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1. Introduction In the second half of January 2009, a prominent stratospheric sudden warming (SSW) occurred after a cold and undisturbed early winter. The warming (hereafter referred to as MSW09) was accompanied by clear splitting of the polar vortex due to unusual development of wave number 2 SSW events are described by an abrupt temperature warming of the polar stratosphere associated with breakdown of the cold polar vortex. They are generally classified into two categories on a degree of
1. Introduction In the second half of January 2009, a prominent stratospheric sudden warming (SSW) occurred after a cold and undisturbed early winter. The warming (hereafter referred to as MSW09) was accompanied by clear splitting of the polar vortex due to unusual development of wave number 2 SSW events are described by an abrupt temperature warming of the polar stratosphere associated with breakdown of the cold polar vortex. They are generally classified into two categories on a degree of
1. Introduction The significant response of the northern winter stratosphere to El Niño–Southern Oscillation (ENSO) has been widely reported in a large number of observational ( Manzini et al. 2006 ; Garfinkel and Hartmann 2007 , 2008 ; Free and Seidel 2009 ; Xie et al. 2012 ) and modeling ( Sassi et al. 2004 ; García-Herrera et al. 2006 ; Taguchi and Hartmann 2006 ; Ineson and Scaife 2009 ; Bell et al. 2009 ; Cagnazzo and Manzini 2009 ; Cagnazzo et al. 2009 ; Garfinkel et al. 2012
1. Introduction The significant response of the northern winter stratosphere to El Niño–Southern Oscillation (ENSO) has been widely reported in a large number of observational ( Manzini et al. 2006 ; Garfinkel and Hartmann 2007 , 2008 ; Free and Seidel 2009 ; Xie et al. 2012 ) and modeling ( Sassi et al. 2004 ; García-Herrera et al. 2006 ; Taguchi and Hartmann 2006 ; Ineson and Scaife 2009 ; Bell et al. 2009 ; Cagnazzo and Manzini 2009 ; Cagnazzo et al. 2009 ; Garfinkel et al. 2012
1. Introduction Sudden stratospheric warming (SSW) is the most drastic dynamic process in the stratosphere, characterized by a decelerated or reversed westerly jet surrounding the polar vortex and a reversed temperature gradient between high and midlatitudes over the course of a few days. During major warming events, a remarkable two-way coupling between the stratosphere and troposphere has been well documented ( Eliassen and Palm 1961 ; Matsuno 1970 ; Butchart et al. 1982 ; Kodera et al
1. Introduction Sudden stratospheric warming (SSW) is the most drastic dynamic process in the stratosphere, characterized by a decelerated or reversed westerly jet surrounding the polar vortex and a reversed temperature gradient between high and midlatitudes over the course of a few days. During major warming events, a remarkable two-way coupling between the stratosphere and troposphere has been well documented ( Eliassen and Palm 1961 ; Matsuno 1970 ; Butchart et al. 1982 ; Kodera et al
1. Introduction A sudden stratospheric warming (SSW) is an abrupt warming event in the polar stratosphere. It occurs mostly in mid- and late winter (January and February) and almost exclusively in the Northern Hemisphere ( Charlton and Polvani 2007 ). During an event, the polar stratospheric temperature increases by several tens of degrees within a few days and eventually becomes warmer than that of the midlatitudes, reversing the climatological gradient. At the same time, the prevailing
1. Introduction A sudden stratospheric warming (SSW) is an abrupt warming event in the polar stratosphere. It occurs mostly in mid- and late winter (January and February) and almost exclusively in the Northern Hemisphere ( Charlton and Polvani 2007 ). During an event, the polar stratospheric temperature increases by several tens of degrees within a few days and eventually becomes warmer than that of the midlatitudes, reversing the climatological gradient. At the same time, the prevailing
1. Introduction The stratospheric aerosol layer consists of submicrometer-sized particles composed primarily of liquid solutions of sulfuric acid and water, with traces of other materials, such as ammonium sulfates. The layer was first identified by Junge et al. (1961) ; hence, it is often referred to as the “Junge” layer. Many studies have been performed to explain the formation, growth, and removal of stratospheric particles (e.g., Castleman et al. 1974 ; Hofmann et al. 1976 ; Turco et al
1. Introduction The stratospheric aerosol layer consists of submicrometer-sized particles composed primarily of liquid solutions of sulfuric acid and water, with traces of other materials, such as ammonium sulfates. The layer was first identified by Junge et al. (1961) ; hence, it is often referred to as the “Junge” layer. Many studies have been performed to explain the formation, growth, and removal of stratospheric particles (e.g., Castleman et al. 1974 ; Hofmann et al. 1976 ; Turco et al
1. Introduction Southern Hemisphere (SH) tropospheric climate variability is connected to El Niño–Southern Oscillation (ENSO), particularly during the austral summer period. Additionally, strong ENSO events are also known to impact the stratospheric circulation, predominantly in the Northern Hemisphere (NH) winter, and subsequently providing a “stratospheric pathway” onto NH surface climate ( Butler et al. 2014 ; Domeisen et al. 2019 ). This leads to the questions: To what extent does
1. Introduction Southern Hemisphere (SH) tropospheric climate variability is connected to El Niño–Southern Oscillation (ENSO), particularly during the austral summer period. Additionally, strong ENSO events are also known to impact the stratospheric circulation, predominantly in the Northern Hemisphere (NH) winter, and subsequently providing a “stratospheric pathway” onto NH surface climate ( Butler et al. 2014 ; Domeisen et al. 2019 ). This leads to the questions: To what extent does
1. Introduction The sharp boundary between the troposphere and stratosphere has been largely explained as the result of convective cloud-top entrainment (e.g., Staley 1960 ; Reid and Gage 1981 ; Held 1982 ; Sherwood and Dessler 2003 ). The tropopause is defined not only by the jump in temperature lapse rate but also by strong gradients in water vapor and ozone concentrations. In midlatitudes, the jet stream often has its maximum speed at the tropopause level. It is suspected that these
1. Introduction The sharp boundary between the troposphere and stratosphere has been largely explained as the result of convective cloud-top entrainment (e.g., Staley 1960 ; Reid and Gage 1981 ; Held 1982 ; Sherwood and Dessler 2003 ). The tropopause is defined not only by the jump in temperature lapse rate but also by strong gradients in water vapor and ozone concentrations. In midlatitudes, the jet stream often has its maximum speed at the tropopause level. It is suspected that these
1. Introduction In the decades following the first observations of a major sudden stratospheric warming (SSW) by Scherhag (1952) , various metrics were developed to classify extreme events in the stratosphere ( Butler et al. 2015 ). During an SSW, the winter stratosphere rapidly warms and the climatological westerly polar vortex decelerates, often reversing entirely. Thus the earliest SSW definitions adopted by the World Meteorological Organization (WMO) focused on temperature gradient and
1. Introduction In the decades following the first observations of a major sudden stratospheric warming (SSW) by Scherhag (1952) , various metrics were developed to classify extreme events in the stratosphere ( Butler et al. 2015 ). During an SSW, the winter stratosphere rapidly warms and the climatological westerly polar vortex decelerates, often reversing entirely. Thus the earliest SSW definitions adopted by the World Meteorological Organization (WMO) focused on temperature gradient and
Characteristics of Stratospheric Winds over Jiuquan (41.1°N, 100.2°E) Using Rocketsonde Data in 1967–20041. Introduction The stratospheric wind is an important factor in gas, energy, and momentum transportations, which influences the atmospheric dynamics ( Baumgaertner 2007 ; Hildebrand et al. 2012 ; Shepherd 2007 ). It is also critical for the safety of rocket launches, falling points prediction of spacecraft recovery, and the design of stratospheric airships ( Schmidt et al. 2006 ; Polmar 2001 ). Studies on stratospheric winds are based on various measurements. The meteorological parameters
1. Introduction The stratospheric wind is an important factor in gas, energy, and momentum transportations, which influences the atmospheric dynamics ( Baumgaertner 2007 ; Hildebrand et al. 2012 ; Shepherd 2007 ). It is also critical for the safety of rocket launches, falling points prediction of spacecraft recovery, and the design of stratospheric airships ( Schmidt et al. 2006 ; Polmar 2001 ). Studies on stratospheric winds are based on various measurements. The meteorological parameters
1. Introduction Previous studies have shown that the stratospheric polar vortex plays a critical role in the interaction between the stratosphere and troposphere (e.g., Baldwin and Dunkerton 1999 , 2001 ; Thompson et al. 2002 ; Charlton and Polvani 2007 ; Kidston et al. 2015 ; Martineau and Son 2015 ; Xie et al. 2016 ; Zhang et al. 2016 ). Variations in the stratospheric polar vortex can extend downward into the troposphere and affect the tropospheric jet streams ( Baldwin and Dunkerton
1. Introduction Previous studies have shown that the stratospheric polar vortex plays a critical role in the interaction between the stratosphere and troposphere (e.g., Baldwin and Dunkerton 1999 , 2001 ; Thompson et al. 2002 ; Charlton and Polvani 2007 ; Kidston et al. 2015 ; Martineau and Son 2015 ; Xie et al. 2016 ; Zhang et al. 2016 ). Variations in the stratospheric polar vortex can extend downward into the troposphere and affect the tropospheric jet streams ( Baldwin and Dunkerton
