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Objectives Globally, the mass proliferation of phytoplankton driven by climate change has emerged as a significant societal issue. This study analyzes over two decades of long-term hydraulic, hydrological, and water quality data collected from the lower Nakdong River, along with changes in phytoplankton community biomass. The aim is to evaluate long-term trends in water quality and the ecological changes occurring in this region. Methods The monitoring site in the lower Nakdong River is Mulgeum, where samples were collected weekly from January 2000 to December 2021 for the analysis of physicochemical water quality characteristics, as well as phytoplankton abundance and species composition. The hydrological status was assessed using flow rate data from the Jin-dong (Haman) station of the Nakdong River, along with rainfall data from the Korea Meteorological Administration for eight regions influencing the lower Nakdong River. Results and Discussion Analysis of the annual average concentration changes of water quality parameters at the Mulgeum intake site in the lower Nakdong River found that water quality has generally improved since the construction period (2009-2012) of the weir. This improvement is attributed to the strengthening of T-P water quality standards for sewage treatment plant discharges in 2012, which resulted in enhanced phosphorus treatment at wastewater facilities in the river's middle and upper regions. Consequently, significant reductions were observed in the annual average concentrations of BOD, NO3-N, T-N, and T-P. Evaluating long-term changes in flow rate and rainfall, it was found that both annual average rainfall and flow rate decreased after the weir was installed, particularly from May to September when temperatures rise. Rainfall decreased by approximately 8% to 38%, while flow rate decreased by 46% to 62%. Long-term temperature changes indicated that summer temperatures increased by 0.9oC to 1.4oC, and winter temperatures rose by 1.6oC to 2.0oC, resulting in an overall annual average increase of about 1.3oC. An analysis of long-term changes in phytoplankton biomass and community composition revealed an increase in average biomass from 3,639 cells/mL before the weir was installed to 4,034 cells/mL afterward, representing an increase of about 11%. In winter, the dominance period and biomass of diatoms decreased, while in summer, the biomass and dominance period of cyanobacteria increased. Notably, in August, biomass increased approximately 7.5 times, rising from 2,009 cells/mL before the dam to 15,059 cells/mL afterward. This significant increase was identified as a key factor in the overall rise in phytoplankton biomass following the weir's installation. Conclusion Recent climate change impacts, such as rising average temperatures and shifting rainfall patterns, have become increasingly evident in South Korea. This study utilizes over 20 years of long-term data to demonstrate that, in the lower Nakdong River, there has been a gradual decline in both rainfall and flow rates, accompanied by an increase in average temperatures. Consequently, the dominance period and biomass of diatoms have decreased. In contrast, cyanobacteria, which thrive in warmer conditions, have experienced an extended dominance period into early spring and late autumn as a result of rising temperatures, leading to an overall increase in cyanobacterial biomass.

Turbidity, as a key indicator of water quality linked to underwater light attenuation, is crucial for evaluating water quality. Control in high-turbidity water environments plays a critical role in navigable rivers. For this purpose, our study proposed a framework for analyzing the spatio-temporal variation of turbidity and its driving factors in a navigable and turbid river using in situ measurement data, satellite data, socioeconomic data, a power index function model, and correlation analysis. The results show that the proposed model is feasible for quantitative turbidity monitoring of the Xitiaoxi River. Its upstream turbidity is lower than downstream, with seasonal averages for spring, summer, autumn, and winter of 93.9, 111.3, 113.5, and 120.9 NTU, respectively. Furthermore, the turbidity in the middle and lower reaches of the Xitiaoxi River continuously increased before 2005 and began to decline after 2005 due to the policy of mining moratorium. This trend is especially noticeable at monitoring points along the main stream of the Xitiaoxi River, such as downstream of the Xitiaoxi River (S1), Gangkou station (S2), middle reaches of the Xitiaoxi River (S4), Hengtangcun station (S6), upper stream of the Xitiaoxi River (S7), and Huxi River (S8). Mining and shipping have significantly contributed to the turbidity of the target river. This framework offers a practical approach for assessing the environmental impacts of both natural and anthropogenic factors, thereby providing valuable insights for river management practices. [ABSTRACT FROM AUTHOR]

Bohai Bay is an important spawning and nursery habitat for a variety of economically important fish inhabiting the Yellow and Bohai seas. Based on a meta-analysis of historical data spanning 40 years, combined with a field survey of current fish habitat conditions conducted in Bohai Bay, a long-term dataset containing early life resource surveys (including 53 voyages, from 1982 to 2021) of marine Osteichthyes was built. Based on statistical analyses, long-term trends in ichthyoplankton assemblage structure, biodiversity, and synchrony were interpreted. The results indicate that ichthyoplankton assemblage structure and the center of gravity for spawning and nursery habitats in Bohai Bay are currently experiencing continuous replacement. Seasonal variations in ichthyoplankton assemblage structure, abundance index, predominant taxa, and species diversity levels are evident. Spawning and nursery habitats are concentrated in the central and inner part of Bohai Bay west of 118º30'E. Compared with survey results from the 1980s, the taxonomic composition and abundance of the ichthyoplankton assemblage structure have changed considerably. The function of Bohai Bay as a spawning and nursery habitat for traditionally economically important fish has declined significantly. The abundance index and taxon number of ichthyoplankton in Bohai Bay fell to a historic low in the early 2010s, then rebounded significantly. The taxa number of ichthyoplankton decreased from 39 in the 1980s to 31 in the early 1990s, 34 in the late 1990s, and 22 in the 2000s to pre-2010s, then further decreased to 21 in the early 2010s. From the middle 2010s, it recovered to a certain degree, increasing to 40 species just prior to 2020. The current number of pelagic egg taxa is 22, 80% of the number in the 1980s, and 88% of the abundance in the 1980s. The current (2020—2021) number of larval fish taxa is 26, almost identical to that in the 1980s, with an abundance 1.33 times greater than that in the 1980s. Interannual and interdecadal variations in fish egg and larvae species diversity fluctuated drastically. Interannual taxon substitution was noticeable. However, the substitution rate has increased significantly in recent years. Spawning, habitat, and temperature adaptation studies of breeding stock indicate that the number of taxa first decreased, then increased. The annual proportion of the number of taxa to pelagic eggs decreased, while the proportion of the number of taxa to adhesive eggs and eggs with egg membrane filaments increased. The annual proportion of continental shelf pelagic-neritic fish taxa increased, while the continental shelf demersal and benthopelagic taxa decreased. The ecological density of numbers in the early life history (EDN-ELH) of Konosirus punctatus, Sardinella zunasi, Larimichthys polyactis, Trichiurus japonicus, Lateolabrax maculatus, and Cynoglossus semilaevis decreased significantly, whereas the EDN-ELH of Engraulis japonicus, Scomberomorus niphonius, Thryssa kammalensis, and Sillago japonica increased. Ichthyoplankton abundance in Bohai Bay mainly depends on environmental conditions in the spawning habitat, fishing intensity, and the degree of damage to the early life stages of fish resources. The temporal variation and succession of the ichthyoplankton assemblage structure in Bohai Bay were the specific manifestations of the multidimensional niche disturbance and structural performance deterioration of the fishery resources under the dual disturbance of global warming and overfishing.

Based on the MODIS (moderate-resolution imaging spectroradiometer) AOD (aerosol optical depth) and MEIC (multi-resolution emission inventory for China) in Northeast China from 2003 to 2022, the spatial distribution and interannual trend of AOD in Northeast China are analyzed. Effects of meteorological factors and anthropogenic emissions on AOD changes in Northeast China are discussed. Results show that the AOD maximum in central Liaoning is 0.6, followed by an average AOD of 0.4 in western Jilin and 0.3 in Heilongjiang. The average AOD in Northeast China is lower than that in north China, Yangtze River Delta and other frequent pollution areas. High AOD occurs in spring and summer in Northeast China, and it decreases spatially in autumn while increases in winter. The summer AOD in Liaoning is significantly higher than that in other regions, when the average value in central Liaoning and the Bohai Rim increases to 0.6. The highest values of AOD in different seasons occur in Liaoning, followed by Jilin and Heilongjiang. The increase of AOD in summer is mainly related to environmental humidity, and adverse meteorological conditions and local emissions have certain effects on near-surface atmospheric extinction in winter. The annual occurrence frequency of AOD in the range of [0.1, 0.2) and [0.2, 0.3) in Liaoning is up to 50%, the annual occurrence frequency of AOD in the range of [0.1, 0.2) in Jilin and Heilongjiang is up to 25%-30%, and the annual occurrence frequency of extreme clean condition in Heilongjiang is up to 15%. Affected by dust events in spring, the occurrence frequency of AOD [0.2, 0.3) and AOD [0.3, 0.4) in Northeast China is 25%. The regional average value of AOD in Northeast China is higher in 2003 and 2014, which is mainly influenced by boundary layer meteorological elements and anthropogenic emission of SO2, PM2.5, organic carbon (OC) and NO2. In Northeast China, AOD is negatively correlated with boundary layer height and average wind speed, and positively correlated with anthropogenic emissions. The correlation coefficient between AOD and anthropogenic emissions of SO2, PM2.5 and OC is the highest in Liaoning. From 2003 to 2022, AOD in Liaoning shows a weak negative growth trend (about-0.1 per decade), while the AOD in Jilin and Heilongjiang shows little change trend. From the perspective of seasonal interannual trend, there is a transition from a negative increasing trend in spring to a positive increasing trend in summer before 2012. After 2013, the summer AOD in Northeast China shows a negative growth trend (-0.3 per decade), which confirms that the contribution of summer aerosol to atmospheric extinction in Northeast China is decreasing in the past 10 years.

Based on data from the Gurbantunggut Desert, the largest fixed/semi-fixed desert in China, and ERA5-Land reanalysis data, the long-term variations and spatial surface heat source (SHS) differences in the Gurbantunggut Desert are discussed herein. The results show the following: (1) The hourly SHS at the Kelameili station during the 2013–2021 period was a weak heat source at night; contrastingly, it was a strong heat source during the day. The duration of the hourly SHS increased gradually from January to July, but it decreased gradually from July to December. The daily SHS showed obvious seasonal variation, reaching the maximum in summer and the minimum in winter. The ERA5-Land reanalysis can reproduce all the variation characteristics of the SHS well. (2) The climatology (i.e., multi-year mean) of the monthly SHS intensity was lower than 50 W/m2 during the January–March and September–December periods in the Gurbantunggut Desert, indicating a weak heat source. On the other hand, the climatology recorded in April–August was higher than 50 W/m2, with a strong heat source. From the perspective of spatial distribution, the eastern and western regions of the Gurbantunggut Desert show strong heat sources, while the central region shows weak heat sources. The spatial distribution of the first and second modes of the empirical orthogonal function (EOF) decomposition reflected the consistent spatial variability and a north–south (or east–west) polarity variation of the monthly SHS in the Gurbantunggut Desert, respectively. (3) The yearly SHS showed negative anomalies during the 1950–1954, 1964–1982 and 2004–2015 periods, and positive anomalies during the 1955–1963, 1983–2003 and 2016–2021 periods in the Gurbantunggut Desert. Additionally, the time series of the SHS anomalies was positively correlated with the Interdecadal Pacific Oscillation (IPO) index. During the negative IPO phase, the yearly SHS showed a negative anomaly in the Gurbantunggut Desert, while the yearly SHS showed a positive anomaly during the positive IPO phase in most regions of the Gurbantunggut Desert. [ABSTRACT FROM AUTHOR]

Long-term variations in precipitation during the major rainy periods in Japan--the Baiu (June-July) and Akisame (September-October) seasons--are investigated using precipitation records from 44 weather stations in western to eastern Japan over the past 120 years (1901 - 2020). The total amount of Baiu precipitation has increased over the 1901 - 2020 period, mainly during the mid-late stages of the season (late June-July) over regions on the Sea of Japan side of the country. Conversely, the precipitation amount during the Akisame season has decreased, mainly during the mid-stage (late September-early October) over all regions. The frequency and intensity of heavy precipitation have generally increased in both seasons, but the trends are much stronger for the Baiu season than for the Akisame season. A prominent positive trend, 23.5 % (100 yr)-1 (18.1 % °C-1), which is much higher than the Clausius-Clapeyron rate (approximately 7 % °C-1), is observed for the Sea of Japan side of western Japan for the seasonal maximum one-day precipitation total during the Baiu season. It may be noteworthy that the observed long-term trends differ greatly between the Baiu and Akisame seasons even though the statistical significances of the trends are not so high, because similar differences between the two rainy seasons are found in the results of global warming simulations. [ABSTRACT FROM AUTHOR]

Vulnerability of each stock in the catches from trawl fisheries in the Gulf of Thailand was assessed by productivity susceptibility analysis. Separate assessments were made based on type of trawler (otter-board, pair and beam) and vessel size (SS, S, M, L and XL, according to gross tonnage). Catches were distinctly different among trawler types and were dominated by demersal fishes, pelagic fishes and shrimps in the otter-board, pair and beam trawlers, respectively. The stocks of over 200 taxa were included in the study; high-vulnerability taxa were found for all trawl types and sizes, except the beam trawler size S. Only seven (7) taxa were classified as high vulnerability, including four (4) teleost taxa, namely Saurida elongata, Plotosus spp., Gymnothorax spp. and Sphyraena spp., and three (3) elasmobranch taxa, namely Carcharhinus spp., Brevitrygon heterura and Neotrygon kuhlii. Meanwhile, as many as 26 high-medium vulnerability taxa were found in catches by otter-board trawler size L, which included not only fishes but also cephalopods. Trends and variation in fish landings of 20 high and high-medium vulnerability taxa were analyzed. Eighteen (18) taxa showed monotonic trends, both continuous and discontinuous, in their time series of annual landings, but not Muraenesox spp. nor Uroteuthis spp. The long-term variations in fish landings ranged mostly between 40% and 50%. The short-term variations showed positive absolute and relative skewness, i.e., mostly between 10% and 20%. Results of this study highlight the taxa that require a precautionary approach for fishery management and warrant comprehensive fish stock assessment. Such data will allow more accurate determination of their status compared to the reference points and facilitate better management of trawl fisheries in the Gulf of Thailand. [ABSTRACT FROM AUTHOR]

Sandstorm is a disastrous weather phenomenon that often occurs in arid and semi-arid areas, endangering the ecological environment and affecting people's lives and property safety seriously. Since the 21st century, the sandstorm weather in the Yellow River Basin has ameliorated obviously. However, the causes of the long-term trends in sandstorms during 21st century were still unknown. In this study, fifteen influencing factors from five aspects: ecology, meteorology, hydrology, geography and man-made were selected to comprehensively analyze the driving mechanism of sandstorm activities in the Yellow River Basin since the 21st century, and the effect of each influencing factor on sandstorm weather was quantified. The results indicated that ecological, meteorological and geographical factors had dominant impacts on the spatio-temporal variation of sandstorms during 2000–2021, while hydrological and human factors played little role in the long-term variation of sandstorms. Sandstorms frequently occurred in semi-desert or grassland or non-high vegetation covered areas in spring. Vegetation coverage, precipitation, surface pressure, surface roughness, and soil moisture content were negatively correlated with sandstorms, while wind speed, friction velocity, evaporation, and soil temperature were positively correlated with sandstorms. Precipitation, runoff, evaporation, soil moisture content, soil temperature, and surface temperature indirectly acted on normalized brightness temperature dust index (NBTDI) and sandstorms by changing soil texture. Normalized Vegetation Index (NDVI) had direct negative effects on NBTDI, while wind speed 10 m (WS10m), slope of sub-gridscale orography (SOSGO), and forecast surface roughness (FSR) had direct positive effects on NBTDI. This study comprehensively revealed the dominant factors and their driving mechanism of sandstorm weather in the Yellow River Basin since the 21st century, which had practical application value for the prevention of sandstorms. [Display omitted] • Spatial heterogeneity existed in sandstorms drives across different regions during 2000–2021. • Precipitation, runoff, evaporation, soil moisture, and temperature indirectly affect sandstorms through soil texture. • SP, NDVI, ST, E, R and WS10m on the long-term change of sandstorm were more important. • Vegetation, evaporation, runoff, slope negatively affect sandstorms; wind, temperature positively. [ABSTRACT FROM AUTHOR]

Based on data from the Gurbantunggut Desert, the largest fixed/semi-fixed desert in China, and ERA5-Land reanalysis data, the long-term variations and spatial surface heat source (SHS) differences in the Gurbantunggut Desert are discussed herein. The results show the following: (1) The hourly SHS at the Kelameili station during the 2013–2021 period was a weak heat source at night; contrastingly, it was a strong heat source during the day. The duration of the hourly SHS increased gradually from January to July, but it decreased gradually from July to December. The daily SHS showed obvious seasonal variation, reaching the maximum in summer and the minimum in winter. The ERA5-Land reanalysis can reproduce all the variation characteristics of the SHS well. (2) The climatology (i.e., multi-year mean) of the monthly SHS intensity was lower than 50 W/m2 during the January–March and September–December periods in the Gurbantunggut Desert, indicating a weak heat source. On the other hand, the climatology recorded in April–August was higher than 50 W/m2, with a strong heat source. From the perspective of spatial distribution, the eastern and western regions of the Gurbantunggut Desert show strong heat sources, while the central region shows weak heat sources. The spatial distribution of the first and second modes of the empirical orthogonal function (EOF) decomposition reflected the consistent spatial variability and a north–south (or east–west) polarity variation of the monthly SHS in the Gurbantunggut Desert, respectively. (3) The yearly SHS showed negative anomalies during the 1950–1954, 1964–1982 and 2004–2015 periods, and positive anomalies during the 1955–1963, 1983–2003 and 2016–2021 periods in the Gurbantunggut Desert. Additionally, the time series of the SHS anomalies was positively correlated with the Interdecadal Pacific Oscillation (IPO) index. During the negative IPO phase, the yearly SHS showed a negative anomaly in the Gurbantunggut Desert, while the yearly SHS showed a positive anomaly during the positive IPO phase in most regions of the Gurbantunggut Desert.

Upland forest soil is an important CH4 sink that plays a key role in climate change mitigation. China features large areas of various types of forest, but spatiotemporal variation in CH4 flux has not yet been clarified. Here, we analyzed variation in CH4 flux and the effects of environmental variables on the CH4 flux of forest in China using in situ observational data. Upland forest soil absorbed CH4 at a rate of 0.24 ± 0.02 g m−2 yr−1. The CH4 uptake rate (0.46 ± 0.10 g m−2 yr−1) of warm temperate deciduous broad-leaved forest was the highest. Soil alkali-hydrolyzable nitrogen was the only factor significantly correlated with CH4 uptake variation among vegetation zones. A break point in CH4 uptake over the study period (from 1997 to 2020) was detected in 2015. CH4 uptake slightly decreased until 2015 and increased after 2015. The mean CH4 uptake of the period after 2015 (0.44 ± 0.07 g m−2 yr−1) was significantly higher than that before 2015 (0.20 ± 0.02 g m−2 yr−1). Atmospheric nitrogen deposition was negatively related to interannual CH4 uptake. Our findings suggest that the CH4 uptake of upland forest soil will continue to increase over the next few decades as China accelerates efforts to achieve its carbon neutrality goal, and this would result in continuous decreases in nitrogen deposition through various pathways. [ABSTRACT FROM AUTHOR]

Regional variations in atmospheric moisture residence time (RT) highlight the need to obtain independent observation indexes to constrain different model-based estimates. Stable isotopes of oxygen and hydrogen naturally exist in water molecules that can provide such observational constraints. We analyzed the relationship between RT and precipitation isotopes (δ2H and δ18O) across different climatic zones in Eurasia from 1980 to 2020. Our analysis reveals that: (1) Both precipitation isotopes and RT showed significant increasing trends during 1980–2020. The increase in RT corresponds to weakened net isotopic distillation over Eurasia, suggesting reduced atmospheric circulation intensity under warming conditions. (2) The spatial patterns of RT and precipitation isotopes vary significantly among different moisture source regions, reflecting distinct moisture transport and precipitation formation processes. (3) On long-term scales, RT generally shows positive correlations with precipitation isotopes, except in plateau regions. The RT-δ18O relationship exhibits latitude-dependent variations, with similar slopes in regions sharing common moisture sources. These findings enhance our understanding of the long-term controls on precipitation isotopic composition and atmospheric moisture cycling patterns across Eurasia. • The relationship between RT and δ18O varies obviously with latitude. • RT and precipitation isotopes vary with moisture source regions rather than simple inland-monsoon division. • Long-term increases in RT indicate weakening atmospheric circulation over Eurasia. [ABSTRACT FROM AUTHOR]

The influence of snow cover on the dynamics of soil temperature in the modern climatic conditions of the Eurasian Subarctic was investigated through a quantitative assessment of the features of the seasonal and long-term variation of parameters. Seasonal and long-term values of soil temperature for stable snow period decrease from west to east: a decrease of snow thickness and air temperature from west to east of Eurasia leads to a weakening of the heat-insulating properties of the snow cover with a significant decrease in regional air temperatures. With the emergence of a stable snow cover, the soil temperature seasonal and long-term standard deviation sharply decreases compared to the autumn and spring periods. With the appearance of snow cover, the soil temperature standard deviation drops sharply compared to the autumn and spring periods. An exception is the northeast of Siberia: here, a relatively small thickness of snow determines a noticeable dependence of the course of soil temperature on the dynamics of surface air temperature. There are no significant long-term trends in soil temperature due to its low variability during winter period. Analysis of the course of the studied characteristics anomalies showed an insignificant and non-systematic number of their coincidences. Currently, we have not found similar research results for large regions. The revealed patterns can be used in the analysis of the results of monitoring the state of the land surface, in the development of remote sensing algorithms, in the refinement of predictive scenarios of environmental changes.

The shipboard measurements over approximately 55 years in the southwestern part of the East Sea (Sea of Japan) demonstrate a remarkable basin-wide, interannual-interdecadal variability in the temperature-based thickness of the East Sea Intermediate Water (ESIW) whose temporal variability shows strong correlation with the density-based thickness (r = 0.97). Relevant to the long-term variability of the ESIW thickness, clear changes in horizonal and vertical features have been observed at the intermediate layer in the mid-1990s, such as 1) increases in vertical temperature gradient in the thermocline by shoaling of 2°C–5°C isotherms, 2) relatively high correlations among isotherms in the interdecadal timescale, 3) appearance of zonal phase difference in the ESIW thickness variability after the mid-1990s, and 4) correlation phase change between the Arctic Oscillation Index and the ESIW thickness. The ESIW thickness could be smaller when its formation is weaker and when the formation of deep-water mass below it becomes stronger. Based on the features observed, we hypothesized on the regime shift concerning the East Sea meridional overturning circulation; before the mid-1990s, active deep-water formation mainly controlled the ESIW layer variability, but after the mid-1990s, the ESIW formation rate predominantly affected its own thickness variability.

The concentration and structure of nutrients play a key role in sustaining marine ecosystems. In recent decades, the change in nutrient input from land has led to significant changes in nutrient concentration and structure in the marginal sea and has had an important impact on the coastal ecosystem. Based on historical data from 1984 to 2016, the long-term variations in nutrients and their potential influencing factors, were analyzed in the Changjiang River Estuary. The concentration of dissolved inorganic nitrogen (DIN) increased gradually from 1984 to 2003, but after 2003 the concentration began to decrease. Compared with DIN, the change in dissolved inorganic phosphate (DIP) had a delayed effect and has exhibited a slow downward trend since 2005. The decreases in DIN and DIP are mainly due to the improvement of wastewater treatment efforts and chemical fertilizer use efficiency in recent years. The retention of nutrients by the Three Gorges Reservoir (TGR) has been another important factor since its completion in 2003, especially because the large amount of particulate phosphorus retained by the TGR has led to a significant decrease in the total phosphorus flux into the sea, which is the main reason for the decrease in DIP. The vatiations of DIP and DIN have been instrumental in causing the observed changes of phytoplankton community in the Changjiang River Estuary.

Atmospheric compositions and acid rain are closely related to atmospheric environment, weather, and climate change. In this study, the concentration levels and long-term trends of CO2, CH4, O3, PM2.5, PM10, and acid rain were presented at the Mt. Waliguan global baseline station in Qinghai, Shangdianzi and Lin'an regional background stations in the North China Plain (NCP) and the Yangtze River Delta region (YRD) of China based on the data observed until 2018. Significant increasing trends of CO2 were found at all of these stations. At Mt. Waliguan, the concentration levels and growth rate were consistent with the average values in the Northern Hemisphere (NH) and those observed at the Mauna Loa station in Hawaii. The CH4 also showed a upward tendency similar to that observed in NH. Compared with the observations at Mt. Waliguan global baseline station, the CO2 and CH4 mole fractions were higher at Shangdianzi and Lin'an regional background stations, indicating the important contributions of anthropogenic activities to the regional background level of CO2 and CH4. The annual averaged surface ozone showed increasing trends at Mt. Waliguan and Shangdianzi stations, whereas no clear trend was found at Lin'an station. Similar variations in the patterns of aerosol concentrations at Shangdianzi and Lin'an were found according to the PM2.5 or PM10 observations. Overall, the aerosol concentrations at both stations shown declining trends since the observations. However, two periods of high particle concentrations occurred in 2006–2007 and 2013–2014. The annual mean aerosol concentrations have continuously decreased after 2013–2014, indicating the effectiveness of pollution control in the NCP and YRD, especially since the implementation of the ‘Action Plan for Prevention and Control of Air Pollution’ in September 2013. Comparative analysis of aerosol with acid rain showed that the period with high concentrations of aerosols in the early years was consistent with that of severe acid rain pollution, suggesting that both aerosol pollution and severe acid rain are closely related to coal combustion emissions in China. As a result of the control of coal combustion emissions for acid and SO2, NOx emissions have contributed more substantially to aerosols due to the rapid growth of vehicle ownership. A comparison of the trends of aerosols with the maximum daily 8-h average of surface ozone (MDA8) at Shangdianzi and Lin'an stations revealed the complicated relationship between aerosol reduction and ozone production, i.e., together with the continuous improvement of particulate pollution in the NCP and YRD, the MDA8 at both stations showed a decreasing trend at first but subsequently increased after 2014 with aerosols remaining reduced. Such different variation patterns of the MDA8 with PM2.5 (or PM10) indicated the high challenge of synergic control of aerosol and ozone pollution in China.

Vulnerability of each stock in the catches from trawl fisheries in the Gulf of Thailand was assessed by productivity susceptibility analysis. Separate assessments were made based on type of trawler (otter-board, pair and beam) and vessel size (SS, S, M, L and XL, according to gross tonnage). Catches were distinctly different among trawler types and were dominated by demersal fishes, pelagic fishes and shrimps in the otter-board, pair and beam trawlers, respectively. The stocks of over 200 taxa were included in the study; high-vulnerability taxa were found for all trawl types and sizes, except the beam trawler size S. Only seven (7) taxa were classified as high vulnerability, including four (4) teleost taxa, namely Saurida elongata, Plotosus spp., Gymnothorax spp. and Sphyraena spp., and three (3) elasmobranch taxa, namely Carcharhinus spp., Brevitrygon heterura and Neotrygon kuhlii. Meanwhile, as many as 26 high-medium vulnerability taxa were found in catches by otter-board trawler size L, which included not only fishes but also cephalopods. Trends and variation in fish landings of 20 high and high-medium vulnerability taxa were analyzed. Eighteen (18) taxa showed monotonic trends, both continuous and discontinuous, in their time series of annual landings, but not Muraenesox spp. nor Uroteuthis spp. The long-term variations in fish landings ranged mostly between 40% and 50%. The short-term variations showed positive absolute and relative skewness, i.e., mostly between 10% and 20%. Results of this study highlight the taxa that require a precautionary approach for fishery management and warrant comprehensive fish stock assessment. Such data will allow more accurate determination of their status compared to the reference points and facilitate better management of trawl fisheries in the Gulf of Thailand.

Long-term variation of nitrate in the East Sea was monitored in order to investigate impact of Three Gorges Dam (TGD) in the Changjiang River's upstream, China and Nakdong River's estuary dam, Korea. Tracing source of nitrate was another objective in this study. For this study, nutrient data were collected for 20 years from 1999 to 2018 in the East Sea, and divided into 4 sections, and evaluated whether a significant difference exists among the averages of nitrate concentrations. The concentrations of nitrate were affected by the major rivers (the Nakdong and the Taehwa Rivers) and Tsushima Warm Current (TWC) which diverged from the Kuroshio Current passing through East China Sea (ECS). Our results also indicated that long-term nitrate concentrations decreased and its reasons. First, the construction of TGD in the upstream of the Changjiang River may have resulted in the decrease of the nitrate supply in the river and ECS which is carried by TWC, toward the East Sea. Second, decrease in the nitrate flux of the Nakdong River's estuary due to the construction of the estuary dam and sewer treatment plant could also be a factor for the nitrate decrease in the East Sea. Therefore, anthropogenic activities from the Nakdong River and Changjiang River had a long-term effect on the East Sea's nitrate concentrations. The amount of nitrate runoff reduced by the anthropogenic activities influenced the nitrate levels over a long period by the flow of currents in the East Sea. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is a potent and long-lived greenhouse gas that contributes to global warming with a global warming potential (GWP) 298 times that of carbon dioxide (CO2). In this paper, we analyzed the trend of N2O concentration in vertical layers of the stratosphere from 2005 to 2020 using the N2O observed from the Microwave Limb Sounder (MLS) that is on board the Aura satellite. We found that the local N2O concentration showed a downward trend in the lower stratosphere but rose or fluctuated in the upper stratosphere. The reduction reached −5 ppb/yr at pressure levels of 31.62 hPa and 68.13 hPa, with a confidence level of over 90%. The growth was around 1–2 ppb/yr in the upper stratosphere. In addition, a concentration anomaly was observed in the tropical stratosphere in 2013. After the appearance of this anomaly, the N2O concentration in the middle and lower layers of the tropical stratosphere was lower than before 2013. We speculated that the enhancement of the Brewer–Dobson circulation (BDC) upwelling before and after stratospheric sudden warming (SSW) is the main reason for the abnormal concentration distribution in 2013. Stratospheric N2O has changed significantly in the past 16 years with the mutual coupling effect of BDC and SSW and such changes can have further impact on the chemical equilibrium and radiation balance in the stratosphere, as well as on the persistent climate-warming trend.

Long-term trend of crop yields has been widely studied in global scales to find which crops and which geographic regions offer the best hope of meeting food demands, and which regions needed the most improvements. In this study, a mathematical method was applied to analyze spatial patterns in long-term temporal trends of three major crops’ yields in Japan archipelago. The changes in annual yields of rice, wheat, and soybean over a period of about 60 years in all 47 prefectures of Japan was analyzed by using the data of agricultural records. For all the three crops, the nationwide yields previously improved, but currently were stagnating in Japan. The result suggests that the annual yields were not improving in 53, 85, and 89% of those prefectures in Japan for rice, wheat, and soybean, respectively. The spatial patterns in temporal trends show that the percentage of number of yield-not-improving prefecture was higher in low latitude regions than high latitude regions. These results highlight the increasingly difficult challenge of meeting the growing demands and stagnating supplies in daily staple foods not only for agricultural scientists but also for Japanese society.

Plenty of dust aerosols are emitted into the atmosphere in East Asian regions and significantly impact the regional environment and climate. In the past decade, the frequency of dust storm outbreaks has largely declined in the sources of Asian dust. However, it is still rarely reported how the dust properties after long-range transport in the downstream regions respond to this downtrend. Here we report on the long-term characteristics of dust aerosols over central China with the observations of a polarization lidar at Wuhan (30.5°N, 114.4°E) during 2010–2020. The dust optical depths (DOD) exhibit a decrease trend with a rate of −0.011 yr−1, accounting for 22% of the decrease rate for total aerosol optical depths (AOD) in Wuhan. The mass concentration and columnar mass density of dust also decline with a rate of −2.03 μg·m−3·yr−1 and -1.97 mg·m−2·yr−1, respectively. Spring and winter are the most active seasons for dust intrusion, with seasonal mean DOD of 0.21 and 0.15, respectively. Compared with spring, dust aerosols in winter generally concentrate at lower levels below 1.0 km with a slightly smaller particle depolarization ratio of 0.11 (0.14 in spring), attributing to the weakened nonspherical shape of dust particles under wintertime high-level moisture/polluted conditions. Both the surface PM 10 concentration and lidar-derived dust mass concentration at 0.3 km present a downtrend with a rate of −8.0 μg·m−3·yr−1 and -20.1 μg·m−3·yr−1, respectively. This study provides a comprehensive long-term and seasonal analysis of dust properties in central China, which can supplement our understanding of the feedback in the downstream regions to the reduction of dust emissions in the deserts of East Asia. • Dust aerosols are observed in central China during 2010–2020 with ground-based polarization lidar. • Dust optical depths (DOD) exhibit a decrease of −0.011 yr−1, accounting for 22% decrease rate for total AOD. • Dust frequently intrudes into Wuhan in spring and winter, with DOD of 0.21 and 0.15. • Dust in winter concentrates at lower levels (<1.0 km) with a smaller PDR (0.11) than in spring (0.14). [ABSTRACT FROM AUTHOR]

The East Asian winter monsoon (EAWM) exhibits long-term variations in intensity and spatial pattern, though the latter one is less understood. To investigate the long-term spatial variations of the EAWM and their possible causes, we propose a new position index of the EAWM by quantifying the low-level East Asian stream (EAS) of cold airmass in the Lagrangian sense. Based on the new-defined index, we find that the EAS undergoes an evident zonal shift between two channels over the land and coast. At interdecadal timescale, the peak location of the EAS is displaced eastward, with an increasing southward cold airmass flux at the coast since the mid-1960s. The interannual shift of the EAS presents not only the zonal oscillation of peak location between two channels but also the width changes of coastal channel over the northwestern Pacific. These shifts in the EAS are related to the strength changes of two source cold airmass streams from Siberia or Bering Sea, which are associated with the phase changes in the upper-tropospheric atmospheric teleconnections. At interdecadal timescale, the phase change in the North Atlantic Oscillation modulates the zonal shift in the EAS via the East Atlantic-West Russia teleconnection. At interannual timescale, the Pacific/North American teleconnection becomes the dominant factor altering the zonal shift and width change of the EAS.

Using high-resolution satellite-derived sea surface temperature (SST) data from September 1981 to December 2015, the present study develops a new index to detect the long-term variation in mesoscale eddy activity over the Kuroshio Extension (KE) region. This eddy activity index (EAI) highlights the strength of eddy-induced poleward heat transport and has obvious advantages over the other existing KE indices in depicting the low-frequency changes in KE eddy activity. An analysis of the EAI shows that over the long term, the KE eddy activity variability presents a significant spectral peak of about 8 years and is not directly modulated by wind-driven oceanic Rossby waves generated in the central North Pacific. When the EAI is positive, the strengthened KE eddy activity significantly enhances the heat release from ocean to atmosphere over the Kuroshio–Oyashio confluence region (KOCR). This induces an anomalous dipole pattern of near-surface baroclinicity over this region that can persist for up to 6 months, favoring a weakened and northward-moving East Asian jet, and vice versa. It is believed that the new EAI will facilitate future studies focusing on the climatic effects of the KE eddy activity variation.

The Tibetan Plateau (TP) has been experiencing warming and wetting since the 1980s. Under such circumstances, we estimated the summer latent heat flux (LE) using the maximum entropy production model driven by the net radiation, surface temperature, and soil moisture of three reanalysis datasets (ERA5, JRA-55, and MERRA-2) at the Ali site over the western TP during 1980-2018. Compared with the observed LE of the Third Tibetan Plateau Atmospheric Scientific Experiment, the coefficient of determination, root-mean-square error, and mean bias error of the estimated summer LE are 0.57, 9.3 W m−2, and −2.25 W m−2 during 2014-2016, respectively, which are better than those of LE of the reanalysis datasets. The estimated long-term summer LE presents a decreasing (an increasing) trend of −7.4 (1.8) W m−2 decade−1 during 1980-1991 (1992-2018). The LE variation is closely associated with the local soil moisture influenced by precipitation, glacier, and near-surface water conditions at the Ali site. The summer soil moisture also presents a decreasing (an increasing) trend of −0.082 (0.022) decade−1 during 1980-1991 (1992-2018). The normalized difference vegetation index generally shows the consistent trend with LE at the Ali site.

An article contains the data on the investigations of season and long-term variations of radiation safety indexes of the water of some underground sources and centralized water-supply system of Tver city.

Abstract Concentrations of atmospheric pollutants over East China have varied considerably during the past decades. These variations are partly due to variations of human activities, e.g., increasing energy consumption and implementation of government emission control policies, and partly to natural fluctuations. This study aims to separate the effects of natural processes and anthropogenic activities on the increase/decrease of the concentrations of some of the most important pollutants (SO 2 , NO 2 , CO and aerosols) over East China in the last decade. This was achieved by the comparison of the temporal variations in long-term time series of satellite-retrieved aerosol optical depth (AOD) and vertical column densities (VCDs) of SO 2 , NO 2 , and CO, with those in model-simulated time series of the natural variations only. The latter were created by the use of the same anthropogenic emissions throughout the whole simulation, while using re-analysis data (MERRA) to describe meteorological processes and natural emissions. Thus, the comparison between observed and simulated temporal variations reveals the effects due to anthropogenic emissions only, assuming that the atmospheric processes affect natural and anthropogenic species in the same way. In the analysis, a Kolmogorov–Zurbenko (KZ) filter is used to extract long-term components from both the observed and simulated data and normalization to the situation at a certain reference point is used to eliminate bias between observations and simulations. By this new method, natural and anthropogenic contributions to long-term variations of trace gases and AOD are quantitatively estimated. The results show that NO 2 VCDs increased from 2004 to 2011 by 76% and of the overall increase in this period only 1% ± 1% was attributed to natural factors, 99% ± 1% attributed to anthropogenic factors. AOD increased by 24% between 2001 and 2011 and of the overall increase 24% ± 32% was due to natural factors and 76% ± 32% was due to anthropogenic factors. SO 2 VCDs decreased by 15% from 2007 to 2013, natural and anthropogenic factors contributed respectively 16% ± 14% and 84% ± 14% to the overall decrease in this period. CO decreased since 2003 with 13% and of the overall decrease 6% ± 6% was due to natural factors and 94% ± 6% was due to anthropogenic factors. Highlights • A new method to separate natural and anthropogenic contributions to long-term variations of SO 2 , NO 2 , CO, and AOD. • Quantified natural and anthropogenic contributions. • Variations of trace gases and AOD are mostly attributed to anthropogenic activities. [ABSTRACT FROM AUTHOR]

The Eastern Baltic Stone Age is characterized by several major shifts in tool technology. Our picture of cultural change is currently based on typological variation in well-preserved bone tools, ceramics, stone tools, and on diversity in lithic raw-material use. These variations have partly been interpreted as the result of external influences, and partly as internal development. However, the understanding of relations with neighbouring regions is still limited. Recent decades have seen a growing interest in the chaîne opératoire approach and technological analysis, and their relevance for studying intra-site activity and development of skill, and for describing ancient technologies has been demonstrated. Technological and cultural relationships in the North European Stone Age have also been discussed within this frame. In this article, we take a new approach, employing variation in lithic technological craft traditions as proxy for investigating long-term development and variability in lines of communication. This study addresses three chronological contexts of the Latvian Stone Age, based on technological analysis of 26 sites. In describing the overall development in stone technology during the period c 10 500--2900 calBC, the article demonstrates not only technological variations but also af- firms fluctuation/change in directions of social contacts throughout the Stone Age, demonstrating variation in knowledge transmission and communication routes across large geographical areas. [ABSTRACT FROM AUTHOR]

Long-term trend of crop yields has been widely studied in global scales to find which crops and which geographic regions offer the best hope of meeting food demands, and which regions needed the most improvements. In this study, a mathematical method was applied to analyze spatial patterns in long-term temporal trends of three major crops' yields in Japan archipelago. The changes in annual yields of rice, wheat, and soybean over a period of about 60 years in all 47 prefectures of Japan was analyzed by using the data of agricultural records. For all the three crops, the nationwide yields previously improved, but currently were stagnating in Japan. The result suggests that the annual yields were not improving in 53, 85, and 89% of those prefectures in Japan for rice, wheat, and soybean, respectively. The spatial patterns in temporal trends show that the percentage of number of yield-not-improving prefecture was higher in low latitude regions than high latitude regions. These results highlight the increasingly difficult challenge of meeting the growing demands and stagnating supplies in daily staple foods not only for agricultural scientists but also for Japanese society. [ABSTRACT FROM AUTHOR]

We present observations of CH4 concentrations from the lower to upper troposphere (LT and UT) over Japan during 1988–2010 based on aircraft measurements from the Tohoku University (TU). The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM). Tropospheric CH4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH4 sources, while LT CH4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH4-rich air from Asian regions elevates UT CH4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH4 decreases nearly monotonically with altitude in winter–spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH4 sources in South Asia and East Asia to the summertime high CH4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH4 emission signals particularly from Asia.

Ambient fine particulate matter samples were collected during 2009–2013 in Chengdu, a megacity in western China, and the samples were speciated into organic carbon (OC), elemental carbon (EC), char-EC, soot-EC, eight carbon fractions, inorganic elements and water-soluble ions. Char-EC and soot-EC contribute to the better understanding of the sources and properties of EC. The highest levels of most carbon fractions were found in winter and May. The higher OC/EC ratio in winter suggests higher SOC fraction in winter, and higher char-EC/soot-EC ratio in May are the direct consequences of straw burning activities. Source contributions to PM 2.5 and carbonaceous aerosols were quantified using the ME2 receptor model. Major contributors to OC in PM 2.5 are vehicular exhaust (36.5%), coal combustion & straw burning (35.2%) and SOC (27.0%). The first two categories also contributed 51.4% and 49.3% of char-EC in PM 2.5 . Vehicular exhaust dominated soot-EC, contributing 63.0% to soot-EC in PM 2.5 . SOC contributed to high OC levels in winter due to the increase of precursor emissions and stable meteorological conditions. Coal combustion & straw burning show higher contributions to OC, char-EC and soot-EC in winter months and in May, which can be explained, in part, by increased coal consumption in winter and straw burning activities in May. Vehicular exhaust contributions are not strongly associated with monthly nor weekday-weekend patterns, resulting in that soot-EC vary insignificantly by month nor by weekday. [ABSTRACT FROM AUTHOR]

We reviewed the long-term trends and inter-annual variations in the surface shortwave irradiance in China and Japan. Pyranometer observations revealed decreases followed by increases in the shortwave irradiance in China and Japan between the 1960s and 2000s, while obvious long-term trends were not evident in the satellite observations after 1983. In China, surface shortwave irradiance decreased from 1961 until around 1990, but then began to increase. In Japan, on the contrary, the decreasing trend stopped in the 1960s, with little inter-annual variation during the 1970s and 1980s, and an increase began around 1990. The causes of the differences between the shortwave irradiance trends in China and Japan were ascribed to an increase in light-absorbing aerosols in China that began in the 1960s and a decrease in absorbing aerosols in Japan that began in the late 1970s. Absorbing aerosols decrease both direct and diffuse radiation, while non-absorbing aerosols decrease direct radiation but increase diffuse radiation. Although these aerosol influences are generally found under clear sky conditions, absorbing aerosols could have direct effects even under cloudy sky conditions. The trends of surface shortwave irradiance in China and Japan are in line with the so-called global dimming and brightening dimming processes, although the phases of the minimum periods in the two regions slightly differed. An increase in anthropogenic aerosol was responsible for the variation in the shortwave irradiance through the direct radiative effect of aerosol in the polluted area, while indirect radiative effects, i.e., changes in cloud cover due to an increase in cloud condensation nuclei, dominated in pristine areas. The effects of other factors, such as variations in water vapor and natural aerosol levels, appear to be small compared to the effects of cloud and anthropogenic aerosols. [ABSTRACT FROM AUTHOR]

Coastal environment has been disturbed by human activities for a long time, especially in the rapidly urbanizing and industrializing areas. Although the surrounding area has achieved great economic success in the past 30 years, Western Xiamen Bay (China) is seriously affected by pollutants and is facing increasing ecological pressure. Because of this, Xiamen was selected in 1994 as a demonstration site for implementing an integrated coastal management program, which included a series of measures for protecting the coastal environment. However, coastal environment is dynamic, complex and site-specific, and thus a scientific quantitative evaluation framework is necessary for environment quality analysis and effective coastal management. In this study, we used oceanographic knowledge together with quantitative methods (Bai-Perron's structural break test) to analyze the long-term variations of water quality indices (pH, DO, COD, DIN, PO 4 -P and Oil) in Western Xiamen Bay. In addition, we compared with other coastal areas to identify the effectiveness of phosphorus-based nutrient management measures and predicted the probable variation trend in the future. The results show that in Western Xiamen Bay: (1) the concentrations of DO and Oil in seawater are effectively controlled by local coastal management measures; (2) seawater acidification will continue to worsen based on the present situation; and (3) the P-limitation treatment strategies are effective and PO 4 -P concentration starts to fall according to the multiple statistical analysis and Environmental Kuznets Curve. This paper hopes to provide an epitome of the conflicts and consolations between socioeconomic development and environmental quality in the past, and hints for coastal management in the future. [ABSTRACT FROM AUTHOR]

Rainwater samples were collected monthly from Fukushima, Japan, in 2012–2014 and analysed for 127 I and 129 I. These are combined with previously reported data to investigate atmospheric levels and behaviour of Fukushima-derived 129 I before and after the 2011 nuclear accident. In the new datasets, 127 I and 129 I concentrations between October 2012 and October 2014 varied from 0.5 to 10 μg/L and from 1.2 × 10 8 to 6.9 × 10 9 atoms/L respectively, resulting in 129 I/ 127 I atomic ratio ranges from 3 × 10 −8 to 2 × 10 −7 . The 127 I concentrations were in good agreement with those in the previous period from March 2011 to September 2012, whereas the 129 I concentrations and 129 I/ 127 I ratios followed declining trends since the accident. Although 129 I concentrations in five samples during the period of 2013–2014 have approached the pre-accident levels, 129 I concentrations in most samples remained higher values in winter and spring-summer. The high 129 I levels in winter and spring-summer are most likely attributed to local resuspension of the Fukushima-derived radionuclide-bearing fine soil particles deposited on land surfaces, and re-emission through vegetation taking up 129 I from contaminated soil and water, respectively. Long-term declining rate suggests that contribution of the Fukushima-derived 129 I to the atmosphere would become less since 2014. [ABSTRACT FROM AUTHOR]

Accurate measurements of wet mercury (Hg) deposition are critically important for the assessment of ecological responses to pollutant loading. The Hg in wet deposition was measured over a 3-year period in the southeastern Tibetan Plateau. The volume-weighted mean (VWM) total Hg (Hg T ) concentration was somewhat lower than those reported in other regions of the Tibetan Plateau, but the VWM methyl-Hg concentration and deposition flux were among the highest globally reported values. The VWM Hg T concentration was higher in non-monsoon season than in monsoon season, and wet Hg T deposition was dominated by the precipitation amount rather than the scavenging of atmospheric Hg by precipitation. The dominant Hg species in precipitation was mainly in the form of dissolved Hg, which indicates the pivotal role of reactive gaseous Hg within-cloud scavenging to wet Hg deposition. Moreover, an increasing trend in precipitation Hg concentrations was synchronous with the recent economic development in South Asia. [ABSTRACT FROM AUTHOR]

Continuous measurements of ozone (O 3) and nitrogen oxides (NO x = NO + NO 2) were conducted from 2007 to 2019 in Hong Kong in order to evaluate the effectiveness of control strategies for NO x emission from diesel commercial vehicles (DCV). DCV control programs were periodically applied in three phases starting from 2007, 2010 and 2014. It was found that NO and NO 2 levels decreased during the study period but more dramatically after the implementation of DCV Phase III than pre-DCV Phase III. Source apportionment analysis confirmed that the ambient NO and NO 2 in Hong Kong attributed to the regulated DCV emissions in Phase III reduced at rates of 5.1–14.4 ppbv/yr in roadside environment and 1.6–3.1 ppbv/yr in suburban area. Despite overall NO x reduction, increased NO 2 /NO x ratios were recorded during the study period possibly due to the application of diesel particulate filter (DPF) in DCVs. However, after introducing DCV Phase III, observed O 3 values experienced more dramatic increasing trends in most areas of Hong Kong than pre-DCV Phase III. Model simulations revealed that O 3 production rate kept increasing and turned to be less sensitive to NO x from 2014 to 2019. On the roadside, net O 3 production rate was more than doubled during 2014–2019 owing to NO x reduction. Moreover, the levels of oxidants (OH, HO 2 and RO 2) were 1.5–5 times those before 2014. In suburban environment, NO x reduction also facilitated O 3 production and radical cycling, but made smaller contributions than those on the roadside during 2014–2019. This study unraveled that NO x reductions benefited from DCV regulations caused increase in surface O 3 and fueled O 3 photochemistry in various environments. More stringent control measures on emissions of VOCs, especially those with high OH reactivity, might help to better mitigate O 3 pollution. [Display omitted] • DCV control programs, especially Phase III led to NO x decrease in urban Hong Kong. • O 3 production rate increased and became less sensitive to NO x after DCV Phase III. • Roadside O 3 production rate was more than doubled owing to NO x reduction. • More stringent control measures on VOC emissions are suggested for O 3 mitigation. [ABSTRACT FROM AUTHOR]

Numerical simulations on oceanic 134Cs and 137Cs dispersions were intensively conducted in order to assess an effect of the radioactive cesium on the North Pacific environment with a focus on the long-term variation of the radioactive cesium concentration after the Fukushima disaster that occurred in March 2011. The amounts of 134Cs and 137Cs released into the ocean were estimated using oceanic monitoring data, whereas the atmospheric deposition was calculated through atmospheric dispersion simulations. The highly accurate ocean current reanalyzed through a three-dimensional variational data assimilation enabled us to clarify the time series of the 134Cs and 137Cs concentrations in the North Pacific. It was suggested that the main radioactive cesium cloud due to the direct oceanic release reached the central part of the North Pacific, crossing 170°W one year after the Fukushima disaster. The radioactive cesium was efficiently diluted by meso-scale eddies in the Kuroshio Extension region and its concentration in the surface, intermediate, and deep layers had already been reduced to the pre-Fukushima background value in the wide area within the North Pacific 2.5 years after the Fukushima disaster. [ABSTRACT FROM AUTHOR]

The effects of meteorological conditions controlled by specific synoptic patterns on regional surface ozone episodes have been widely discussed. However, the impacts of synoptic climate systems and their interaction on long-term variation of ozone are less known. In this study, we use the daily meteorological data and hourly surface ozone concentrations in the summer of 1950–2014 from CMIP6 to investigate the relationship between ozone variations and synoptic climate types (SCTs). Eight SCTs are identified by an objective circulation classification method of an R package called synoptReg. Our results show that the mainland of China is controlled by the low-pressure system for SCT1–5, while dominated by Siberian high for SCT6–8. During SCT1–5 days, the interactions of Asian continental low, Western Pacific Subtropical High (WPSH), warm ridge at 700 hPa, high-level shallow Asian trough, westerly belt, and topography lead to high surface temperature, low relative humidity, and poor diffusion over Northern China with frequent ozone exceedance days. However, the low-level ozone concentrations over Northern China are shown under SCT6–8, affected by the weakened Asian continental low, enhanced Siberian high, stronger WPSH, and denser westerly belt. While over Southern China, ozone concentrations are higher for SCT6–8 than SCT1–5, due to the significantly reduced cloud and precipitation affected by the delivery of cold dry air mass from high latitudes to the South. The interdecadal variabilities of ozone during all SCTs may be controlled by the large-scale climate system of the East Asian monsoon. • Relationships of synoptic climate types and spatiotemporal variations of historical ozone are investigated. • The impacts of synoptic climate system interaction on meteorological conditions and ozone are analyzed. • The interdecadal ozone variation is controlled by the East Asian monsoon. [ABSTRACT FROM AUTHOR]

We present observations of CH4 concentrations from the lower to upper troposphere (LT and UT) over Japan during 1988-2010 based on aircraft measurements from the Tohoku University (TU). The analysis is aided by simulation results using an atmospheric chemistry transport model (i.e. ACTM). Tropospheric CH4 over Japan shows interannual and seasonal variations that are dependent on altitudes, primarily reflecting differences in air mass origins at different altitudes. The long-term trend and interannual variation of CH4 in the LT are consistent with previous reports of measurements at surface baseline stations in the northern hemisphere. However, those in the UT show slightly different features from those in the LT. In the UT, CH4 concentrations show a seasonal maximum in August due to efficient transport of air masses influenced by continental CH4 sources, while LT CH4 reaches its seasonal minimum during summer due to enhanced chemical loss. Vertical profiles of the CH4 concentrations also vary with season, reflecting the seasonal cycles at the respective altitudes. In summer, transport of CH4-rich air from Asian regions elevates UT CH4 levels, forming a uniform vertical profile above the mid-troposphere. On the other hand, CH4 decreases nearly monotonically with altitude in winter-spring. The ACTM simulations with different emission scenarios reproduce general features of the tropospheric CH4 variations over Japan. Tagged tracer simulations using the ACTM indicate substantial contributions of CH4 sources in South Asia and East Asia to the summertime high CH4 values observed in the UT. This suggests that our observations over Japan are highly sensitive to CH4 emission signals particularly from Asia. [ABSTRACT FROM AUTHOR]

Background and Aims Functional groups of species interact and coevolve in space and time, forming complex networks of interacting species. A long-term study of temporal variation of an ant–plant network is presented with the aims of: (1) depicting its structural changes over a 20-year period; (2) detailing temporal variation in network topology, as revealed by nestedness and modularity analysis and other parameters (i.e. connectance, niche overlap); and (3) identifying long-term turnover in taxonomic structure (i.e. switches in ant resource use or plant visitor assemblages according to taxa). Methods Fieldwork was carried out at La Mancha, Mexico, and ant–plant interactions were observed between 1989 and 1991, between 1998 and 2000, and between May 2010 and 2011. Occurrences of ants on extrafloral nectaries (EFNs) were recorded. The resulting ant–plant networks were constructed from qualitative presence–absence data determined by a species–species matrix defined by the frequency of occurrence of each pairwise ant–plant interaction. Key Results Network variation across time was stable and a persistent nested structure may have contributed to the maintenance of resilient and species-rich communities. Modularity was lower than expected, especially in the most recent networks, indicating that the community exhibited high overlap among interacting species (e.g. few species were hubs in the more recent network, being partly responsible for the nested pattern). Structurally, the connections created among modules by super-generalists gave cohesion to subsets of species that otherwise would remain unconnected. This may have allowed an increasing cascade-effect of evolutionary events among modules. Mutualistic ant–plant interactions were structured 20 years ago mainly by the subdominant nectarivorous ant species Camponotus planatus and Crematogaster brevispinosa, which monopolized the best extrafloral nectar resources and out-competed other species with broader feeding habits. Through time, these ants, which are still present, lost their position as network hubs and diminished in their importance in structuring the network; simultaneously, plants gained in importance. Conclusions The long-term network analysis reveals a decrease in attended plant species richness, a notable increase in plant species participation from 1990 to 2010 (sustained by less plant taxonomic similarity in the older 1990 network), an increase in the number of ant species and a diminishing dominance of super-generalist ants. The structure of the community has remained highly nested and connected with low modularity, suggesting overall a more participative, homogeneous, cohesive interaction network. Although previous studies have suggested that interactions between ants and EFN-bearing plants are susceptible to seasonality, abiotic factors and perturbation, this cohesive structure appears to be the key for biodiversity and community maintenance. [ABSTRACT FROM PUBLISHER]

Abstract: Strong positive correlation between sporadic E layers and the solar activity and the long-term declining trend of Es were found in this paper. Then the feed-forward back propagation neural networks (NNs) were used to simulate the long-term variation of Es at four stations and predict foEs yearly average values. The inputs used for NNs are the yearly mean values of foEs in the daytime of the past ten years and the yearly averaged data of solar 10.7cm radio flux (F107) of the present year, and the output is the present yearly mean value of daytime foEs. The outputs of trained NNs have high correlation with the desired values and the foEs yearly mean values predicted by NNs have good agreement with the observed data. The results indicate that NNs can make full use of the observed data to simulate the long variation rule of Es. Also, the results confirm the effect of solar activity on Es. [Copyright &y& Elsevier]

Nitrous oxide (N2O) is a potent and long-lived greenhouse gas that contributes to global warming with a global warming potential (GWP) 298 times that of carbon dioxide (CO2). In this paper, we analyzed the trend of N2O concentration in vertical layers of the stratosphere from 2005 to 2020 using the N2O observed from the Microwave Limb Sounder (MLS) that is on board the Aura satellite. We found that the local N2O concentration showed a downward trend in the lower stratosphere but rose or fluctuated in the upper stratosphere. The reduction reached −5 ppb/yr at pressure levels of 31.62 hPa and 68.13 hPa, with a confidence level of over 90%. The growth was around 1–2 ppb/yr in the upper stratosphere. In addition, a concentration anomaly was observed in the tropical stratosphere in 2013. After the appearance of this anomaly, the N2O concentration in the middle and lower layers of the tropical stratosphere was lower than before 2013. We speculated that the enhancement of the Brewer–Dobson circulation (BDC) upwelling before and after stratospheric sudden warming (SSW) is the main reason for the abnormal concentration distribution in 2013. Stratospheric N2O has changed significantly in the past 16 years with the mutual coupling effect of BDC and SSW and such changes can have further impact on the chemical equilibrium and radiation balance in the stratosphere, as well as on the persistent climate-warming trend. [ABSTRACT FROM AUTHOR]

Aims Here, the aim is to assess long-term clinical variation (CV) of N-terminal pro-brain natriuretic peptide (NT-proBNP) in stable chronic heart failure (CHF) patients. The proposed use of NT-proBNP for monitoring of CHF patients will require accurate information about long-term CV of the peptide. [ABSTRACT FROM PUBLISHER]

The source strength of volatile organic compounds (VOCs) emitted by vegetation is of great interest for the understanding of processes in atmospheric chemistry and climate change. In this study terpene emissions from branches of European beech ( Fagus sylvatica L.) were studied in a deciduous forest. Using the branch enclosure technique changes in the emission pattern and the variation of emission rates over the year were investigated over two consecutive vegetation periods. More than 10 monoterpene compounds were found in the emissions, among which sabinene dominates. For most compounds the emission pattern changed only slightly over the year. Interestingly, two compounds tentatively identified as para-cymene and cis-ocimene showed differences in the emission behaviour in late summer compared to the other terpenes. In contrast to previous studies our investigation characterise European beech as a strong emitter. For the main compounds the emission rates changed up to two orders of magnitude as a function of temperature and light over the day. In general, highest emission rates were observed in summer and lowest in fall. A seasonality was characterized by a temperature independent decline of emissions in late summer, resulting in changes of the standard emission rate on the order of one magnitude. A standard emission factor of up to 3.5 nmol m−2s−1 for the sum of measured terpenes was calculated. No emissions were found in early spring even though leaves were fully developed and temperature and light conditions were moderate. The results underline the importance of characterising the annual variation of the emission behaviour. Especially for the up-scaling to global VOC emissions, seasonal influences have to be considered to achieve realistic emission inventories. [ABSTRACT FROM AUTHOR]

Abstract: Recent research pointed out the question of missing OH reactivity in a forest system and the question for unknown highly reactive biogenic emissions. In this study we show that coniferous forests are an important source of highly reactive hydrocarbons, the sesquiterpenes. We investigated the seasonality of terpene emissions from Scots pine to work out influences on atmospheric chemistry in different seasons for both mono- and sesquiterpenes. Especially sesquiterpenes (C15) change dramatically in their contribution to the terpene emissions of Scots pine. Fourteen sesquiterpenes and oxygenated compounds were found in the emissions. In spring, the pattern was most complex with all 14 compounds being emitted, whereas in summer and fall it was reduced to 1,8-cineol and camphor. The emission pattern of the monoterpenes varied only slightly. The main compounds emitted were α-pinene, β-pinene, and 3-carene representing up to 90% of the total terpene emission. The total monoterpene emission rates varied from below detection limit to 460pmolm−2 s−1 with highest emission rates found in June. Standard emission rates of the main compounds calculated from the monthly measured diurnal emission courses varied considerably over the year. Highest values were found in spring and early summer with up to 700pmolm−2 s−1. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate properties long-term variations in galactic cosmic ray intensity as an important possible link in the connection between solar activity variation and global climate change. There are two main aims of the paper: (1) to estimate how solar activity influences on galactic CR long-term variations, what are the relative role in this influence of convection-diffusion modulation and drift modulation and (2) to estimate the expected part of global climate change which may be caused by the influence of solar activity cycle on climate through 11- and 22-year cosmic ray variations. [Copyright &y& Elsevier]

Abstract: On the basis of results obtained in our paper [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], we determine: the dimension of the Heliosphere (modulation region), radial diffusion coefficient and other parameters of convection–diffusion; drift mechanisms of long-term variations of cosmic ray (CR) dependence on particle energy; level of solar activity (SA); and generally, the solar magnetic field. We obtain this important information on the basis of CR and SA data in the past, taking into account the theory of convection–diffusion and global drift modulation of galactic CR in the Heliosphere. By using these results and other regularly published predictions of expected SA variation in the near future, as well as predictions of the next SA cycle, we may make predictions of long-term cosmic ray intensity variation expected in the near future (up to 10–12 years). In [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], properties of connections between long-term variation in CR intensity and some part of a global climate change were estimated, controlled by solar activity through CR. We show that in this way we may make predictions of some part of a global climate change expected in the near future (up to 10–12 years and maybe more, depending upon the period during which definite predictions of SA can be made), controlled by solar activity through CR. In this case, estimations of expected long-term changes in the planetary distribution of cutoff rigidities, which also influence CR intensity, as well as CR-influenced effects on global climate variation, become important. [Copyright &y& Elsevier]