The Atlantic Meridional Overturning Circulation(AMOC)is a crucial component of the Earth’s climate system due to its fundamental role in heat distribution,carbon and oxygen transport,and the weather.Other climate com...The Atlantic Meridional Overturning Circulation(AMOC)is a crucial component of the Earth’s climate system due to its fundamental role in heat distribution,carbon and oxygen transport,and the weather.Other climate components,such as the atmosphere and sea ice,influence the AMOC.Evaluating the physical mechanisms of those interactions is paramount to increasing knowledge about AMOC’s functioning.In this study,the authors used outputs from the Community Earth System Model version 2 and observational data to investigate changes in theAMOC and the associated physical processes.Two DECK experiments were evaluated:piControl and 1pctCO_(2),with an annual increase of 1%of atmospheric CO_(2).The analysis revealed a significant decrease in the AMOC,associated with changes in mixed layer depth and buoyancy in high latitudes of the North Atlantic,resulting in the shutdown of deep convection and potentially affecting the formation of North Atlantic Deep Water and Antarctic Bottom Water.A vital aspect observed in this study is the association between increased runoff and reduced water evaporation,giving rise to a positive feedback process.Consequently,the rates of freshwater spreading have intensified during this period,which could lead to an accelerated disruption of the AMOC beyond the projections of existing models.展开更多
The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2)...The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.展开更多
The tropospheric impact of Arctic ozone loss events is still debatable.In this study we investigate that question,using the ERA5 reanalysis and long-term integration by a climate-chemistry coupled model(CESM2-WACCM).W...The tropospheric impact of Arctic ozone loss events is still debatable.In this study we investigate that question,using the ERA5 reanalysis and long-term integration by a climate-chemistry coupled model(CESM2-WACCM).We begin with the frequency of Arctic ozone loss events.On average,such events occur once in early spring every 14−15 years in ERA5 data and in the model,both of which estimate that roughly 40%of the strong polar vortex events in March are coupled with Arctic ozone loss,the remaining 60%being uncoupled.The composite difference between the two samples might be attributed to the pure impact of the Arctic ozone loss-that is,to ozone loss alone,without the concurrent impact of strong polar vortices.Arctic ozone loss is accompanied by an increase in total ozone in midlatitudes,with the maximum centered in the Central North Pacific.Contrasting Arctic ozone loss events with pure strong polar vortex events that are uncoupled with ozone loss,observations confirm that the stratospheric Northern Annular Mode reverses earlier for the former.For pure strong vortex events in early spring(without Arctic ozone loss),the cold anomalies can extend from the stratosphere to the middle troposphere;when such events are strong,the near surface warm anomalies are biased toward the continents.In contrast,during the other 40%of strong early-spring polar vortex events,those coupled with ozone loss,a concurrent and delayed warming of the near surface over the Arctic and its neighboring areas is observed,due to vertical redistribution of solar radiation by the change in the ozone.展开更多
Anthropogenic emission inventory for aerosols and reactive gases is crucial to the estimation of aerosol radiative forcing and climate effects.Here,the anthropogenic emission inventory for AerChemMIP,endorsed by CMIP6...Anthropogenic emission inventory for aerosols and reactive gases is crucial to the estimation of aerosol radiative forcing and climate effects.Here,the anthropogenic emission inventory for AerChemMIP,endorsed by CMIP6,is briefly introduced.The CMIP6 inventory is compared with a country-level inventory(i.e.,MEIC)over China from 1986 to 2015.Discrepancies are found in the yearly trends of the two inventories,especially after 2006.The yearly trends of the aerosol burdens simulated by CESM2 using the two inventories follow their emission trends and deviate after the mid-2000s,while the simulated aerosol optical depths(AODs)show similar trends.The difference between the simulated AODs is much smaller than the difference between model and observation.Although the simulated AODs agree with the MODIS satellite retrievals for country-wide average,the good agreement is an offset between the underestimation in eastern China and the overestimation in western China.Low-biased precursor gas of SO_(2),overly strong convergence of the wind field,overly strong dilution and transport by summer monsoon circulation,too much wet scavenging by precipitation,and overly weak aerosol swelling due to low-biased relative humidity are suggested to be responsible for the underestimated AOD in eastern China.This indicates that the influence of the emission inventory uncertainties on simulated aerosol properties can be overwhelmed by model biases of meteorology and aerosol processes.It is necessary for climate models to perform reasonably well in the dynamical,physical,and chemical processes that would influence aerosol simulations.展开更多
Climate drift refers to spurious long-term changes that may be inherent in coupled models when external forcing factors are fixed. Understanding the sources of this drift and tuning the drift are crucial for obtaining...Climate drift refers to spurious long-term changes that may be inherent in coupled models when external forcing factors are fixed. Understanding the sources of this drift and tuning the drift are crucial for obtaining reasonable simulations from coupled models. To prepare for the upcoming Coupled Model Intercomparison Project Phase 6, a new coupled model has been constructed based on the Community Earth System Model and the Grid-point Atmospheric Model of IAP LASG version 2. However, the surface temperature predicted by the new model is too underestimated, and this underestimation is caused by a type of climate drift, i.e., ‘‘initial shock.'' This study analyzes the source of the cold surface temperature from the perspective of energy balance and attempts to reduce the surface temperature drift by tuning the relative humidity threshold for low cloud.展开更多
基金This work was possible through the financing of PEC-20480 Project between Royal Dutch Shell(Shell)and the Laboratório de Métodos Computacionais em Engenharia(LAMCE)and through the doctoral fellowship funding by CNPq for Elisa Passos Case number 141819/2016-2the postdoctoral fellowship funding by FAPERJ E 10/2020-Edital Inteligência Artificial Case Number E-26/203.327/2022-Enrollment No.Scholarship 2015.08297.7 for Lívia Sancho.
文摘The Atlantic Meridional Overturning Circulation(AMOC)is a crucial component of the Earth’s climate system due to its fundamental role in heat distribution,carbon and oxygen transport,and the weather.Other climate components,such as the atmosphere and sea ice,influence the AMOC.Evaluating the physical mechanisms of those interactions is paramount to increasing knowledge about AMOC’s functioning.In this study,the authors used outputs from the Community Earth System Model version 2 and observational data to investigate changes in theAMOC and the associated physical processes.Two DECK experiments were evaluated:piControl and 1pctCO_(2),with an annual increase of 1%of atmospheric CO_(2).The analysis revealed a significant decrease in the AMOC,associated with changes in mixed layer depth and buoyancy in high latitudes of the North Atlantic,resulting in the shutdown of deep convection and potentially affecting the formation of North Atlantic Deep Water and Antarctic Bottom Water.A vital aspect observed in this study is the association between increased runoff and reduced water evaporation,giving rise to a positive feedback process.Consequently,the rates of freshwater spreading have intensified during this period,which could lead to an accelerated disruption of the AMOC beyond the projections of existing models.
基金Supported by the National Natural Science Foundation of China(No.42090042)the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.2019BT02H594)the Chinese Academy of Sciences(Nos.XDB42010304,133244KYSB20190031,183311KYSB20200015,SCSIO202201)。
文摘The role of sea surface temperature(SST)variability in the pre-monsoonal(April to July)intraseasonal oscillation(ISO)over the South China Sea(SCS)is investigated using the Community Earth System Model Version 2(CESM2).An Atmospheric Model Intercomparison Project(AMIP)simulation forced by daily sea surface temperatures(SSTs)derived from a parallel coupled general circulation model(CGCM)run was compared with observations and the mother coupled simulation.In the coupled model,the SST warming leads the peak convection about 1/4 period as in observations.The paralell uncoupled model fails to simulate this phase relationship,implying the importance of air-sea coupling in reproducing realistic ISO.Due to the near-quadrature phase relationship between SST and precipitation ISOs during the ISO events,it is difficult to distinguish the active/passive role of SST from observations alone.Significant correlation in intraseasonal precipitation between the daily SST-forced AMIP and mother CGCM runs indicates that SST plays a role in driving the atmospheric ISO.
基金supported by the National Natural Science Foundation of China(Grant NO.91837311).
文摘The tropospheric impact of Arctic ozone loss events is still debatable.In this study we investigate that question,using the ERA5 reanalysis and long-term integration by a climate-chemistry coupled model(CESM2-WACCM).We begin with the frequency of Arctic ozone loss events.On average,such events occur once in early spring every 14−15 years in ERA5 data and in the model,both of which estimate that roughly 40%of the strong polar vortex events in March are coupled with Arctic ozone loss,the remaining 60%being uncoupled.The composite difference between the two samples might be attributed to the pure impact of the Arctic ozone loss-that is,to ozone loss alone,without the concurrent impact of strong polar vortices.Arctic ozone loss is accompanied by an increase in total ozone in midlatitudes,with the maximum centered in the Central North Pacific.Contrasting Arctic ozone loss events with pure strong polar vortex events that are uncoupled with ozone loss,observations confirm that the stratospheric Northern Annular Mode reverses earlier for the former.For pure strong vortex events in early spring(without Arctic ozone loss),the cold anomalies can extend from the stratosphere to the middle troposphere;when such events are strong,the near surface warm anomalies are biased toward the continents.In contrast,during the other 40%of strong early-spring polar vortex events,those coupled with ozone loss,a concurrent and delayed warming of the near surface over the Arctic and its neighboring areas is observed,due to vertical redistribution of solar radiation by the change in the ozone.
基金supported by the State Key Program of National Natural Science Foundation of China(Grant No.41830966)supported by the National Natural Science Foundation of China(Grant Nos.2017YFC1501403,42030606,and 41705125)。
文摘Anthropogenic emission inventory for aerosols and reactive gases is crucial to the estimation of aerosol radiative forcing and climate effects.Here,the anthropogenic emission inventory for AerChemMIP,endorsed by CMIP6,is briefly introduced.The CMIP6 inventory is compared with a country-level inventory(i.e.,MEIC)over China from 1986 to 2015.Discrepancies are found in the yearly trends of the two inventories,especially after 2006.The yearly trends of the aerosol burdens simulated by CESM2 using the two inventories follow their emission trends and deviate after the mid-2000s,while the simulated aerosol optical depths(AODs)show similar trends.The difference between the simulated AODs is much smaller than the difference between model and observation.Although the simulated AODs agree with the MODIS satellite retrievals for country-wide average,the good agreement is an offset between the underestimation in eastern China and the overestimation in western China.Low-biased precursor gas of SO_(2),overly strong convergence of the wind field,overly strong dilution and transport by summer monsoon circulation,too much wet scavenging by precipitation,and overly weak aerosol swelling due to low-biased relative humidity are suggested to be responsible for the underestimated AOD in eastern China.This indicates that the influence of the emission inventory uncertainties on simulated aerosol properties can be overwhelmed by model biases of meteorology and aerosol processes.It is necessary for climate models to perform reasonably well in the dynamical,physical,and chemical processes that would influence aerosol simulations.
基金supported by the CAS Strategic Priority Research Program (XDA05110304)the National 973 Basic Research Program of China (2015CB954102)the National Natural Science Foundation of China (41330527, 41205079, and 41305040)
文摘Climate drift refers to spurious long-term changes that may be inherent in coupled models when external forcing factors are fixed. Understanding the sources of this drift and tuning the drift are crucial for obtaining reasonable simulations from coupled models. To prepare for the upcoming Coupled Model Intercomparison Project Phase 6, a new coupled model has been constructed based on the Community Earth System Model and the Grid-point Atmospheric Model of IAP LASG version 2. However, the surface temperature predicted by the new model is too underestimated, and this underestimation is caused by a type of climate drift, i.e., ‘‘initial shock.'' This study analyzes the source of the cold surface temperature from the perspective of energy balance and attempts to reduce the surface temperature drift by tuning the relative humidity threshold for low cloud.
