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( Waliser et al. 1993 ), the moisture of the upper troposphere and cloud-ice increase, driven by tropical deep convection. This effect greatly enhances the water vapor feedback ( Su et al. 2006 ), although no specific measure of its dependence on the surface temperature and humidity has been suggested. Clear-sky OLR data from the Earth Radiation Budget Experiment (ERBE) in 1985–88 were compared with outputs of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4
( Waliser et al. 1993 ), the moisture of the upper troposphere and cloud-ice increase, driven by tropical deep convection. This effect greatly enhances the water vapor feedback ( Su et al. 2006 ), although no specific measure of its dependence on the surface temperature and humidity has been suggested. Clear-sky OLR data from the Earth Radiation Budget Experiment (ERBE) in 1985–88 were compared with outputs of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4
nonetheless the dynamical backbone of the troposphere. Yet discrete modes are the signature of systems of finite extent: a semi-infinite stratified atmosphere yields a continuum spectrum of modes, much as the Fourier transform in the infinite line, as opposed to the discrete Fourier series associated with finite intervals. This has led to arguments by R. Lindzen that these discrete tropospheric modes are just a fallacy of overly simplified theoretical models, and that the atmosphere “is characterized by a
nonetheless the dynamical backbone of the troposphere. Yet discrete modes are the signature of systems of finite extent: a semi-infinite stratified atmosphere yields a continuum spectrum of modes, much as the Fourier transform in the infinite line, as opposed to the discrete Fourier series associated with finite intervals. This has led to arguments by R. Lindzen that these discrete tropospheric modes are just a fallacy of overly simplified theoretical models, and that the atmosphere “is characterized by a
of the Rossby–Kelvin instability]. Equatorial superrotation can be further enhanced by a reduction in the breaking of baroclinic eddies originating in midlatitudes, which decelerates the flow in the tropics under Earthlike conditions ( Laraia and Schneider 2015 ; Polichtchouk and Cho 2016 ). On Earth, the stratosphere superrotates during the westerly phase of the quasi-biennial oscillation (QBO; see Baldwin et al. 2001 ), but the climatological winds of the troposphere do not superrotate. The
of the Rossby–Kelvin instability]. Equatorial superrotation can be further enhanced by a reduction in the breaking of baroclinic eddies originating in midlatitudes, which decelerates the flow in the tropics under Earthlike conditions ( Laraia and Schneider 2015 ; Polichtchouk and Cho 2016 ). On Earth, the stratosphere superrotates during the westerly phase of the quasi-biennial oscillation (QBO; see Baldwin et al. 2001 ), but the climatological winds of the troposphere do not superrotate. The
1. Introduction Despite decades of inquiry, the role of undiluted moist-adiabatic ascent in tropical oceanic deep convection remains a point of debate. Key aspects of the ongoing debate can be captured by four unanswered questions. The first is a simple question of existence: outside of tropical cyclones, do parcels of oceanic boundary layer air convect to the upper troposphere undiluted? The key word here is “undiluted,” as in not having entrained environmental air. Since this is a simple
1. Introduction Despite decades of inquiry, the role of undiluted moist-adiabatic ascent in tropical oceanic deep convection remains a point of debate. Key aspects of the ongoing debate can be captured by four unanswered questions. The first is a simple question of existence: outside of tropical cyclones, do parcels of oceanic boundary layer air convect to the upper troposphere undiluted? The key word here is “undiluted,” as in not having entrained environmental air. Since this is a simple
1. Introduction In this report we examine the tropospheric precursors and horizontal structure of the multiple-week extratropical stratosphere–troposphere interaction events highlighted by Baldwin and Dunkerton (1999 , 2001 ) and numerous follow-on studies (e.g., Cohen et al. 2002 ; Baldwin et al. 2003 ; Polvani and Waugh 2004 ; Limpasuvan et al. 2004 , 2005 ; Reichler et al. 2005 ). These events consist of an annular-mode ( Thompson and Wallace 2000 ) signature that starts in the
1. Introduction In this report we examine the tropospheric precursors and horizontal structure of the multiple-week extratropical stratosphere–troposphere interaction events highlighted by Baldwin and Dunkerton (1999 , 2001 ) and numerous follow-on studies (e.g., Cohen et al. 2002 ; Baldwin et al. 2003 ; Polvani and Waugh 2004 ; Limpasuvan et al. 2004 , 2005 ; Reichler et al. 2005 ). These events consist of an annular-mode ( Thompson and Wallace 2000 ) signature that starts in the
convergence zone (ITCZ) that follows the apparent latitudinal movement of the sun ( Hastenrath 1995 ). This convergence and the differential surface heating between ocean and continent trigger and maintain the low-level humid monsoon flux from the Guinea Gulf. In opposition to the low-level southwesterly flow, a northeasterly advection (Harmattan) of a dry and warm Saharan air layer (SAL) develops in the mean troposphere sloping up the monsoon layer. The conflict of these two air masses of different
convergence zone (ITCZ) that follows the apparent latitudinal movement of the sun ( Hastenrath 1995 ). This convergence and the differential surface heating between ocean and continent trigger and maintain the low-level humid monsoon flux from the Guinea Gulf. In opposition to the low-level southwesterly flow, a northeasterly advection (Harmattan) of a dry and warm Saharan air layer (SAL) develops in the mean troposphere sloping up the monsoon layer. The conflict of these two air masses of different
1. Introduction The stratospheric polar vortex (SPV) is a unique circulation system in the extratropical stratosphere of both hemispheres that forms due to seasonal radiative cooling in winter ( Andrews et al. 1987 ). The variation of SPV is dynamically coupled to the troposphere from winter to spring via atmospheric waves ( Baldwin and Dunkerton 1999 , 2001 ; Waugh and Polvani 2010 ), among which the planetary-scale Rossby wave is essential ( Andrews et al. 1987 ). The variability of
1. Introduction The stratospheric polar vortex (SPV) is a unique circulation system in the extratropical stratosphere of both hemispheres that forms due to seasonal radiative cooling in winter ( Andrews et al. 1987 ). The variation of SPV is dynamically coupled to the troposphere from winter to spring via atmospheric waves ( Baldwin and Dunkerton 1999 , 2001 ; Waugh and Polvani 2010 ), among which the planetary-scale Rossby wave is essential ( Andrews et al. 1987 ). The variability of
subject of considerable debate in the recent literature (e.g., Manzini et al. 2003 ). A robust bidirectional dynamical coupling between the stratosphere and troposphere has been observed in the boreal extratropics during winter ( Thompson and Wallace 1998 ; Baldwin et al. 2003 ; McDaniel and Black 2005 ) in association with intraseasonal variability in the northern annular mode (NAM). The NAM is the primary mode of circulation variability in the Northern Hemisphere extratropics and its lower
subject of considerable debate in the recent literature (e.g., Manzini et al. 2003 ). A robust bidirectional dynamical coupling between the stratosphere and troposphere has been observed in the boreal extratropics during winter ( Thompson and Wallace 1998 ; Baldwin et al. 2003 ; McDaniel and Black 2005 ) in association with intraseasonal variability in the northern annular mode (NAM). The NAM is the primary mode of circulation variability in the Northern Hemisphere extratropics and its lower
1. Introduction Temperature and water vapor play a crucial role in weather and climate. Accurate global water vapor and temperature estimates, particularly in the middle and lower troposphere (LT), are extremely important for understanding the physics of convective cloud systems, precipitation, the hydrological cycle, and the energy balance of the earth ( Crook 1996 ; Lee et al. 1991 ; Mueller et al. 1993 ; Weckwerth et al. 1996 ; Webster and Stephens 1984 ). To more accurately assess
1. Introduction Temperature and water vapor play a crucial role in weather and climate. Accurate global water vapor and temperature estimates, particularly in the middle and lower troposphere (LT), are extremely important for understanding the physics of convective cloud systems, precipitation, the hydrological cycle, and the energy balance of the earth ( Crook 1996 ; Lee et al. 1991 ; Mueller et al. 1993 ; Weckwerth et al. 1996 ; Webster and Stephens 1984 ). To more accurately assess
1. Introduction It is now well established that robust stratosphere–troposphere coupling occurs during boreal winter in connection with intraseasonal variations in the northern annular mode (NAM; see Thompson and Wallace 1998 ; Baldwin and Dunkerton 2001 ; McDaniel and Black 2005 ). This coupling is associated with a vertically coherent zonal wind anomaly pattern extending from the earth’s surface upward into the middle stratosphere. At stratospheric altitudes the NAM is manifested by
1. Introduction It is now well established that robust stratosphere–troposphere coupling occurs during boreal winter in connection with intraseasonal variations in the northern annular mode (NAM; see Thompson and Wallace 1998 ; Baldwin and Dunkerton 2001 ; McDaniel and Black 2005 ). This coupling is associated with a vertically coherent zonal wind anomaly pattern extending from the earth’s surface upward into the middle stratosphere. At stratospheric altitudes the NAM is manifested by
