Winter Maximum Research Articles

Contrasting Responses of Ion Concentration Variations to Atmospheric Patterns in Central Himalayan Ice Cores

AbstractWe analyzed the water‐soluble chemical composition of an 81.2‐m‐long ice core collected in 2019 from 6,000 m elevation on a south‐facing glacier in the Nepal Himalaya. The ice core chronology is based on variability in nitrate and calcium ions, which reveal an apparently seasonal periodicity (with winter maxima) throughout the core's length. Two annual boundaries are consistent with the tritium peak representing nuclear tests conducted in 1963 CE and with the spike in sulfate ions due to the eruption of Krakatau in 1883 CE. The ice core spans 145 years from 1875 to 2019 CE. Dating uncertainties due to the layer counting methodology were estimated as year for 1963–2019 CE and years for 1875–1963 CE. Comparison with earlier ice cores drilled on the northern side of the Himalayas revealed that the ion components exhibit inverse correlations with two key climatic indices: the North Atlantic Oscillation and Southern Oscillation Index. Composite analysis of reanalysis climate data suggests that these inverse relationships reflect springtime pressure patterns, which show regional differences between the northern and southern sides of the Himalayan range.

Local conditions have greater influence than provenance on sugar maple (Acer saccharum Marsh.) frost hardiness at its northern range limit.

In temperate and boreal ecosystems, trees undergo dormancy to avoid cold temperatures during the unfavorable season. This phase includes changes in frost hardiness, which is minimal during the growing season and reaches its maximum in winter. Quantifying frost hardiness is important to assess the frost risk and shifts of species distribution under a changing climate. We investigate the effect of local conditions and intra-specific variation on frost hardiness in sugar maple (Acer saccharum Marsh.). Seedlings belonging to seven provenances from the northern area of the species' range were planted at two sites in Quebec, Canada. LT50, i.e., the lethal temperature for 50% of the cells, was measured monthly with the Relative Electrolyte Leakage (REL) method on branches and buds from September 2021 to July 2022. LT50 varied between -4°C in summer (July) and-68°C in winter (February). Autumnal acclimation rates (September to early December) and mid-winter frost hardiness (December to early March) were similar in both sites. Samples in the southern site deacclimated faster than in the northern site between March and July, because of a warmer and earlier spring. No difference in frost hardiness was detected between provenances. Our results suggest that the frost hardiness trait is similar within the northern part of the sugar maple distribution, with local weather conditions having a greater influence than provenance. We demonstrate that LT50 in sugar maple can exceed -55°C, far below the minimum temperatures occurring in winter at the northern limit of the species. In order to minimize the risk of damage from extreme frost events exceeding tree frost hardiness, a careful evaluation of site characteristics is more important than provenance selection. Other factors should also be considered within the context of changing climate, in particular the phenology of maple and avoidance of late frost in spring.

Synthesizing Spatiotemporal Structures of the North Atlantic Tripole

AbstractThe interannual‐to‐decadal variability of sea surface temperature and height in the North Atlantic exhibits a tripolar pattern. Here, we explore the spatiotemporal structure, including the vertical, of the North Atlantic tripole using observations and reanalysis data in 1993–2021. For the first time, we demonstrate that the tripole's vertical structure across the Mid‐Atlantic Bight continental shelf and slope differs from that in the ocean interior. The tripole strongly projects in the Slope Water north of the Gulf Stream mean path, marked with temperature changes across the water column not maintained by air‐sea heat flux. Over the shelf, the tripole‐associated sea level, temperature, and ocean current are weak. In the ocean interior, the tripole temperature variability is apparent in the upper 100 m in the tropics and three times as deep in the subtropics. The tripole imprints resemble those of the North Atlantic Oscillation, peaking after the dominant atmospheric mode's winter maximum.

Long-term measurements of seasonal snowpacks indicate increases in mid-winter snowmelt and earlier snowpack disappearance in the northeastern U.S.

Snowpacks are changing in northeastern North America as the regional climate warms, yet the relative influence of changes in precipitation compared to changes in ablation on snowpacks is poorly understood. We use 56 years of weekly snow water equivalent (SWE) measurements from three locations within a study site which vary in elevation and aspect, paired with adjacent daily climate measurements, to investigate relationships between climate and snowpack onset, maximum, and disappearance. Maximum snowpack size and snowpack duration are shrinking at all sites, at rates ranging from 4.3 days/decade at the coldest site to 9.6 days/decade at the warmest site. The shorter snowpack duration at all sites results from an earlier snowpack disappearance, stemming largely from reduced winter maximum snowpack sizes. Trends in snowpack establishment dates vary, with the south-facing site showing a trend toward later establishment but the two north-facing sites showing no change. The date of the maximum snowpack size varies by aspect and elevation but is not changing at any site. Using a 0° C threshold for frozen vs. liquid precipitation, we only observed a decrease in the proportion of precipitation falling in frozen form at the warmer, south-facing site in the winter period. In contrast, the total weekly snowpack ablation in the winter period has been increasing at least marginally at each site, even at sites which do not show increases in thawing conditions. Ablation increases range from 0.4 cm/decade at the warmest site, to 1.4 and 1.2 cm/decade at the north-facing sites. The south-facing site shows only marginally significant trends in total winter ablation, which we interpret as being limited by the smaller snowpack at this site. Overall, we conclude that rising air temperatures are leading to warmer, more sensitive snowpacks and this change becomes evident before those temperatures lead to changes in precipitation form.

Sizing large-scale industrial heat pump for heat recovery from treated municipal sewage in coal-fired district heating system

Electrification of district heating and deep integration of sectors of national economies are fundamental elements of the future smart energy systems. This paper discusses the problem of optimal sizing of large-scale high-temperature heat pumps using treated sewage water as a heat source in a coal-fired district heating system. The study presents an approach to modelling of heat pump system that enables techno-economic analysis for investment decision making. Such analysis is enabled by a black-box-type identification model of the selected industrial heat pump. The model was developed based on the data generated by physical modelling of the heat pump using Ebsilon Professional software. In addition, it is proposed that the heat pump system is integrated with a dedicated photovoltaic power plant. The case study takes into consideration site-specific technical, economic, ecological, and legal constraints, weather conditions, hydraulic performance of the heat-ing network, and variability of loads within the sewage and the district heating systems. The results revealed that the proposed modelling approach is effective regarding multiple simulations and system optimisation. In addition, it was found that large-scale heat pump projects can be technically feasible and profitable if the heat pump is appropriately sized and operated. In the given case, the optimum size of the heat pump for a city of around 180 000 inhabitants is around 12 MW under maximum winter load.

On the problem of estimating the snowiness of winters by different methods by the example of the Yuzhno-Sakhalinsk city

The problem of estimating a snowiness (a snow coverage) of a territory is considered by many authors, but still nowadays no common approach to its solution is reached. Different authors use different characteristics in their works for estimating the winter snowiness. In this work the snowiness of winters was estimated using different parameters to determine the most representative one. The area ща study is the Yuzhno-Sakhalinsk urban district. The data for the past 36 years (1986–2022) were used to determine the types of the winter snowiness in this district. The following nine methods have been applied: the maximum winter snow reserve; by the amount of solid precipitation; by the average winter thickness of snow cover from the weather station and by snow survey; by the average greatest ten-day thickness of snow cover; by the amount of precipitation in the form of snow; the method of N.N. Galakhov; the Schultz coefficient; and the maximum winter snow cover thickness. The results obtained are very contradictory. Thus, the types of snowiness completely coincided in only 17% of winters; while in 58% of winters the types of snowiness coincided by 2/3 of the above indicators. Estimation of snowiness using various parameters gives closer results when using data on snow reserve at the beginning of snowmelt and the average winter thickness of snow cover (coincidence in 78% of cases). The reason is that a major part of the above methods uses the values of only one parameter. But given that snowiness is a complex indicator, it would be reasonable to consider all possible parameters at the same time. It is impossible to develop a unified approach to estimating winter snowiness, since the parameters chosen for this problem depend on the goal of the determination. It would also be worthwhile to select a methodology for estimating winter snowiness depending on the tasks set, and on the availability and reliability of the initial meteorological data for the analysis. Such work is also complicated by the insufficient volume of meteorological data, as well as due to gaps in them.

Long-term investigation of the irrigation intervals and supplementary irrigation strategies effects on winter wheat in the U.S. Central High Plains based on a combination of crop modeling and field studies

Implementing optimized irrigation strategies to achieve acceptable wheat yield while conserving groundwater resources is critical for extensively irrigated regions. Field experiments regarding winter wheat irrigation management were conducted for two growing seasons (2013–2014 and 2014–2015) to calibrate and validate the AquaCrop model. To determine proper parameterization of the AquaCrop model for various data availability conditions, the model performance was tested for calibration based on three different datasets, including a) calibration based on a full irrigation condition (CA 1), b) calibration based on a dryland condition (CA 2), and c) calibration based on diverse irrigation conditions, which included full irrigation, different deficit irrigation levels, and dryland (CA 3). The CA 3 calibration scenario resulted in the model's highest accuracy in simulating biomass, grain yield, total soil water, and seasonal evapotranspiration during the calibration and validation process. However, the model performance was also convenient when calibration based on full irrigation conditions was pursued. The calibrated and validated AquaCrop model based on the CA3 was used to analyze long-term (36-year) irrigation management scenarios for identifying the optimized water-conservative winter wheat irrigation strategies. The long-term analysis emphasized that increasing irrigation intervals from 7 to 15 or 20 days could reduce groundwater withdrawal by 52–64 % while expecting a 14–19 % reduction in grain yield. By implementing one 25 mm irrigation after planting and two 25 mm depth irrigation events at jointing or leaf growth stages, 91 % of Kansas's average winter wheat yield (2.88 tons/ha) could be achieved. During wet years, the 1.2 ton/ha reduction in biomass and 0.27–0.62 ton/ha reduction in grain yield is expected irrespective of irrigation management strategies. Considerable uncertainty was detected in grain yield production during dry years under dryland (rainfed) conditions. The maximum winter wheat production could be achieved under normal years, establishing a balance between precipitation and heat units. Our agro-hydrological analysis revealed that the highest irrigation water use efficiency could be attained by the application of two 25 mm irrigation events at jointing or flag leaf growth stages during normal years, the application of two irrigation events during jointing or heading during wet years, and two 25 mm irrigations at heading or flowering during dry years. The results of this research could be used as a baseline for producers of the U.S. Central High Plains and semi-arid regions with similar climate characteristics to cope with water scarcity in winter wheat production.

Influence of quasi-biennial oscillations (QBO) on the stratospheric polar vortex in the Antarctic

For many years, the dominant opinion in the literature has been that the stratospheric polar vortex is weaker in the easterly phase of the QBO than in the westerly phase, which is known as the Holton–Tan effect. While for the Northern Hemisphere vortex this is true during winter, for the Southern Hemisphere vortex the dependence on the QBO is observed only in spring. This feature is usually explained by the greater intensity of the Southern Hemisphere vortex compared to the Northern Hemisphere vortex, and the QBO can modulate its strength only during the vortex breaking season in October-November. Usually, the vortex response to the QBO is determined based on the equatorial wind direction at a certain vertical level, and the conclusions depend strongly on the level at which the QBO phase is determined. However, it has long been shown that using the equatorial wind sign at one or even a combination of several levels is not quite correct because it does not take into account the time of descent of the QBO wind relative to the seasons of the year, and it is not known at what altitudes the QBO wind has the strongest influence on the extratropical stratosphere. Due to the variable period of the QBO cycles, the phase relationship between the seasonal cycle and the QBO cycle is constantly changing, resulting in many variants of the vertical structure of the wind QBO during the Antarctic winter vortex and ozone hole. However, the seasonal regularities of QBO used in this work lead to a strictly limited number of possible variants of coincidence of the phases of the QBO cycles with the seasons of the year, which allows us to reveal typical features of interannual variations of the polar vortex and ozone hole in the Antarctic that are due to the QBO. The analysis of observational data indicates unexpected peculiarities of the QBO modulation of the stratospheric polar vortex in the Antarctic. The QBO effect in the vortex intensity is observed not only in spring during the weakening phase of the winter vortex, but also during the vortex maximum in June–August. At the same time, changes in the wind speed of the vortex during its maximum in winter are opposite to those in the spring during the ozone hole period. If the winter vortex is more intense (weak), then during the ozone hole period the vortex is weaker (more intense) than the average level.

Temperature and carotid intima-medial thickness: The coronary artery risk development in young adults (CARDIA) study

BackgroundFew studies have examined the role of long-term (≥1 year) ambient temperature with quantitative traits of early-stage cardiovascular disease (CVD) such as carotid intima-medial thickness (cIMT). Our objective was to examine associations between temperature and cIMT, a measure of subclinical atherosclerosis. MethodsThis study examined data from 3257 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study, aged 18–30 years at baseline (1985–1986). We used North America Land Data Assimilation System data to derive 12 metrics of ambient daily temperature: Mean, minimum, maximum, and standard deviation temperature in summer, winter, and year-round. We examined associations with cIMT in separate cross-sectional multivariable models at CARDIA year 20 (2005–2006) as well as stratified analyses by self-reported race and sex. We also prospectively examined cumulative temperature by summing temperature variables from Y0-Y20. ResultsAccounting for study center attenuated most associations between cIMT and ambient temperature exposure, but the winter standard deviation remained associated (overall β = −0.0104 mm/°C, 95 % CI: −0.0150 to −0.0059). Minimum summer temperature was also associated with cIMT in the overall study population (β = 0.0020 mm/°C, 95 % CI: 0.0005–0.0035). Associations did not differ substantially by race, but women had stronger associations than men. Cumulative temperature was not associated with cIMT. ConclusionsOur findings suggest a role of geography, particularly ambient temperature in cIMT. Future research to address potential residual confounding is necessary, but if validated these findings have implications for policy and strategies to mitigate health impacts of climate change.

Mesospheric Ozone Depletion during 2004–2024 as a Function of Solar Proton Events Intensity

Solar proton events (SPEs) affect the Earth’s atmosphere, causing additional ionization in the high-latitude mesosphere and stratosphere. Ionization rates from such solar proton events maximize in the stratosphere, but the formation of ozone-depleting nitrogen and hydrogen oxides begins at mesospheric altitudes. The destruction of mesospheric ozone is associated with protons with energies of about 10 MeV and higher and will strongly depend on the intensity of the flux of these particles. Most studies investigating the impact of SPEs on the characteristics of the middle atmosphere have been based on either simulations or reanalysis datasets, and some studies have used satellite observations to validate model results. We study the impact of SPEs on cold-season ozone loss in both the northern and southern hemispheres using Aura MLS mesospheric ozone measurements over the 2004 to 2024 period. Here, we show how strongly SPEs can deplete polar mesospheric ozone in different hemispheres and attempt to evaluate this dependence on the intensity of solar proton events. We found that moderate SPEs consisting of protons with an energy of more than 10 MeV and a flux intensity of more than 100 pfu destroy mesospheric ozone in the northern hemisphere up to 47% and in the southern hemisphere up to 33%. For both hemispheres, the peak of winter ozone loss was observed at about 76 km. In the northern hemisphere, maximum winter ozone loss was observed on the second day after a solar proton event, but in the southern hemisphere, winter ozone depletion was already detected on the first day. In the southern hemisphere, mesospheric ozone concentrations return to pre-event levels on the ninth day after a solar proton event, but in the northern hemisphere, even on the tenth day after a solar proton event, the mesospheric ozone layer may not be fully recovered. The strong SPEs with a proton flux intensity of more than 1000 pfu lead to a maximum winter ozone loss of up to 85% in the northern hemisphere, and in the southern hemisphere winter, ozone loss reaches 73%.

Impact of river-discharged freshwater on surface ocean environments revealed by synergistic use of satellite measurements in the East China Sea

River discharge forms a plume of low-salinity water that spreads offshore, delivering terrestrial substances into the ocean and thus plays a critical role in controlling marine environments as well as the carbon cycle. This study investigated how freshwater discharged from the Changjiang impacts the physical and biological responses and oceanic uptake of carbon dioxide (CO2) in the northern East China Sea (ECS) by combining the recently available sea surface salinity (SSS) product from the Soil Moisture Active Passive (SMAP) mission with other satellite measurements of sea surface temperature (SST) and chlorophyll-a (chl-a) concentration. The partial pressure of CO2 (pCO2) and its interannual variability were estimated using empirical regression with satellite-derived environmental variables. The bias-corrected SMAP SSS revealed that river discharge largely contributed to the distinct interannual SSS variations, with a seasonal cycle reaching a maximum in winter and a minimum in summer. Compared to the SST and chl-a anomalies, we observed an increase in SST and primary production in the region where sea surface freshening was robust. Freshwater from rivers contributes to sea surface warming by trapping heat from the atmosphere at the surface layer. Nutrient-enriched freshwater within the buoyant plume enhances phytoplankton production, which in turn enriches the ocean surface with chl-a. Simultaneously, the pCO2 was relatively low in the region where the SST and primary production were high, highlighting that the heat and riverine nutrients trapped within the buoyant plume contributed to the reduction in pCO2 by promoting the biological uptake of CO2. The estimates conducted here illustrate the synergistic utility of multiple satellite measurements for the evaluation of CO2 uptake capacity, complemented by in situ measurements of river-dominated marginal seas.

The impact of climate on the dominant height and climate thresholds for P. elliottii, P. taeda, P. patula, and P. patula x P. tecunumanii plantation forests

Plantation forests were introduced into South Africa to satisfy the regional demand for wood-based products, which are largely found in the Mpumalanga province. To better understand the impacts of climate on the dominant height growth of commercially important plantation species, enumeration data collected from 2012 to 2023 was scrutinised, representing 34740 plots in 2082 plantation compartments. Statistically significant multiple linear regression models were developed to predict dominant heights for Pinus elliottii, Pinus taeda, Pinus patula, and Pinus patula x Pinus tecunumanii hybrids using climate variables as independent factors. Mean annual maximum temperature was statistically significant when modelling dominant height for P. elliottii, while winter maximum temperature was significant for P . taeda, P. patula, and P. patula x P. tecunumanii. Rainfall was found to be significant for P. elliottii and P. taeda, while spring rainfall was found to be more important when modelling dominant height for P. patula. Interestingly, autumn rainfall was found to have a negative impact on dominant height growth of P. taeda and P. patula, while rainfall was not significant in P. patula x P. tecunumanii. The findings imply that the southern pines have water thresholds, while Mexican pines are more temperature limited than water limited.

Podnebne projekcije temperature zraka in padavin za porečja Ledave, Pesnice in Vipave do konca 21. stoletja

As part of the project ‚CeVoTak‘, Integrated Management of Small Water Retention and Soil Erosion Prevention Measures in Agricultural Catchments, we studied changing temperature and precipitation conditions up to the year 2100. The study was conducted on agricultural lands in the catchments of the Ledava and Pesnica rivers in the sub-Pannonian region and the Vipava river in the sub-Mediterranean region. A common climate database was used to create the climate projections - RCM (Regional Climate Model) simulations from the project EURO-CORDEX and scenarios RCP (Representative Concentration Pathway), RCP2.6, 4.5 and 8.5. The projections were prepared for three time periods 2011-2040; 2041-2070 and 2071-2100 for 6 different regional climate models for average, minimum and maximum air temperatures and precipitation. Analysis of the ensemble of model simulations for all scenarios shows similar results for the basin of all rivers, an increase in temperature (maximum in winter, minimum in spring), with high confidence for all scenarios and periods. Projections of precipitation are less reliable, but show an increase in annual precipitation due to the winter increase. The use of climate change projections with expert interpretation is essential for determining the vulnerability of individual areas and building resilience through the implementation of climate change adaptation.

Technical note: Retrieval of the supercooled liquid fraction in mixed-phase clouds from Himawari-8 observations

Abstract. The supercooled liquid fraction (SLF) in mixed-phase clouds (MPCs) is an essential variable of cloud microphysical processes and climate sensitivity. However, the SLF is currently calculated in spaceborne remote sensing only as the cloud phase–frequency ratio of adjacent pixels, which results in a loss of the original resolution in observations of cloud liquid or ice content within MPCs. Here, we present a novel method for retrieving the SLF in MPCs based on the differences in radiative properties of supercooled liquid droplets and ice particles at visible (VIS) and shortwave infrared (SWI) channels of the geostationary Himawari-8. Liquid and ice water paths are inferred by assuming that clouds are composed of only liquid or ice, with the real cloud water path (CWP) expressed as a combination of these two water paths (SLF and 1-SLF as coefficients), and the SLF is determined by referring to the CWP from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The statistically relatively small cloud phase spatial inhomogeneity at a Himawari-8 pixel level indicates an optimal scene for cloud retrieval. The SLF results are comparable to global SLF distributions observed by active instruments, particularly for single-layered cloud systems. While accessing the method's feasibility, SLF averages are estimated between 74 % and 78 % in Southern Ocean (SO) stratocumulus across seasons, contrasting with a range of 29 % to 32 % in northeastern Asia. The former exhibits a minimum SLF around midday in summer and a maximum in winter, while the latter trend differs. This novel algorithm will be valuable for research to track the evolution of MPCs and constrain the related climate impact.

Biological outliers: essential elements to understand the causes and consequences of reductions in maximum photochemical efficiency of PSII in plants

Main conclusionBy studying Cistus albidus shrubs in their natural habitat, we show that biological outliers can help us to understand the causes and consequences of maximum photochemical efficiency decreases in plants, thus reinforcing the importance of integrating these often-neglected data into scientific practice.Outliers are individuals with exceptional traits that are often excluded of data analysis. However, this may result in very important mistakes not accurately capturing the true trajectory of the population, thereby limiting our understanding of a given biological process. Here, we studied the role of biological outliers in understanding the causes and consequences of maximum photochemical efficiency decreases in plants, using the semi-deciduous shrub C. albidus growing in a Mediterranean-type ecosystem. We assessed interindividual variability in winter, spring and summer maximum PSII photochemical efficiency in a population of C. albidus growing under Mediterranean conditions. A strong correlation was observed between maximum PSII photochemical efficiency (Fv/Fm ratio) and leaf water desiccation. While decreases in maximum PSII photochemical efficiency did not result in any damage at the organ level during winter, reductions in the Fv/Fm ratio were associated to leaf mortality during summer. However, all plants could recover after rainfalls, thus maximum PSII photochemical efficiency decreases did not result in an increased mortality at the organism level, despite extreme water deficit and temperatures exceeding 40ºC during the summer. We conclude that, once methodological outliers are excluded, not only biological outliers must not be excluded from data analysis, but focusing on them is crucial to understand the causes and consequences of maximum PSII photochemical efficiency decreases in plants.

Seasonal variation of background counting rates in liquid scintillation counting

A liquid scintillation background sample was measured daily in a custom-built TDCR counter for more than 17 months. The double and triple coincidence counting rates exhibit an annual sinusoidal fluctuation with a maximum in winter and a minimum in summer. Possible correlations with air temperature, air humidity, radon concentration and secondary cosmic radiation were investigated. The observation of a correlation with the ambient dose equivalent rate H˙*(10)SCR originating from the charged component of secondary cosmic radiation and an anti-correlation with the effective atmospheric temperature Teff suggest that the seasonal fluctuations in the background counting rate may be primarily driven by temporal variations in the muon flux at ground level. Additionally, a correlation was found with the indoor 222Rn concentration in air.

Evaluating Health Risks of Volatile Organic Compounds in Various UK Environments: Insights from Health Indices

The health risks of twelve volatile organic compounds (VOCs) across three sites in the UK were analysed across an 11-year period (2013–2023) using US EPA proposed health indices; Inhalation Unit Risk (IUR) and Reference Concentration (RfC) for carcinogenic and non-carcinogenic risk, respectively. Significant decreases in carcinogenic risk were observed over the study period for 1, 3-butadiene, with reductions of 63%, 36%, and 45% at urban traffic, suburban background and rural background sites, respectively. Similar decreases in the carcinogenic risk associated with benzene (52%, 28% and 27%) and toluene (50%, 38% and 51%) are found for the three site types, respectively. However, the carcinogenic risk of these three pollutants still exceeds the acceptable threshold of 1 × 10-6 at the urban traffic and suburban background sites, necessitating further emission control strategies. Conversely, the carcinogenic risk associated with isoprene has increased at the urban traffic site over the study period. The study revealed a decrease of 51%, 39% and 37% of the total non-carcinogenic risk at all three sites over the study period. The seasonal variations in carcinogenic and non-carcinogenic health risks of pollutants with anthropogenic origin exhibit winter maxima and summer minima. Moreover, diurnal variations of pollutants with anthropogenic origin demonstrate a bimodal distribution reflecting that of traffic flow, e.g., peaks around 08:00 LT and 18:00 LT, corresponding with rush hours. This trend demonstrates the influence of traffic sources supported by the characteristic species ratio whereby Toluene/Benzene (T/B) ratios were less than two (0.72, and 0.42 at suburban and rural background sites, respectively), illustrating the influence of vehicular emissions. Despite following the same bimodal trend suggesting the dominance of vehicular emission sources, mean T/B ratios at urban traffic sites were consistently above 2 for all years considered (average 2.76) suggesting other VOC sources are becoming more dominant at this site.

Warm winters are associated to more intense West Nile virus circulation in southern Spain

ABSTRACT West Nile virus (WNV) is the most widely distributed mosquito-borne flavivirus in the world. This flavivirus can infect humans causing in some cases a fatal neurological disease and birds are the main reservoir hosts. WNV is endemic in Spain, and human cases have been reported since 2004. Although different studies analyse how climatic conditions can affect the dynamics of WNV infection, very few use long-term datasets. Between 2003 and 2020 a total of 2,724 serum samples from 1,707 common coots (Fulica atra) were analysed for the presence of WNV-specific antibodies. Mean (SD) annual seroprevalence was 24.67% (0.28) but showed high year-to-year variations ranging from 5.06% (0.17) to 68.89% (0.29). Significant positive correlations (p < 0.01) were observed between seroprevalence and maximum winter temperature and mean spring temperature. The unprecedented WNV outbreak in humans in the south of Spain in 2020 was preceded by a prolonged period of escalating WNV local circulation. Given current global and local climatic trends, WNV circulation is expected to increase in the next decades. This underscores the necessity of implementing One Health approaches to reduce the risk of future WNV outbreaks in humans. Our results suggest that higher winter and spring temperatures may be used as an early warning signal of more intense WNV circulation among wildlife in Spain, and consequently highlight the need of more intense vector control and surveillance in human inhabited areas.

Improving Satellite Chlorophyll-a Retrieval in the Turbid Waters of the Bay of Fundy, Canada

AbstractThe Bay of Fundy is a highly productive ecosystem within the Northwest Atlantic where extreme tides and strong currents result in a large gradient of sediment concentrations across and along the bay. We processed daily satellite data from the MODerate resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite from 2003 to 2021 at 300-m resolution to understand and quantify spatial and temporal trends in chlorophyll-a concentration (chl-a, a measure of phytoplankton biomass), and suspended particulate matter concentration (SPM) in the Bay of Fundy surface waters. To account for high sediment loading (up to 100’s g m−3) and moderate chl-a (median in situ chl-a of 1.5 mg m−3 from 2003 to 2021), coefficients of the OC3M chl-a algorithm were regionally tuned using in situ chl-a data, and satellite-derived SPM was incorporated within the chl-a retrieval algorithm to account for possible bias. The updated new algorithm was denoted as OCX-SPMCor. Chl-a computed using OCX-SPMCor showed better performance against in situ chl-a than the generic OC3M with a coefficient of determination that increased from 0.01 to 0.28 and a root mean square logarithmic error that decreased by 35%. Unlike previous remote sensing studies, OCX-SPMCor correctly predicted the particular chl-a seasonality in the Bay of Fundy, which does not follow the typical occurrence of spring/fall blooms as observed in the adjacent Gulf of Maine and Scotian Shelf. For the first time, satellite-predicted chl-a aligned with the phenology of in situ chl-a, where chl-a continually increased from April to June and remained high all summer, with a small secondary summer peak before decreasing in the fall. SPM seasonality followed an opposite trend where SPM reached a maximum in winter and a minimum in summer. A small number of matchups and high temporal variability on the hourly time scale precluded a robust assessment of the satellite-derived SPM. However, comparisons between time series of remotely sensed and in situ SPM demonstrated the ability of the satellite-derived SPM to capture temporal variations, though the absolute values may be slightly underestimated. Accurate maps of phytoplankton biomass and sediment concentrations are essential variables required for effective management and conservation of marine ecosystems in the Bay of Fundy.

Air-soil cycling of oxygenated, nitrated and parent polycyclic aromatic hydrocarbons in source and receptor areas

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, OPAHs and NPAHs, are semivolatile air pollutants which are distributed and cycling regionally. Subsequent to atmospheric deposition to and accumulation in soils they may re-volatilise, a secondary source which is understudied.We studied the direction of air-soil mass exchange fluxes of 12 OPAHs, 17 NPAHs, 25 PAHs and one alkylated PAH in two rural environments being influenced by the pollutant concentrations in soil and air, by season, and by land cover. The OPAHs and NPAHs in samples of topsoil, of ambient air particulate and gas phases and in the gas-phase equilibrated with soil were analysed by GC-APCI-MS/MS. The pollutants soil burdens show a pronounced seasonality, a winter maximum for NPAHs and PAHs and a summer maximum for OPAHs. One order of magnitude more OPAH and parent PAH are found stored in forest soil than in nearby grassland soil. Among a number of 3–4 ring PAHs, the OPAHs benzanthrone and 6H-benzo(c,d)pyren-6-one, and the NPAHs 1- and 2-nitronaphthalene, 9-nitrophenanthrene and 7-nitrobenz(a)anthracene are found to re-volatilise from soils at a rural background site in central Europe in summer. At a receptor site in northern Europe, net deposition of polycyclic aromatic compounds (PACs) prevails and re-volatilisation occurs only sporadic.Re-volatilisation of a number of PACs, including strong mutagens, from soils in summer and even in winter indicates that long-range atmospheric transport of primary PAC emissions from central Europe to receptor areas might be enhanced by secondary emissions from soils.