Vertical Circulation Research Articles

Climatological changes in East Asian winter monsoon circulation in a warmer future

The assessment of future climate changes can be challenging if the anthropogenic influence on these changes cannot be determined. Understanding anthropogenic effects on climate variability may improve decadal predictability. In the present study, we investigated the changes in the climatology of the East Asian winter monsoon circulation and evaluated the extent to which these changes are regulated by global warming. We focused on the interannual fluctuation in the upper-level westerly jet stream and its connection with the underlying monsoon circulation, including the strength of the midlevel coastal trough and the zonal contrast in surface pressure. Evaluation of climatological changes in the relationships among various circulation patterns, particularly in the context of present and future decades of global warming, may help scholars differentiate between natural and anthropogenic effects on monsoon dynamics. Reduced interannual fluctuation in the jet stream was noted over the last half century, as was considerably increased global surface temperature. Thus, the monsoon related vertical circulation patterns will tend to become disconnected from each other. In a warmer future, global warming induced suppression of the jet stream's interannual fluctuation and its detachment from the low-level monsoon circulation may be common, and these events may be perturbed by climate oscillations.

THEORETICAL BASIS OF THE ECONOMIC ATTRACTIVENESS OF USING HEAT PUMPS IN CITY INFRASTRUCTURE

The use of heat pumps, as the main equipment for heating water, can be used for the first stage of water heating, since it requires less energy use. Water heating in the year of its maximum use by the heating network or autonomous equipment is taken into account when choosing a heat pump by capacity. A heat exchanger can be used to dispose of heat in small areas of the collectors. In the research, the search for an economically attractive project with a quick payback period and low cost with the provision of hot water supply appears. Further calculation of the project should offer financial attractiveness and practical use for existing condominiums and boiler houses. The object of research in the work is dormitories No. 7 and 8 of the National University of Water Management and Nature Management, Rivne. The existing hot water supply system and its cost to consumers were chosen as the basic economic coefficient. Capital and operating costs are included in the cost of the heat pump and the payback period is calculated. Alternatives to the heat pump are natural gas boilers and an electric boiler, which also take into account the costs of accumulative water heating. The costs of connecting to a centralized hot water supply network and the cost of a boiler or water heater are not taken into account. It is known that composites with organic binders are characterized by a high intensity of strength gain. Traditionally, the works were limited to the determination of strength characteristics (destructive stress during compression, bending, etc.) due to the same time segments of hardening (structuring) for different temperatures; later, analytical expressions describing the change in the strength of composites over a wide period of time were found. It was established that the analytical expressions used for organic composites (based on polyester resins, furfural-acetone monomer, methyl methacrylate, etc.) have a private nature and do not take into account the specifics of the strength process of composites based on other binders. In the first option, the existing elements of the HOT WATER SUPPLY system are used: the heating line from the CTP and from the boiler house along the street. Karnaukhova, 41. In the second option, the following elements of the hot water supply system are designed, built and installed: vertical probes (wastewater wells), heat pump, accumulator tanks, circulation pumps and pipelines. In the third, elements of the hot water supply system are designed, built and installed: heat exchanger pipe, heat pump, accumulator tanks, pipelines. The paper considers a technical and economic comparison of hot water supply systems: - traditional from centralized hot water supply; - with the help of a heat pump, which uses the heat of the soil and waste water. Keywords: heat pump, economic attractiveness, water heating, domestic hot water, thermal energy, heat capacity, waste water, energy potential.

Variations of Summertime SSTA Independent of ENSO in the Maritime Continent and Their Possible Impacts on Rainfall in the Asian–Australian Monsoon Region

Abstract The sea surface temperature anomalies (SSTA) in the Maritime Continent (MC) region are mainly related to local variability, ENSO, and the Indian Ocean dipole. Using the reanalysis data from NOAA and NCEP–NCAR, by employing the empirical orthogonal function (EOF) analysis, we have explored the principal mode of ENSO-independent summertime SSTA in the MC and its associations with regional climate anomalies. After ENSO signals have been removed, the leading mode of SSTA in the MC exhibits a uniformly signed pattern, which mainly varies on an interannual time scale. The maintenance mechanisms of the ENSO-independent SSTA are different in different subregions, especially over the region south of Java and the tropical northwestern Pacific. When the time coefficient of the first leading EOF mode (EOF1) is positive, warmer SSTAs are observed in the area south of Java. The oceanic dynamic heating there facilitates the warmer SSTA. Thus, the Gill-type response of the atmosphere is found over the region south of Java. The diabatic cooling in the atmosphere is dominant over the tropical northwestern Pacific where the warmer SSTA is maintained by the absorption of solar radiation due to less cloud cover there. A tilted vertical circulation is hence formed, linking the tropical southeastern Indian Ocean with the tropical northwestern Pacific. The anomalous circulations in the Asian–Australian monsoon region are affected by this ENSO-independent SSTA mode, resulting in decreased summer rainfall anomaly in the region near the southeast coast of China and increased winter precipitation anomaly over the extratropical region of Australia.

Interannual variability of the double easterly jets over the tropical western Pacific and their effects on tropical cyclone genesis

AbstractDifferent from other upper‐tropospheric jet stream that owns the single jet axis, the tropical easterly jet (TEJ) generally splits into two branches over the tropical western Pacific where the TEJ inflows from June to September, with the north branch locating near 20°N and the south branch appearing near the equator. However, how these double easterly jets change from year to year and whether they have effects on the tropical cyclones (TCs) over the tropical western Pacific are still unknown. Observational evidence has demonstrated that the double easterly jets in the TEJ's inflow region exhibit an out‐of‐phase relationship in the interannual time scale and is significantly related to the TCs genesis. Corresponding to a stronger south branch and a weaker north branch, the accelerated (decelerated) easterly wind for the south (north) branch would induce a northerly (southerly) ageostrophic wind, thus triggering an upper‐tropospheric divergence between the double easterly jets. This divergence can further lead to anomalous ascending flows over the western North Pacific, which turns out to be the primary cause that increases the TCs number over there. The results highlight that the out‐of‐phase variation of the double easterly jets could dynamically modulate the occurrence of the TCs over the western North Pacific by inducing the secondary vertical circulation.

ASSESSING THE EFFICIENCY OF VERTICAL MOVEMENTS IN ACADEMIC BUILDINGS IN CALEB UNIVERSITY IMOTA LAGOS: A CRITICAL APPRAISAL

Vertical circulation is a key factor in optimizing the design of any multi story building and the key to a successful functioning of the building design. For a multistory building, the placement of the stairs, escalators, and elevators frequently determines the floor design, further aiding in the building's optimization. The methodology for this research is the qualitative one using the observation and site survey of the selected buildings in the school. In order to accommodate the expanding student population and ensure that students with special needs may participate in the educational system, school designs must be developed from outward horizontal layouts to upward vertical structures. As a result, this study looked at the efficiency of vertical accessibility components in multi-story buildings at Caleb University, Imota Lagos, Nigeria in order to identify areas for improvement and contribute to ways of promoting social inclusion in educational settings. A digital camera and a study-developed observation guide were used. It is recommended that the management of Caleb University will respond positively by creating a more conducive vertical movements and ramps where necessary as pointed out by this research. Researchers, students, educators, policymakers, and building design professionals will find this study beneficial in resolving concerns related to universal design of the academic built environment, particularly in terms of ensuring adequate vertical movement elements in high-rise public buildings.

Quantitative evaluation on the suitable flow region inside the shielding device of submersible aquaculture facility

The primary purpose of the aquaculture facility is to provide a comfortable living environment and achieve welfare aquaculture for cultured fish in the open sea. Nevertheless, it has been a challenge to accurately assess the suitable flow region of the cultured fish inside the aquaculture facility for the severe ocean environment, which is a pressing concern for aquaculture farmers. First, the maximum domed swimming speed (MDSS) is used as an indicator to assess the swimming ability of Sciaenops ocellatus in this study, which can be measured through a vertical circulation water channel. Subsequently, the porous media theory is adopted and applied to predict the flow field inside the shielding device of the submersible aquaculture facility based on the shear stress transport k-omega turbulence model using the computational fluid dynamics (CFD) approach. In addition, combining the swimming ability of Sciaenops ocellatus and current speed distribution inside the shielding device of a submersible aquaculture facility, the suitable flow region is quantitatively assessed. The results indicate that when middle height, the inclined angle and net solidity are 0.4 m, 3π/12 and 0.65, respectively, the current speed inside the shielding device attenuates below the maximum domed swimming speed of Sciaenops ocellatus - 0.76 m/s and meets the survival of Sciaenops ocellatus for the actual sea condition with an incident current speed of 1.5 m/s. In addition, a suitable flow region for Sciaenops ocellatus, which is 204.512 m3 and accounts for 17.76% of the total aquaculture volume, is formed and located inside the shielding device, close to the downstream sides, and gradually extends towards the middle of the shielding device. Based on the swimming ability of Sciaenops ocellatus, using numerical means to describe the suitable flow region in detail is to provide clear and macroscopic guidance for aquaculture farmers.

Non-equilibrium solute transport in dipole flow tracer test (DFTT) considering the mixing effect in the wellbore

Dipole flow tracer test (DFTT) has been proposed to estimate the vertical distribution of hydrogeological parameters by fitting the simulated and observed breakthrough curves (BTCs) in the extraction chamber of a vertical circulation well (VCW). Previous studies of DFTT models neglected the non-equilibrium sorption of tracer and the mixing process in the wellbore, which have been proved to strongly influence the estimation accuracy of the DFTT. In this study, we developed an improved DFTT model considering a two-site non-equilibrium sorption of the tracer as well as the impact of the mixing effects on the BTC behavior in both the extraction and injection chambers. The results indicate that when interpreting the DFTT with commonly-used organic tracers, an overestimation and underestimation occurs, especially when the models do not account for sorption and consider equilibrium sorption, respectively. In addition, the mixing effect was observed to affect the transport process as well as the BTC behaviors in the DFTT, leading to an overestimation of the dispersivity. The improved model proposed in this work was used to interpret the DFTT test conducted with Rhodamine WT (RWT) at the Lizzie Field Site, North Carolina. Results showed that the improved model had better performance in interpreting the DFTT compared to the stream tube model proposed by Sutton et al. (2000). This is especially when fluorescent dyes such as RWT or Rhodamine B are used as tracers. Furthermore, unlike previous models, the improved DFTT model is not limited as it is fit for tracers with various types of sorption properties. Meanwhile, the consideration for mixing effect in the wellbore, characterized by an ordinary differential equation, promotes the DFTT interpretation accuracy and also has great potential in the simulation of in situ remediation of subsurface contaminants through VCW, especially for in-well bioreactor technology.

A data-driven modeling approach for the sustainable remediation of persistent arsenic (As) groundwater contamination in a fractured rock aquifer through a groundwater recirculation well (IEG-GCW®)

Persistent arsenic (As) pollution sources from anthropogenic activities pose a serious threat to groundwater quality. This work aims to illustrate the application of an innovative remediation technology to remove As from a heavily contaminated fractured aquifer at a historically polluted industrial site. Groundwater circulation well (GCW) technology was tested to significantly increase and accelerate the mobilization and removal of As in the source area. The GCW extracts and re-injects groundwater at different depths of a vertical circulation well. By pumping out and reinjecting in different screen sections of the well, the resulting vertical hydraulic gradients create recirculation cells and affect and mobilize trapped contaminants that cannot be influenced by traditional pumping systems. The first 45-m deep IEG-GCW® system was installed in 2020, equipped with 4 screen sections at different depths and with an above-ground As removal system by oxidation and filtration on Macrolite (Enki). A geomodeling approach supports both remediation and multi-source data interpretation. The first months of operation demonstrate the hydraulic effectiveness of the IEG-GCW® system in the fractured rock aquifer and the ability to significantly enhance As removal compared to conventional pumping wells currently feeding a centralized treatment system. The recirculation flow rate amounts to about 2 m3/h. Water pumped and treated by the GCW system is reintroduced with As concentrations reduced by an average of 20%–60%. During the pilot test, the recirculating system removed 23 kg As whilst the entire central pump-and-treat (P&T) system removed 129 kg, although it treated 100 times more water volume. The P&T plant removed 259 mg As per m3 of pumped and treated groundwater while the GCW removed 4814 mg As per m3 of the treated groundwater. The results offer the opportunity for a more environmentally sustainable remediation approach by actively attacking the contamination source rather than containing the plume.

Vertical Motions in Orographic Cloud Systems over the Payette River Basin. Part II: Fixed and Transient Updrafts and Their Relationship to Forcing

Abstract Updrafts in wintertime cloud systems over mountainous regions can be described as fixed, mechanically driven by the terrain under a given ambient wind and stability profile (i.e., vertically propagating gravity waves tied to flow over topography), and transient, associated primarily with vertical wind shear and conditional instability within passing weather systems. This analysis quantifies the magnitude of fixed and transient updraft structures over the Payette River basin sampled during the Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE). Vertical motions were retrieved from Wyoming Cloud Radar measurements of radial velocity using the algorithm presented in Part I. Transient circulations were removed, and fixed orographic circulations were quantified by averaging vertical circulations along repeated cross sections over the same terrain during the campaign. Fixed orographic vertical circulations had magnitudes of 0.3–0.5 m s−1. These fixed vertical circulations were composed of a background circulation in which transient circulations were embedded. Transient vertical circulations are shown to be associated with transient wave motions, cloud-top generating cells, convection, and turbulence. Representative transient vertical circulations are illustrated, and data from rawinsondes over the Payette River basin are used to infer the relationship of the vertical circulations to shear and instability. Maximum updrafts are shown to exceed 5 m s−1 within Kelvin–Helmholtz waves, 4 m s−1 associated with transient gravity waves, 3 m s−1 in generating cells, 6 m s−1 in elevated convection, 4 m s−1 in surface-based deep convection, 5 m s−1 in boundary layer turbulence, and 9 m s−1 in shear-induced turbulence.

Comment on “The Cross‐Shore Component in the Vertical Structure of Wave‐Induced Currents and Resulting Offshore Transport” by Lu et al.

AbstractUnderstanding wave‐current interactions is crucial to coastal engineering projects and management. However, research gaps still exist in literature, especially on how tides can affect wave dynamics in shallow waters where depth is strongly affected by tidal height variation. This commentary highlights some of these unresolved issues, for an example, in the study of Lu et al. (2021, https://doi.org/10.1029/2021jc017311). We argue that without applying a fully coupled wave‐current model, vertical and horizontal circulation in the surf zone and offshore of embayed beaches can be very different to wave‐driven currents without considering tidal forcing as Lu et al. (2021, https://doi.org/10.1029/2021jc017311) appears to have done.

Influence of Entrainment on Centimeter-Scale Cloud Microphysics in Marine Stratocumulus Clouds Observed during CSET

Abstract Cloud microphysical relationships observed during the Cloud System Evolution in the Trades (CSET) campaign held between Northern California and Hawaii were analyzed to study the effects of entrainment and subsequent mixing of free-tropospheric and cloudy air on cloud microphysical properties of marine stratocumulus clouds. The data measured by Holographic Detector for Clouds (HOLODEC) were extensively used because they could provide the 3D positions and sizes of droplets within sample volume on the centimeter scale, making it possible to explore the 3D spatial distribution of droplets, which has not been possible for conventional cloud probes. This study focused on analyzing the 3D spatial distribution of droplets and visual traits of inhomogeneous mixing and on quantifying the relationship between 3D spatial distributions and traits of inhomogeneous mixing. Two types of spatial distributions are compared. The first is measured droplet spatial distribution and the second type is generated randomly distributed droplets using the Monte Carlo approach, that is, to analyze whether or not clustering is strong enough to classify as a clustered distribution for a hologram. The difference between the two types of spatial distributions depends on whether they are affected by entrainment and mixing. The holograms observed near the cloud top, where the effects of entrainment and mixing would be immediate, showed relatively high confidence in the significance test for spatially clustered populations of droplets. Moreover, spatially clustered holograms appeared to exhibit stronger visual traits of inhomogeneous mixing than perfectly randomly distributed holograms only when observed near the cloud top. On the other hand, these characteristics did not appear for holograms observed deeper into the cloud where the effects of entrainment and mixing would be reduced. Such 3D structural characteristics of droplet distributions seem to be consistent with vertical circulation mixing.

Vertical Motions in Orographic Cloud Systems over the Payette River Basin. Part III: An Evaluation of the Impact of Transient Vertical Motions on Targeting during Orographic Cloud Seeding Operations

Abstract In Part II, two classes of vertical motions, fixed (associated with vertically propagating gravity waves tied to flow over topography) and transient (associated primarily with vertical wind shear and conditional instability within passing weather systems), were diagnosed over the Payette River basin of Idaho during the Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE). This paper compares vertical motions retrieved from airborne Doppler radial velocity measurements with those from a 900-m-resolution model simulation to determine the impact of transient vertical motions on trajectories of ice particles initiated by airborne cloud seeding. An orographic forcing index, developed to compare vertical motion fields retrieved from the radar with the model, showed that fixed vertical motions were well resolved by the model while transient vertical motions were not. Particle trajectories were calculated for 75 cross-sectional pairs, each differing only by the observed and modeled vertical motion field. Wind fields and particle terminal velocities were otherwise identical in both trajectories so that the impact of transient vertical circulations on particle trajectories could be isolated. In 66.7% of flight-leg pairs, the distance traveled by particles in the model and observations differed by less than 5 km with transient features having minimal impact. In 9.3% of the pairs, model and observation trajectories landed within the ideal target seeding elevation range (>2000 m), whereas, in 77.3% of the pairs, both trajectories landed below the ideal target elevation. Particles in the observations and model descended into valleys on the mountains’ lee sides in 94.2% of cases in which particles traveled less than 37 km.

Analysis of Microsurface Characteristics during Micro-Electrochemical Texturing on Stainless Steel

A novel approach of Micro-electrochemical Texturing (MET) is a realistic substitute for generating surface textures of machined surface. Several conventional and non-conventional techniques i.e., embossing, sand blasting, pinning, LBM, EDM etc. are available for generating microsurface textures, but creates several problems to generate microtextured surfaces which reduce the quality and lower the productivity. To overcome these limitations, this research proposes a unique microsurface texturing method namely, micro-electrochemical texturing, based on electrochemical reaction. Due to the high flexibility of the micro-electrochemical texturing system, micro-texturing features, surface roughness and its performance can be easily changed by varying the micro-electrochemical parameters. In this research paper, this process is developed to fabricate the microsurface textures on stainless steel specimens economically with less time. The experimental results of surface characteristics generated on workpiece utilizing the developed setup with vertical cross flow electrolyte circulation system in micro-electrochemical texturing method are presented. The effects of duty ratio and voltage on performance criteria i.e., material removal rate (MRR), taper kerf angle and surface roughness are investigated. The obtained overall surface roughness value on the stainless-steel samples machined by micro-electrochemical texturing technique is 0.08μm.

An Assessment of the Relation between Architectural and Structural Systems in the Design of Tall Buildings in Turkey

Many professionals from several disciplines need to cooperate in designing and constructing tall buildings since their design and construction require more complex systems and technologies in terms of structure, installation, facade, vertical circulation and fire systems compared to low-rise buildings. The architects who design tall buildings have to know the architectural and structural design considerations of tall buildings and their interrelations well. This study is expected to reveal the status of tall buildings completed in Turkey and help designers understand architectural forms, floor plans, core planning and structural systems of tall buildings. For this purpose, the factors affecting architectural and structural design were examined, and the relation between the architectural–structural system was revealed for tall buildings completed in Turkey. In order to study architectural and structural considerations, 230 constructed tall buildings in Turkey were selected and analyzed in detail. According to the results of the study, it is seen that the prismatic form is widely used as the building tower form in Turkey, the shear-frame system as the structural system, the residential function as the building function, the single symmetrical central core as the building core, and the rectangular plan as the building floor plan alike.

Vertical circulation due to deep-water renewal and phytoplankton blooms in the tropical fjord of Ambon Bay, eastern Indonesia

This study provides the first observational evidence on the role of deep-water renewal in triggering phytoplankton blooms in a rare shallow-silled tropical fjord (Ambon Bay). Seasonal variation in the tidal-induced deep-water intrusions into inner Ambon Bay (IAB, the fjord basin) upwardly displaces water from the IAB deep layer towards the surface. The budget method was employed to quantify vertical mixing in the deep layer of IAB (below sill depth) post-intrusions (stagnant periods). Within a spring-neap sequence (~ 2 weeks), deep-water intrusion pulses in IAB were observed to be more frequent in the easterly monsoon (July, eight pulses) than the transitional season (October, three pulses). These intrusion pulses uplifted the resident deep waters of IAB with rates of 2.4 - 4.0 m/day in the easterly monsoon and 1.5 - 1.8 m/day in the transitional season. Depth-averaged vertical diffusion coefficient (Kv) in the deep layer of IAB slightly varied between easterly monsoon (3.3 × 10-4 m2/s) and transitional season (3.7 × 10-4 m2/s). The parameterization of the vertical mixing-stratification relationship (Kv ∝ [N2]-β) in the IAB deep layer was found to be larger in easterly monsoon (β = 1.104) than in transitional season (β = 0.694). Chlorophyll-a concentration in the water column of IAB increased during uplifting events with phytoplankton bloom conditions (> 5 mg/m3) found only in the easterly monsoon. The described uplift mechanism as a driver of phytoplankton blooms should be included in future analyses of water quality for IAB.

How has the North Pacific Gyre Oscillation affected peak season tropical cyclone genesis over the western North Pacific from 1965 to 2020?

The North Pacific Gyre Oscillation (NPGO) is an important mode of decadal variability in North Pacific sea surface temperature (SST) and sea surface height. This study investigated the potential influence of the NPGO on spatial characteristics of peak season (July to October) tropical cyclone genesis (TCG) number over the western North Pacific (WNP) from 1965 to 2020. We show that the NPGO was the first leading empirical orthogonal function mode of North Pacific SST during the peak tropical cyclone season in that time. On a decadal time scale, the NPGO has opposite impacts on TCG in the west and east WNP. The relatively weak positive correlation west of 140° E and the strong negative correlation east of 140° E result in an overall significant negative correlation between the NPGO and WNP total TCG number (r = −0.49), which is much more robust than the relationship between the Pacific Decadal Oscillation and TCG. The critical factors of the NPGO that affect TCG are vertical motion in the west WNP and vertical wind shear (VWS) in the east WNP. The positive NPGO pattern could induce an anomalous off-equatorial vertical circulation, resulting in an upward motion and increased convective precipitation in the west WNP, favoring local TCG. The anomalous convective precipitation enhances the zonal gradient of the atmospheric heat source in the east WNP, increasing VWS. The North Pacific low-level anticyclonic and upper-level cyclonic associated with the NPGO further enhance the VWS in the east WNP and lead to the negative low-level relative vorticity, inhibiting local TCG. This study emphasizes the importance of the climate impact of the NPGO in recent decades. The findings here have significant implications for the decadal prediction of change in WNP TCG.

Role of Water Vapor Modulation From Multiple Pathways in the Occurrence of a Record‐Breaking Heavy Rainfall Event in China in 2021

AbstractExtreme torrential rainfall events are low‐probability events. A “China‐Record Extremely Heavy Rainfall” (CREHR) event with rain rate of 201.9 mm/hr occurred on 20 July in Zhengzhou in North China. Using high‐density meteorological observations, ERA5 reanalysis data, remote sensing data from China's FY‐4A satellite, and numerical simulation, we revealed that sufficient warm–humid airflows were continuously transported to the Zhengzhou area via multiple pathways that were mainly modulated by the large‐scale western Pacific subtropical high to the north along with the anomalies of the westerly belt and a meso‐scale binary typhoon system. At the local scale, under the combined action of the vertical circulation that caused low‐level convergence and high‐level divergence, and the rapid uplift of water vapor related to the blocking by mountainous terrain, this CREHR event was eventually triggered. Particularly, our present work shows the roles of both typhoon Cempaka and meso‐scale convective systems to south of Henan province can not be ignored, producing a strong super‐thick water vapor transport layer. The existence of the binary typhoon raises the level of uncertainty involved in the water vapor transport of this CREHR event.

Influence of Atmospheric 10–20 Day Low Frequency Oscillation on Regional Strong Cooling Events in the Winter of Northern China over the Past 40 Years

Using daily minimum temperature data at 2481 stations provided by the National Meteorological Information Center (China) and the daily reanalysis data from NCEP/NCAR during the period from 1980 to 2019, the effects of atmospheric low frequency oscillations (LFOs) on the regional strong cooling events (RSCEs) in the winter of northern China are investigated, and the extended range forecast signals of the RSCEs are extracted. The results show that: (1) The frequency of RSCEs is higher before the year 2000 and then decreases, but its interannual variability increases. There are 10–20, 20–30 and 30–60 d significant low frequency periods in the regional average minimum temperature in northern China, and the low frequency oscillation with a period of 10–20 d is the most significant. (2) The low frequency key systems affecting RSCEs in the west, middle, and east of northern China are the Ural blocking high and the trough of Lake Balkhash-Baikal (Lake Ba-Bei), the blocking high in the northwest and the low trough in the southeast of Lake Ba-Bei, the Lake Ba-Bei blocking high and the East Asian trough, respectively, and the Siberian High (SH) that expands and moves with the blocking high all the time. The low frequency jets at the upper level are weaker in the north and stronger in the south. (3) The low frequency high potential vorticity (PV) center in the lower stratosphere moves eastward and southward along the 315 K isentropic surface via the north of Lake Ba-Bei, southern Lake Baikal and Northeast China to the Sea of Japan, causing the 2 PVU line to move southward and then the above-mentioned high PV center in the mid-high troposphere to extend vertically. Meanwhile, under the influence of gradually increasing upper level jets and vertical meridional circulation, the high PV column continues to propagate downward to the mid-low troposphere at lower latitudes along the 300–315 K isentropic surfaces, which enhances the low frequency positive vorticity and deepens the key trough. In addition, the convergence in the upper troposphere, the divergence in the lower layer, and the development of descending motion behind the trough lead to the development and southward movement of the SH. (4) At −10 d, the positive and negative low frequency anomalies at 500 hPa geopotential height appearing in the East European Plain and Western Siberian Plain are the extended range forecast signals for RSCEs in the winter of northern China, respectively.

Long-term adaptive response of an oceanic diatom to copper deficiency

Enhanced vertical stratification brought about by warming of the ocean surface is expected to reduce vertical circulation and nutrient input with knock-on effects for phytoplankton. Increased nutrient limitation is one predicted outcome, but how that will impact phytoplankton is uncertain because we do not know how they will adapt. We used copper (Cu) as a model catalytic nutrient to explore the adaptive response of an oceanic diatom to continuous nutrient deprivation in laboratory experiments. Populations of Thalassiosira oceanica maintained under Cu-limiting and sufficient conditions for ~380 generations differed significantly in their abilities to grow in medium containing 1 nM Cu. Continued selection for more than 2000 generations increased Cu use efficiency (CuUE) of a low Cu-adapted (LCuA) population by more than 2-fold compared to the control and ancestral populations. The increase in CuUE resulted from a decrease in the amount of cellular Cu required for growth and an increase in the net carbon assimilation rate. Redistribution of cellular Cu and increased efficiency of photosynthetic reactions are hypothesized to explain the fast rates of maximum electron transport of low Cu-adapted cells despite containing less Cu. The results show that adaptation increased resource use efficiency in phytoplankton, which could reduce the impact of increased nutrient deficiency in the future ocean.

Effects of Low-Frequency Oscillation at Different Latitudes on Summer Precipitation in Flood and Drought Years in Southern China

Based on the daily precipitation data from 753 meteorological stations provided by the National Meteorological Information Center (China) and the daily reanalysis data from NCEP/NCAR and ERA5 during the period from 1980 to 2020, the low-frequency (LF) precipitation characteristics of the typical summer flood and drought years in southern China and their relation to the LF atmospheric circulation at different latitudes are compared and analyzed, and extended-range forecasting signals are given. The results show that: (a) In both flood and drought years, summer precipitation in southern China is controlled by 10–20 day oscillation (quasi-biweekly oscillation, QBWO); (b) LF convection is active in southern China in both flood and drought years, but the convective center is southward in flood years, and the vertical meridional circulation is stronger. The key circulation systems of 500 hPa LF height field in flood and drought years include LF “two ridges and one trough” and LF “+”, “−”, “+” East Asia Pacific (EAP) teleconnection wave train in mid-high latitudes of Eurasia. However, the “two ridges and one trough” in flood years are more westward and meridional than in drought years, and the LF Subtropical High is stronger and more extensive, with more significant westward extension; (c) In flood (drought) years, there is northerly and then westerly (central westerly) dry-cold, northeasterly wet-cold, southwesterly (none), and southeasterly (including southerly across the equator) wet-warm water vapor channels. The sources of dry and wet cold air in flood (drought) years are located near Novaya Zemlya (the eastern West Siberian Plain), the Yellow Sea, and the Bohai Sea (Sea of Japan). Additionally, the sources of wet-warm water vapor include the Arabian Sea, the Bay of Bengal, the western Pacific Ocean, and the sea area of northeastern Australia (the western Pacific Ocean and the northern sea area of Australia); and (d) The LF predictive signals of outgoing longwave radiation (OLR) appear on −11 days, while the signals of the 500 hPa height field are on −9 days. There are both westward and eastward propagation predictive signals in flood years, and only westward spread signals in drought years.