Multi-year Cycles Research Articles

Long-range hydrological drought forecasting using multi-year cycles in the North Atlantic Oscillation

With global temperatures, populations and ecological stressors expected to rise, hydrological droughts are projected to have progressively severe economic and environmental impacts. As a result, hydrological drought forecasting systems have become increasingly important water resource management tools for mitigating these impacts. However, high frequency behaviours in meteorological or atmospheric conditions often limit the lead times of hydrological drought forecasts to seasonal timescales, either through poorer performance of multi-year meteorological forecasts or the lack of multi-year lags in atmosphere-hydrology systems. By contrast, low frequency behaviours in regionally important teleconnection systems (such as the North Atlantic Oscillation, NAO) offer a novel way to forecast hydrological drought at longer lead times. This paper shows that, by using a data-driven modelling approach, long-term behaviours within the NAO can be skilful predictors of hydrological drought conditions at a four-year forecasting horizon. Multi-year semi-periodic patterns in the NAO were used to forecast regional groundwater drought coverage in the UK (proportion of groundwater boreholes in drought), with the greatest forecast performance achieved for longer duration droughts, and for hydrogeological regions with longer response times. Model errors vary from 14 % (proportion of boreholes, (MAE)) in flashy hydrological regions or short droughts (<3 months), to 2 % for longer duration droughts (>8 months). Model fits of r2 up to 0.8 were produced between simulated and recorded regional drought coverage. As such our results show that teleconnection indices can be a skilful predictor of hydrological drought dynamics at multi-year timescales, opening new opportunities for long-lead groundwater drought forecasts to be integrated within existing drought management strategies in Europe and beyond.

Intensification and shutdown of deep convection in the Labrador Sea were caused by changes in atmospheric and freshwater dynamics

Labrador Sea winter convection forms a cold, fresh and dense water mass, Labrador Sea Water, that sinks to the intermediate and deep layers and spreads across the ocean. Convective mixing undergoes multi-year cycles of intensification (deepening) and relaxation (shoaling), which have been also shown to modulate long-term changes in the atmospheric gas uptake by the sea. Here I analyze Argo float and ship-based observations to document the 2012-2023 convective cycle. I find that the highest winter cooling for the 1994-2023 period was in 2015, while the deepest convection for the 1996-2023 period was in 2018. Convective mixing continued to deepen after 2015 because the 2012-2015 winter mixing events preconditioned the water column to be susceptible to deep convection in three more years. The progressively intensified 2012-2018 winter convections generated the largest and densest class of Labrador Sea Water since 1995. Convection weakened afterwards, rapidly shoaling by 800 m per year in the winters of 2021 and 2023. Distinct processes were responsible for these two convective shutdowns. In 2021, a collapse and an eastward shift of the stratospheric polar vortex, and a weakening and a southwestward shift of the Icelandic Low resulted in extremely low surface cooling and convection depth. In 2023, by contrast, convective shutdown was caused by extensive upper layer freshening originated from extreme Arctic sea-ice melt due to Arctic Amplification of Global Warming.

An intense narrow equatorial jet in Jupiter’s lower stratosphere observed by JWST

The atmosphere of Jupiter has east–west zonal jets that alternate as a function of latitude as tracked by cloud motions at tropospheric levels. Above and below the cold tropopause at ~100 mbar, the equatorial atmosphere is covered by hazes at levels where thermal infrared observations used to characterize the dynamics of the stratosphere lose part of their sensitivity. James Webb Space Telescope observations of Jupiter in July 2022 show these hazes in higher detail than ever before and reveal the presence of an intense (140 m s−1) equatorial jet at 100–200 mbar (70 m s−1 faster than the zonal winds at the cloud level) that is confined to ±3° of the equator and is located below stratospheric thermal oscillations that extend at least from 0.1 to 40 mbar and repeat in multiyear cycles. This suggests that the new jet is a deep part of Jupiter’s Equatorial Stratospheric Oscillation and may therefore vary in strength over time.

Destabilization of a seasonal synchronization in a population model with a seasonally varying Allee effect

Climate change causing large seasonal fluctuations is likely to lead to an increase in the average threshold of the Allee effect as well as an increase in its seasonal variability. In this paper, we show that a seasonally synchronized predator-prey system can be strongly destabilized by these changes in the threshold of the Allee effect. The typical result first leads to two-year and multiyear cycles by the principle of period doubling on a folded Möbius strip, up to the emergence of a chaotic and hyper-chaotic attractor living close to the trivial equilibrium corresponding to the extinction of populations. Moreover, this instability of the ecosystem can be hidden for a long time and the transition to its basin of attraction can occur by external perturbation in a random and irreversible manner. We also reveal a double folding of the 1:1 synchronized cycle manifold inside the corresponding Arnold tongue and hysteresis similar to well-known Duffing oscillator.

Extreme precipitation stable isotopic compositions reveal unexpected summer monsoon incursions in the Qilian Mountains

Isotope composition and moisture sources of precipitation are important for understanding water cycles and reconstructing paleoclimate. Based on 15-years' precipitation stable Isotope composition (δ18O and δ2H) from four stations of the Qilian Mountains, we found unique δ18O and δ2H features associated with the incursion of the summer monsoon over the Qilian Mountains, northwestern China. In 12 of the 15 years, similar seasonal variations of δ18O and δ2H confirmed a dominant source of moisture from Westerly circulation, and higher intercepts of the local meteoric water line (LMWL) indicated strong recycling of continental moisture. However, in August 2016 and 2018, extremely low slopes and intercepts of the LMWL, and more negative δ18O and δ2H revealed substantial contributions of the Asian summer monsoon to precipitation of the Qilian Mountains, with extremely heavy precipitation in August 2016. The column moisture flux, land-sea thermal contrast, correlations of precipitation δ18O with East Asian Summer Monsoon Index and Westerlies Index, HYSPLIT modeling results and precipitation δ18O along backward trajectories confirmed incursions of the summer monsoon in August 2016 and 2018. Our redefining of the boundary of the summer monsoon region confirmed the summer monsoon incursion zone can extend to the west of longitude 96°E and north of latitude 40°N in strong monsoon years, corresponding to boundaries of monsoon incursions in the mid-Holocene. Temperature correlated with precipitation δ18O at monthly and shorter time scales, but not for whole seasons or at yearly scale, revealing that summer monsoon incursions are therefore more likely than changing temperature to explain the multi-year cycles in the Qilian Mountains ice archives. Continent-scale shifts in atmospheric circulation strongly influence water resources in the Qilian mountains, and may change in frequency as climate warms. This study therefore has important implications for understanding water resources in the Qilian mountains in the past and into the future.

Rippling: towards untamed domesticity

The paper proposes ‘rippling' as a practice of untamed domesticity that contests the hegemony of the essentialised model of modern nuclear family and its associated domesticity. The conceptualisation of ‘rippling' derives from a context of the dissolved household in contemporary rural China — they are families of China's 285 million floating population who have seen the absence of a middle generation. At the intersection of architecture and anthropology, and with Shigushan village in Wuhan as the primary site of fieldwork since 2015, the point of entry is spatial and ethnographic observations and documentations of everyday practice in and around ordinary self-built family houses. The material traces and empirical evidence manifest a constantly diffused distinction between the domestic and the public, enacted by the rural dissolved household. In this way, the practice of ‘rippling' defies the confinement and codification of domesticity. Importantly, ‘rippling' and ‘dissolving' are a temporary, transient state that has become part of a broader structure rather than an exception. Through inhabiting and altering a multiplicity of spatial, social, and political thresholds, an elastic form of association is enacted, through which the act of mediating between genders, generations, households, neighbours, and the village community is constantly framed, and even spreads to the city through ‘floating’. Spatially stretched from house to territory and temporally coordinated from daily to multi-year cycles, domesticity as such is untamed.

Deformation at the open-vent Erebus volcano, Antarctica, from more than 20 years of GNSS observations

Erebus volcano on Ross Island in Antarctica is an iconic open-vent volcano that has hosted a convecting anorthoclase-rich phonolite lava lake for at least 50 years. Recent magnetotelluric observations have imaged a conduit system originating at least 60km below Erebus. This terminates in a seismically-imaged shallow magma reservoir about 500m NW of the crater with an upper surface at about 500m depth. A narrow and inclined terminal conduit system connects the shallow reservoir to the lava lake. Bomb-ejecting Strombolian eruptions from the lava lake and sporadically active adjacent vents are common. Larger eruptive activity with locally substantially elevated hazard has also been observed, including exceptionally energetic Strombolian activity in 1984 and an Inner Crater phreatic explosion in 1993. Despite sustained degassing and frequent eruptions, geochemical data show the composition of the lava has remained stable for the last 17ka, consistent with the long-lived transcrustal magmatic system underlying the lake.Global Navigation Satellite System (GNSS) data collection on Ross Island began in the late 1990s with campaign observations. In the early 2000s, additional benchmarks were added closer to the summit of Erebus and continuous GNSS (cGNSS) sites were co-located with a seismic network. Today, seven cGNSS sites operate on the summit plateau and flanks of the volcano, and a network of eight campaign benchmarks has been surveyed episodically.We present the first comprehensive geodetic data analysis and modeling results integrating these more than two decades of data collected at Erebus. We resolve long-term subsidence of Ross Island, which a simple viscoelastic model links to the long-term growth of Erebus over the last 20ka. The data also show multi-year cycles of inflation and deflation in the summit area, consistent with activity in the shallow summit magmatic system. These small amplitude (several mm/yr) transient dynamics suggest multi-year pulses of pressurization and depressurization, or geometric changes within the shallow magmatic system that we can reproduce with analytical source models. The most recent inflation pulse lasted from November 2020 until March 2022 when several stations moved radially away from the shallow magmatic system and upwards at 10–15mm/yr. Based on prior cycles, this deformation may result in increased eruptive activity suggesting that continued and enhanced surveillance of Erebus is warranted. These observations contrast with the long-term general stability of the lava lake, but reflect Inner Crater dynamics, which can include changes in lava lake elevation and associated topographic changes of over 20m on multi-year time scales. Our results emphasize the value of long-term and campaign-aided high-accuracy GNSS observations at open-vent volcanoes. This is especially true for volcanoes like Erebus which are remote and may only be accessible for a few months a year, and that deform at amplitudes and periods that may be difficult to resolve with satellite-based radar.

Effects of precipitation, heat, and drought on incidence and expansion of coccidioidomycosis in western USA: a longitudinal surveillance study

Drought is an understudied driver of infectious disease dynamics. Amidst the ongoing southwestern North American megadrought, California (USA) is having the driest multi-decadal period since 800 CE, exacerbated by anthropogenic warming. In this study, we aimed to examine the influence of drought on coccidioidomycosis, an emerging infectious disease in southwestern USA. We analysed California census tract-level surveillance data from 2000 to 2020 using generalised additive models and distributed monthly lags on precipitation and temperature. We then developed an ensemble prediction algorithm of incident cases of coccidioidomycosis per census tract to estimate the counterfactual incidence that would have occurred in the absence of drought. Between April 1, 2000, and March 31, 2020, there were 81 448 reported cases of coccidioidomycosis throughout California. An estimated 1467 excess cases of coccidioidomycosis were observed in California in the 2 years following the drought that occurred between 2007 and 2009, and an excess 2649 drought-attributable cases of coccidioidomycosis were observed in the 2 years following the drought that occurred between 2012 and 2015. These increased numbers of cases more than offset the declines in cases that occurred during drought. An IQR increase in summer temperatures was associated with 2·02 (95% CI 1·84-2·22) times higher incidence in the following autumn (September to November), and an IQR increase in precipitation in the winter was associated with 1·45 (1·36-1·55) times higher incidence in the autumn. The effect of winter precipitation was 36% (25-48) stronger when preceded by two dry, rather than average, winters. Incidence in arid counties was most sensitive to precipitation fluctuations, while incidence in wetter counties was most sensitive to temperature. In California, multi-year cycles of dry conditions followed by a wet winter increases transmission of coccidioidomycosis, especially in historically wetter areas. With anticipated increasing frequency of drought in southwestern USA, continued expansion of coccidioidomycosis, along with more intense seasons, is expected. Our results motivate the need for heightened precautions against coccidioidomycosis in seasons that follow major droughts. National Institutes of Health.

Effects of temperature and precipitation on litterfall phenology in four evergreen broad‐leaved forests of southern China

AbstractVegetative and reproductive growth of subtropical and tropical forests plays an important role in regulating carbon cycle and maintaining food web dynamic balance. Here, we used litterfall and climatic data during 1998–2017 at four evergreen forest sites in southern China to analyze temporal variations of community phenology and their climate drivers. Results show that two southwest forests have unimodal patterns with leaf litterfall peaks during dry season, while two southeast forests have bimodal patterns with the first peaks during rainy season and the second peaks during rainy and dry seasons respectively. Peaks of flower litterfall for the four forests occurred during the transitional period between dry and rainy seasons, while peaks of fruit litterfall appeared either at the end of the rainy season at the two southern sites or in the dry season at the two northern sites. Leaf litterfall correlates significantly positively with preseason maximum temperature at the four sites, but significantly negatively with preseason precipitation at two southwest sites. By contrast, flower and fruit litterfall correlates significantly positively with preseason temperature and precipitation at only three and two sites. Moreover, leaf, flower, and fruit litterfall exhibits a 12‐month cycle, which is consistent with the 12‐month cycle of monthly temperature and precipitation. Flower and fruit litterfall displays also multiyear cycles between 18 and 48 months, however, it is inconsistent with the multiyear cycles of monthly temperature and precipitation. Our study highlights that temperature and precipitation are key factors affecting litterfall variations in different time scales in southern China.Abstract in Chinese is available with online material.

Measuring the effects of COVID-19-related disruption on dengue transmission in southeast Asia and Latin America: a statistical modelling study

SummaryBackgroundThe COVID-19 pandemic has resulted in unprecedented disruption to society, which indirectly affects infectious disease dynamics. We aimed to assess the effects of COVID-19-related disruption on dengue, a major expanding acute public health threat, in southeast Asia and Latin America.MethodsWe assembled data on monthly dengue incidence from WHO weekly reports, climatic data from ERA5, and population variables from WorldPop for 23 countries between January, 2014 and December, 2019 and fit a Bayesian regression model to explain and predict seasonal and multi-year dengue cycles. We compared model predictions with reported dengue data January to December, 2020, and assessed if deviations from projected incidence since March, 2020 are associated with specific public health and social measures (from the Oxford Coronavirus Government Response Tracer database) or human movement behaviours (as measured by Google mobility reports).FindingsWe found a consistent, prolonged decline in dengue incidence across many dengue-endemic regions that began in March, 2020 (2·28 million cases in 2020 vs 4·08 million cases in 2019; a 44·1% decrease). We found a strong association between COVID-19-related disruption (as measured independently by public health and social measures and human movement behaviours) and reduced dengue risk, even after taking into account other drivers of dengue cycles including climatic and host immunity (relative risk 0·01–0·17, p<0·01). Measures related to the closure of schools and reduced time spent in non-residential areas had the strongest evidence of association with reduced dengue risk, but high collinearity between covariates made specific attribution challenging. Overall, we estimate that 0·72 million (95% CI 0·12–1·47) fewer dengue cases occurred in 2020 potentially attributable to COVID-19-related disruption.InterpretationIn most countries, COVID-19-related disruption led to historically low dengue incidence in 2020. Continuous monitoring of dengue incidence as COVID-19-related restrictions are relaxed will be important and could give new insights into transmission processes and intervention options.FundingNational Key Research and Development Program of China and the Medical Research Council.

Impacts of El Niño Southern Oscillation on the dengue transmission dynamics in the Metropolitan Region of Recife, Brazil.

ABSTRACTBackground: This research addresses two questions: (1) how El Niño Southern Oscillation (ENSO) affects climate variability and how it influences dengue transmission in the Metropolitan Region of Recife (MRR), and (2) whether the epidemic in MRR municipalities has any connection and synchronicity. Methods: Wavelet analysis and cross-correlation were applied to characterize seasonality, multiyear cycles, and relative delays between the series. This study was developed into two distinct periods. Initially, we performed periodic dengue incidence and intercity epidemic synchronism analyses from 2001 to 2017. We then defined the period from 2001 to 2016 to analyze the periodicity of climatic variables and their coherence with dengue incidence. Results: Our results showed systematic cycles of 3-4 years with a recent shortening trend of 2-3 years. Climatic variability, such as positive anomalous temperatures and reduced rainfall due to changes in sea surface temperature (SST), is partially linked to the changing epidemiology of the disease, as this condition provides suitable environments for the Aedes aegypti lifecycle. Conclusion: ENSO may have influenced the dengue temporal patterns in the MRR, transiently reducing its main way of multiyear variability (3-4 years) to 2-3 years. Furthermore, when the epidemic coincided with El Niño years, it spread regionally and was highly synchronized.

By wind or wing: pollination syndromes and alternate bearing in horticultural systems.

Cyclical fluctuations in reproductive output are widespread among perennial plants, from multi-year masting cycles in forest trees to alternate bearing in horticultural crops. In natural systems, ecological drivers such as climate and pollen limitation can result in synchrony among plants. Agricultural practices are generally assumed to outweigh ecological drivers that might synchronize alternate-bearing individuals, but this assumption has not been rigorously assessed and little is known about the role of pollen limitation as a driver of synchrony in alternate-bearing crops. We tested whether alternate-bearing perennial crops show signs of alternate bearing at a national scale and whether the magnitude of national-scale alternate bearing differs across pollination syndromes. We analysed the Food and Agriculture Organization of the United Nations time series (1961–2018) of national crop yields across the top-producing countries of 27 alternate-bearing taxa, 6 wind-pollinated and 21 insect-pollinated. Alternate bearing was common in these national data and more pronounced in wind-pollinated taxa, which exhibited a more negative lag-1 autocorrelation and a higher coefficient of variation (CV). We highlight the mutual benefits of integrating ecological theory and agricultural data for (i) advancing our understanding of perennial plant reproduction across time, space and taxa, and (ii) promoting stable farmer livelihoods and global food supply.This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.

Captura de Langosta en Baja California y su relación con la Actividad Solar

Es creciente el interés por conocer los vínculos entre el comportamiento de la Actividad Solar (AS) y del Clima Espacial con numerosos procesos de la biosfera y en particular, los relacionados con la extracción de especies marinas. En este trabajo se relacionó la serie de tiempo anual (1959-2018) de captura de langosta por varias cooperativas pesqueras a lo largo de la Península de Baja California, México, con los ciclos multianuales de la AS, con el objetivo de revelar si se cumple la hipótesis de asociación entre estas variables. La relación estadística y análisis espectral entre las dos series muestran un marcado sincronismo entre las series de tiempo y la presencia en los volúmenes de captura del período principal de 11 años de la AS. Se explica la posible conexión AS-clima-océano con la variabilidad pesquera del crustáceo. Teniendo en cuenta los volúmenes de captura de langosta y la importancia económica que ello constituye para la región, se considera un aspecto importante para su posible aplicación práctica y explotación de este conocimiento en el marco de la tendencia en los ecosistemas debido a la variabilidad climática.&#x0D; Palabras claves: Clima Espacial, Clima, Producción Pesquera.

Life in fluctuating environments.

Variability in the environment defines the structure and dynamics of all living systems, from organisms to ecosystems. Species have evolved traits and strategies that allow them to detect, exploit and predict the changing environment. These traits allow organisms to maintain steady internal conditions required for physiological functioning through feedback mechanisms that allow internal conditions to remain at or near a set-point despite a fluctuating environment. In addition to feedback, many organisms have evolved feedforward processes, which allow them to adjust in anticipation of an expected future state of the environment. Here we provide a framework describing how feedback and feedforward mechanisms operating within organisms can generate effects across scales of organization, and how they allow living systems to persist in fluctuating environments. Daily, seasonal and multi-year cycles provide cues that organisms use to anticipate changes in physiologically relevant environmental conditions. Using feedforward mechanisms, organisms can exploit correlations in environmental variables to prepare for anticipated future changes. Strategies to obtain, store and act on information about the conditional nature of future events are advantageous and are evidenced in widespread phenotypes such as circadian clocks, social behaviour, diapause and migrations. Humans are altering the ways in which the environment fluctuates, causing correlations between environmental variables to become decoupled, decreasing the reliability of cues. Human-induced environmental change is also altering sensory environments and the ability of organisms to detect cues. Recognizing that living systems combine feedback and feedforward processes is essential to understanding their responses to current and future regimes of environmental fluctuations.This article is part of the theme issue ‘Integrative research perspectives on marine conservation’.

Integrating Disturbance, Seasonality, Multi-Year Temporal Dynamics, and Dormancy Into the Dynamics and Conservation of Metacommunities

The metacommunity framework has rapidly become a dominant concept used by ecologists to understand community assembly. By emphasizing extinction-colonization dynamics, dispersal, and species’ niche requirements in determining community structure, metacommunity theory unifies local and regional processes as integral to species distributions across landscapes. Metacommunity structure has traditionally been treated as static. However, habitat characteristics and community composition can shift through time because of factors like seasonal dynamics, ecosystem disturbance, multi-year climate variation (e.g., El Niño Southern Oscillation), and production and emergence of dormant propagules. In most systems, the relevance of such temporal variation for the structure and persistence of metacommunities is an open question that is of potential importance for conservation and management. We evaluate and synthesize the theory and concepts relevant to four major forms of temporal dynamics that are pertinent to metacommunities: disturbance, seasonality, multi-year climate variation, and dormancy. For each type of dynamic we review the theoretical underpinnings and empirical evidence to evaluate how the dynamic drives temporal variation in metacommunity structure. We also consider how major forms of anthropogenic change further influence these patterns. Our survey highlights that seasonal climatic differences can modify the distribution and availability of resources and connectivity, with consequences for species’ use of the landscape and species interactions. Disturbance and multi-year climate cycles can increase the importance of dispersal, but implications for environmental filtering and species interactions remain unresolved. Dormant life stages serve to anchor habitat patches and species pools in space and highlight the importance of dispersal-dormancy tradeoffs and environmental variation for metacommunity structure. Temporal variability in biotic and abiotic conditions associated with these drivers can modify the relative strengths of dispersal, environmental filtering, and species interactions, three biological processes that drive metacommunity structure. Inclusion of spatiotemporal drivers creates patterns of species diversity that differ from traditional metacommunity ideas. We use these insights to highlight research needs, suggest a reconceptualization of metacommunities as undergoing continuous change, and discuss the implications of temporal dynamism for the conservation and management of metacommunities.

Analyzing Patterns of Seed Production for Chinese Torreya

Chinese Torreya (Torreya grandis cv. Merrillii) is an important economic tree in China, but there are limited studies on its seed production. We analyzed the patterns of historical seed production at two major sites (Zhaojiazhen and Jidongzhen) for Chinese Torreya from different perspectives. The results indicated that there were no 3-year or multiyear cycles in its seed production. A positive correlation existed between the average seed production and the average annual air temperature in 5 or 10 years at both study sites. There was no trend of the increasing coefficient of variance (cv) in seed production, but the cv generally increased before 1975, and became flat after that time. Frequency power law existed in seed production at both sites, but Taylor’s Law existed only at Zhaojiazhen. The multiscale entropy decreased with time scales, and the patterns were similar at both sites. Our research results provide a new understanding of seed production for Chinese Torreya.

Northern Harriers Have a Geographically Broad Four-Year Migration Cycle

We used observation data from major hawk-watch sites in northeastern North America to assess multiyear cycles in breeding productivity of the Northern Harrier (Circus hudsonius). We found that autumn totals of migrating harriers for 1983–2017 autocorrelated positively at the 4-yr lag for interior, but not Atlantic coastal, counts. The autocorrelation was especially high for harriers counted in October. The autumn counts of south-bound harriers were not correlated with counts of north-bound harriers in the previous spring. Interannual differences in atmospheric circulation during migration in 1983–2017, as expressed by the autumn North Atlantic Oscillation Index, correlated with the autumn harrier counts but did not have a 4-yr cycle. The temporal pattern revealed in this study should be considered when using counts of autumn migrants to infer regional population trends. Future research could focus on the cause of the cyclic pattern in harrier numbers. One obvious question concerns the relationship between spring populations of meadow voles (Microtus pennsylvanicus), which are important prey for harriers during breeding, and harrier numbers reported during the subsequent autumn migration.

Separate seasons of infection and reproduction can lead to multi-year population cycles

Many host–pathogen systems are characterized by a temporal order of disease transmission and host reproduction. For example, this can be due to pathogens infecting certain life cycle stages of insect hosts; transmission occurring during the aggregation of migratory birds; or plant diseases spreading between planting seasons. We develop a simple discrete-time epidemic model with density-dependent transmission and disease affecting host fecundity and survival. The model shows sustained multi-annual cycles in host population abundance and disease prevalence, both in the presence and absence of density dependence in host reproduction, for large horizontal transmissibility, imperfect vertical transmission, high virulence, and high reproductive capability. The multi-annual cycles emerge as invariant curves in a Neimark–Sacker bifurcation. They are caused by a carry-over effect, because the reproductive fitness of an individual can be reduced by virulent effects due to infection in an earlier season. As the infection process is density-dependent but shows an effect only in a later season, this produces delayed density dependence typical for second-order oscillations. The temporal separation between the infection and reproduction season is crucial in driving the cycles; if these processes occur simultaneously as in differential equation models, there are no sustained oscillations. Our model highlights the destabilizing effects of inter-seasonal feedbacks and is one of the simplest epidemic models that can generate population cycles.

About the role of environmental factors in carcinogenesis

There were found out the connections of the activity of the Sun and smoke of forest fires with the incidence of various forms of benign and malignant neoplasms in the population of young children 0-4 years old, in Khabarovsk Region, Russia. Thus, it was determined that so-called “sporadic” fluctuations in the incidence of neoplasms in the child population are not random. They are caused by long multi-year cycles of changes in the complex of environmental factors. The authors identified this phenomenon as “Alternative oncogenesis”, meaning by it the predominant occurrence of various forms of neoplasms in a certain period of time due to a change in the parameters of the complex of environmental factors. A proposed hypothesis is: ecologically linked oxidative stress as a cause of the epigenomic modulation leading to an imbalance between semaphorins and integrins that brings to oncogenesis.

Reconstruction of Hydrometeorological Data in Lake Urmia Basin by Frequency Domain Analysis Using Additive Decomposition

Frequency domain analysis using an additive decomposition method is proposed to reconstruct the missing hydrometeorological data of selected sites in Lake Urmia basin in Iran. Precipitation, evaporation, streamflow and groundwater time series are used for this aim. Trends, within- and multi-year cycles, and randomness are taken into account to reconstruct each of the time series for which models are developed, calibrated and validated separately. Statistical similarity between the observed and reconstructed time series is checked. Statistical characteristics including the average, standard deviation, skewness, and the first-order autocorrelation coefficient are well preserved at the reconstructed time series. A conceptual water budget model is also established to check for the consistency between the reconstructed and the observed datasets. The water budget model is taken as a quantitative way to confirm that the frequency domain analysis using the additive decomposition is an effective method for the reconstruction of the missing hydrometeorological data based on the case study performed for the Lake Urmia basin in Iran.