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
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
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
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
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
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 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).
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 "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