Search Results
1. Introduction In the tropics, the thermal boundary between the stratosphere and troposphere is well defined by the coldest level, the so-called cold-point tropopause (CPT). Thermal characteristics of the CPT have been extensively examined as they play a crucial role in stratosphere–troposphere coupling and exchange ( Holton et al. 1995 ). For instance, transport of water vapor from the troposphere to the stratosphere is to a great extent controlled by temperature at the CPT. Because the air
1. Introduction In the tropics, the thermal boundary between the stratosphere and troposphere is well defined by the coldest level, the so-called cold-point tropopause (CPT). Thermal characteristics of the CPT have been extensively examined as they play a crucial role in stratosphere–troposphere coupling and exchange ( Holton et al. 1995 ). For instance, transport of water vapor from the troposphere to the stratosphere is to a great extent controlled by temperature at the CPT. Because the air
of Northern Hemisphere stratospheric final warming events . J. Atmos. Sci. , 64 , 2932 – 2946 , doi: 10.1175/JAS3981.1 . Black , R. X. , and B. A. McDaniel , 2007b : Interannual variability in the Southern Hemisphere circulation organized by stratospheric final warming events . J. Atmos. Sci. , 64 , 2968 – 2974 , doi: 10.1175/JAS3979.1 . Black , R. X. , B. A. McDaniel , and W. A. Robinson , 2006 : Stratosphere–troposphere coupling during spring onset . J. Climate , 19
of Northern Hemisphere stratospheric final warming events . J. Atmos. Sci. , 64 , 2932 – 2946 , doi: 10.1175/JAS3981.1 . Black , R. X. , and B. A. McDaniel , 2007b : Interannual variability in the Southern Hemisphere circulation organized by stratospheric final warming events . J. Atmos. Sci. , 64 , 2968 – 2974 , doi: 10.1175/JAS3979.1 . Black , R. X. , B. A. McDaniel , and W. A. Robinson , 2006 : Stratosphere–troposphere coupling during spring onset . J. Climate , 19
coordinate. Triangular truncation at wavenumber 42 is used and there are 15 levels between the surface and σ = 0.0185. Unlike some sGCMs used to investigate stratosphere–troposphere coupling, the model intentionally does not include a fully resolved stratosphere and does not exhibit a stratospheric polar vortex. The mean state is maintained by Newtonian relaxation of temperature toward a zonally symmetric equilibrium state. In the original configuration used in HBD05 and SBH09 , this relaxation
coordinate. Triangular truncation at wavenumber 42 is used and there are 15 levels between the surface and σ = 0.0185. Unlike some sGCMs used to investigate stratosphere–troposphere coupling, the model intentionally does not include a fully resolved stratosphere and does not exhibit a stratospheric polar vortex. The mean state is maintained by Newtonian relaxation of temperature toward a zonally symmetric equilibrium state. In the original configuration used in HBD05 and SBH09 , this relaxation
; therefore, the wave structure in the troposphere cannot be approximated well using upward-propagating waves alone. Conversely, solving for the wave field using the simplified approach in the presence of back-reflection at the tropopause leads to unphysical incoming internal waves in the upper atmosphere, which clearly do no satisfy the radiation condition there. The key factor is to enforce the proper radiation condition in the upper atmosphere as well as the kinematic and dynamic boundary conditions at
; therefore, the wave structure in the troposphere cannot be approximated well using upward-propagating waves alone. Conversely, solving for the wave field using the simplified approach in the presence of back-reflection at the tropopause leads to unphysical incoming internal waves in the upper atmosphere, which clearly do no satisfy the radiation condition there. The key factor is to enforce the proper radiation condition in the upper atmosphere as well as the kinematic and dynamic boundary conditions at
, minima in O 3 ( Park et al. 2007 ), and high values of SO 2 and aerosols ( Yu et al. 2017 ; Vernier et al. 2011 , 2015 ; Lamarque et al. 2012 ) within the anticyclone in the upper troposphere and lower stratosphere (UTLS) throughout summer. This is a result of the combined effects of deep convection and anticyclone caused by the Asian monsoon ( Ploeger et al. 2017 ). Pollutants can be transported from the boundary layer to the upper troposphere within 30 min, or even less, due to strong updrafts
, minima in O 3 ( Park et al. 2007 ), and high values of SO 2 and aerosols ( Yu et al. 2017 ; Vernier et al. 2011 , 2015 ; Lamarque et al. 2012 ) within the anticyclone in the upper troposphere and lower stratosphere (UTLS) throughout summer. This is a result of the combined effects of deep convection and anticyclone caused by the Asian monsoon ( Ploeger et al. 2017 ). Pollutants can be transported from the boundary layer to the upper troposphere within 30 min, or even less, due to strong updrafts
1. Introduction It is now well established that the distribution of tracers in the upper troposphere and the lower stratosphere (UTLS) strongly depends on the transport and mixing properties of the flow. It is also well established that the dominant isentropic motion induces a chaotic type of tracer advection, giving rise to strongly inhomogeneous stirring (and thus, in the presence of diffusion, inhomogeneous mixing). 1 This segregates tracers into distinct well-mixed reservoirs separated by
1. Introduction It is now well established that the distribution of tracers in the upper troposphere and the lower stratosphere (UTLS) strongly depends on the transport and mixing properties of the flow. It is also well established that the dominant isentropic motion induces a chaotic type of tracer advection, giving rise to strongly inhomogeneous stirring (and thus, in the presence of diffusion, inhomogeneous mixing). 1 This segregates tracers into distinct well-mixed reservoirs separated by
-equilibrium hypothesis of Raymond (1995) , the convective and large-scale downdrafts into the subcloud layer must, on average, balance surface enthalpy fluxes in order that there are no large tendencies of entropy in the subcloud layer. Assuming that both convective downdrafts and large-scale subsidence into the subcloud layer both transport a value of moist static energy characteristic of the middle troposphere, Emanuel (1995) showed that the updraft mass flux is given by where is the large-scale vertical
-equilibrium hypothesis of Raymond (1995) , the convective and large-scale downdrafts into the subcloud layer must, on average, balance surface enthalpy fluxes in order that there are no large tendencies of entropy in the subcloud layer. Assuming that both convective downdrafts and large-scale subsidence into the subcloud layer both transport a value of moist static energy characteristic of the middle troposphere, Emanuel (1995) showed that the updraft mass flux is given by where is the large-scale vertical
1. Introduction The characteristics of the upper-troposphere/lower-stratosphere (UT/LS) region are intrinsically determined by those of both spheres. The balance of processes that regulate its dynamical, radiative, and chemical characteristics is at the heart of the debate on UT/LS exchanges. In particular, the quantification of the respective role of convective overturning in the troposphere and radiative and/or diabatic overturning in the stratosphere in determining the entry of atmospheric
1. Introduction The characteristics of the upper-troposphere/lower-stratosphere (UT/LS) region are intrinsically determined by those of both spheres. The balance of processes that regulate its dynamical, radiative, and chemical characteristics is at the heart of the debate on UT/LS exchanges. In particular, the quantification of the respective role of convective overturning in the troposphere and radiative and/or diabatic overturning in the stratosphere in determining the entry of atmospheric
1. Introduction Diffusion processes in the free atmosphere play an important role in the transport of momentum, heat, and mass on global and regional scales, although the eddy diffusivity there is much smaller than that in the atmospheric boundary layer. In particular, diffusion processes of minor constituents in the upper troposphere and lower stratosphere are essential to global warming, stratospheric ozone depletion, and transboundary air pollution problems because they govern the exchange
1. Introduction Diffusion processes in the free atmosphere play an important role in the transport of momentum, heat, and mass on global and regional scales, although the eddy diffusivity there is much smaller than that in the atmospheric boundary layer. In particular, diffusion processes of minor constituents in the upper troposphere and lower stratosphere are essential to global warming, stratospheric ozone depletion, and transboundary air pollution problems because they govern the exchange
) demonstrate enhanced seasonal forecast skill for the tropospheric circulation in the Northern Hemisphere following onset of SSWs. Regarding the Southern Hemisphere spring (when stratospheric variability is large), Roff et al. (2011) obtain better forecast skill in the troposphere several weeks after the initialization in a higher-vertical-resolution model than in a lower-resolution model. Comparing five seasonal forecasting models, Maycock et al. (2011) show that although the models underestimate the
) demonstrate enhanced seasonal forecast skill for the tropospheric circulation in the Northern Hemisphere following onset of SSWs. Regarding the Southern Hemisphere spring (when stratospheric variability is large), Roff et al. (2011) obtain better forecast skill in the troposphere several weeks after the initialization in a higher-vertical-resolution model than in a lower-resolution model. Comparing five seasonal forecasting models, Maycock et al. (2011) show that although the models underestimate the
