A subseasonal-to-seasonal(S2S) forecast system(FS) has recently been released based on the fully coupled Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM). This study evaluated the subseasonal ...A subseasonal-to-seasonal(S2S) forecast system(FS) has recently been released based on the fully coupled Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM). This study evaluated the subseasonal prediction skill of this system via a 21-year hindcast experiment for the period 2000–20 with eight ensemble members.Results showed moderate-to-high skill for the primary atmospheric variables. The most accurate predictions emerged in the cold season but were largely confined within tropical bands as the forecast lead time was increased. Compared with the NCEP S2S FS, the CAMS-CSM S2S FS showed comparable subseasonal skill for 500-h Pa geopotential height, but slightly higher(lower) skill for precipitation(2-m temperature). The skillful lead time in the CAMS-CSM S2S FS for the Madden–Julian Oscillation and North Atlantic Oscillation reached 20 and 10 days, respectively, consistent with the NCEP S2S FS. Consequently, these findings guide future research on subseasonal predictability based on the CAMS-CSM S2S FS, and where efforts should be focused to improve the prediction system.展开更多
This paper describes the historical simulations produced by the Chinese Academy of Meteorological Sciences(CAMS)climate system model(CAMS-CSM),which are contributing to phase 6 of the Coupled Model Intercomparison Pro...This paper describes the historical simulations produced by the Chinese Academy of Meteorological Sciences(CAMS)climate system model(CAMS-CSM),which are contributing to phase 6 of the Coupled Model Intercomparison Project(CMIP6).The model description,experiment design and model outputs are presented.Three members’historical experiments are conducted by CAMS-CSM,with two members starting from different initial conditions,and one excluding the stratospheric aerosol to identify the effect of volcanic eruptions.The outputs of the historical experiments are also validated using observational data.It is found that the model can reproduce the climatological mean states and seasonal cycle of the major climate system quantities,including the surface air temperature,precipitation,and the equatorial thermocline.The long-term trend of air temperature and precipitation is also reasonably captured by CAMS-CSM.There are still some biases in the model that need further improvement.This paper can help the users to better understand the performance and the datasets of CAMS-CSM.展开更多
Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO_2 forcing ultimately, which is essential for carbon reduct...Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO_2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences(CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5(CMIP5). Based on two idealized CO_2 forcing scenarios, i.e.,abruptly quadrupled CO_2 and CO_2 increasing 1% per year, the equilibrium climate sensitivity(ECS) and transient climate response(TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean(MME) of CMIP5 due to compensation of a relatively low ocean heat uptake(OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback(λSWCL) over the tropical Indo-Pacific Ocean.The CMIP5 ensemble shows that more negative λSWCL is related to larger increase in low-level(925–700 hPa)cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λSWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λSWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λSWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses.展开更多
This study evaluates the performance of CAMS-CSM(the climate system model of the Chinese Academy of Meteorological Sciences) in simulating the features, dynamics, and teleconnections to East Asian climate of the El N...This study evaluates the performance of CAMS-CSM(the climate system model of the Chinese Academy of Meteorological Sciences) in simulating the features, dynamics, and teleconnections to East Asian climate of the El Ni?o–Southern Oscillation(ENSO). In general, fundamental features of ENSO, such as its dominant patterns and phase-locking features, are reproduced well. The two types of El Ni?o are also represented, in terms of their spatial distributions and mutual independency. However, the skewed feature is missed in the model and the simulation of ENSO is extremely strong, which is found—based on Bjerknes index assessment—to be caused by underestimation of the shortwave damping effect. Besides, the modeled ENSO exhibits a regular oscillation with a period shorter than observed. By utilizing the Wyrtki index, it is suggested that this periodicity bias results from an overly quick phase transition induced by feedback from the thermocline and zonal advection. In addition to internal dynamics of ENSO,its external precursors—such as the North Pacific Oscillation with its accompanying seasonal footprinting mechanism, and the Indian Ocean Dipole with its 1-yr lead correlation with ENSO—are reproduced well by the model. Furthermore, with respect to the impacts of ENSO on the East Asian summer monsoon, although the anomalous Philippine anticyclone is reproduced in the post-El Ni?o summer, it exhibits an eastward shift compared with observation;and as a consequence, the observed flooding of the Yangtze River basin is poorly represented, with unrealistic air–sea interaction over the South China Sea being the likely physical origin of this bias. The response of wintertime lowertropospheric circulation to ENSO is simulated well, in spite of an underestimation of temperature anomalies in central China. This study highlights the dynamic processes that are key for the simulation of ENSO, which could shed some light on improving this model in the future.展开更多
The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the res...The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the results indicate that this new model is able to reasonably simulate the annual cycle and seasonal mean of the precipitation, as well as the vertical shear of large-scale zonal wind in the tropics. The model also reproduces the eastward and northward propagating oscillation signals similar to those found in observations. The simulation of BSISO is generally in agreement with the observations in terms of variance center, periodicity, and propagation, with the exception that the magnitude of BSISO anomalous convections are underestimated during both its eastward propagation along the equator and its northward propagation over the Asian–Pacific summer monsoon region. Our preliminary evaluation of the simulated BSISO by CAMS-CSM suggests that this new model has the capability, to a certain extent, to capture the BSISO features, including its propagation zonally along the equator and meridionally over the Asian monsoon region.展开更多
The ability of climate models to correctly reproduce clouds and the radiative effects of clouds is vitally important in climate simulations and projections.In this study,simulations of the shortwave cloud radiative ef...The ability of climate models to correctly reproduce clouds and the radiative effects of clouds is vitally important in climate simulations and projections.In this study,simulations of the shortwave cloud radiative effect(SWCRE)using the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM)are evaluated.The relationships between SWCRE and dynamic–thermodynamic regimes are examined to understand whether the model can simulate realistic processes that are responsible for the generation and maintenance of stratus clouds.Over eastern China,CAMS-CSM well simulates the SWCRE climatological state and stratus cloud distribution.The model captures the strong dependence of SWCRE on the dynamic conditions.Over the marine boundary layer regions,the simulated SWCRE magnitude is weaker than that in the observations due to the lack of low-level stratus clouds in the model.The model fails to simulate the close relationship between SWCRE and local stability over these regions.A sensitivity numerical experiment using a specifically designed parameterization scheme for the stratocumulus cloud cover confirms this assertion.Parameterization schemes that directly depict the relationship between the stratus cloud amount and stability are beneficial for improving the model performance.展开更多
The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model perfo...The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model performance in simulating the convectively coupled equatorial waves(CCEWs) by comparing the daily output of precipitation from a 23-yr coupled run with the observational precipitation data from Global Precipitation Climatology Project(GPCP). Four dominant modes of CCEWs including the Kelvin, equatorial Rossby(ER), mixed Rossby–gravity(MRG), tropical depression-type(TD-type) waves, and their annual mean and seasonal cycle characteristics are investigated respectively. It is found that the space–time spectrum characteristics of each wave mode represented by tropical averaged precipitation could be very well simulated by CAMS-CSM, including the magnitudes and the equivalent depths. The zonal distribution of wave associated precipitation is also well simulated, with the maximum centers over the Indian Ocean and the Pacific Ocean. However, the meridional distribution of the wave activities is poorly simulated, with the maximum centers shifted from the Northern Hemisphere to the Southern Hemisphere, especially the Kelvin, MRG, and TD waves. The seasonal cycle of each wave mode is generally captured by the model, but their amplitudes over the Southern Hemisphere during boreal winter are grossly overestimated. The reason for the excessive wave activity over the southern Pacific Ocean in the simulation is discussed.展开更多
The Madden–Julian Oscillation(MJO)has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting.We evaluate the ability of the Chinese Academy of Met...The Madden–Julian Oscillation(MJO)has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting.We evaluate the ability of the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM)to represent the MJO by using the diagnostic method proposed by the US Climate Variability and Predictability Program(CLIVAR)MJO Working Group(MJOWG).In general,the model simulates some major characteristics of MJO well,such as the seasonality characteristics and geographical dependence,the intensity of intraseasonal variability(ISV),dominant periodicity,propagation characteristics,coherence between outgoing longwave radiation(OLR)and wind,and life cycle of MJO signals.However,there are a few biases in the model when compared with observational/reanalyzed data.These include an overestimate of precipitation in the convergence zone of the North and South Pacific,a slightly weaker eastward propagation,and a shift in the dominant periodicity toward lower frequencies with slower speeds of eastward propagation.The model gives a poor simulation of the northward propagation of MJO in summer and shows less coherence between the MJO convection and wind.The role of moistening in the planetary boundary layer(PBL)in the eastward/northward propagation of MJO was also explored.An accurate representation of the vertical titling structure of moisture anomalies in CAMS-CSM leads to moistening of the PBL ahead of convection,which accounts for the eastward/northward propagation of MJO.Poor simulation of the vertical structure of the wind and moisture anomalies in the western Pacific leads to a poor simulation of the northward propagation of MJO in this area.Budget analysis of the PBL integral moisture anomalies shows that the model gives a good simulation of the moisture charging process ahead of MJO convection and that the zonal advection of moisture convergence term has a primary role in the detour of MJO over the Maritime Continent.展开更多
As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circul...As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circulation, and their variabilities substantially impact the climate in mid-high latitudes. A 35-yr(1979-2013) simulation by the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM) was carried out based on observed sea surface temperature and sea ice data. The ability of CAMS-CSM in simulating horizontal and vertical structures of the NAM and SAM, relation of the NAM to the East Asian climate, and temporal variability of the SAM is examined and validated against the observational data. The results show that CAMS-CSM captures the zonally symmetric and out-of-phase variations of sea level pressure anomaly between the midlatitudes and polar zones in the extratropics of the NH and SH. The model has also captured the equivalent barotropic structure in tropospheric geopotential height and the meridional shifts of the NH and SH jet systems associated with the NAM and SAM anomalies. Furthermore, the model is able to reflect the variability of northern and southern Ferrel cells corresponding to the NAM and SAM anomalies. The model reproduces the observed relationship of the boreal winter NAM with the East Asian trough and air temperature over East Asia. It also captures the upward trend of the austral summer SAM index during recent decades. However, compared with the observation, the model shows biases in both the intensity and center locations of the NAM's and SAM's horizontal and vertical structures. Specifically, it overestimates their intensities.展开更多
A new coupled climate system model(CSM) has been developed at the Chinese Academy of Meteorological Sciences(CAMS) by employing several state-of-the-art component models. The coupled CAMS-CSM consists of the modified ...A new coupled climate system model(CSM) has been developed at the Chinese Academy of Meteorological Sciences(CAMS) by employing several state-of-the-art component models. The coupled CAMS-CSM consists of the modified atmospheric model [ECmwf-HAMburg(ECHAM5)], ocean model [Modular Ocean Model(MOM4)], sea ice model [Sea Ice Simulator(SIS)], and land surface model [Common Land Model(CoLM)]. A detailed model description is presented and both the pre-industrial and "historical" simulations are preliminarily evaluated in this study.The model can reproduce the climatological mean states and seasonal cycles of the major climate system quantities,including the sea surface temperature, precipitation, sea ice extent, and the equatorial thermocline. The major climate variability modes are also reasonably captured by the CAMS-CSM, such as the Madden–Julian Oscillation(MJO), El Ni?o–Southern Oscillation(ENSO), East Asian Summer Monsoon(EASM), and Pacific Decadal Oscillation(PDO).The model shows a promising ability to simulate the EASM variability and the ENSO–EASM relationship. Some biases still exist, such as the false double-intertropical convergence zone(ITCZ) in the annual mean precipitation field,the overestimated ENSO amplitude, and the weakened Bjerknes feedback associated with ENSO; and thus the CAMS-CSM needs further improvements.展开更多
基金jointly funded by the National Key Research and Development Program (Grant No.2022YFC3004203)the National Natural Science Foundation of China (Grant No.42375033)the Basic Scientific Research and Operation Foundation of the Chinese Academy of Meteorological Sciences (Grant Nos.2023Z018, 2024KJ013, and 2023KJ036)。
文摘A subseasonal-to-seasonal(S2S) forecast system(FS) has recently been released based on the fully coupled Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM). This study evaluated the subseasonal prediction skill of this system via a 21-year hindcast experiment for the period 2000–20 with eight ensemble members.Results showed moderate-to-high skill for the primary atmospheric variables. The most accurate predictions emerged in the cold season but were largely confined within tropical bands as the forecast lead time was increased. Compared with the NCEP S2S FS, the CAMS-CSM S2S FS showed comparable subseasonal skill for 500-h Pa geopotential height, but slightly higher(lower) skill for precipitation(2-m temperature). The skillful lead time in the CAMS-CSM S2S FS for the Madden–Julian Oscillation and North Atlantic Oscillation reached 20 and 10 days, respectively, consistent with the NCEP S2S FS. Consequently, these findings guide future research on subseasonal predictability based on the CAMS-CSM S2S FS, and where efforts should be focused to improve the prediction system.
基金supported by the National Key Research and Development Program of China(Grant No.2019YFC1510001)the National Natural Science Foundation of China(Grant No.91637210)+1 种基金the Basic Research Fund of CAMS(Grant No.2018Z007)the Jiangsu Collaborative Innovation Center for Climate Change。
文摘This paper describes the historical simulations produced by the Chinese Academy of Meteorological Sciences(CAMS)climate system model(CAMS-CSM),which are contributing to phase 6 of the Coupled Model Intercomparison Project(CMIP6).The model description,experiment design and model outputs are presented.Three members’historical experiments are conducted by CAMS-CSM,with two members starting from different initial conditions,and one excluding the stratospheric aerosol to identify the effect of volcanic eruptions.The outputs of the historical experiments are also validated using observational data.It is found that the model can reproduce the climatological mean states and seasonal cycle of the major climate system quantities,including the surface air temperature,precipitation,and the equatorial thermocline.The long-term trend of air temperature and precipitation is also reasonably captured by CAMS-CSM.There are still some biases in the model that need further improvement.This paper can help the users to better understand the performance and the datasets of CAMS-CSM.
基金Supported by the National Key Research and Development Program(2017YFA0603503)National Natural Science Foundation of China(41605057 and 41661144009)
文摘Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO_2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences(CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5(CMIP5). Based on two idealized CO_2 forcing scenarios, i.e.,abruptly quadrupled CO_2 and CO_2 increasing 1% per year, the equilibrium climate sensitivity(ECS) and transient climate response(TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean(MME) of CMIP5 due to compensation of a relatively low ocean heat uptake(OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback(λSWCL) over the tropical Indo-Pacific Ocean.The CMIP5 ensemble shows that more negative λSWCL is related to larger increase in low-level(925–700 hPa)cloud over the tropical Indo-Pacific under warming, which can explain about 90% of λSWCL in CAMS-CSM. Static stability of planetary boundary layer in the pre-industrial simulation is a critical factor controlling the low-cloud response and λSWCL across the CMIP5 models and CAMS-CSM. Evidently, weak stability in CAMS-CSM favors lowcloud formation under warming due to increased low-level convergence and relative humidity, with the help of enhanced evaporation from the warming tropical Pacific. Consequently, cloud liquid water increases, amplifying cloud albedo, and eventually contributing to the unusually negative λSWCL and low ECS in CAMS-CSM. Moreover, the OHU may influence climate feedbacks and then the ECS by modulating regional sea surface temperature responses.
基金Supported by the National Key Research and Development Program of China(2018YFC1506002,2017YFC1502302,and2016YFA0602104)Key Research Program of Xinjiang Meteorological Bureau(ZD201802)+1 种基金China Meteorological Administration Special Public Welfare Research Fund(GYHY201506013)National Natural Science Foundation of China(41205058,41375062,41405080,41505065,41606019,and 41605116)
文摘This study evaluates the performance of CAMS-CSM(the climate system model of the Chinese Academy of Meteorological Sciences) in simulating the features, dynamics, and teleconnections to East Asian climate of the El Ni?o–Southern Oscillation(ENSO). In general, fundamental features of ENSO, such as its dominant patterns and phase-locking features, are reproduced well. The two types of El Ni?o are also represented, in terms of their spatial distributions and mutual independency. However, the skewed feature is missed in the model and the simulation of ENSO is extremely strong, which is found—based on Bjerknes index assessment—to be caused by underestimation of the shortwave damping effect. Besides, the modeled ENSO exhibits a regular oscillation with a period shorter than observed. By utilizing the Wyrtki index, it is suggested that this periodicity bias results from an overly quick phase transition induced by feedback from the thermocline and zonal advection. In addition to internal dynamics of ENSO,its external precursors—such as the North Pacific Oscillation with its accompanying seasonal footprinting mechanism, and the Indian Ocean Dipole with its 1-yr lead correlation with ENSO—are reproduced well by the model. Furthermore, with respect to the impacts of ENSO on the East Asian summer monsoon, although the anomalous Philippine anticyclone is reproduced in the post-El Ni?o summer, it exhibits an eastward shift compared with observation;and as a consequence, the observed flooding of the Yangtze River basin is poorly represented, with unrealistic air–sea interaction over the South China Sea being the likely physical origin of this bias. The response of wintertime lowertropospheric circulation to ENSO is simulated well, in spite of an underestimation of temperature anomalies in central China. This study highlights the dynamic processes that are key for the simulation of ENSO, which could shed some light on improving this model in the future.
基金Supported by the National Key Research and Development Program(2016YFA0601504)National Basic Research and Development(973)Program of China(2015CB453203)+1 种基金National Natural Science Foundation of China(41675068)Basic Research Funds of the Chinese Academy of Meteorological Sciences(2015Z002)
文摘The boreal summer intraseasonal oscillation(BSISO) is simulated by the Climate System Model(CSM) developed at the Chinese Academy of Meteorological Sciences(CAMS), China Meteorological Administration. Firstly, the results indicate that this new model is able to reasonably simulate the annual cycle and seasonal mean of the precipitation, as well as the vertical shear of large-scale zonal wind in the tropics. The model also reproduces the eastward and northward propagating oscillation signals similar to those found in observations. The simulation of BSISO is generally in agreement with the observations in terms of variance center, periodicity, and propagation, with the exception that the magnitude of BSISO anomalous convections are underestimated during both its eastward propagation along the equator and its northward propagation over the Asian–Pacific summer monsoon region. Our preliminary evaluation of the simulated BSISO by CAMS-CSM suggests that this new model has the capability, to a certain extent, to capture the BSISO features, including its propagation zonally along the equator and meridionally over the Asian monsoon region.
基金Supported by the National Key Research and Development Program of China(2017YFC1502202 and 2016YFA0602101)National Natural Science Foundation of China(41875135 and 91637210)
文摘The ability of climate models to correctly reproduce clouds and the radiative effects of clouds is vitally important in climate simulations and projections.In this study,simulations of the shortwave cloud radiative effect(SWCRE)using the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM)are evaluated.The relationships between SWCRE and dynamic–thermodynamic regimes are examined to understand whether the model can simulate realistic processes that are responsible for the generation and maintenance of stratus clouds.Over eastern China,CAMS-CSM well simulates the SWCRE climatological state and stratus cloud distribution.The model captures the strong dependence of SWCRE on the dynamic conditions.Over the marine boundary layer regions,the simulated SWCRE magnitude is weaker than that in the observations due to the lack of low-level stratus clouds in the model.The model fails to simulate the close relationship between SWCRE and local stability over these regions.A sensitivity numerical experiment using a specifically designed parameterization scheme for the stratocumulus cloud cover confirms this assertion.Parameterization schemes that directly depict the relationship between the stratus cloud amount and stability are beneficial for improving the model performance.
基金Supported by the National Key Research and Development Program of China(2018YFC1505801)National Natural Science Foundation of China(41705059)Startup Fund for Introduced Talents of Nanjing University of Information Science&Technology
文摘The Chinese Academy of Meteorological Sciences developed a Climate System Model(CAMS-CSM) to participate in the upcoming Coupled Model Intercomparison Project phase 6(CMIP6). In this study, we assessed the model performance in simulating the convectively coupled equatorial waves(CCEWs) by comparing the daily output of precipitation from a 23-yr coupled run with the observational precipitation data from Global Precipitation Climatology Project(GPCP). Four dominant modes of CCEWs including the Kelvin, equatorial Rossby(ER), mixed Rossby–gravity(MRG), tropical depression-type(TD-type) waves, and their annual mean and seasonal cycle characteristics are investigated respectively. It is found that the space–time spectrum characteristics of each wave mode represented by tropical averaged precipitation could be very well simulated by CAMS-CSM, including the magnitudes and the equivalent depths. The zonal distribution of wave associated precipitation is also well simulated, with the maximum centers over the Indian Ocean and the Pacific Ocean. However, the meridional distribution of the wave activities is poorly simulated, with the maximum centers shifted from the Northern Hemisphere to the Southern Hemisphere, especially the Kelvin, MRG, and TD waves. The seasonal cycle of each wave mode is generally captured by the model, but their amplitudes over the Southern Hemisphere during boreal winter are grossly overestimated. The reason for the excessive wave activity over the southern Pacific Ocean in the simulation is discussed.
基金Supported by the National Key Research and Development Program of China(2018YFC1505906)National Basic Research(973)Program of China(2015CB453203 and 2010CB950404)+1 种基金National Natural Science Foundation of China(41505065,41375062,and41775066)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406022)
文摘The Madden–Julian Oscillation(MJO)has a significant impact on global weather and climate and can be used as a predictability resource in extended-term forecasting.We evaluate the ability of the Chinese Academy of Meteorological Sciences Climate System Model(CAMS-CSM)to represent the MJO by using the diagnostic method proposed by the US Climate Variability and Predictability Program(CLIVAR)MJO Working Group(MJOWG).In general,the model simulates some major characteristics of MJO well,such as the seasonality characteristics and geographical dependence,the intensity of intraseasonal variability(ISV),dominant periodicity,propagation characteristics,coherence between outgoing longwave radiation(OLR)and wind,and life cycle of MJO signals.However,there are a few biases in the model when compared with observational/reanalyzed data.These include an overestimate of precipitation in the convergence zone of the North and South Pacific,a slightly weaker eastward propagation,and a shift in the dominant periodicity toward lower frequencies with slower speeds of eastward propagation.The model gives a poor simulation of the northward propagation of MJO in summer and shows less coherence between the MJO convection and wind.The role of moistening in the planetary boundary layer(PBL)in the eastward/northward propagation of MJO was also explored.An accurate representation of the vertical titling structure of moisture anomalies in CAMS-CSM leads to moistening of the PBL ahead of convection,which accounts for the eastward/northward propagation of MJO.Poor simulation of the vertical structure of the wind and moisture anomalies in the western Pacific leads to a poor simulation of the northward propagation of MJO in this area.Budget analysis of the PBL integral moisture anomalies shows that the model gives a good simulation of the moisture charging process ahead of MJO convection and that the zonal advection of moisture convergence term has a primary role in the detour of MJO over the Maritime Continent.
基金Supported by the National Natural Science Foundation of China(41775084 and 41405102)National Key Research and Development Program of China(2018YFC1505706)Basic Research Special Project of Chinese Academy of Meteorological Sciences(2019Z008)
文摘As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circulation, and their variabilities substantially impact the climate in mid-high latitudes. A 35-yr(1979-2013) simulation by the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM) was carried out based on observed sea surface temperature and sea ice data. The ability of CAMS-CSM in simulating horizontal and vertical structures of the NAM and SAM, relation of the NAM to the East Asian climate, and temporal variability of the SAM is examined and validated against the observational data. The results show that CAMS-CSM captures the zonally symmetric and out-of-phase variations of sea level pressure anomaly between the midlatitudes and polar zones in the extratropics of the NH and SH. The model has also captured the equivalent barotropic structure in tropospheric geopotential height and the meridional shifts of the NH and SH jet systems associated with the NAM and SAM anomalies. Furthermore, the model is able to reflect the variability of northern and southern Ferrel cells corresponding to the NAM and SAM anomalies. The model reproduces the observed relationship of the boreal winter NAM with the East Asian trough and air temperature over East Asia. It also captures the upward trend of the austral summer SAM index during recent decades. However, compared with the observation, the model shows biases in both the intensity and center locations of the NAM's and SAM's horizontal and vertical structures. Specifically, it overestimates their intensities.
基金Supported by the National Key Research and Development Program of China(2016YFE0102400)National Natural Science Foundation of China(91637210 and 91737306)Basic Research Fund of the Chinese Academy of Meteorological Sciences(2018Z007)
文摘A new coupled climate system model(CSM) has been developed at the Chinese Academy of Meteorological Sciences(CAMS) by employing several state-of-the-art component models. The coupled CAMS-CSM consists of the modified atmospheric model [ECmwf-HAMburg(ECHAM5)], ocean model [Modular Ocean Model(MOM4)], sea ice model [Sea Ice Simulator(SIS)], and land surface model [Common Land Model(CoLM)]. A detailed model description is presented and both the pre-industrial and "historical" simulations are preliminarily evaluated in this study.The model can reproduce the climatological mean states and seasonal cycles of the major climate system quantities,including the sea surface temperature, precipitation, sea ice extent, and the equatorial thermocline. The major climate variability modes are also reasonably captured by the CAMS-CSM, such as the Madden–Julian Oscillation(MJO), El Ni?o–Southern Oscillation(ENSO), East Asian Summer Monsoon(EASM), and Pacific Decadal Oscillation(PDO).The model shows a promising ability to simulate the EASM variability and the ENSO–EASM relationship. Some biases still exist, such as the false double-intertropical convergence zone(ITCZ) in the annual mean precipitation field,the overestimated ENSO amplitude, and the weakened Bjerknes feedback associated with ENSO; and thus the CAMS-CSM needs further improvements.
