Frontal Zone Research Articles

Remote dynamic and thermodynamic effects of typhoons on Meiyu–Baiu precipitation in Japan assessed with bogus typhoon experiments

To advance comprehensive knowledge of typhoon-induced remote precipitation and anomalous atmospheric circulations during the early summer rainy season (Meiyu-Baiu), we performed numerical simulations in which different bogus typhoons are imbedded in the July climatological mean field as ideal initial and lateral boundary conditions using a regional atmospheric model, and we compared experiments with and without the bogus typhoon. The dominance of an anomalous local high (ALH) remotely induced by a typhoon leads to a poleward shift of the primary Meiyu–Baiu frontal zone in the form of the enhancement of the North Pacific subtropical high (NPSH). Typhoon-induced negative potential vorticity advection plays a dominant role in forming the ALH around Japan. Despite the shift of the frontal zone, heavy precipitation in excess of 100 mm per day occurs along the Pacific coast of western Japan, which is triggered by two primary moisture inflows. One is the low-level moisture inflow along the moisture conveyor belt (MCB), which is an appreciable low-level moisture flux zone stretching from the Indian Ocean to a typhoon over the western North Pacific, due to the intensified horizontal pressure gradient between the typhoon and the NPSH. The MCB is more robust in the experiment in which the typhoon is close to the South China Sea where the monsoon westerlies prevail. The parcels along the MCB bring moisture into western Japan even though moisture losses due to condensation occur on the way, to some degree. The other is the moisture inflow through the atmospheric boundary layer along the southwestern periphery of the NPSH. The parcels along the NPSH periphery easily receive moisture from the underlying ocean as they approach western Japan. Both inflows are enhanced by the ALH formation over Japan. The combined effect of the typhoon and its induced ALH is responsible for the prominence of the two major moisture inflows into western Japan, leading to local heavy precipitation in that region.

Spatiotemporal variability of micronekton at two central North Pacific Fronts

The North Pacific Subtropical Frontal Zone (STFZ) seasonally aggregates economically important fish and protected species. The aggregation of top predators is hypothesized to be a response to convergent flow at the prominent thermohaline Subtropical Front (STF) in the STFZ and a sharp northward increase in primary productivity, the Transition Zone Chlorophyll Front (TZCF), which is thought to link primary productivity to top predators via secondary and tertiary consumers. Given existing data gaps in our knowledge on forage biomass, distribution, and composition in the area, characteristics of micronekton, forage for top predators, were investigated using in situ multi-frequency active acoustics from three springtime shipboard surveys conducted along the 158°W meridional. The effects of STF and TZCF on micronekton was accessed using in situ CTD profiles. Results of this study showed a significant positive effect of the STF on micronekton biomass. The acoustic data implied that the STF also acted as a boundary for the distribution of micronekton with differing taxonomic composition from south to its north. The TZCF, as well as Chl-a concentrations, did not show a significant effect on micronekton relative biomass or composition that might be due to effects of larger-scale variability masked in the in situ data. Contrary to expectation, significantly higher relative micronekton biomass was associated with higher temperatures, the mechanisms of which still need to be determined.

Distribution, hosts and long-term decline in abundance of the Patagonian lamprey inferred from diet assessment of albatrosses

Knowledge of lampreys during their marine phase is limited, and for the southern hemisphere species was gleaned from their predators (albatrosses) in the 1970s. Taking advantage of new methodologies and long-term data on predator diet and distributions, we infer diverse aspects of lamprey distribution and ecology. DNA analyses indicated that albatrosses at South Georgia prey on Patagonian lamprey Geotria macrostoma, originating from Argentina. Their core pelagic distribution when free swimming appears to be the Antarctic Polar Frontal zone (APFZ), and not South Georgia waters as assumed previously. If so, the APFZ would be the first known hotspot in abundance of an anadromous lamprey in oceanic waters. We could not identify a teleost fish that would be a likely host. Instead, we infer that the lamprey may prey on baleen whales, based on comparison of stable isotope ratios in lamprey with candidate host species, timing of appearance in albatross diets coincident with whale migrations, and circumstantial evidence (unexplained scarring recorded during the whaling era). We suggest that the lamprey do not tolerate cold Antarctic waters, and detach from southerly-migrating whales at the thermal boundary of the APFZ, where they become accessible to albatrosses in surface waters. Given strong evidence that relative importance of prey in seabird diets reflects availability in foraging areas, the steep decrease in the annual consumption of lamprey by albatrosses at South Georgia from > 550 tonnes in 1975–1976 and 1986, to very low levels in most years since 2012, is likely to indicate a major population decrease. Despite our unconventional means of assessing the population trend, there is a compelling case for listing of Patagonian lamprey at least as Near threatened by the International Union for the Conservation of Nature, and an urgent need to better understand anthropogenic threats in Argentina.

Siderophore production and utilization by marine bacteria in the North Pacific Ocean

AbstractSiderophores are strong iron‐binding molecules produced and utilized by microbes to acquire the limiting nutrient iron (Fe) from their surroundings. Despite their importance as a component of the iron‐binding ligand pool in seawater, data on the distribution of siderophores and the microbes that use them are limited. Here, we measured the concentrations and types of dissolved siderophores during two cruises in April 2016 and June 2017 that transited from the iron‐replete, low‐macronutrient North Pacific Subtropical Gyre through the North Pacific Transition Zone (NPTZ) to the iron‐deplete, high‐macronutrient North Pacific Subarctic Frontal Zone (SAFZ). Surface siderophore concentrations in 2017 were higher in the NPTZ (4.0–13.9 pM) than the SAFZ (1.2–5.1 pM), which may be partly attributed to stimulated siderophore production by environmental factors such as dust‐derived iron concentrations (up to 0.51 nM). Multiple types of siderophores were identified on both cruises, including ferrioxamines, amphibactins, and iron‐free forms of photoreactive siderophores, which suggest active production and use of diverse siderophores across latitude and depth. Siderophore biosynthesis and uptake genes and transcripts were widespread across latitude, and higher abundances of these genes and transcripts at higher latitudes may reflect active siderophore‐mediated iron uptake by the local bacterial community across the North Pacific. The variability in the taxonomic composition of bacterial communities that transcribe putative ferrioxamine, amphibactin, and salmochelin transporter genes at different latitudes further suggests that the microbial groups involved in active siderophore production and usage change depending on local conditions.

The effect of load and binding position on the friction of cross-country skis

This study investigates the effect of moving the binding and adjusting the normal load on friction for a modern cross-country ski. The binding was moved 10 cm forward and backward from the normal position. The results showed that moving the binding backward on the ski reduced the friction at cold (−10 °C) and warm air temperatures (+5 °C). At intermediate temperatures (−2 °C), neither changes to the binding position nor the total load affected the friction coefficient. Measurement of pressure zone profiles revealed that moving the binding backward reduced the apparent contact area, increased the average contact pressure, increased the peak pressure in the rear zone and increased the spacing between the front and rear contact zones of the ski.

The Influences of the Multi‐Scale Sea Surface Temperature Anomalies in the North Pacific on the Jet Stream in Winter

AbstractUsing Climate Forecast System Reanalysis (CFSR) data and numerical simulations, the impacts of the multi‐scale sea surface temperature (SST) anomalies in the North Pacific on the boreal winter atmospheric circulations are investigated. The basin‐scale SST anomaly as the Pacific Decadal Oscillation (PDO) pattern, a narrow meridional band of frontal‐scale smoothed SST anomaly in the subtropical front zone (STFZ) and the spatial dispersed eddy‐scale SST anomalies within the STFZ are the three types of forcings. The results of statistical methods find that all three oceanic forcings may correspond to the winter North Pacific jet changing with the similar pattern. Furthermore, several atmospheric general circulation model simulations are used to reveal the differences and detail processes of the three forcings. The basin‐scale cold PDO‐pattern SST anomaly first causes negative turbulent heat flux anomalies, atmospheric cooling, and wind deceleration in the lower atmosphere. Subsequently, the cooling temperature with an amplified southern lower temperature gradient and baroclinity brings a lagging middle warming because of the enhanced atmospheric eddy heat transport. The poleward and upward development of baroclinic fluctuations eventually causes the acceleration of the upper jet. The smoothed frontal‐ and eddy‐scales SST anomalies in the STFZ cause comparable anomalous jet as the basin‐scale by changing the upward baroclinic energy and Eliassen‐Palm fluxes. The forcing effects of multi‐scales SST anomalies coexist simultaneously in the mid‐latitude North Pacific, which can cause similar anomalous upper atmospheric circulations. This is probably why it is tricky to define the certain oceanic forcing to the specific observed atmospheric circulation variation.

Phytoplankton dynamics in nearshore regions of the western Antarctic Peninsula in relation to a variable frontal zone in the Gerlache Strait

The Gerlache Strait is a narrow channel that separates the western coast of the Antarctic Peninsula (WAP) from the Palmer Archipelago. This area is characterized by the presence of interconnected fjords, bays, islands, and channels that serve as a refuge for megafauna during summer. Through the framework of FjordPhyto – a citizen science collaboration with the International Association of Antarctica Tour Operators (IAATO) vessels – we assessed phytoplankton biomass and composition in surface waters of six under-explored nearshore areas connected to the Gerlache Strait (between 64° and 65° S) during three consecutive seasons, from November to March (2016–2019). During the first two seasons, we found significant differences in the phytoplankton community distribution and successional patterns to the north and south of the sampling area; the greatest differences were evidenced mainly in the months of high biomass, December and January. During December, cryptophytes bloomed in the north, while microplanktonic diatoms dominated in the south, and during January, small centric diatoms dominated in the north, while prasinophytes bloomed in the south. This spatial distinction in phytoplankton communities were mainly associated with the occurrence of a surface thermal front in the Gerlache Strait around 64.5° S. The presence of the front separating warm waters to the north and colder waters to the south, during the months of December to February, was confirmed by the analysis of 10 years of remote sensing data. By contrast, during the third season, low biomass prevailed, and no differences in the phytoplankton composition between the north and south areas were observed. The third season was the coldest of the series, with smaller differences in water temperature north and south of the usual front location. This study shows for the first time a complete overview of the phytoplankton composition throughout the entire growth season (November through March) in the nearshore areas of the WAP between 64° and 65° S. The results of this work contribute to the understanding of the phytoplankton community in relation to small scale physical features during the Antarctic austral summer.

The Ocean Surface Current in the East China Sea Computed by the Geostationary Ocean Color Imager Satellite

High-frequency observations of surface current field data over large areas and long time series are imperative for comprehending sea-air interaction and ocean dynamics. Nonetheless, neither in situ observations nor polar-orbiting satellites can fulfill the requirements necessary for such observations. In recent years, geostationary satellite data with ultra-high temporal resolution have been increasingly utilized for the computation of surface flow fields. In this paper, the surface flow field in the East China Sea is estimated using maximum cross-correlation, which is the most widely used flow field computation algorithm, based on the total suspended solids (TSS) data acquired from the Geostationary Ocean Color Imager satellite. The inversion results were compared with the modeled tidal current data and the measured tidal elevation data for verification. The results of the verification demonstrated that the mean deviation of the long semiaxis of the tidal ellipse of the inverted M2 tide is 0.0335 m/s, the mean deviation of the short semiaxis is 0.0276 m/s, and the mean deviation of the tilt angle is 6.89°. Moreover, the spatially averaged flow velocity corresponds with the observed pattern of tidal elevation changes, thus showcasing the field’s significant reliability. Afterward, we calculated the sea surface current fields in the East China Sea for the years 2013 to 2019 and created distribution maps for both climatology and seasonality. The resulting current charts provide an intuitive display of the spatial structure and seasonal variations in the East China Sea circulation. Lastly, we performed a diagnostic analysis on the surface TSS variation mechanism in the frontal zone along the Zhejiang coast, utilizing inverted flow data collected on 3 August 2013, which had a high spatial coverage and complete time series. Our analysis revealed that the intraday variation in TSS in the local surface layer was primarily influenced by tide-induced vertical mixing. The research findings of this article not only provide valuable data support for the study of local ocean dynamics but also verify the reliability of short-period surface flow inversion of high-turbidity waters near the coast using geostationary satellites.

Understanding the role of water evaporation and condensation in applied smoldering systems

Accurately resolving the way energy is stored and transferred is critical to applied smoldering systems in porous media. Water evaporation and condensation are important mechanisms in the energy conservation of smoldering. This is particularly important when significant water presence can affect the potential for self-sustained smoldering as it occurs in a broad range of practical applications. This paper describes a one-dimensional smoldering model considering water phase change. The model was calibrated to a series of wet smoldering experiments of GAC varying initial water saturation from 5 to 20%. The results show that introducing simple calibration constants on the thermal properties of a wet porous medium can accurately predict the transient and spatial resolution of the progression of evaporation, condensation, and smoldering reactions. A sensitivity analysis suggests that wet smoldering could be improved by increasing fuel concentration and injected airflow, which provides practical insights into wet smoldering applications. In addition, the model was applied to establish five characteristic zones for the wet smoldering front: evaporation, condensation, pre-heating, smoldering, and cooling. The evaporation and condensation zones challenge smoldering propagation due to the high water saturation. The pre-heating zone represents the region separating the smoldering front and evaporation zone, which serves as an important dry buffer and requires a minimum thickness (4 mm) to avoid extinction.

Solid phase extraction of ocean dissolved organic matter with PPL cartridges: efficiency and selectivity

Our current knowledge of the chemical composition of ocean dissolved organic matter (DOM) is limited, mainly because of its extreme molecular diversity, low concentration of individual compounds and the elevated ionic strength of ocean waters. As a result, many analytical methods require a previous extraction step. The efficiency and selectivity of the extraction method defines the representativeness of the extracted DOM fraction. Nowadays, the most widespread procedure for concentrating DOM is solid phase extraction (SPE) using styrene divinyl benzene polymer cartridges (PPL). Here, we investigate the effect of SPE-PPL on DOM elemental and optical properties to assess the efficiency and selectivity of this extraction method on water samples from the main intermediate and deep water masses of Arctic, Mediterranean and Antarctic origin present in the Cape Vert Frontal Zone (CVFZ, NW Africa). Furthermore, North and South Atlantic Central waters converge in this area and coastal DOM is injected by the giant upwelling filament of Cape Blanc. On one side, the colored fraction of DOM (CDOM) presented extraction efficiencies comparable to that of the bulk dissolved organic carbon (DOC), but decreased significantly with increasing wavelength, suggesting an affinity of PPL cartridges for low molecular weight organic compounds. While the protein-like fluorescent fraction of DOM (FDOM) was also extracted with the same efficiency than DOC, the extraction efficiency of the humic-like fraction was comparatively much higher. On the other side, dissolved organic nitrogen (DON) extraction efficiencies were about half that of DOC. These contrasting extraction efficiencies of the different DOM pools indicated that the extracts were enriched in N-poor, low molecular weight and recalcitrant DOM, therefore showing less variability than the corresponding bulk DOM. Furthermore, DOC, DON, CDOM and FDOM extracted were not homogeneous through the water column but displayed certain significant differences among water masses in both efficiency and selectivity.

Interannual variability of surface bio-optical characteristics in the frontal zones of the Indian sector of the Southern Ocean during austral summer

Surface bio-optical constituents (Chl-a, light-absorption coefficient of phytoplankton (aph (443)), detritus (ad(443)), coloured dissolved organic matter (aCDOM(443))), and hydrographic variables were studied across the fronts along 57.5°E during 2011, 2013 and 2015 in the Indian sector of Southern Ocean to understand their interannual variability and phytoplankton pigment package effect. Latitudinal increases of Chl-a, aph(443), and aCDOM(443) were observed in 2011 and 2013. Mean Chl-a was higher in 2013 than in 2015 and 2011. The Chl-a specific absorption (a*ph(443)) latitudinally decreased implying ‘pigment package effect’ with increasing latitude. Interannually increase of aph blue (443)/red (675) ratio suggested higher non-photosynthetic absorption during 2013 and 2015 than in 2011. The relative contributions of bio-optical constituents to total absorption (at) showed interannual decrease in aph(443) and increase in aCDOM(443) and ad(443) inferring phytoplankton growth and decay phases. The robust aph(443)-Chl-a relationship during 2011 was used to derive aph(443) for other years, which holds good for in situ and satellite-derived counterparts. aCDOM(443) positively correlated with Chl-a and negatively with CDOM-spectral slope (S300-500), suggesting autochthonous sources. Satellite-retrieved Chl-a, aph(443) showed significant correlation (p < 0.001) with in situ data. This study provides baseline bio-optical data for understanding phytoplankton size-class, and improvement of bio-optical algorithms in this relatively inaccessible polar region.

Summer Habitat and Fishing Ground of &lt;i&gt;Ommastrephes bartramii&lt;/i&gt; Related with the North Pacific Subarctic Frontal Zone Using Long-term Field Research Data

The neon flying squid, Ommastrephes bartramii, is an economically important oceanic squid species that has been harvested commercially in the North Pacific by Japan, Korea, China, and Taiwan. The Fisheries Research Agency (FRA) of Japan conducted long-term research for this species from 1980 to 2009 using commercial vessels to clarify the resource ecology and it obtained a total dataset of approximately 9,000 days, where following from this and to better clarify the relationship between habitat preference and oceanographic conditions, a generalized additive model was applied and mapped onto the Simple Ocean Data Assimilation ocean/sea ice reanalysis (SODA) data. The resultant habitat map of the squid showed an area of high abundance at the Subarctic Frontal Zone (SAFZ), with abundance areas increasing the squid abundance from April to August. The SAFZ extends from 40°N to 43°N separating the cold, low-salinity, subarctic water to the north from the waters of the North Pacific Transition Zone to the south. This high abundance area intersects between subarctic area and temperate area. It has characteristic nutrient regimes, productivity cycles, and nektonic faunal compositions. This paper suggests that the SAFZ thus plays an important role in North Pacific ecosystems by providing an optimal balance between environmental temperature and food density for the neon flying squid.

Geoenvironmental GIS development to investigate Landslides and Slope Instability along Frontal zone of Central Himalaya

The Frontal Himalayan terrain comprises of Lesser Himalaya and Siwalik Hills; is highly susceptible to landslide disaster due to active tectonics, scrappy geology, steep slope, and reshaping geomorphology. Besides that, hydrological impacts of land use degradation and climate change enhancing the vulnerability of the terrain. Keep in view this; the Dabka watershed, falls in frontal zone of central Himalaya has been selected for case illustration. Geospatial analysis advocates that the areas of the most stressed geo-environment (comprises of very steep slopes above 30°, geology of Lower Krol and Lariakanta formation, geomorphology of moist areas and debris sites and land use of barren land) have high density (5–10 landsides km2) of landslides whereas the areas of least stressed geo-environment (comprises of gentle slopes below 10°, geology of Kailakhan and Siwalik formation, geomorphology of depositional terraces and land use of dense forest) have low density of landslides (2 landsides km2). Out of total 340 landslides in the region, 198 are active landsides whereas 51 and 91 are reactivated and old landsides respectively. Geospatial analysis of landslide areas reveals that across the region total 804.33 ​ha land has been degraded by landslides which account for 11.65% of the total area of the Dabka watershed. The wedge failure analysis suggests that there are 3–4 sets of rock joints across the region and most of the sites are unsafe as their safety factors are less than 1.

Geodynamic aspects of the metallogeny-magmatic zonality relationship of orogenic volcanic-plutonic belts

Research subject. The orogenic marginal-continental and collisional volcanic-plutonic belts, and the zonality of magmatism and metallogeny within them, as well as the relationship of endogenous metallogeny with magmatic zonality and geodynamics of belt formation.Materials and methods include the long-term studies of the Devonian and Upper-Paleozoic belts of Kazakhstan and the Cretaceous-Paleogenic belt of Sikhote-Alin; an analysis of the alterations in the material parameters of magmatites; the identification of the front and rear parts of the belts and the arrangement features of metallogenic zones within their limits; and the data on other belts of the world.Results. For the marginal continental belts, an asymmetric change of the tholeiitic and low-potassium magmatites of the calcareous-alkaline petrochemical series of the frontal zone of the belt into the magmatites of the high-potassium branch of the calcareous-alkaline and shoshonite series of the rear zone (Devonian and Upper Paleozoic belts of Kazakhstan) has been established. In the same direction, the elemental, as well as the genetic type of deposits changes: pyrite copper-polymetallic frontal zones are replaced by molybdenum-copper-porphyry rear zones (near the border with the frontal zone) and then by rare metal ones. This is also characteristic of the Andean and Okhotsk-Chukchi belts. The collision belts are characterised by symmetrical zonality with a change from rare metal deposits in the centre to copper-polymetallic deposits at the edges (Mongolia). In some cases (Sikhote-Alin and Japan), the continuity of the marginal-continental belt is disrupted as a result of the mantle diapir (or plume), symmetrical magmatic and metallogenic zonality occurs with the change of polymetallic manifestations (near the ocean–continent boundary) to rare-metal ones in the distance. Conclusions. The change in the material parameters of the magmatites of the marginal-continental belts correlates with the removal of their ranges from the ocean–continent transition zone to the interior of the latter. In this case, copper-polymetallic pyrite ore formations are replaced by copperporphyry and then by rare metal ones in this direction. This is due to subduction processes. The collision situation is characterised by a symmetrical zonality of material magmatic parameters with respect to the crowding zone and a symmetrical arrangement of metallogenic zones with a change of rare metal deposits in the crowding zone to copper and polymetallic along the frame. These data are important for metallogenic prediction, as well as for palaeotectonic reconstructions.

Organization of planktonic Tintinnina assemblages in the Atlantic Ocean

Marine plankton have different biogeographical distribution patterns. However, it is not clear how the entire plankton assemblage is composed of these species with distinct biogeographical patterns. Tintinnina (tintinnids) is single-celled planktonic protozoa commonly used as model organisms in planktonic studies. In this research, we investigated the organization of Tintinnina assemblages along the Atlantic Meridional Transect (AMT) spanning over 90 degrees of latitude during the 29th AMT cruise (2019). Tintinnina with high frequency of occurrence was classified into four biogeographic distribution patterns (equatorial, gyre, frontal, and deep Chl a maximum) according to their vertical and horizontal distribution. All species falling within each distribution pattern formed a sub-assemblage. Equatorial sub-assemblage dominated in upper waters of the equatorial zone and gyre centres. Equatorial and frontal sub-assemblages co-dominated in upper waters of the frontal zones. Deep Chlorophyll a maximum Layer (DCM) sub-assemblage dominated in the DCM waters. Some Tintinnina species with high abundance could be used as indicator species of sub-assemblages. The Tintinnina assemblages in the northern and southern hemispheres exhibited asymmetry in terms of species composition. The latitudinal gradient of Tintinnina species richness was bimodal, which was shaped by the superposition of the species number of the four sub-assemblages with latitude. The result of this study contributes to the understanding of Tintinnina assemblage in the equatorial zone and subtropical gyres of the Pacific and Indian Ocean. It is also valuable for predicting the influence of global warming on changes in Tintinnina distribution and species richness.

Phytoplankton dynamics, growth and microzooplankton grazing across the subtropical frontal zone, east of New Zealand

Elevated but variable phytoplankton biomass and productivity is often associated with the subtropical front (STF) where nitrogen-limited subtropical and iron-limited subantarctic waters mix. To understand variability within the STF east of New Zealand, we assessed phytoplankton community structure, growth, and grazing dynamics in relation to physico-chemical conditions across 23 stations distributed along the Chatham Rise region during late autumn-early winter. Serial dilution experiments were coupled with size-fractionated chlorophyll a (Chla) analysis (Total and <20 μm) and flow-cytometry (Synechococcus and picoeukaryote numbers, <2 μm) to estimate phytoplankton growth and microzooplankton grazing rates. Within the broad STF zone, subantarctic influenced waters (SAIW), frontal zone (FZ), and subtropical influenced waters (STIW) were delimited based on salinity, temperature and nutrient gradients. The chlorophyll a biomass (TChla) of phytoplankton and the abundance of larger sized cells (>20 μm chlorophyll a) peaked in FZ waters but declined steadily southwards into the colder SAIW, and rapidly reduced north into the STIW. Chlorophyll a <2 μm peaked in the northern STIW. Phytoplankton growth (TChla) was higher in warmer STIW (μ = 0.49 ± 0.07 day−1) than in iron limited SAIW (μ = 0.29 ± 0.06 day−1) but was on average moderate (μ = 0.42 ± 0.05 day−1) when compared to previous studies in the region. Microzooplankton grazing on TChla was lower (m = 0.17 ± 0.04 day−1) than growth and accounted for half of daily primary production (m:μ, 0.47 ± 0.06). Growth in the <20 μm Chla size fraction was higher (μ = 0.52 ± 0.06 day−1) but a larger proportion was consumed by microzooplankton (m:μ = 0.64 ± 0.06). Picoeukaryotes showed the fastest growth (1.49 ± 0.13 day−1) and grazing (1.43 ± 0.11 day−1) rates on average, which peaked in the FZ but remained closely balanced across different waters (m:μ = 1.00 ± 0.02). Conversely, Synechococcus rates peaked in STIW and decreased southwards, with growth (μ = 0.42 ± 0.08 day−1) generally exceeding grazing (m = 0.28 ± 0.06 day−1) across all regions. Our results indicate differences in grazing together with nutrient (likely iron) availability were the primary factors controlling phytoplankton dynamics in the STF zone. These factors also affected the accumulation of larger phytoplankton biomass in the FZ, including the potential for export or transfer to higher trophic levels.

Agulhas leakage extension and its influences on South Atlantic surface water hydrography during the Pleistocene

The inter-ocean transfer of warm and salty water through the Agulhas leakage is regarded as a significant factor influencing the South Atlantic's surface and intermediate water hydrography. To evaluate the extension of Agulhas leakage for the past 1.2 Ma, planktonic foraminiferal assemblage from Ocean Drilling Program Hole 1088B, within the vicinity of AL, and Hole 1090B, located south of the significant Agulhas retroflection region, were generated. The Hole 1088B shows higher abundance of tropical and sub-tropical assemblage. The combination of Globigerinoides ruber, Trilobatus sacculifer, Globigerinoides conglobatus and Globorotalia menardii has previously been defined as the Agulhas leakage fauna [ALF]. The pulse-like amplification of the ALF record at major glacial-interglacial transitions indicates these were periods of strengthened Agulhas leakage with subsequent shedding of Agulhas rings and filaments as far as ∼41°S. From ∼450 ka, the frontal zone exhibits strong ALF variations with evident increase at glacial-interglacial transitions of Marine Isotopic Stages (MIS) 12, 10, 8 and 6, suggesting vigorous eddy mixing and a shift in the leakage zone towards the subantarctic waters. The migration of the Subtropical Convergence and Neogloboquadrina pachyderma (s) coiling ratios during these glacial-interglacial transitions supports the southward expansion of Agulhas leakage. The ALF record is supported by the δ18O record of Globigerina bulloides from hole 1088B, which identify a major anomaly at MIS 10, with depleted δ18O values towards the glacial termination. Simultaneously, the results from Hole 1090B show restricted presence of tropical-subtropical assemblage with their appearance reported only at glacial-interglacial transitions of the MIS 16, 12, 10 and 8. The curtailed ALF index and dominance of the subpolar species N. pachyderma (s) indicate the termination of Agulhas leakage before reaching the Subantarctic zone. The ODP sites chosen for the study reveal the intensification of Agulhas leakage and southward shift of the major leakage zone into the subantarctic zone during the Pleistocene glacial-interglacial transitions.

Study on the influence of drafting forms in front drafting zone of ring spinning frame on fiber motion and yarn quality

Double apron drafting is the general drafting form in the front zone of the ring spinning frame. In the double apron drafting system, the top apron and the bottom apron form an elastic tensor gauge, which can better control the movement of floating fibers and improve yarn quality. In order to investigate quantitatively the influence of the top apron and bottom apron on fiber movement and yarn quality in the double apron drafting system, the differences of fiber acceleration point distribution, yarn irregularity and yarn strength spun by double apron drafting, single apron drafting and simple roller drafting under different process conditions were compared. Compared with simple roller drafting, double apron drafting and single apron drafting can effectively control the fiber movement in the drafting zone. With the increase of fiber length, the difference between the distribution of fiber acceleration points obtained by double apron drafting and that obtained by single apron drafting gradually decreases. When the fiber length is greater than 32 mm, the difference is small. Besides, by analyzing the improvement rate of the top apron and bottom apron on yarn irregularity and yarn strength under different drafting settings, it was found that the overall improvement rate of the bottom apron on the yarn quality was higher than that of the top apron, especially for manmade fiber yarns. Even in some cases, the strength of viscose yarn spun by the single apron drafting process is higher than that of the double apron drafting process.

Field of the atmospheric water vapor as a characteristic of heat and dynamic processes at the ocean surface observed by the microwave radiometric means from space

An approach to indication and analysis of heat and dynamic processes at the ocean surface and in the atmosphere with the methods of satellite passive microwave radiometry is considered. It bases on a responsiveness of the oceanic and atmospheric up-going microwave radiation to these processes in the spectral band of its attenuation in the atmosphere water vapor, which seems to be as kind of window of the "radio visibility" from satellites. The effectiveness of that approach is caused by the fact that atmospheric water vapor is an active participant (agent) in its heat interaction with the ocean surface and, at the same time, serves as its reliable quantitative indicator. Measured from satellites, natural microwave radiation of the atmospheric water vapor gives distinct signals of changes occurring in the frontal, storm and cyclonic zones in the ocean; they are manifested in the form of pics or jumps of the brightness temperature. The paper provides various examples of the study of such processes as the ocean-atmosphere heat interaction at the middle latitudes of the North Atlantic, origination and propagation of the tropical hurricanes in the Gulf of Mexico and Caribbean Sea, atmospheric water vapor transport in the tropical Atlantic and its influence on cyclogenesis in the Gulf of Mexico, etc. The data of satellite, ship and buoy measurements are widely used to attain and verify results of our study.

The characteristics and evolution process of presummer intense regional rainfall over the Pearl River Delta metropolitan region

AbstractThe presummer intense regional rainfall events (RREs) over the Pearl River Delta (PRD) metropolitan region have been defined using rainy stations, maximum instantaneous regional rainfall coefficient (RRCt) and maximum rainfall intensity based on the rain gauge data from 2008 to 2017. Most of intense RREs with the maximum rainfall intensity about 20–60 mm·h−1 and the lifetime shorter than 24 h have the primary rainfall peak from noon to afternoon. Based on the rainfall pattern at 3 h prior to the events start, the intense RREs can be classified into two groups that one is southeastward propagation mode originating from the northwestern mountains of PRD and another is coastal mode from South China Sea (SCS). During the premonsoon‐onset period, the first type of RREs is the main mode causing the heavy rain in the cities of the inland region owing to the anomalous cold air from north confronting the wet and warm air from south with the increased southwesterly winds resulting in the strengthening frontal zone and moisture convergence. After the summer monsoon onset, the main rainfall pattern changes to the coastal mode having the significant impact on the coastal cities. The obvious anomalous cyclonic circulation related with the increased moisture convergence in the coastal regions providing the favourable conditions of the convection initiation and development. The study of the characteristics and evolution process of preceding intense RREs can improve the forecasting skills and reduce the risk of urban inundation.