Short-period Events Research Articles

Asymmetric Boreal Summer Intraseasonal Oscillation Events over the Western North Pacific and Their Impacts on East Asian Precipitation

Abstract The boreal summer intraseasonal oscillation (BSISO) is the most prominent tropical subseasonal signature. Due to the restriction of methodology used to extract BSISO, most of the previous studies ignored its asymmetry. This study reexamines the BSISO events over the western North Pacific (WNP) for 1985–2010 with a hierarchical cluster analysis. Two categories of BSISO events are classified, the long-period (20–60 day) and short-period (10–20 day) events. The long-period BSISO events manifest as a northward-propagating mode with a significant phase asymmetry characterized by a fast development, but a slow decay of the intraseasonal convection. The phase asymmetry is found to be determined by the BSISO-induced amplitude-asymmetric sea surface temperature (SST) anomalies, in which the suppressed convection-induced positive SST anomalies are stronger than the active convection-induced negative ones. Such amplitude-asymmetric SST anomalies result from the nonlinear relationship between convection and surface downward shortwave radiation flux anomalies caused by the cloud transmission effect. The stronger positive SST anomalies–induced turbulence flux anomalies act as a negative feedback onto the atmosphere, making the transition from the convection suppressed phase to the active phase earlier and faster. The fast-developing convection tends to cause a fast northeastward retreat of the preceding enhanced western North Pacific subtropical high. Accordingly, the middle and lower reaches of Yangtze River valley experience a rapid reversal from the increased precipitation to the decreased. The asymmetric BSISO events over WNP and their impacts revealed in this study would provide a new potential for subseasonal-to-seasonal forecast of the East Asian summer monsoon precipitation.

A probabilistic linguistic opinion dynamics method based on the DeGroot model for emergency decision-making in response to COVID-19

Emergency decision-making entails a multi-criteria problem with a short period and urgent events, which creates difficulties for decision makers to undertake an optimal decision. To ensure the validity and rationality of decision results, the probabilistic linguistic term set is adopted to represent the evaluation information of experts because it can assign different probabilities or importance to different linguistic terms, which is closely related to human cognition. In addition, to portray the dynamic changes in the emergency decision-making process, this study develops a new dynamics method based on the DeGroot model with probabilistic linguistic information. First, to simulate the transition matrix of probabilistic linguistic opinions, the basic operational rules are defined based on the transformation function and expectation function. Next, three forms of influence matrices incorporating similarity, self-persistence, and authority degrees are constructed, and the consensus conditions of the models are discussed. Then, considering the social networks and incomplete trust relationships between experts, a fourth trust-based influence matrix is devised. A case study of emergency decision-making for assessing response plans to COVID-19 is performed to verify the feasibility and effectiveness of the dynamic method. Furthermore, a sensitivity analysis is conducted. Finally, comparisons with classical methods are performed to illustrate the superiorities of the proposed algorithms.

Times Associated With Source-to-Sink Propagation of Environmental Signals During Landscape Transience

Sediment archives in the terrestrial and marine realm are regularly analyzed to infer changes in climate, tectonic, or anthropogenic boundary conditions of the past. However, contradictory observations have been made regarding whether short period events are faithfully preserved in stratigraphic archives; for instance, in marine sediments offshore large river systems. On the one hand, short period events are hypothesized to be non-detectable in the signature of terrestrially derived sediments due to buffering during sediment transport along large river systems. On the other hand, several studies have detected signals of short period events in marine records offshore large river systems. We propose that this apparent discrepancy is related to the lack of a differentiation between different types of signals and the lack of distinction between river response times and signal propagation times. In this review, we (1) expand the definition of the term ‘signal’ and group signals in sub-categories related to hydraulic grain size characteristics, (2) clarify the different types of ‘times’ and suggest a precise and consistent terminology for future use, and (3) compile and discuss factors influencing the times of signal transfer along sediment routing systems and how those times vary with hydraulic grain size characteristics. Unraveling different types of signals and distinctive time periods related to signal propagation addresses the discrepancies mentioned above and allows a more comprehensive exploration of event preservation in stratigraphy – a prerequisite for reliable environmental reconstructions from terrestrially derived sedimentary records.

A Simple Method for Near-Real-Time Monthly Nighttime Light Image Production

Compared with previous nighttime light (NTL) data, the Black Marble product developed by NASA in recent years is the most advanced NTL product, which plays an important role in regional activity monitoring and special events (process) tracking due to its excellent timeliness (near-real-time release) and global data coverage capability. Currently, among the Black Marble products, the VNP46A2 product is not updated in a timely manner and VN46AX is still under development. Thus, VNP46A1, which is released in near real time, has become a key product available to the public, although it is affected by cloud cover and moonlight. To obtain high-quality near-real-time monthly NTL images and reduce the data gaps before VNP46AX is released, a simple processing scheme based on VNP46A1 is proposed in this letter. The results show that the proposed processing chain can effectively filter cloud-polluted pixels and alleviate the interference of moonlight radiation. The near-real-time monthly NTL (NRTMNTL) data generated by the scheme achieve a higher correlation with VNP46A2 and present a better visual purity. The near-real-time data availability and parameter-free input make the proposed scheme more applicable for short-period events tracking.

Presenting a Model Based on Fuzzy Application to Optimize the Time of IBS Projects in Gas Refineries

Nowadays, the construction industry has started to embrace IBS as a method of attaining better construction quality and productivity and reducing risks related to occupational safety and health. The built of pre-fabricated component in factories reduces many problems related to lack of purposing uncertainty in scheduling calculation and time management of projects. In the case of using IBS method for managing time in projects, former studies such as Allan Tay’s research, indicates that this method can save up at least 29% of overall completion period versus the conventional method. But beside mentioned advantages of this technical method, the projects could be optimized more and more in scheduling calculations. This issue is critical in gas refineries, since special parameters such as risk of spreading poison H 2 S gas and mandatory of performing projects in short time period events such as maintenance overhauls demands to perform projects in optimum time. Custom scheduling calculation of project planning uses the Critical Path Method (CPM) as a tool for Planning Project’s activities. The researches of this paper’s authors indicated that Fuzzy Critical Path Method (FCPM) is the best technique to manage the uncertainty in project scheduling and can save up the construction project’s time versus the custom methods. This paper aims to present a model based on fuzzy application in CPM calculations to optimize the time of Industrial Building System.

Detection of the rapid variability in the Q2237+0305 quasar

Rapid intrinsic variability has been detected for the first time in the Einstein Cross QSO 2237+0305, a radio quiet flat spectrum quasar at z=1.7 that is quadruply lensed by a foreground galaxy at z=0.04. The observed short-period event at the time scale of several days and with amplitudes of about 0.1-0.2 mag can be traced in the light curves of the 2004 observing season for all macroimages and in all the three filters (V, R and I). The accuracy of the existing estimates of the time delays in Q2237+0305 is insufficient to either confirm or disprove the estimations of time delays based on the lens models of this system, especially taking into account the presence of strong microlensing events. The detected short-period variations in the Q2237+0305 light curves have made possible to obtain new estimates of the time delays, which are more accurate as compared to the earlier determinations by other authors.

Do Annual Stock Price Effects of Extreme Cash Dividend Pay-Out Events Differ from Their Short Term Effects?

In this paper, we assess the long-term stock price impact of 1327 cash dividend payment initiations and 1156 cash dividend payment omissions of firms listed on the NYSE and the NASDAQ, from 1972 to 2012. In particular we compare the annual returns of dividend initiating and omitting firms and firms that are equally likely to initiate (or omit). We find larger price effects during the years of cash dividend initiation and omission than is measured by earlier short period event studies, but we find no price impact after the year has elapsed. When measuring such long-run effects, contemporaneous (same year) determinants of price effects may confound the findings of pure dividend initiations or omissions. We therefore test whether there are also unexpected changes in the contemporaneous determinants of returns, and we find that risk measures and net income differ systematically between firms that initiate (or omit) and firms that have similar characteristics, but do not change their payout policy. When correcting for such effects we find that systematic risk does not influence concurrent returns in the years of initiations or omissions, though total risk does. Idiosyncratic risk changes only influence the returns after dividend omissions. With and without correction for ‘contemporaneous’ factors, we find –also for several robustness tests- that the one year price impact of initiations is larger than that of omissions, which suggests that the surprise effects of dividend omissions are on average smaller than those of dividend initiations.

Projected increases in summer and winter UK sub-daily precipitation extremes from high-resolution regional climate models

Summer (June–July–August; JJA) UK precipitation extremes projections from two UK Met Office high-resolution (12 km and 1.5 km) regional climate models (RCMs) are shown to be resolution dependent. The 1.5 km RCM projects a uniform () increase in 1 h JJA precipitation intensities across a range of return periods. The 12 km RCM, in contrast, projects decreases in short return period (≦̸5 years) events but strong increases in long return period (⩾20 years) events. We have low physical and statistical confidence in the 12 km RCM projections for longer return periods. Both models show evidence for longer dry periods between events. In winter (December–January–February; DJF), the models show larger return level increases (⩾40%). Both DJF projections are consistent with results from previous work based on coarser resolution models.

The role of foraminifera as indicators of the Late Pleistocene–Holocene palaeoclimatic fluctuations on the deltaic environment: The example of Tiber delta succession (Tyrrhenian margin, Italy)

The palaeoclimatic and palaeoenvironmental reconstruction of the last 39.0 kyr of the central Tyrrhenian shelf are presented in this paper. Micropalaeontological, sedimentological and stable isotopic data integrated by radiocarbon dates were determined from three cores drilled in the Tiber delta sequence (TDS), which constitutes one of the most complete Late Quaternary high-frequency depositional sequences in the Mediterranean area. Short-period climate variations that induced short-period events caused changes in the Tiber run-off and increased the sediment supply and grain size in the delta system. The three cores, with different thicknesses, record all the system tracts forming the TDS. Three intervals corresponding to the Early and Late Lowstand, Transgressive and Highstand System Tracts (TST and HST) were recognised. The first is characterised by shoreface/inner shelf deposits and corresponds to a general cooling period characterised by short warmer periods (approximately 1.0 kyr), confirming the climatic variability of MIS 3/MIS 2. A very condensed deposition affected the second interval, which is characterised by a very low sedimentation rate corresponding to the TST of TDS. The third interval, corresponding to Holocene shelf deposits, shows small climatic oscillations that mark an enhanced seasonality typical of the modern Tyrrhenian regime. At the millennial scale, two warm intervals (Copper Age and Late Bronze Age/II century AC) alternating with two cold humid intervals (Bond cycle B3/RCC: 4.2–3.8 kyr BP of Mayewski events and the Little Ice Age) have been recognised.

FROM LARGE-SCALE LOOPS TO THE SITES OF DENSE FLARING LOOPS: PREFERENTIAL CONDITIONS FOR LONG-PERIOD PULSATIONS IN SOLAR FLARES

Long-period quasi-periodic pulsations (QPPs) of solar flares are a class apart from shorter period events. By involving an external resonator, the mechanism they call upon differs from traditional QPP models, but has wider applications. We present a multi-wavelength analysis of spatially resolved QPPs, with periods around 10 minutes, observed in the X-ray spectrum primarily at energies between 3 and 25 keV. Complementary observations obtained in Hα and radio emission in the kHz to GHz frequency range, together with an analysis of the X-ray plasma properties provide a comprehensive picture that is consistent with a dense flaring loop subject to periodic energization and thermalization. The QPPs obtained in Hα and type III radio bursts, with similar periods as the QPPs in soft X-rays, have the longest periods ever reported for those types of data sets. We also report 1-2 GHz radio emission, concurrent with but unrestricted to the QPP time intervals, which is multi-structured at regularly separated narrowband frequencies and modulated with ~18 minute periods. This radio emission can be attributed to the presence of multiple quiet large-scale loops in the background corona. Large scale but shorter inner loops below may act as preferential resonators for the QPPs. The observations support interpretations consistent with both inner and outer loops subject to fast kink magnetohydrodynamic waves. Finally, X-ray imaging indicates the presence of double coronal sources in the flaring sites, which could be the particular signatures of the magnetically linked inner loops. We discuss the preferential conditions and the driving mechanisms causing the repeated flaring.

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

Abstract. As part of the SpreadFEx campaign, coordinated optical and radio measurements were made from Brazil to investigate the occurrence and properties of equatorial Spread F, and to characterize the regional mesospheric gravity wave field. All-sky image measurements were made from two sites: Brasilia and Cariri located ~10° S of the magnetic equator and separated by ~1500 km. In particular, the observations from Brasilia provided key data in relatively close proximity to expected convective sources of the gravity waves. High-quality image measurements of the mesospheric OH emission and the thermospheric OI (630 nm) emission were made during two consecutive new moon periods (22 September to 9 November 2005) providing extensive data on the occurrence and properties of F-region depletions and regional measurements of the dominant gravity wave characteristics at each site. A total of 120 wave displays were observed, comprising 94 short-period events and 26 medium-scale gravity waves. The characteristics of the small-scale waves agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions for the Brasilia and Cariri datasets. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short-period events, suggesting they originated from the same source regions. Medium-scale waves are generally less susceptible to wind filtering effects and modeling studies utilizing these data have successfully identified localized regions of strong convection, mainly to the west of Brasilia, as their most likely sources (Vadas et al., 2009).

Evidence of sediment resuspension by nonlinear internal waves on the western Portuguese mid-shelf

In-situ observations of nonlinear internal waves (NIWs) propagating over the northern shelf of Portugal, near the Nazaré submarine canyon (39°47.4′N/009°11.4′W), and evidence of their action on the bottom, are presented and discussed. Synthetic Aperture Radar (SAR) images from this margin suggest the generation of NIWs over the canyon head (39°35′N/009°25′W) and the subsequent propagation directly to the mid-shelf. An observational program was conducted in this area in the summer of 2004, between August 29th and September 1st, to study these short-period internal waves. Temperature and current high resolution measurements were made with thermistor chains and acoustic Doppler current profilers (ADCPs), moored along the canyon generated NIW track, at the 82 m isobath. A simultaneous ENVISAT SAR image was obtained during the experiment. These observations were complemented by a CTD survey and bottom sediment sampling. Collected data show the propagation of large amplitude internal solitons forcing strong bottom current pulses. Turbidity profiles and ADCP echo variability suggest the remobilization of the mid-shelf bottom sediments induced by these short-period events. Calculations of bottom shear stress, induced by the observed canyon generated NIWs, reveal an energetic internal wave activity that can complement, during summer, the role of winter swell in sediment resuspension over the mid-shelf. This work is a contribution to the European project EUROSTRATAFORM, whose objectives include the study of the specific canyon systems dynamics and related sedimentary impacts on the European continental margin.

BOWEN, D. Q. (ed.) 1999. A Revised Correlation of Quaternary Deposits in the British Isles. Geological Society Special Report no. 23. ii+174 pp. London, Bath: Geological Society of London. Price £39.00, US $65.00 (paperback); members' price £19.00, US $32.00. ISBN 1 86239 042 8.

Just how does one cope with the Quaternary? In terms of geological time, it’s a mere blip: two million years or so. As if it were some kind of stratigraphical Tardis, though, this slender temporal frame conceals an enormous, and growing, volume of stratigraphy. Consider just lithostratigraphy: deposits on land are plastered as almost countless smears and patches over hills and valleys, rather than forming neat layercakes. These oddly shaped deposits were once squeezed, with a little pushing and shoving, into a corset of four climatic cycles. Now, there are around a hundred major oxygen isotope stages, reflecting major climatic swings, and a yet greater number of shorter-period events such as Dansgaard–Oescher cycles and Heinrich events. All of these events influenced sedimentation yet, paradoxically, most of the terrestrial formations seem to belong to …

Yellow and East China Seas response to winds and currents

The influences of the Kuroshio Current (KUC), Taiwan Warm Current (TWC), and surface wind stress on the Yellow and East China Seas (YES) are examined using tracers in a Princeton Ocean Model. Two experiments are performed: one with wind stress and one without. Seasonal variations in the inflow and outflow of the TWC and Tsushima Current are specified to examine the effects of the current transports. Two separate tracers are inserted into each model experiment to track the pattern of KUC and TWC waters into the YES. The two main areas of KUC and TWC water movement into the Yellow Sea are the southern entrance to the Yellow Sea trough and the Yangtze Relict River valley. Results indicate that KUC and TWC waters advect into the Yellow Sea regardless of wind stress. However, in the Yellow Sea during winter the wind stress increases KUC and TWC concentration at 20 m. The wind stress also produces short time period events that horizontally advect water masses and spatially smooth seasonally averaged water mass concentrations. The bottom Ekman layer appears to be one of the mechanisms driving the northward bottom flow across the East China Sea shelf. The bottom friction layer is stronger in summer when the TWC velocity is high. The bottom friction layer draws KUC water across the bottom of the continental shelf into the Yangtze Relict River valley and generates upwelling along the Chinese coast.

Les surcotes et les décotes marines à Brest, étude statistique et évolution

Sea surges (positive or negative) are short-period events (several hours to several days) among the most extreme oceanic phenomena resulting from climatic variability. A statistical study of hourly tide-gauge records at Brest does not allow any clear trend in long-term variations of these extreme sea levels to be detected. However, the frequency of extreme positive sea surges has increased recently (1953–1994), whereas extreme and sub-extreme negative sea surges has decreased. Such trends for the highest values strengthen the prevalence of positive sea surges over negative ones. The general evolution appears to be organised around several time scales, with a strong interannual variability superimposed on periods of amplification or regression of decennial order.

Effect of earth tide on deep well water level

On the basis of the partial differential equations of the water level in a deep well that is affected by the bulk strain tide, the boundary conditions of permeating each other between aquifer and well are considered. The solutions of the equations have been obtained by the superposition principle, inpulse theorem and separation of the variations. Some suitable values are given to the parameters of well aquifer in the solutions. By means of the numerical calculation the relations among the well tide coefficients and phase lag phenomenon of response of the well level to earth tides is well interpreted. The parametric studies and the obtained graphs show that the more the radius of casing in a well, the porosity of an aquifer and the bulk compressibility for solid matrix of an aquifer, the less the transmissibility of an aquifer, then the less the tidal coefficient of well level, while the more the phase lag for well level to respond to the tide is. The response of the well level to the tide of longer period is better than the shorter period events.

Ordovician magnetostratigraphy: Llanvirn-Caradoc limestones of the Baltic platform

SUMMARY Palaeomagnetic sampling has been performed covering 43 stratigraphic levels within the Baltoscandian Ordovician carbonates. After removing a ubiquitous PermoCarboniferous (287 f 14 Ma) remagnetization between 200 and 500 C, a LlanvirnCaradoc reversal stratigraphy is delineated by components with maximum unblocking temperatures up to 550-580C. Three reversed (SE, down) and three normal (NW, up) antipodal polarity intervals have been recognized. A primary/early diagenetic remanence age is therefore inferred for the stratigraphically linked polarity chrons. Primary magnetizations are resident in detrital/biogenic or early diagenetically formed single- and pseudo-single domain magnetite phases and subordinate early diagenetic.pigmentary haematite. The recognition of a primary remanence within these well-dated Ordovician carbonates has the following important tectonic and magnetostratigraphic consequences. (1) Accurate time-calibration of the Baltic APW path implies that rapid counterclockwise rotation took place in late Tremadoc and Llandeilo times. The ArenigLlanvirn epochs are characterized by a 'still stand'. Baltica occupied intermediate to high Southerly latitudes during the early Ordovician (Tremadoc-Llanvirn). Systematic northward drift is recognized in post-Llanvirn times. (2) A time-calibrated Ordovician reversal stratigraphy is proposed. Presently available data suggest the geomagnetic field was predominantly reversely polarized during Tremadoc and Arenig times. Two normal polarity zones of short duration are identified within mid-Llanvirn and mid-Llandeilo strata. Discontinuities within the succession may mask other short-period events. Late Llandeilo to mid-Caradoc times were then characterized by a normal polarity field.

An interpretation of induced magnetic variations near Shillong and Gulmarg

Short-period events such as bays and storm sudden commencements (SSCs) have been analysed to investigate the nature of induced magnetic variations at two Indian magnetic observatories: Shillong and Gulmarg. It seems that near Gulmarg there is obvious connection between the induced magnetic variations and the two large scale features; the main central thrust (MCT) and the main boundary fault (MBF) in the north-west direction. The Dauki fault, an approximately east-west conductor, seems to be responsible for the conductivity anomalies at SHL.

Source characteristics of the Kunashiri strait earthquake of December 6, 1978 as deduced from strain seismograms

A great intermediate-depth earthquake (M JMA = 7.7) occurred on December 6, 1978 beneath the Kunashiri strait in the southern part of the Kurile arc. Strain seismograms recorded by the three components of a fused-quartz extensometer at the Erimo Geophysical Observatory are used to study the source process of this earthquake. The seismograms show a notable sequence of pulses with a short-period of several seconds. The sequence follows the first P-wave arrival and lasts for ∼ 60 s after the first S-wave arrival. Furthermore, a long-period (∼ 60 s) wave arriving at the first P time appears on each seismogram. From the short-period pulse sequence, at least 18 distinct events which have a total seismic moment of 2.5 × 10 27 dyne · cm can be identified during ∼ 60 s by comparing the synthetic seismograms to the observed ones. However, the amplitude of the observed long-period wave cannot be explained enough by the sequence of short-period events. From this fact it may be concluded that this earthquake contains, in addition to short-period events, a main long-period event with a source process time (rupture time) of ∼ 60 s and a seismic moment of 4.5 × 10 27 dyne · cm. The observed strain steps, in both magnitude and shape, are also explained well by the complex multiple shock sequence.

A possible explanation of conductivity anomalies near Ujjain and Jaipur

Short-period events such as bays and SSCs have been analysed to investigate the nature of conductivity anomalies at two Indian magnetic observatories: Ujjain (UJJ) and Jaipur (JAI). The induction vectors calculated for these events indicate a high electrical conductivity contrast to the north-west of these stations. To determine an exact cause of anomaly, the direction of induced electric currents is estimated from horizontal disturbance vector $$(\vartriangle \vec B_A )$$ taking Alibag (ABG) as a normal station. These induced currents are found to flow south-west near JAI and westward near UJJ. It is suggested that possible cause of anomaly at JAI is a sub-surface conductivity contrast (possibly asthenospheric upwelling) along the Aravalli belt where high heat flow measurements have been reported. At UJJ, an approximately east-west conductor north of it seems to be responsible for conductivity anomalies.