Effects of extratropical solar penetration on the North Atlantic Ocean circulation and climate are investigated using a coupled ocean-atmosphere model.In this model,solar penetration generates basinwide cooling and wa...Effects of extratropical solar penetration on the North Atlantic Ocean circulation and climate are investigated using a coupled ocean-atmosphere model.In this model,solar penetration generates basinwide cooling and warming in summer and winter,respectively.Associated with SST changes,annual mean surface wind stress is intensified in both the subtropical and subpolar North Atlantic,which leads to acceleration of both subtropical and subpolar gyres.Owing to warming in the subtropics and significant saltiness in the subpolar region,potential density decreases(increases) in the subtropical(subpolar)North Atlantic.The north-south meridional density gradient is thereby enlarged,accelerating the Atlantic meridional overturning circulation(AMOC).In addition,solar penetration reduces stratification in the upper ocean and favors stronger vertical convection,which also contributes to acceleration of the AMOC.展开更多
Tropical cyclones(TCs)not only passively respond to climate change,but also play an important role in vertical mixing of the upper ocean and in driving oceanic heat transport.Using a fully coupled climate model,the au...Tropical cyclones(TCs)not only passively respond to climate change,but also play an important role in vertical mixing of the upper ocean and in driving oceanic heat transport.Using a fully coupled climate model,the authors investigate the potential effect of TC-induced vertical mixing on the El Nino–Southern Oscillation(ENSO)and East Asian monsoon in the mid-Piacenzian,during which global TCs are estimated to have been stronger.Sensitivity experiments indicate that the TC-induced oceanic mixing over global storm basins leads to additional warming over the eastern tropical Pacific and a deeper thermocline in the mid-Piacenzian,whereas it dampens the interannual variability of ENSO.Regarding the East Asian monsoon circulations,low-level(850 hPa)summer and winter winds are intensified in response to enhanced vertical mixing,with a southward/westward shift of the western North Pacific high and westerly jet in summer and a deepened East Asian trough in winter.These climatic features are largely reproduced in the experiment with enhanced vertical mixing only over the central-eastern North Pacific.These results may shed light on TC feedbacks associated with vertical mixing and advance our understanding on mid-Piacenzian climate.展开更多
The flux of carbon dioxide （CO2） from soil surface presents an important component of carbon （C） cycle in terrestrial ecosystems and is controlled by a number of biotic and abiotic factors. In order to better unde...The flux of carbon dioxide （CO2） from soil surface presents an important component of carbon （C） cycle in terrestrial ecosystems and is controlled by a number of biotic and abiotic factors. In order to better understand characteristics of soil CO2 flux （FCO2） in subtropical forests, soil FCO2 rates were quantified in five adjacent forest types （camphor tree forest, Masson pine forest, mixed camphor tree and Masson pine forest, Chinese sweet gum forest, and slash pine forest） at the Tianjiling National Park in Changsha, Hunan Province, in subtropical China, from January to December 2010. The influences of soil temperature （Tsoil）, volumetric soil water content （0soiI）, soil pH, soil organic carbon （SOC） and soil C/nitrogen （N） ratio on soil FCO2 rates were also investigated. The annual mean soil FCO2 rate varied with the forest types. The soil FCO2 rate was the highest in the camphor tree forest （3.53 ± 0.51 μmol m-2 s-I）, followed by, in order, the mixed, Masson pine, Chinese sweet gum, and slash pine forests （1.53 ± 0.25 μmol m-2 sl）. Soil FCO2 rates from the five forest types followed a similar seasonal pattern with the maximum values occurring in summer （July and August） and the minimum values during winter （December and January）. Soil FCO2 rates were correlated to Tsoil and 0soil, but the relationships were only significant for Tsoil. No correlations were found between soil FCO2 rates and other selected soil properties, such as soil pH, SOC, and C/N ratio, in the examined forest types. Our results indicated that soil FCO2 rates were much higher in the evergreen broadleaved forest than coniferous forest under the same microclimatic environment in the study region.展开更多
基金Supported by the Key Project of National Natural Science Foundation of China(No.41130859)the Innovation Team Project(No.40921004)
文摘Effects of extratropical solar penetration on the North Atlantic Ocean circulation and climate are investigated using a coupled ocean-atmosphere model.In this model,solar penetration generates basinwide cooling and warming in summer and winter,respectively.Associated with SST changes,annual mean surface wind stress is intensified in both the subtropical and subpolar North Atlantic,which leads to acceleration of both subtropical and subpolar gyres.Owing to warming in the subtropics and significant saltiness in the subpolar region,potential density decreases(increases) in the subtropical(subpolar)North Atlantic.The north-south meridional density gradient is thereby enlarged,accelerating the Atlantic meridional overturning circulation(AMOC).In addition,solar penetration reduces stratification in the upper ocean and favors stronger vertical convection,which also contributes to acceleration of the AMOC.
基金funded by the National Natural Science Foundation of China [grant number 41772179]the Young Elite Scientists Sponsorship Program by China Association for Science and Technology [grant number 2017QNRC001]
文摘Tropical cyclones(TCs)not only passively respond to climate change,but also play an important role in vertical mixing of the upper ocean and in driving oceanic heat transport.Using a fully coupled climate model,the authors investigate the potential effect of TC-induced vertical mixing on the El Nino–Southern Oscillation(ENSO)and East Asian monsoon in the mid-Piacenzian,during which global TCs are estimated to have been stronger.Sensitivity experiments indicate that the TC-induced oceanic mixing over global storm basins leads to additional warming over the eastern tropical Pacific and a deeper thermocline in the mid-Piacenzian,whereas it dampens the interannual variability of ENSO.Regarding the East Asian monsoon circulations,low-level(850 hPa)summer and winter winds are intensified in response to enhanced vertical mixing,with a southward/westward shift of the western North Pacific high and westerly jet in summer and a deepened East Asian trough in winter.These climatic features are largely reproduced in the experiment with enhanced vertical mixing only over the central-eastern North Pacific.These results may shed light on TC feedbacks associated with vertical mixing and advance our understanding on mid-Piacenzian climate.
基金Supported by the National Forestry Public Welfare Research Program of China(Nos.201104005 and 200804030)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-10-0151)+1 种基金the 100 Talents Program of Hunan Province,China(No.2011516)Central South University of Forestry and Technology,China(No.0842)
文摘The flux of carbon dioxide （CO2） from soil surface presents an important component of carbon （C） cycle in terrestrial ecosystems and is controlled by a number of biotic and abiotic factors. In order to better understand characteristics of soil CO2 flux （FCO2） in subtropical forests, soil FCO2 rates were quantified in five adjacent forest types （camphor tree forest, Masson pine forest, mixed camphor tree and Masson pine forest, Chinese sweet gum forest, and slash pine forest） at the Tianjiling National Park in Changsha, Hunan Province, in subtropical China, from January to December 2010. The influences of soil temperature （Tsoil）, volumetric soil water content （0soiI）, soil pH, soil organic carbon （SOC） and soil C/nitrogen （N） ratio on soil FCO2 rates were also investigated. The annual mean soil FCO2 rate varied with the forest types. The soil FCO2 rate was the highest in the camphor tree forest （3.53 ± 0.51 μmol m-2 s-I）, followed by, in order, the mixed, Masson pine, Chinese sweet gum, and slash pine forests （1.53 ± 0.25 μmol m-2 sl）. Soil FCO2 rates from the five forest types followed a similar seasonal pattern with the maximum values occurring in summer （July and August） and the minimum values during winter （December and January）. Soil FCO2 rates were correlated to Tsoil and 0soil, but the relationships were only significant for Tsoil. No correlations were found between soil FCO2 rates and other selected soil properties, such as soil pH, SOC, and C/N ratio, in the examined forest types. Our results indicated that soil FCO2 rates were much higher in the evergreen broadleaved forest than coniferous forest under the same microclimatic environment in the study region.
