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1. Introduction The atmospheric circulation over subtropical oceans is dominated by basin-scale anticyclones in summer, associated with subsidence, low-level divergence, and anticyclonic wind curl ( Fig. 1 ). The subtropical anticyclones are responsible for the formation of monsoons, subtropical deserts, and Mediterranean-type climate. Given its profound climatic impact, the formation mechanism for the subtropical anticyclone has been thoroughly studied ( Ting 1994 ; Chen et al. 2001
1. Introduction The atmospheric circulation over subtropical oceans is dominated by basin-scale anticyclones in summer, associated with subsidence, low-level divergence, and anticyclonic wind curl ( Fig. 1 ). The subtropical anticyclones are responsible for the formation of monsoons, subtropical deserts, and Mediterranean-type climate. Given its profound climatic impact, the formation mechanism for the subtropical anticyclone has been thoroughly studied ( Ting 1994 ; Chen et al. 2001
1. Introduction The dry regions of the tropical and subtropical troposphere have a significant impact on the water vapor feedback and the atmospheric response to increased anthropogenic gases ( Houghton et al. 2001 ). The relative transparency of a layer of dry air (20% relative humidity) inserted into the average tropical humidity profile was shown by Cau et al. (2005) to lead to an increase in outgoing longwave radiation of about 3 W m −2 (100 hPa) −1 thickness in a clear-sky scenario
1. Introduction The dry regions of the tropical and subtropical troposphere have a significant impact on the water vapor feedback and the atmospheric response to increased anthropogenic gases ( Houghton et al. 2001 ). The relative transparency of a layer of dry air (20% relative humidity) inserted into the average tropical humidity profile was shown by Cau et al. (2005) to lead to an increase in outgoing longwave radiation of about 3 W m −2 (100 hPa) −1 thickness in a clear-sky scenario
1. Introduction By examining atmospheric temperature trends since 1979 based on satellite-borne microwave sounding unit (MSU) data, Fu et al. (2006) identified the enhanced stratospheric cooling and tropospheric warming in the 15°–45° latitude belts in both hemispheres. The changes in meridional tropospheric temperature gradients in the vicinity of the jets provide evidence that the subtropical jets have been shifting poleward ( Fu et al. 2006 ). However, no interpretation has been presented
1. Introduction By examining atmospheric temperature trends since 1979 based on satellite-borne microwave sounding unit (MSU) data, Fu et al. (2006) identified the enhanced stratospheric cooling and tropospheric warming in the 15°–45° latitude belts in both hemispheres. The changes in meridional tropospheric temperature gradients in the vicinity of the jets provide evidence that the subtropical jets have been shifting poleward ( Fu et al. 2006 ). However, no interpretation has been presented
elevation ranges between 1500 and 2500 m ( Fig. 1 ) and then it rises sharply to about 5000 m ASL at subtropical latitudes (25°–35°S). Thus, the subtropical Andes strongly block the zonal flow and separate two distinctive climatic regimes: a relatively cold and dry regime to the west, and a warmer and moister regime to the east ( Seluchi and Marengo 2000 ). At the synoptic scale, the Andes produce a marked disruption in the structure and evolution of the weather systems that cross the continent
elevation ranges between 1500 and 2500 m ( Fig. 1 ) and then it rises sharply to about 5000 m ASL at subtropical latitudes (25°–35°S). Thus, the subtropical Andes strongly block the zonal flow and separate two distinctive climatic regimes: a relatively cold and dry regime to the west, and a warmer and moister regime to the east ( Seluchi and Marengo 2000 ). At the synoptic scale, the Andes produce a marked disruption in the structure and evolution of the weather systems that cross the continent
1. Introduction Subtropical mode water (STMW), identified as a thermostad or a pycnostad, is formed in winter by intense vertical mixing. Because the evolution of the convection essentially depends on sea surface cooling, STMW is thought to memorize wintertime cooling at the sea surface. Additionally, the temporal variations in volume and temperature of STMW are considered to have an influence on upper ocean stratification and heat content because STMW has a relatively large volume in the
1. Introduction Subtropical mode water (STMW), identified as a thermostad or a pycnostad, is formed in winter by intense vertical mixing. Because the evolution of the convection essentially depends on sea surface cooling, STMW is thought to memorize wintertime cooling at the sea surface. Additionally, the temporal variations in volume and temperature of STMW are considered to have an influence on upper ocean stratification and heat content because STMW has a relatively large volume in the
1. Introduction The subtropical anticyclones in summer are planetary-scale atmospheric circulation systems in the lower troposphere. There are two major subtropical anticyclones over the Northern Hemisphere, the North Pacific subtropical anticyclone (NPSA) and the North Atlantic subtropical anticyclone (NASA). The poleward flow on the western flank of the subtropical anticyclone transports abundant moisture into eastern subtropical continental areas such as East Asia and the eastern
1. Introduction The subtropical anticyclones in summer are planetary-scale atmospheric circulation systems in the lower troposphere. There are two major subtropical anticyclones over the Northern Hemisphere, the North Pacific subtropical anticyclone (NPSA) and the North Atlantic subtropical anticyclone (NASA). The poleward flow on the western flank of the subtropical anticyclone transports abundant moisture into eastern subtropical continental areas such as East Asia and the eastern
1. Introduction The large areas of marine stratocumulus (Sc) located in the eastern subtropical basins of Earth’s oceans ( Fig. 1a ) cool the climate significantly. Characterized by turbulent motions on scales significantly smaller than the typical resolution in general circulation models (GCMs), low-clouds must be parameterized using large-scale thermodynamic and dynamic variables in these models. These parameterizations struggle to simulate the spatial low-cloud cover (LCC) correctly in
1. Introduction The large areas of marine stratocumulus (Sc) located in the eastern subtropical basins of Earth’s oceans ( Fig. 1a ) cool the climate significantly. Characterized by turbulent motions on scales significantly smaller than the typical resolution in general circulation models (GCMs), low-clouds must be parameterized using large-scale thermodynamic and dynamic variables in these models. These parameterizations struggle to simulate the spatial low-cloud cover (LCC) correctly in
as DLE ridges, even though they do not induce exponential separation of particles. To distinguish these shear-type LCS from hyperbolic (i.e., attracting or repelling) LCS, we use stability results from Haller (2002) . Shear-type LCS turn out to play an important role in the present flow, as these LCS act as Lagrangian boundaries of a subtropical jet stream. The dataset we analyze here contains high-resolution three-dimensional numerical weather prediction simulations combined with in situ
as DLE ridges, even though they do not induce exponential separation of particles. To distinguish these shear-type LCS from hyperbolic (i.e., attracting or repelling) LCS, we use stability results from Haller (2002) . Shear-type LCS turn out to play an important role in the present flow, as these LCS act as Lagrangian boundaries of a subtropical jet stream. The dataset we analyze here contains high-resolution three-dimensional numerical weather prediction simulations combined with in situ
1. Introduction Water vapor plays an essential role in earth’s climate as a mediator of radiative feedbacks in the response of the climate system to perturbations. In particular, the infrared water vapor feedback is strongest in the free troposphere ( Held and Soden 2000 ). Since the infrared radiative forcing associated with changes in atmospheric water vapor concentration scales approximately with relative rather than absolute concentration changes, the subtropical free troposphere has the
1. Introduction Water vapor plays an essential role in earth’s climate as a mediator of radiative feedbacks in the response of the climate system to perturbations. In particular, the infrared water vapor feedback is strongest in the free troposphere ( Held and Soden 2000 ). Since the infrared radiative forcing associated with changes in atmospheric water vapor concentration scales approximately with relative rather than absolute concentration changes, the subtropical free troposphere has the
1. Introduction One of the most ubiquitous responses of current global climate models (GCMs) to greenhouse warming is the tendency to reduce climatological precipitation in much of the global subtropics and to increase it throughout the high latitudes ( Solomon et al. 2007 ), potentially on time scales of a few decades or less ( Seager et al. 2007 ). Here we compare two prominent, independent characterizations of the twenty-first-century precipitation responses in the World Climate Research
1. Introduction One of the most ubiquitous responses of current global climate models (GCMs) to greenhouse warming is the tendency to reduce climatological precipitation in much of the global subtropics and to increase it throughout the high latitudes ( Solomon et al. 2007 ), potentially on time scales of a few decades or less ( Seager et al. 2007 ). Here we compare two prominent, independent characterizations of the twenty-first-century precipitation responses in the World Climate Research
