Profiler Data Research Articles

Multiple Characteristics of Precipitation Inferred from Wind Profiler Radar Doppler Spectra

A methodology to process radar wind profiler Doppler spectra is presented and implemented for an UHF Degreane PCL1300 system. First, double peak signal detection is conducted at each height level and, then, vertical continuity checks for each radar beam ensure physically consistent measurements. Second, horizontal and vertical wind, kinetic energy flux components, Doppler moments, and different precipitation-related variables are computed. The latter include a new precipitation type estimate, which considers rain, snow, and mixed types, and, finally, specific variables for liquid precipitation, including drop size distribution parameters, liquid water content and rainfall rate. The methodology is illustrated with a 48 h precipitation event, recorded during the Cerdanya-2017 field campaign, carried out in the Eastern Pyrenees. Verification is performed with a previously existing process for wind profiler data regarding wind components, plus precipitation estimates derived from Micro Rain Radar and disdrometer observations. The results indicated that the new methodology produced comparable estimates of wind components to the previous methodology (Bias < 0.1 m/s, RMSE ≈ 1.1 m/s), and was skilled in determining precipitation type when comparing the lowest estimate of disdrometer data for snow and rain, but did not correctly identify mixed precipitation cases. The proposed methodology, called UBWPP, is available at the GitHub repository.

Laser Remote Sensing of Lake Kinneret by Compact Fluorescence LiDAR.

Harmful algal blooms in freshwater reservoirs became a steady phenomenon in recent decades, so instruments for monitoring water quality in real time are of high importance. Modern satellite remote sensing is a powerful technique for mapping large areas but cannot provide depth-resolved data on algal concentrations. As an alternative to satellite techniques, laser remote sensing is a perspective technique for depth-resolved studies of fresh or seawater. Recent progress in lasers and electronics makes it possible to construct compact and lightweight LiDARs (Light Detection and Ranging) that can be installed on small boats or drones. LiDAR sensing is an established technique; however, it is more common in studies of seas rather than freshwater reservoirs. In this study, we present an experimental verification of a compact LiDAR as an instrument for the shipborne depth profiling of chlorophyll concentration across the freshwater Lake Kinneret (Israel). Chlorophyll depth profiles of 3 m with a 1.5 m resolution were measured in situ, under sunlight conditions. A good correlation (R2 = 0.89) has been established between LiDAR signals and commercial algae profiler data. A non-monotonic algae depth distribution was observed along the boat route during daytime (Tiberias city–Jordan River mouth–Tiberias city). The impact of high algal concentration on water temperature laser remote sensing has been studied in detail to estimate the LiDAR capability of in situ simultaneous measurements of temperature and chlorophyll concentration.

There is no geophysical evidence for the Mahuika Crater on the continental shelf southwest of New Zealand

ABSTRACT This study examines new bathymetric and geophysical evidence that questions the existence of the Mahuika Crater: a proposed impact depression 20.2 km wide lying on the continental shelf ∼250 km SW of New Zealand. Multibeam echo sounder and sub-bottom profiler data across the published location of the crater were collected and synthesised with existing bathymetric data for the wider region to assess the validity of such a claim. We conclude that there is no geophysical basis for the existence for the Mahuika impact crater in the region, the initial presumption of a crater was unsubstantiated, and is a myth propagated in the literature.

Insight into contrasting patterns of sedimentation from shelf edge to base-of-slope on the Mozambique-Zambezi margin (17°30′S-20°S) during the last 40 ka

The pattern of sediment dispersal and the location of sediment depocentres on continental margins can be very complex in both space and time. We aim at investigating how significantly external and internal factors, such as river runoff, bottom current and sliding can deviate the sediment dispersal from a simplistic fully sea-level controlled spreading. In this study we examined the sedimentation at two transects across the Mozambique-Zambezi slope between 17°20S-20°S, where multibeam bathymetry, sub-bottom profiler data and sediment cores were acquired. The period investigated spans the last 40 cal ka BP with a focus on the contrast between the last glacial (lowstand) and the Holocene (highstand) periods. Results show contrasting patterns of sediment dispersal, deposition and preservation. Sea level fluctuation remains the main forcing and most of the sediment from the Zambezi River settled on the inner shelf since the last sea level rise. However, we found that two major depocentres have developed on the upper slope during the Holocene consequent to the interaction of bottom currents with seabed morphologies at the shelf edge and at the upper slope. Early Holocene sliding in the north-east and in the south-west upper slope is a secondary but yet major factor of sediment transfer to the deep domain. Identified preconditioning factors for sliding on the slope are related to lowstand sediment loading and fluid circulation on the upper slope, and erosion at the base of slope of a plastered drift. Triggering must be related to margin wide mechanisms such as changes in hydrostatic pressure and reorganisation of sediment dispersal, subsequent to the post-glacial sea level rise, or maybe a period of regional seismicity. Climatic conditions in the Zambezi River watershed during the Bolling-Allerod and Younger Dryas periods are recorded and imprinted on the upper slope in the form of a detrital rich layer and a prominent slope-wide high-amplitude reflector. All over the continental slope, plastering of sediment deposits by bottom currents is pervasive and shows a morphological continuum from erosional scours at the base of slope to sediment waves on the upper slope and a possible interaction between along and across slope transport processes. We conclude that, in addition to sea level, the interplay of external and internal factors such as oceanic circulation and sliding, together with margin morphology, lead to the development of unexpected depocentres on the continental slopes. Thus, the study of modern marine analogues is crucial to avoid misleading interpretation of fossil deposits in terms of paleo sea level and more generally of paleo-environmental conditions.

Impact of Lidar Data Assimilation on Simulating Afternoon Thunderstorms near Pingtung Airport, Taiwan: A Case Study

This study focused on improving the forecasting of the afternoon thunderstorm (AT) event on 5 August 2018 near Pingtung Airport in southern Taiwan through a three-dimensional variational data assimilation system using Doppler lidar-based wind profiler data from the Weather and Research Forecast model. The assimilation of lidar wind profiler data had a positive impact on predicting the occurrence and development of ATs and wind fields associated with the local circulations of the sea–land breeze and the mountains. Evaluation of the model quantitative precipitation forecast by using root-mean-square error analysis, Pearson product–moment correlation coefficient analysis, Spearman rank correlation coefficient analysis, and threat and bias scores revealed that experiments using data assimilation performed much better than those not using data assimilation. Among the experiments using data assimilation, when the implementation time of assimilation of the wind profiler data in the model was closer to the occurrence time of the observed ATs, the forecast performance greatly improved. Overall, our assimilation strategy has crucial implications for the prediction of short-duration intense rainfall caused by ATs with small temporal and spatial scales of few hours and a few tens of kilometers. Our strategy can help guarantee the flight safety of aircraft.

Northeast Greenland: ice‐free shelf edge at 79.4°N around the Last Glacial Maximum 25.5–17.5 ka

The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17‐NG‐ST01‐019G, from 323‐m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS‐14C dates, sedimentological (ice‐rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub‐bottom profiler) data. The oldest sediments at the study site are dated to 25.5–17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very rich in both planktic and benthic foraminifera and macrofossils of excellent preservation. The faunas show that the site generally was affected by a strong flow of relatively warm subsurface Atlantic Water during the LGM and Early Holocene. Conditions turned more polar with cold bottom water flow in the Middle–Late Holocene (c. 7.5 ka to Recent) with presence of mainly agglutinated benthic foraminiferal species. Our data from the LGM also indicate that the deposits were mixed by iceberg scouring, confirmed by the geophysical data showing extensive ploughing of the sediments on the outer shelf area. The results further indicate that the Greenland Ice Sheet did not reach to the edge of the NE Greenland shelf at 79.4°N during the LGM 24–18 ka.

Transition from Balanced to Unbalanced Motion in the Eastern Tropical Pacific

Abstract Kinetic energy associated with inertia–gravity waves (IGWs) and other ageostrophic phenomena often overwhelms kinetic energy due to geostrophic motions for wavelengths on the order of tens of kilometers. Understanding the dependencies of the wavelength at which balanced (geostrophic) variability ceases to be larger than unbalanced variability is important for interpreting high-resolution altimetric data. This wavelength has been termed the transition scale. This study uses acoustic Doppler current profiler (ADCP) data along with auxiliary observations and a numerical model to investigate the transition scale in the eastern tropical Pacific and the mechanisms responsible for its regional and seasonal variations. One-dimensional kinetic energy wavenumber spectra are separated into rotational and divergent components, and subsequently into vortex and wave components. The divergent motions, most likely predominantly IGWs, account for most of the energy at wavelengths less than 100 km. The observed regional and seasonal patterns in the transition scale are consistent with those from a high-resolution global simulation. Observations, however, show weaker seasonality, with only modest wintertime increases in vortex energy. The ADCP-inferred IGW wavenumber spectra suggest that waves with near-inertial frequency dominate the unbalanced variability, while in model output, internal tides strongly influence the wavenumber spectrum. The ADCP-derived transition scales from the eastern tropical Pacific are typically in the 100–200-km range.

Long-Term Warm–Cold Phase Shifts in the Gerlache Strait, Western Antarctic Peninsula

The Gerlache Strait plays an important role for the transports of heat, nutrients, and primary producers between the northern West Antarctic Peninsula (WAP) and the continental shelf in the southern WAP. The means, seasonal variations, and long-term trends of currents in the Gerlache Strait are analyzed based on Acoustic Doppler Current Profiler (ADCP) data between 1999 and 2016 available from the Joint Archive for Shipboard ADCP (JASADCP) dataset. The results revealed that the mean currents between the sea surface and 300 m in the Gerlache Strait (known as the Gerlache Strait Current) were predominantly northeastward, associated with the northeastward intrusion of Modified Circumpolar Deep Water (MCDW). The variance ellipses of currents were in parallel to the principal axis of the strait. The currents reached the maximum during austral spring and summer and were minimum during austral winter. The long-term trends revealed that the mean currents were southwestward during austral fall or winter before 2005, and the northeastward currents increased between 1999 and 2011, weakened, and reversed between 2011 and 2016. The long-term shifts between warm and cold phases in the Gerlache Strait were associated with shifts between the dominance of northeastward and southwestward currents in the strait, which are respectively associated with the intrusion of warm MCDW in the south and the transport of cold water from the Bransfield Strait in the north.

3D Structure of the Ras Al Hadd Oceanic Dipole

In the Arabian Sea, southeast of the Arabian peninsula, an oceanic dipole, named the Ras Al Hadd (RAH) dipole, is formed each year, lying near the Ras Al Hadd cape. The RAH dipole is the association of a cyclonic eddy (CE) to the northeast, with an anticyclonic eddy (AE) to the southwest. This dipole intensifies in the summer monsoon and disappears during the winter monsoon. This dipole has been described previously, but mostly for its surface expression, and for short time intervals. Here, we describe the 3D structure of this dipole over the 2000–2015 period, by combining colocalized ARGO float profiler data (a total of 7552 profiles inside and outside the RAH dipole) with angular momentum eddy detection and tracking algorithm (AMEDA) surface data. We show first the different water masses in and near the RAH dipole. The presence of the Persian Gulf water (PGW) below 200 m depth is confirmed in both eddies. Arabian Sea high salinity water (ASHSW) is found exclusively in the AE; a layer of fresh and cold water is observed above 100 m depth in both eddies. By analyzing the potential density structures, we show that the CE has a surface-intensified structure while the AE is subsurface-intensified. The sea level anomaly shows a 0.04 m elevation above the AE and a 0.2 m depression over the CE. The CE has a faster geostrophic velocity, (vertical velocity, respectively) 0.6 m s−1 than the AE, 0.15 m s−1 (respectively, 3 m day−1 for the CE and 0.6 m day−1 for the AE). After presenting the vertical structure of the dipole, we show the dominance of the nonlinear Ekman pumping in the CE over the linear pumping affecting the dipole. As a consequence, we explain the CE’s longer lifetime by its intensity and shallowness, and by its sensitivity to the interaction with the atmosphere (in particular the wind stress) and with neighboring eddies. We examined the possible (co)existence of symmetric, barotropic, and baroclinic instabilities in both eddies. These instabilities coexist near the surface in both eddies. They are intensified for the CE, which suggests that the CE is unstable and the AE is rather stable or may need a long time to be unstable.

Estimation of inward nutrient flux from offshore into semi-enclosed sea (Tokyo Bay, Japan) based on in-situ data

In previous studies, to address the problem caused by eutrophication and oligotrophication in coastal waters, nutrient cycles have been estimated using bio-geophysical models. These studies strictly evaluated land-derived nutrient loading but not the nutrient loading from offshore. This study demonstrated the quantitation of the offshore-derived nutrient-loading based on in-situ data not based on a bio-geochemical model in the semi-enclosed Tokyo Bay, Japan affected by oligotrophication and discusses about the contribution of a decadal change in the inward nutrient flux to oligotrophication. The inward water flux from offshore was calculated using Ferry-mounted current profiler data. The dissolved inorganic nutrient concentrations of the inward water were estimated using the in-situ sea temperature following the negative correlation relationship between the sea temperature and nutrient concentration. Estimated inward nutrient flux from the Pacific Ocean peaks in March (spring) and the amount of the inward nitrogen has the same order of magnitude as the land-derived input. Notable variability of the inward nutrient flux was confirmed during 2010–2019. The significant decadal change of the inward water mass flux was not confirmed because of the lack of significant decadal changes in the in-situ controlling factors identified by the hydrodynamic model. The decadal decreasing trend in the total nitrogen of inward water suggests a decrease in the inward nutrient flux which contributes to the oligotrophication in Tokyo Bay.

Vector correlation between modeled gradient wind and observed high-altitude wind of a translating tropical cyclone

This study investigated the validity of three existing gradient wind models for a translating tropical cyclone by analyzing vector correlations between the modeled gradient wind and the observed wind. Modeled gradient wind vectors were computed using the three models used or proposed by Georgiou (1986), Yoshizumi (1968), and Wang et al. (2017). For the observed wind, we used high-altitude wind profiler data obtained during the passage around Japan of Typhoon Faxai 2019 and Typhoon Haishen 2020. Of the three gradient wind models studied, the one used most commonly, i.e., that of Georgiou, yielded the lowest correlation coefficient. The gradient wind model of Wang et al. generally yielded the highest correlation coefficient among the three models, with the least deviation from the observed wind in terms of both wind speed and wind direction. The performance of the three gradient wind models was found consistent with the magnitude of the residuals in the momentum conservation equation, and with the case study results for two hurricanes presented in our previous study.

Multiannual Seafloor Dynamics around a Subtidal Rocky Reef Habitat in the North Sea

Rocky reefs provide complex structures in the otherwise largely sand-dominated coastal North Sea. Therefore, these reefs are highly important natural habitats for the functioning of coastal ecosystems, as they provide shelter, refuge and nursery grounds for various mobile and sessile species. In the North Sea, the spatial distribution of these habitats has been intensively investigated over recent years. However, these studies generally provide static accounts of the current state of these reef systems, but limited data exist on the temporal variations in sediment dynamics at and around natural rocky reefs. In this study, we provide observations from a multiannual time series of hydroacoustic seafloor surveys conducted at an isolated rocky reef in the North Sea. We use multibeam bathymetry and side-scan sonar backscatter data in combination with video observations, sediment sampling, and sub-bottom profiler data to assess the long-term variations of the rocky reef system. The reef is located in water depths between 11 and 17 m with an areal extent of ~0.5 km2 and is surrounded by mobile sands. The topography of the rocky reef appears to create a distinct hydrodynamic system that permits mobile sands to settle or move into bathymetrical deeper parts of the reef. Our results suggest a very dynamic system surrounding the reef with large scale scouring, sediment reworking and transport, while the shallower central part of the reef remains stable over time. We demonstrate the importance of hydrodynamics and current scouring around reefs for the local variability in seafloor properties over time. These small-scale dynamics are likewise reflected in the spatial distribution of sessile species, which are less abundant in proximity to mobile sands. The hydroacoustic mapping and monitoring of seafloor dynamics at higher spatial and temporal resolutions presents an important future direction in the study of valuable coastal habitats.

ADCP Observations of Currents and Suspended Sediment in the Macrotidal Gulf of Martaban, Myanmar

The Ayeyarwady and Thanlwin Rivers, which drain Myanmar, together form one of the largest point sources of freshwater and sediment to the global ocean. Combined, these rivers annually deliver an estimated 485 Mt of sediment to the northern Andaman Sea. This sediment contributes to a perennially muddy zone within the macro-tidal Gulf of Martaban, but little is known about the processes that dominate dispersal and trapping of sediment there, as very few water column observations are available. A research cruise in December 2017 provided a rare opportunity to obtain Acoustic Doppler Current Profiler (ADCP) data along transects from the Gulf of Martaban and adjacent continental shelf. Two transects were obtained from the outer portion of the Gulf of Martaban in water depths that ranged from about 20–35 m. These showed very fast currents, especially during flood tide conditions, exceeding 1.5 m/s. The backscatter record from the ADCP indicated asymmetries in distribution of suspended sediment during the ebb versus flood phase of the tide. During ebb tidal conditions, the backscatter record indicated that sediment was transported in either a surface advected layer, or fairly well-mixed throughout the water column. In contrast, during flood tidal conditions, sediment was confined to the bottom boundary layer, even though the velocities were faster during flood than the ebb conditions. The vertical structure of the currents during flood tide conditions indicated the presence of sediment–induced stratification because currents within the near-bed turbid layers were relatively slow, but speeds increased markedly above these layers. This albeit limited dataset provides an exciting glimpse into the dynamics of sediment transport within the muddy, macrotidal Gulf of Martaban, and implies the importance of tidal straining and bottom nepheloid layer formation there.

Seasonal Variation and Governing Dynamics of the Mixed Layer in the Indian Sector of the Southern Ocean

AbstractThe dynamics involved in the variability of temperature, salinity, and density distributions in the upper layer of the Indo‐Pacific sector of the Southern Ocean were studied using Acoustic Doppler Current Profiler and Conductivity Temperature Depth data from a mini triangle trans‐ocean buoy network mooring deployed at 60°S and 140°E between January 15th and 19th December 2012, together with hydrographic casts, reanalysis outputs, and satellite imagery. Spectral analysis confirmed that near‐inertial internal waves are a major factor transporting energy downward to the lower boundary of the mixed layer (ML), with 12.5 J m−3 or 45% of the mean surface energy being able to reach deeper than the ML depth during one of the analyzed events. During a period of net heat loss from the ocean surface to the atmosphere, most of the energy was concentrated below the maximum shear layer, at around 80 m depth. Internal wave events were found to be linked to scalar diffusivity increases of up to two orders of magnitude. A box model clarified that surface cooling plays the most significant role in mixing surface waters during winter, but it is not enough to explain variability below 100 m depth, where horizontal advection and eddy enhancement are also important in modulating warm water flux. Our results elucidate how wind energy might enhance mixing, even in ice‐covered regions, while influencing depths greater than previously thought.

Analysis on distribution characteristics of velocities over depth in a coastal area

Based on the continuous Acoustic Doppler Current Profiler (ADCP) data at two stations in the Strait of Georgia, Canada, spatiotemporal variation characteristics of the eastern and northern velocity component over depth was analyzed, and dominant tidal components M2, K1 and O1at each layer were extracted through tidal current harmonic analysis. Main results are: (1) The vertical flow velocity in the study area has significant stratification, and the flow velocity generally decreases with the increase of water depth. Analysis of standard deviation of the flow in direction of east–west (u) and north–south​ (v) components shows that the standard deviation of u component at station 1 varied from 76.24 cm/s to 10.12 cm/s at depth of 20 m or more, while the standard deviation of v component varied from 99.65 cm/s to 11.6 cm/s. The standard deviation of component u at station 2 varied from 51.73 cm/s to 9.68 cm/s. While the standard deviation of component v changes from 93.56 cm/s to 11.39 cm/s, and the standard deviation below 20 m does not change significantly. It indicates that the velocity variation over depth is bounded at 20 m, the above gradient is relatively large, and the below gradient is relatively small; (2) Tidal pattern coefficient F of station 1 is 1.06, and that of station 2 is 1.15, both are 0.5<F≤2.0, thus, this area was dominated by the irregular semi-diurnal tide. The averaged value of the shallow water tide influence coefficient G is 0.084 and 0.063 at station 1 and 2, respectively, both are greater than 0.04. This indicates that the shallow water tide is significant in tidal currents; (3) The tidal current ellipse of the two stations is a reciprocating flow as a whole. The flow is dominated by M2 component, followed by K1 and O1. The surface tidal ellipse is larger than other layers. This research can provide theoretical basis and reference significance for the evaluation and utilization of tidal current energy.

Sequence stratigraphic evolution of the Kumano forearc basin during the last deglaciation: Influence of eustasy and tectonically-controlled shelf morphology on deep-marine sediment dynamics

We focus here on the different forcings that controlled the deep-marine sediment dynamics and associated stratigraphic pattern in the Nankai subduction zone, especially in the Kumano forearc basin. In this study, based on high-resolution subbottom profiler data, we investigate the Upper Pleistocene–Holocene deposits of the tectonically active Kumano forearc basin to better understand the role of glacio-eustatic forcing and tectonic-morphological controls on the sedimentation patterns in the basin. We recognize three distinct seismic units that characterize the different stages of the last to current interglaciation cycle. Chaotic debris- and mud-flow deposits, intercalated with turbidites accumulating mainly in the deep basin, are related to a lowstand stage when rivers were directly connected to canyon heads. The transgressive stage, covering the deglaciation period, is characterized by a high proportion of turbidites and a decrease in chaotic deposits. The flooding and development of the Ise Bay at ~10 ka, resulted in starvation of the deep basin where mostly hemipelagic deposits occur. However, some dilute flows still reached the proximal area of the basin depositing some turbidites. We identify an interplay between the global sea-level rise and the shelf morphology, both having a strong control on the deep-marine stratigraphic pattern of the Kumano Basin. The rise of sea level triggered a disconnection between the river mouth and canyon head, thus inducing a general retrogradation of sediment-gravity flow deposits throughout the deglaciation. The shelf morphology, which is mainly driven by tectonic uplift (narrow shelf) or subsidence (wide shelf), directly played on the connection between the river and deep-marine system and on the accommodation space in the shallow-marine environment. Although it does not appear as a dominant control, climatic control, especially the influence of the East Asian summer monsoon during deglaciation cannot be neglected. It most likely contributed to an increase in sandy sediment supply occurring at the beginning of the transgressive stage.The highlight of our study is related to the tectonically-controlled shelf morphology and its role on the deep-marine stratigraphic pattern. The northwestern area of the Kumano Basin, undergoing significant tectonic-related uplift, is defined by a narrow shelf (<10 km) and sustained sediment supply to the basin throughout the deglaciation and highstand period. However, under similar eustatic and climatic conditions, the eastern area characterized by the development of the subsiding Ise bay (wide shelf > 90 km), shows a decrease in sand supply to the basin toward the end of the deglaciation. A strong control of the shelf morphology on the deep-marine stratigraphic pattern is also observed in other forearc basins along the Nankai subduction zone undergoing similar eustatic and climatic conditions.

Derivation of High-Resolution Meteorological Parameters for Use in Airport Wind Shear Now-Casting Applications

Methods for now-casting adverse weather conditions with the potential to cause disruption to aircraft landings often make use of real-time measurements at high temporal resolution. This paper describes processing methodologies developed to derive meteorological parameters from such measurements recorded in the vicinity of Hong Kong International Airport, specifically a radiometer in King’s Park, a wind profiler and surface anemometer on Cheung Chau Island and weather buoys in the Pearl River estuary. These parameters are suitable for use as input to a now-casting application of the computationally efficient airflow model, FLOWSTAR, which has previously been shown to predict mountain waves generated by flow over Lantau Island to the southeast of the airport. Radiosonde data from King’s Park have been used to test the radiometer processing method; the novel approach of using minimum and maximum potential temperature deviations from a series of height-dependent linear profiles to derive radiometer inversion layer parameters generates data that compares well with values derived from corresponding radiosonde profiles. Mountain wave strength depends on the magnitude of wind speed in the inversion layer; wind profiler data can be used to estimate typical and maximum wind speeds and associated wind directions using estimates of inversion layer depth derived from the radiometer data. With estimates of surface sensible heat flux appropriate for the airport’s coastal location calculated using a marine boundary layer scheme, a dataset of meteorological parameters at 20-min resolution has been derived for input into the FLOWSTAR model. The combination of automated meteorological data processing methods and flow field modelling has the potential to form part of a now-casting system for determining strong wind shear conditions at the airport.

DFF와 압흔 경계 구분을 이용한 수직 압흔 변위 측정 방법에 관한 연구

Measuring imprint is important to evaluate material’s mechanical property through indentation test. In this study, we propose a measurement method for vertical imprint displacement after an indentation test. we divided the imprint into two regions, a file-up region with small displacement and a sloped region with large displacement. We estimated the focus value with different sized Laplacian operators for the separated regions. Then, we combined these results and estimated the depth map using the depth from focus (DFF) method. We constructed the median line of the depth map from the center of the imprint and compared results to contact profiler data. Comparing the results for the three materials (Al 1050 - T6, Al 5052 - H32, Al 6061 - T651), the maximum error rate was found to be 5%. In future studies, this result can be used for the estimation of material properties using FEM data.

Porewater Geochemical Assessment of Seismic Indications for Gas Hydrate Presence and Absence: Mahia Slope, East of New Zealand’s North Island

We compare sediment vertical methane flux off the Mahia Peninsula, on the Hikurangi Margin, east of New Zealand’s North Island, with a combination of geochemical, multichannel seismic and sub-bottom profiler data. Stable carbon isotope data provided an overview of methane contributions to shallow sediment carbon pools. Methane varied considerably in concentration and vertical flux across stations in close proximities. At two Mahia transects, methane profiles correlated well with integrated seismic and TOPAS data for predicting vertical methane migration rates from deep to shallow sediment. However, at our “control site”, where no seismic blanking or indications of vertical gas migration were observed, geochemical data were similar to the two Mahia transect lines. This apparent mismatch between seismic and geochemistry data suggests a potential to underestimate gas hydrate volumes based on standard seismic data interpretations. To accurately assess global gas hydrate deposits, multiple approaches for initial assessment, e.g., seismic data interpretation, heatflow profiling and controlled-source electromagnetics, should be compared to geochemical sediment and porewater profiles. A more thorough data matrix will provide better accuracy in gas hydrate volume for modeling climate change and potential available energy content.

Impact of Combined Assimilation of Wind Profiler and Doppler Radar Data on a Convective-Scale Cycling Forecasting System

Abstract The two types of wind observations, profiler and radar radial velocity, have been successfully assimilated into numerical weather prediction (NWP) systems. However, the added value of profiler data, especially from a densely deployed profiler network, is unknown when assimilated together with Doppler radar radial velocity. In this article, two combined assimilation strategies of profilers along with radar radial winds are compared within a convective-scale data assimilation (DA) framework. In strategy I, the profiler data are assimilated with conventional observations to generate an intermediate analysis that acts as a prior for radar data assimilation. In strategy II, both profiler and radar data are considered as storm-scale and assimilated within the same pass. Single- and dual-observation assimilation experiments indicate that for strategy I, the profiler DA improvement can be partly canceled by the potentially negative impact of the assimilation of single-radar radial velocity afterward, particularly when the radial wind is nearly orthogonal to the prevailing wind. For strategy II, important complements are provided when profilers are assimilated within the same pass along with radial winds. The diagnostics for a low-level jet case demonstrate that both strategies facilitate improved analyses and forecasts. But strategy II may bring more moderate analysis increments, which indicate mutual constraints of the profiler and radial winds when assimilated within the same pass. The results obtained in 1-month, retrospective cycling experiments also show that the strategy II outperforms the strategy I with slightly better wind and precipitation forecasts. Significance Statement Due to the high spatial–temporal wind information provided by profiler and radar radial velocity measurements, their combined assimilation would be expected to improve wind analysis. To fully utilize dense profiler data and radar radial wind in future operational applications, this study proposes a suitable assimilation strategy. If the profilers are defined as synoptic-scale observations, the profiler and Doppler radar data must be assimilated in different passes to adopt different length and variance scales. Whereas it is more reasonable to use a small background correlation length consistent with the radial velocity and, therefore, assimilate in the same pass if the profiler data are considered to better sample storm-scale features. Single- and dual-observation experiments indicate that profiler data provide important complements, while the assimilation of single-radar radial wind may yield analyzed wind results that do not depict the ground truth. A low-level jet case and a 1-month impact study further show that the combined assimilation strategy of assimilating both profiler and Doppler radar using smaller background correlation lengths enhances the analysis and forecasting of wind, resulting in more accurate accumulated precipitation forecasts.