Using observations and numerical simulations,this study examines the intraseasonal variability of the surface zonal current(u ISV)over the equatorial Indian Ocean,highlighting the seasonal and spatial differences,and ...Using observations and numerical simulations,this study examines the intraseasonal variability of the surface zonal current(u ISV)over the equatorial Indian Ocean,highlighting the seasonal and spatial differences,and the causes of the differences.Large-amplitude u ISV occurs in the eastern basin at around 80°–90°E and near the western boundary at 45°–55°E.In the eastern basin,the u ISV is mainly caused by the atmospheric intraseasonal oscillations(ISOs),which explains 91%of the standard deviation of the total u ISV.Further analysis suggests that it takes less than ten days for the intraseasonal zonal wind stress to generate the u ISV through the directly forced Kelvin and Rossby waves.Driven by the stronger zonal wind stress associated with the Indian summer monsoon ISO(MISO),the eastern u ISV in boreal summer(May to October)is about 1.5 times larger than that in boreal winter(November to April).In the western basin,both the atmospheric ISOs and the oceanic internal instabilities contribute substantially to the u ISV,and induce stronger u ISV in boreal summer.Energy budget analysis suggests that the mean flow converts energy to the intraseasonal current mainly through barotropic instabilities.展开更多
Urban green spaces(UGS)are relevant to city well-being,as recognized by the United Nations’Sustainable Development Goals(SDGs).However,few studies have studied the temporal use of UGS.This work assessed the seasonal,...Urban green spaces(UGS)are relevant to city well-being,as recognized by the United Nations’Sustainable Development Goals(SDGs).However,few studies have studied the temporal use of UGS.This work assessed the seasonal,weekly,and daily use of three urban green spaces(Vingis Park,Bernardino Garden,and Jomantas Park)in Vilnius(Lithuania).The study is based on an on-site observation-based survey,which recorded users’characteristics,activities,and weather conditions during summer and winter.The results showed that UGS’s seasonal,weekly,and daily use differed according to park and users’characteristics.Parks with a higher diversity of facilities had a high seasonal difference in the number of observed activities.User numbers were higher in the summer for activities with children,social activities,sports,and water activities than in the winter.Jomantas Park had the lowest variability in user characteristics.Weather variables were linked to changes in users’activities.Higher precipitation and lower temperature were associated with reducing the number of users and the diversity of registered activities.Most of the stationary activities were observed during summer.The diversity of the observed activities was associated with the available facilities rather than the park size.The distribution of stationary activities was spatially correlated with facility/equipment(benches,playgrounds,sports,and fitness equipment)and proximity to water features.The results of this study are relevant for UGS design,planning,and management.展开更多
Long-term variations in a sea surface wind speed （WS） and a significant wave height （SWH） are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource ex...Long-term variations in a sea surface wind speed （WS） and a significant wave height （SWH） are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource exploitation, and other activities. The seasonal characteristics of the long-term trends in China＇s seas WS and SWH are determined based on 24 a （1988-2011） cross-calibrated, multi-platform （CCMP） wind data and 24 a hindcast wave data obtained with the WAVEWATCH-III （WW3） wave model forced by CCMP wind data. The results show the following. （1） For the past 24 a, the China＇s WS and SWH exhibit a significant increasing trend as a whole, of 3.38 cm/（s.a） in the WS, 1.3 cm/a in the SWH. （2） As a whole, the increasing trend of the China＇s seas WS and SWH is strongest in March-April-May （MAM） and December-January-February （DJF）, followed by June-July-August （JJA）, and smallest in September-October-November （SON）. （3） The areal extent of significant increases in the WS was largest in MAM, while the area decreased in JJA and DJF; the smallest area was apparent in SON. In contrast to the WS, almost all of China＇s seas exhibited a significant increase in SWH in MAM and DJF; the range was slightly smaller in JJA and SON. The WS and SWH in the Bohai Sea, the Yellow Sea, East China Sea, the Tsushima Strait, the Taiwan Strait, the northern South China Sea, the Beibu Gull and the Gulf of Thailand exhibited a significant increase in all seasons. （4） The variations in China＇s seas SWH and WS depended on the season. The areas with a strong increase usually appeared in DJF.展开更多
Submesoscale processes in marginal seas usually have complex generating mechanisms,highly dependent on the local background flow and forcing.This numerical study investigates the spatial and seasonal differences of su...Submesoscale processes in marginal seas usually have complex generating mechanisms,highly dependent on the local background flow and forcing.This numerical study investigates the spatial and seasonal differences of submesoscale activities in the upper ocean of the South China Sea(SCS)and the different dynamical regimes for sub-regions.The spatial and seasonal variations of vertical vorticity,horizontal convergence,lateral buoyancy gradient,and strain rate are analyzed to compare the submesoscale phenomenon within four sub-regions,the northern region near the Luzon Strait(R1),the middle ocean basin(R2),the western SCS(R3),and the southern SCS(R4).The results suggest that the SCS submesoscale processes are highly heterogeneous in space,with different seasonalities in each sub-region.The submesoscale activities in the northern sub-regions(R1,R2)are active in winter but weak in summer,while there appears an almost seasonal anti-phase in the western region(R3)compared to R1 and R2.Interestingly,no clear seasonality of submesoscale features is shown in the southern region(R4).Further analysis of Ertel potential vorticity reveals different generating mechanisms of submesoscale processes in different sub-regions.Correlation analyses also show the vertical extent of vertical velocity and the role of monsoon in generating submesoscale activities in the upper ocean of sub-regions.All these results suggest that the sub-regions have different regimes for submesoscale processes,e.g.,Kuroshio intrusion(R1),monsoon modulation(R2),frontal effects(R3),topography wakes(R4).展开更多
Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net...Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net radiative heating in the earth-atmospheric system and its relationship with the Asian summer monsoon. As is shown in the result, the zonal deviations of the zonal deviations of the heating, manifested as mutations in direction between land and sea with seasons, is an indication of the thermal difference between them.Being a month earlier than that in the general circulation from spring to summer, the seasonal reversal of directionmay be playing an essential role in triggering the onset and withdrawal of summer monsoon in Asia.展开更多
This paper presents the long-term climate changes of significant wave height(Hs) in 1958–2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts(ECMWF) Reanalysis(ERA-40...This paper presents the long-term climate changes of significant wave height(Hs) in 1958–2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts(ECMWF) Reanalysis(ERA-40) wave data. The linear trends in Hs and regional and seasonal differences of the linear trends for Hs were calculated. Results show that the Hs exhibits a significant increasing trend of about 4.6 cm decade-1 in the global ocean as a whole over the last 44 years. The Hs changes slowly during the periods 1958–1974 and 1980–1991, while it increases consistently during the periods 1975–1980 and 1995–1998. The Hs reaches its lowest magnitude in 1975, with annual average wave height about 2 m. In 1992, the Hs has the maximum value of nearly 2.60 m. The Hs in most ocean waters has a significant increasing trend of 2–14 cm decade-1 over the last 44 years. The linear trend exhibits great regional differences. Areas with strong increasing trend of Hs are mainly distributed in the westerlies of the southern Hemisphere and the northern Hemisphere. Only some small areas show obvious decreasing in Hs. The long-term trend of Hs in DJF(December, January, February) and MAM(March, April, May) is much more stronger than that in JJA(June, July, August) and SON(September, October, November). The linear trends of the Hs in different areas are different in different seasons; for instance, the increasing trend of Hs in the westerlies of the Pacific Ocean mainly appears in MAM and DJF.展开更多
[Objective] The aim was to carry out the genetic analysis on plant height of rice（Oryza sativa L.）cultivated in different seasons.[Method] Three rice parents with great difference in plant height including CB1（83.1...[Objective] The aim was to carry out the genetic analysis on plant height of rice（Oryza sativa L.）cultivated in different seasons.[Method] Three rice parents with great difference in plant height including CB1（83.1 cm）,CB4（105.5 cm）and CB7（115.6 cm）were chosen to construct two parental combinations：CB1×CB4 and CB7×CB4,and the corresponding filial generations P1,F1,P2,B1,B2 and F2 were obtained.The 6 populations were planted in middle and late seasons respectively to measure their height traits.The Akaike＇s information criterion（AIC）of the mixed major gene and polygene model was used to indentify the existence of major genes affecting quantitative traits in B1,B2,F2 populations.When the major genes existed,the genetic effects of the major genes and polygenes and their genetic variance were estimated through segregation analysis.[Result] One additive major gene plus additive-dominance polygenes was the most fitted genetic model for the trait in all B1,B2,F2 populations in two planting seasons.The heritability values of the major genes varied from 38.63% to 78.53% and those of polygenes varied from 1.72% to 36.04%,and the total heritability values were 45.52-92.93%.The additive effect d value of the two genetic populations under two planting seasons was-4.56,-9.16,-7.19,and-9.38,respectively,as suggested that additive effect of the major genes would decrease the express of the plant height trait.[Conclusion] The heritability of plant height trait was affected by planting seasons and the combinations clearly as a whole.展开更多
Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas.However,the ecophysiological mechanisms under-lyi...Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas.However,the ecophysiological mechanisms under-lying the impact of drought on tree growth remains unre-solved.In this study,earlywood and latewood tree-ring growth,δ^(13)C,andδ^(18)O chronologies of Picea mongolica from 1900 to 2013 were developed to clarify the intra-and inter-annual tree-ring growth responses to increasingly fre-quent droughts.The results indicate that annual basal area increment residuals(BAI_(res)),which removed tree age and size effects,have significantly decreased since 1960.How-ever,the decreasing trend of earlywood BAI_(res) was higher than that of latewood.Climate response analysis suggests that the dominant parameters for earlywood and latewood proxies(BAI_(res),δ^(13)C andδ^(18)O)were drought-related climate variables(Palmer drought severity index,temperature,rela-tive humidity,and vapor pressure deficit).The most signifi-cant period of earlywood and latewood proxies’responses to climate variables were focused on June-July and July-August,respectively.BAI_(res),andδ^(13)C were significantly affected by temperature and moisture conditions,whereasδ^(18)O was slightly affected.Decreasing stomatal conduct-ance due to drought outweighed the influence of increasing CO_(2) on intrinsic water use efficiency(iWUE),and ultimately led to a decline in BAI_(res).Compared to latewood,the faster decreasing BAI_(res) and smaller increasing iWUE of early-wood suggested trees were more vulnerable to water stress in the early growing season.Our study provides insights into the inter-and intra-annual mechanisms of tree-ring growth in semi-arid regions under rising CO_(2) and climate change.展开更多
High-mountain stream ecosystems are recognized as ideal arenas for natural experiments and for ecological monitoring and assessment research,owing to their sensitivity to climate gradients and human-mediated disturban...High-mountain stream ecosystems are recognized as ideal arenas for natural experiments and for ecological monitoring and assessment research,owing to their sensitivity to climate gradients and human-mediated disturbances.In this study,we chose a subtropical mountainous stream system in southwestern China,to explore the spatiotemporal patterns and driving factors of taxonomic,phylogenetic,and functional beta diversity of macroinvertebrate assemblages.We found that taxonomic beta diversity was highest(on average,0.577 in spring and 0.645 in autumn)across seasons,followed by phylogenetic(0.491 and 0.545)and functional(0.350 and 0.383)beta diversity,with the replacement component predominantly(57%–73%)contributing to all three facets of diversity.The taxonomic local contributions to beta diversity(LCBD)values were roughly equivalent among different sites in both spring and autumn,whereas phylogenetic LCBD(PLCBD)and functional LCBD(XLCBD)indices varied from site to site.Therefore,we recommend prioritizing site conservation based on LCBD,PLCBD,and XLCBD values to optimize biodiversity conservation strategies.The three-facets of dissimilarities were all somewhat higher in autumn than spring,possibly due to recolonization events in the metacommunity after the summer flood.Variation partitioning analysis indicated that environmental factors were more important than spatial factors in structuring all three facets of beta diversity and their components,although different sets of variables were identified as important for different diversity facets and between seasons.In summary,our study offers valuable insights into the patterns and drivers of macroinvertebrate beta diversity in high mountain streams and lays a baseline for targeted conservation strategies in these ecosystems.展开更多
Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aeros...Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aerosol mass spectrometer （HR- ToF-AMS, Aerodyne Research Inc., USA） was deployed in urban Beijing in August and October 2012. The mean OA mass concentration in autumn was 30 4-30 μg m-3, which was higher than in summer （13 4-6.9 μg m-3）. The elemental anal- ysis found that OA was more aged in summer （oxygen-to-carbon （O/C） ratios were 0.41 and 0.32 for summer and autumn, respectively）. Positive matrix factorization （PMF） analysis identified three and five components in summer and autumn, re- spectively. In summer, an oxygenated OA （OOA）, a cooking-emission-related OA （COA）, and a hydrocarbon-like OA （HOA） were indentified. Meanwhile, the OOA was separated into LV-OOA （low-volatility OOA） and SV-OOA （semi-volatile OOA）; and in autumn, a nitrogen-containing OA （NOA） was also found. The SOA （secondary OA） was always the most important OA component, accounting for 55% of the OA in the two seasons. Back trajectory clustering analysis found that the origin of the air masses was more complex in summer. Southerly air masses in both seasons were associated with the highest OA loading, while northerly air masses were associated with the lowest OA loading. A preliminary study of OA components, especially the POA （primary OA）, in different periods found that the HOA and COA all decreased during the National Day holiday period, and HOA decreased at weekends compared with weekdays.展开更多
The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS....The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS. Surface water samples for studying include the Red river, Nhue river and Kim Nguu river, Thanh Nhan lake, Yen So lake and Van Quan lake were collected in the dry season (April) and the rainy season (August) in 2015. The stable isotope analysis results showed that the δ<sup>18</sup>O values is a range from -42.53‰ to -64.05‰ and, the δ<sup>2</sup>H values is the range from -5.09‰ to -8.79‰ under global meteoric waterline (in the water vapor region). The δ<sup>2</sup>H results of the rivers and lakes in the dry season are more negative than the rainy season with a small difference. The δ<sup>18</sup>O results of lakes in the dry season are more negative than the rainy season, but the δ<sup>18</sup>O results of river in the dry season are more positive than the rainy season. The results of the EC, BOD, COD, DO, TSS analysis showed that surface water environment has changed clearly in the two seasons and the contamination level in the dry season is usually higher than the rainy season. The lakes and rivers strongly influenced by human activities led to seriously pollution are Van Quan lake and Yen So lake, Nhue river and Kim Nguu river.展开更多
In the northern slope of Tianshan Mountains in Xinjiang, the Manas River is a river with relatively large runoff. However, with the passage of time, the suspended sediment transport of the Manas River has shown an obv...In the northern slope of Tianshan Mountains in Xinjiang, the Manas River is a river with relatively large runoff. However, with the passage of time, the suspended sediment transport of the Manas River has shown an obvious increase trend. The reasons for this situation are mainly due to the increase in the runoff of the Manas River and the obvious water and soil loss in the upstream area. The analysis of sediment change and its influencing factors in Manas River is very important for the ecological research of water resources in Xinjiang region, and is also an important research content in the local soil and water conservation work. This article will then launch a scientific analysis of this, hoping to provide reference for professionals.展开更多
Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to th...Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to the insufficient information about thecharacteristics of varieties.So,it is impor-tant to find ways of determining the potential展开更多
Imidazole(IM)particles in the atmosphere affect climate,atmospheric chemical reactions,and human health.However,research on IM particles in the Sichuan Basin(SCB),one of the areas of China affected most heavily by haz...Imidazole(IM)particles in the atmosphere affect climate,atmospheric chemical reactions,and human health.However,research on IM particles in the Sichuan Basin(SCB),one of the areas of China affected most heavily by haze,remains very scarce.This study used single-particle aerosol mass spectrometry to investigate IM-containing particles in Chengdu,one of the megacities in the SCB,during summer and winter before and after implemen-tation of the Three-year Action Plan to Win the Blue-Sky Defense War(BSDW).We found that IM-containing particles accounted for 1.2%–12.0%of all detected particles,and they highly mixed with carbonaceous com-ponents,secondary inorganic species,and organic nitrogen.From before to after the BSDW,the proportion of IM-containing particles decreased by 1.8%in summer,but increased by 9.6%in winter.Ammonium/amines and carbonyl compounds were closely related to IM-containing particles;the highest proportion of IM-containing particles occurred in particles mixed with amines and carbonyls.The number fraction of IM-containing particles in all seasons was higher at night than during daytime.The potential source areas of IM-containing particles showed notable narrowing after the BSDW,and the high-value areas were found distributed closer to Chengdu and its surrounding areas.In the winter before the BSDW,most IM-containing particles(>70%)were mixed with organic carbon(OC)particles,and the contributions of OC and mixed organic–elemental carbon(OC-EC)particles increased with aggravation of pollution,whereas OC-EC and Metal particles played a more crucial role in the winter after the BSDW.展开更多
Seasonal differences of temperature are crucial components of the Earth's climate system.However,the relatively short observational record,especially for East Asia,has limited progress in understanding seasonal di...Seasonal differences of temperature are crucial components of the Earth's climate system.However,the relatively short observational record,especially for East Asia,has limited progress in understanding seasonal differences.In this study,we identify ten tree-ring chronologies separately correlated with local winter(December-February)temperatures and twelve different tree-ring chronologies separately correlated with summer(June-August)temperatures across East Asia.Using these discrete seasonal tree-ring chronologies,we develop two independent winter and summer temperature reconstructions covering the period 1376-1995 CE for East Asia,and compare them with model simulations.Our reconstructions show a more significant volcanic cooling and earlier onset of modern warming in summer than in winter.The reconstructed summer-minus-winter temperature decreased since as early as the late 19th century,which has driven the current state of seasonal temperature difference to out of the natural variability since the 1370s.Climate models could generally reproduce the variability and trends in seasonal reconstructions,but might largely underestimate seasonal differences due to the fact that seasonal expressions on external forcing and modes of internal variability are too small.Our study highlights the importance of using proxy-based seasonal reconstructions to evaluate the performance of climate models,and implies a substantial weakening of seasonal temperature differences in the future.展开更多
Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ov...Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.展开更多
基金The National Natural Science Foundation of China under contract Nos 41822602,41976016 and 4207602the Strategic Priority Research Program of Chinese Academy of Sciences under contract Nos XDB42000000,XDA20060502 and XDA15020901+4 种基金the Guangdong Basic and Applied Basic Research Foundation under contract No.2021A1515011534the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)under contract Nos GML2019ZD0302 and GML2019ZD0306the fund of Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences under contract No.ISEE2021ZD01the fund of State Key Laboratory of Tropical Oceanography under contract No.LTOZZ2002the fund of Youth Innovation Promotion Association of Chinese Academy of Sciences under contract No.Y2021093.
文摘Using observations and numerical simulations,this study examines the intraseasonal variability of the surface zonal current(u ISV)over the equatorial Indian Ocean,highlighting the seasonal and spatial differences,and the causes of the differences.Large-amplitude u ISV occurs in the eastern basin at around 80°–90°E and near the western boundary at 45°–55°E.In the eastern basin,the u ISV is mainly caused by the atmospheric intraseasonal oscillations(ISOs),which explains 91%of the standard deviation of the total u ISV.Further analysis suggests that it takes less than ten days for the intraseasonal zonal wind stress to generate the u ISV through the directly forced Kelvin and Rossby waves.Driven by the stronger zonal wind stress associated with the Indian summer monsoon ISO(MISO),the eastern u ISV in boreal summer(May to October)is about 1.5 times larger than that in boreal winter(November to April).In the western basin,both the atmospheric ISOs and the oceanic internal instabilities contribute substantially to the u ISV,and induce stronger u ISV in boreal summer.Energy budget analysis suggests that the mean flow converts energy to the intraseasonal current mainly through barotropic instabilities.
基金the Portuguese Foundation for Science and Technology(FCT)through the PhD grant SFRH/BD/149710/2019,which is attributed to the first authorthe institutional scientific employment program-contract CEECINST/00077/2021 attributed to Carla Ferreira.
文摘Urban green spaces(UGS)are relevant to city well-being,as recognized by the United Nations’Sustainable Development Goals(SDGs).However,few studies have studied the temporal use of UGS.This work assessed the seasonal,weekly,and daily use of three urban green spaces(Vingis Park,Bernardino Garden,and Jomantas Park)in Vilnius(Lithuania).The study is based on an on-site observation-based survey,which recorded users’characteristics,activities,and weather conditions during summer and winter.The results showed that UGS’s seasonal,weekly,and daily use differed according to park and users’characteristics.Parks with a higher diversity of facilities had a high seasonal difference in the number of observed activities.User numbers were higher in the summer for activities with children,social activities,sports,and water activities than in the winter.Jomantas Park had the lowest variability in user characteristics.Weather variables were linked to changes in users’activities.Higher precipitation and lower temperature were associated with reducing the number of users and the diversity of registered activities.Most of the stationary activities were observed during summer.The diversity of the observed activities was associated with the available facilities rather than the park size.The distribution of stationary activities was spatially correlated with facility/equipment(benches,playgrounds,sports,and fitness equipment)and proximity to water features.The results of this study are relevant for UGS design,planning,and management.
基金The National Basic Research Program of China under contract Nos 2015CB453200,2013CB956200,2012CB957803 and2010CB950400the National Natural Science Foundation of China under contract Nos 41275086 and 41475070
文摘Long-term variations in a sea surface wind speed （WS） and a significant wave height （SWH） are associated with the global climate change, the prevention and mitigation of natural disasters, and an ocean resource exploitation, and other activities. The seasonal characteristics of the long-term trends in China＇s seas WS and SWH are determined based on 24 a （1988-2011） cross-calibrated, multi-platform （CCMP） wind data and 24 a hindcast wave data obtained with the WAVEWATCH-III （WW3） wave model forced by CCMP wind data. The results show the following. （1） For the past 24 a, the China＇s WS and SWH exhibit a significant increasing trend as a whole, of 3.38 cm/（s.a） in the WS, 1.3 cm/a in the SWH. （2） As a whole, the increasing trend of the China＇s seas WS and SWH is strongest in March-April-May （MAM） and December-January-February （DJF）, followed by June-July-August （JJA）, and smallest in September-October-November （SON）. （3） The areal extent of significant increases in the WS was largest in MAM, while the area decreased in JJA and DJF; the smallest area was apparent in SON. In contrast to the WS, almost all of China＇s seas exhibited a significant increase in SWH in MAM and DJF; the range was slightly smaller in JJA and SON. The WS and SWH in the Bohai Sea, the Yellow Sea, East China Sea, the Tsushima Strait, the Taiwan Strait, the northern South China Sea, the Beibu Gull and the Gulf of Thailand exhibited a significant increase in all seasons. （4） The variations in China＇s seas SWH and WS depended on the season. The areas with a strong increase usually appeared in DJF.
基金The National Key Research and Development Program of China under contract No.2017YFA0604104the National Natural Science Foundation of China under contract Nos 42176004,92058201 and 41776040the Fundamental Research Funds for the Central Universities under contract No.B220202050.
文摘Submesoscale processes in marginal seas usually have complex generating mechanisms,highly dependent on the local background flow and forcing.This numerical study investigates the spatial and seasonal differences of submesoscale activities in the upper ocean of the South China Sea(SCS)and the different dynamical regimes for sub-regions.The spatial and seasonal variations of vertical vorticity,horizontal convergence,lateral buoyancy gradient,and strain rate are analyzed to compare the submesoscale phenomenon within four sub-regions,the northern region near the Luzon Strait(R1),the middle ocean basin(R2),the western SCS(R3),and the southern SCS(R4).The results suggest that the SCS submesoscale processes are highly heterogeneous in space,with different seasonalities in each sub-region.The submesoscale activities in the northern sub-regions(R1,R2)are active in winter but weak in summer,while there appears an almost seasonal anti-phase in the western region(R3)compared to R1 and R2.Interestingly,no clear seasonality of submesoscale features is shown in the southern region(R4).Further analysis of Ertel potential vorticity reveals different generating mechanisms of submesoscale processes in different sub-regions.Correlation analyses also show the vertical extent of vertical velocity and the role of monsoon in generating submesoscale activities in the upper ocean of sub-regions.All these results suggest that the sub-regions have different regimes for submesoscale processes,e.g.,Kuroshio intrusion(R1),monsoon modulation(R2),frontal effects(R3),topography wakes(R4).
文摘Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net radiative heating in the earth-atmospheric system and its relationship with the Asian summer monsoon. As is shown in the result, the zonal deviations of the zonal deviations of the heating, manifested as mutations in direction between land and sea with seasons, is an indication of the thermal difference between them.Being a month earlier than that in the general circulation from spring to summer, the seasonal reversal of directionmay be playing an essential role in triggering the onset and withdrawal of summer monsoon in Asia.
基金supported by the National Ky Basic Research Development Program(Grant Nos.2015CB453200,2013CB956200,2012CB957803,2010CB950400)the National Natural Science Foundation of China(Grant Nos.41430426,41490642,41275086,41475070)
文摘This paper presents the long-term climate changes of significant wave height(Hs) in 1958–2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts(ECMWF) Reanalysis(ERA-40) wave data. The linear trends in Hs and regional and seasonal differences of the linear trends for Hs were calculated. Results show that the Hs exhibits a significant increasing trend of about 4.6 cm decade-1 in the global ocean as a whole over the last 44 years. The Hs changes slowly during the periods 1958–1974 and 1980–1991, while it increases consistently during the periods 1975–1980 and 1995–1998. The Hs reaches its lowest magnitude in 1975, with annual average wave height about 2 m. In 1992, the Hs has the maximum value of nearly 2.60 m. The Hs in most ocean waters has a significant increasing trend of 2–14 cm decade-1 over the last 44 years. The linear trend exhibits great regional differences. Areas with strong increasing trend of Hs are mainly distributed in the westerlies of the southern Hemisphere and the northern Hemisphere. Only some small areas show obvious decreasing in Hs. The long-term trend of Hs in DJF(December, January, February) and MAM(March, April, May) is much more stronger than that in JJA(June, July, August) and SON(September, October, November). The linear trends of the Hs in different areas are different in different seasons; for instance, the increasing trend of Hs in the westerlies of the Pacific Ocean mainly appears in MAM and DJF.
基金Supported by the Science and Technology Project of Food Production in Jiangxi Province(2006BAD02A04)~~
文摘[Objective] The aim was to carry out the genetic analysis on plant height of rice（Oryza sativa L.）cultivated in different seasons.[Method] Three rice parents with great difference in plant height including CB1（83.1 cm）,CB4（105.5 cm）and CB7（115.6 cm）were chosen to construct two parental combinations：CB1×CB4 and CB7×CB4,and the corresponding filial generations P1,F1,P2,B1,B2 and F2 were obtained.The 6 populations were planted in middle and late seasons respectively to measure their height traits.The Akaike＇s information criterion（AIC）of the mixed major gene and polygene model was used to indentify the existence of major genes affecting quantitative traits in B1,B2,F2 populations.When the major genes existed,the genetic effects of the major genes and polygenes and their genetic variance were estimated through segregation analysis.[Result] One additive major gene plus additive-dominance polygenes was the most fitted genetic model for the trait in all B1,B2,F2 populations in two planting seasons.The heritability values of the major genes varied from 38.63% to 78.53% and those of polygenes varied from 1.72% to 36.04%,and the total heritability values were 45.52-92.93%.The additive effect d value of the two genetic populations under two planting seasons was-4.56,-9.16,-7.19,and-9.38,respectively,as suggested that additive effect of the major genes would decrease the express of the plant height trait.[Conclusion] The heritability of plant height trait was affected by planting seasons and the combinations clearly as a whole.
基金This study was supported by the National Natural Science Foundation of China(42277448,41971104 and 41807431)the National Science Foundation of Shaanxi Province(2019JQ-325)the Fundamental Research Funds for the Central Universities(GK201903068 and GK202206032).
文摘Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas.However,the ecophysiological mechanisms under-lying the impact of drought on tree growth remains unre-solved.In this study,earlywood and latewood tree-ring growth,δ^(13)C,andδ^(18)O chronologies of Picea mongolica from 1900 to 2013 were developed to clarify the intra-and inter-annual tree-ring growth responses to increasingly fre-quent droughts.The results indicate that annual basal area increment residuals(BAI_(res)),which removed tree age and size effects,have significantly decreased since 1960.How-ever,the decreasing trend of earlywood BAI_(res) was higher than that of latewood.Climate response analysis suggests that the dominant parameters for earlywood and latewood proxies(BAI_(res),δ^(13)C andδ^(18)O)were drought-related climate variables(Palmer drought severity index,temperature,rela-tive humidity,and vapor pressure deficit).The most signifi-cant period of earlywood and latewood proxies’responses to climate variables were focused on June-July and July-August,respectively.BAI_(res),andδ^(13)C were significantly affected by temperature and moisture conditions,whereasδ^(18)O was slightly affected.Decreasing stomatal conduct-ance due to drought outweighed the influence of increasing CO_(2) on intrinsic water use efficiency(iWUE),and ultimately led to a decline in BAI_(res).Compared to latewood,the faster decreasing BAI_(res) and smaller increasing iWUE of early-wood suggested trees were more vulnerable to water stress in the early growing season.Our study provides insights into the inter-and intra-annual mechanisms of tree-ring growth in semi-arid regions under rising CO_(2) and climate change.
基金financially supported by the National Natural Science Foundation of China(No.32371744)Impact of Yakang Expressway Project on Rare Fish Provincial Nature Reserve and Aquatic Ecology Monitoring Project(5118012017000513).
文摘High-mountain stream ecosystems are recognized as ideal arenas for natural experiments and for ecological monitoring and assessment research,owing to their sensitivity to climate gradients and human-mediated disturbances.In this study,we chose a subtropical mountainous stream system in southwestern China,to explore the spatiotemporal patterns and driving factors of taxonomic,phylogenetic,and functional beta diversity of macroinvertebrate assemblages.We found that taxonomic beta diversity was highest(on average,0.577 in spring and 0.645 in autumn)across seasons,followed by phylogenetic(0.491 and 0.545)and functional(0.350 and 0.383)beta diversity,with the replacement component predominantly(57%–73%)contributing to all three facets of diversity.The taxonomic local contributions to beta diversity(LCBD)values were roughly equivalent among different sites in both spring and autumn,whereas phylogenetic LCBD(PLCBD)and functional LCBD(XLCBD)indices varied from site to site.Therefore,we recommend prioritizing site conservation based on LCBD,PLCBD,and XLCBD values to optimize biodiversity conservation strategies.The three-facets of dissimilarities were all somewhat higher in autumn than spring,possibly due to recolonization events in the metacommunity after the summer flood.Variation partitioning analysis indicated that environmental factors were more important than spatial factors in structuring all three facets of beta diversity and their components,although different sets of variables were identified as important for different diversity facets and between seasons.In summary,our study offers valuable insights into the patterns and drivers of macroinvertebrate beta diversity in high mountain streams and lays a baseline for targeted conservation strategies in these ecosystems.
基金supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences (Grant No. XDA05100100&XDB05020000)the National Natural Science Foundation of China (Grant Nos. 41230642 & 41275139)
文摘Fine particle of organic aerosol （OA）, mostly arising from pollution, are abundant in Beijing. To achieve a better un- derstanding of the difference in OA in summer and autumn, a high-resolution time-of-flight aerosol mass spectrometer （HR- ToF-AMS, Aerodyne Research Inc., USA） was deployed in urban Beijing in August and October 2012. The mean OA mass concentration in autumn was 30 4-30 μg m-3, which was higher than in summer （13 4-6.9 μg m-3）. The elemental anal- ysis found that OA was more aged in summer （oxygen-to-carbon （O/C） ratios were 0.41 and 0.32 for summer and autumn, respectively）. Positive matrix factorization （PMF） analysis identified three and five components in summer and autumn, re- spectively. In summer, an oxygenated OA （OOA）, a cooking-emission-related OA （COA）, and a hydrocarbon-like OA （HOA） were indentified. Meanwhile, the OOA was separated into LV-OOA （low-volatility OOA） and SV-OOA （semi-volatile OOA）; and in autumn, a nitrogen-containing OA （NOA） was also found. The SOA （secondary OA） was always the most important OA component, accounting for 55% of the OA in the two seasons. Back trajectory clustering analysis found that the origin of the air masses was more complex in summer. Southerly air masses in both seasons were associated with the highest OA loading, while northerly air masses were associated with the lowest OA loading. A preliminary study of OA components, especially the POA （primary OA）, in different periods found that the HOA and COA all decreased during the National Day holiday period, and HOA decreased at weekends compared with weekdays.
文摘The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS. Surface water samples for studying include the Red river, Nhue river and Kim Nguu river, Thanh Nhan lake, Yen So lake and Van Quan lake were collected in the dry season (April) and the rainy season (August) in 2015. The stable isotope analysis results showed that the δ<sup>18</sup>O values is a range from -42.53‰ to -64.05‰ and, the δ<sup>2</sup>H values is the range from -5.09‰ to -8.79‰ under global meteoric waterline (in the water vapor region). The δ<sup>2</sup>H results of the rivers and lakes in the dry season are more negative than the rainy season with a small difference. The δ<sup>18</sup>O results of lakes in the dry season are more negative than the rainy season, but the δ<sup>18</sup>O results of river in the dry season are more positive than the rainy season. The results of the EC, BOD, COD, DO, TSS analysis showed that surface water environment has changed clearly in the two seasons and the contamination level in the dry season is usually higher than the rainy season. The lakes and rivers strongly influenced by human activities led to seriously pollution are Van Quan lake and Yen So lake, Nhue river and Kim Nguu river.
文摘In the northern slope of Tianshan Mountains in Xinjiang, the Manas River is a river with relatively large runoff. However, with the passage of time, the suspended sediment transport of the Manas River has shown an obvious increase trend. The reasons for this situation are mainly due to the increase in the runoff of the Manas River and the obvious water and soil loss in the upstream area. The analysis of sediment change and its influencing factors in Manas River is very important for the ecological research of water resources in Xinjiang region, and is also an important research content in the local soil and water conservation work. This article will then launch a scientific analysis of this, hoping to provide reference for professionals.
文摘Rice is a staple food crop in China.Since the 1950’s,many new varieties havebeen used and resulted in great increase ofyield.However there were still some barriersin the nationwide extension of new varietiesdue to the insufficient information about thecharacteristics of varieties.So,it is impor-tant to find ways of determining the potential
基金supported by Sichuan Science and Technology Program(No.2024NSFSC0060)the National Natural Science Foundation of China(No.U23A2030)the Basic Research Cultivation Support Plan of Southwest Jiaotong University(No.2682023ZTPY016).
文摘Imidazole(IM)particles in the atmosphere affect climate,atmospheric chemical reactions,and human health.However,research on IM particles in the Sichuan Basin(SCB),one of the areas of China affected most heavily by haze,remains very scarce.This study used single-particle aerosol mass spectrometry to investigate IM-containing particles in Chengdu,one of the megacities in the SCB,during summer and winter before and after implemen-tation of the Three-year Action Plan to Win the Blue-Sky Defense War(BSDW).We found that IM-containing particles accounted for 1.2%–12.0%of all detected particles,and they highly mixed with carbonaceous com-ponents,secondary inorganic species,and organic nitrogen.From before to after the BSDW,the proportion of IM-containing particles decreased by 1.8%in summer,but increased by 9.6%in winter.Ammonium/amines and carbonyl compounds were closely related to IM-containing particles;the highest proportion of IM-containing particles occurred in particles mixed with amines and carbonyls.The number fraction of IM-containing particles in all seasons was higher at night than during daytime.The potential source areas of IM-containing particles showed notable narrowing after the BSDW,and the high-value areas were found distributed closer to Chengdu and its surrounding areas.In the winter before the BSDW,most IM-containing particles(>70%)were mixed with organic carbon(OC)particles,and the contributions of OC and mixed organic–elemental carbon(OC-EC)particles increased with aggravation of pollution,whereas OC-EC and Metal particles played a more crucial role in the winter after the BSDW.
基金supported by the National Natural Science Foundation of China(Grant Nos.41888101,41602192,and 41901095)the National Key R&D Program of China(Grant No.2017YFA0603302)+2 种基金the support by the Youth Innovation Promotion Association Foundation of the Chinese Academy of Sciences(Grant No.2018471)supported by the Swedish Research Council(Vetenskapsr?det,Grant No.2018-01272)funded by the Swedish Collegium for A dvanced Study through Riksbankens Jubileusfond。
文摘Seasonal differences of temperature are crucial components of the Earth's climate system.However,the relatively short observational record,especially for East Asia,has limited progress in understanding seasonal differences.In this study,we identify ten tree-ring chronologies separately correlated with local winter(December-February)temperatures and twelve different tree-ring chronologies separately correlated with summer(June-August)temperatures across East Asia.Using these discrete seasonal tree-ring chronologies,we develop two independent winter and summer temperature reconstructions covering the period 1376-1995 CE for East Asia,and compare them with model simulations.Our reconstructions show a more significant volcanic cooling and earlier onset of modern warming in summer than in winter.The reconstructed summer-minus-winter temperature decreased since as early as the late 19th century,which has driven the current state of seasonal temperature difference to out of the natural variability since the 1370s.Climate models could generally reproduce the variability and trends in seasonal reconstructions,but might largely underestimate seasonal differences due to the fact that seasonal expressions on external forcing and modes of internal variability are too small.Our study highlights the importance of using proxy-based seasonal reconstructions to evaluate the performance of climate models,and implies a substantial weakening of seasonal temperature differences in the future.
基金Supported by the Knowledge Innovation Research Program,Chinese Academy of Sciences (KSCX2-SW-105)
文摘Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.
