine descent feasible. TRUS can be used as a complementary method to TPUS to attain more comprehensive and accurate presurgical imaging information in middle compartment prolapse patients.

Aerosol-induced closure of marine cloud cells: enhanced effects in the presence of precipitation

Abstract. The Weather Research Forecasting (WRF) version 4.3 model is configured within a Lagrangian framework to quantify the impact of aerosols on evolving cloud fields. Kilometer-scale simulations utilizing meteorological boundary conditions are based on 10 case study days offering diverse meteorology during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA). Measurements from aircraft, the ground-based Atmosphere Radiation Measurement (ARM) site at Graciosa Island in the Azores, and A-Train and geostationary satellites are utilized for validation, demonstrating good agreement with the WRF-simulated cloud and aerosol properties. Higher aerosol concentration leads to suppressed drizzle and increased cloud water content in all case study days. These changes lead to larger radiative cooling rates at cloud top, enhanced vertical velocity variance, and increased vertical and horizontal wind speed near the base of the lower-tropospheric inversion. As a result, marine cloud cell area expands, narrowing the gap between shallow clouds and increasing cloud optical thickness, liquid water content, and the top-of-atmosphere outgoing shortwave flux. While similar aerosol effects are observed in lightly to non-raining clouds, they tend to be smaller by comparison. These simulations show a relationship between cloud cell area expansion and the radiative adjustments caused by liquid water path and cloud fraction changes. The adjustments are positive and scale as 74 % and 51 %, respectively, relative to the Twomey effect. While higher-resolution large-eddy simulations may provide improved representation of cloud-top mixing processes, these results emphasize the importance of addressing mesoscale cloud-state transitions in the quantification of aerosol radiative forcing that cannot be attained from traditional climate models.

Gust-detection from velocity azimuth display Doppler wind lidar profiling at the WiValdi research park.

This study presents a new retrieval for gusts from Doppler wind lidar (DWL) velocity azimuth display (VAD) scans. The scanning mode which is presented allows for retrieval of mean wind speed, vertical wind speed, turbulence kinetic energy and peak gust speed with a single strategy. It is validated against sonic anemometer measurements at 90 m above ground and a reference DWL gust mode with faster scanning speed at the boundary-layer field site Falkenberg of the DWD. The new algorithm is then run on a multi-year dataset to obtain statistics of gusts at the WiValdi research park. It enables analyses not only at hub height, but also up to 500 m aloft with a reasonable availability above 60%. A case study of a convective cold pool shows the potential of the method to detect and analyze the vertical and horizontal structure of gusts with the proposed method. It highlights the importance of measurements throughout the boundary layer to understand the related physical processes to wind ramps and gusts.

Energy supply during nocturnal endurance flight of migrant birds: effect of energy stores and flight behaviour

BackgroundMigrating birds fly non-stop for hours or even for days. They rely mainly on fat as fuel complemented by a certain amount of protein. Studies on homing pigeons and birds flying in a wind-tunnel suggest that the shares of fat and protein on total energy expenditure vary with flight duration and body fat stores. Also, flight behaviour, such as descending flight, is expected to affect metabolism. However, studies on free flying migrant birds under natural conditions are lacking.MethodsOn a Swiss Alpine pass, we caught three species of nocturnal migrant passerines out of their natural migratory flight. Since most night migrants start soon after dusk, we used time since dusk as a measure of flight duration. We used plasma concentrations of metabolites of the fat, protein, and carbohydrate metabolism as indicators of relative fuel use. We used flight altitudes of birds tracked with radar and with atmospheric pressure loggers to characterize flight behaviour.ResultsThe indicators of fat catabolism (triglycerides, very low-density lipoproteins, glycerol) were positively correlated with body energy stores, supporting earlier findings that birds with high fat stores have a higher fat catabolism. As expected, plasma levels of triglycerides, very low-density lipoproteins, glycerol and ß-hydroxy-butyrate increased at the beginning of the night, indicating that nocturnal migrants increased their fat metabolism directly after take-off. Surprisingly, fat catabolism as well as glucose levels decreased in the second half of the night. Data from radar observations showed that the number of birds aloft, their mean height above ground and vertical flight speed decreased after midnight. Together with the findings from atmospheric pressure-loggers put on three species, this shows that nocturnal migrants migrating over continental Europe descend slowly during about 1.5 h before final landfall at night, which results in 11–30% energy savings according to current flight models.ConclusionsWe suggest that this slow descent reduces energy demands to an extent which is noticeable in the plasma concentration of lipid, protein, and carbohydrate metabolites. The slow descent may facilitate the search for a suitable resting habitat and serve to refill glycogen stores needed for foraging and predator escape when landed.

Sinking rates, orientation, and behavior of pennate diatoms.

Phytoplankton cells are now recognized as dynamic entities rather than as passive and isolated particles because they can actively modulate impacts of selection factors (nutrients, light, turbidity, and mixing) through a wide range of adaptations. Cell shape and/or chain length modulation is one of these processes but has predominantly been studied as an adaptation or an acclimatation to a specific growth limitation (light, nutrients, predation, etc.). In this study we have demonstrated that cell shape and size may have greater roles than previously known in phytoplankton ecology and species adaptation by permitting cell-to-cell signaling and more complex ecological processes that result from it. By exploring microscale biophysical interactions that lead to specific cell reorientation processes, we demonstrated that cell geometry not only modulates cell sinking rates but can also provide fast sensor responses to the cells' environment. Although gyrotaxis has been described in detail for motile phytoplankton cells, our findings illustrate that the reorientation process described here can occur even in non-motile cells within their natural environment. An additional consistent behavior was also recently described for a diatom species (Pseudo-nitzschia delicatessima), and with this study, we extend this observation to Pseudo-nitzschia pungens and Pseudo-nitzschia fraudulenta. Our observations emphasize the generality of this process, which adds a new level of complexity to our understanding of cellular interactions and their network of sensors.