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1. Introduction We are interested in synoptic (time scale of 2–25 days) variability of the intertropical convergence zone (ITCZ) and the closely associated westward-propagating disturbances (WPDs) during the active season in the eastern Pacific. The term WPD is taken to encompass the terms “tropical disturbance” and “tropical cyclone” as well as less-well-developed westward-propagating disturbances or easterly waves. Both the ITCZ and WPD have signatures of a local maximum in lower
1. Introduction We are interested in synoptic (time scale of 2–25 days) variability of the intertropical convergence zone (ITCZ) and the closely associated westward-propagating disturbances (WPDs) during the active season in the eastern Pacific. The term WPD is taken to encompass the terms “tropical disturbance” and “tropical cyclone” as well as less-well-developed westward-propagating disturbances or easterly waves. Both the ITCZ and WPD have signatures of a local maximum in lower
1. Introduction a. The intertropical convergence zone and its multilevel flows The predominant large-scale view of the intertropical convergence zone (ITCZ) describes it as a belt of quasi-steady upward motion between the two large-scale overturnings of the northern and southern Hadley circulations, as illustrated in numerous texts ( Peixoto and Oort 1992 ; Grotjahn 1993 ; James 1994 ; Holton 2004 ; Vallis 2006 ). However, like so many large-scale features of the atmosphere and ocean
1. Introduction a. The intertropical convergence zone and its multilevel flows The predominant large-scale view of the intertropical convergence zone (ITCZ) describes it as a belt of quasi-steady upward motion between the two large-scale overturnings of the northern and southern Hadley circulations, as illustrated in numerous texts ( Peixoto and Oort 1992 ; Grotjahn 1993 ; James 1994 ; Holton 2004 ; Vallis 2006 ). However, like so many large-scale features of the atmosphere and ocean
manifests through trade winds modified by the NPO southern lobe during winter. When the trade winds are intensified (weakened), the ocean surface becomes cool (warm) via wind–evaporation–SST (WES) feedback ( Xie and Philander 1994 ). WES feedback can become more pronounced from winter to summer as the intertropical convergence zone (ITCZ) migrates poleward ( Amaya 2019 ; Amaya et al. 2019 ), relaying subtropical signals to the tropics and forming zonal wind anomalies from the western to central
manifests through trade winds modified by the NPO southern lobe during winter. When the trade winds are intensified (weakened), the ocean surface becomes cool (warm) via wind–evaporation–SST (WES) feedback ( Xie and Philander 1994 ). WES feedback can become more pronounced from winter to summer as the intertropical convergence zone (ITCZ) migrates poleward ( Amaya 2019 ; Amaya et al. 2019 ), relaying subtropical signals to the tropics and forming zonal wind anomalies from the western to central
1. Introduction The intertropical convergence zone (ITCZ) is a band of intense rainfall at the ascending branch of the Hadley circulation, which is centered a few degrees north of the equator in the annual mean ( Gruber 1972 ). The atmospheric and oceanic processes determining the annual-mean latitude of the ITCZ, and the sensitivity of this latitude to changes in climate, have been the focus of considerable research (e.g., Philander et al. 1996 ; Broccoli et al. 2006 ; Kang et al. 2008
1. Introduction The intertropical convergence zone (ITCZ) is a band of intense rainfall at the ascending branch of the Hadley circulation, which is centered a few degrees north of the equator in the annual mean ( Gruber 1972 ). The atmospheric and oceanic processes determining the annual-mean latitude of the ITCZ, and the sensitivity of this latitude to changes in climate, have been the focus of considerable research (e.g., Philander et al. 1996 ; Broccoli et al. 2006 ; Kang et al. 2008
1. Introduction The intertropical convergence zone in the eastern Pacific has been observed to be highly active on the synoptic time scale from summer to fall ( Wang and Magnusdottir 2006 ). Compared to the conventional view of the ITCZ in climatology, in which the ITCZ is the average of many individual convective cells, we are focusing on a different time scale in which these two points of view do not contradict each other. In other words, the climatological ITCZ represents statistical
1. Introduction The intertropical convergence zone in the eastern Pacific has been observed to be highly active on the synoptic time scale from summer to fall ( Wang and Magnusdottir 2006 ). Compared to the conventional view of the ITCZ in climatology, in which the ITCZ is the average of many individual convective cells, we are focusing on a different time scale in which these two points of view do not contradict each other. In other words, the climatological ITCZ represents statistical
1. Introduction The intertropical convergence zone (ITCZ) is the globe-encircling band of converging trade winds and maximum rainfall in the tropics (e.g., Schneider et al. 2014 ). The ITCZ controls the hydrological cycle in the tropics, is intrinsic to tropical climate variability such as El Niño–Southern Oscillation (ENSO) (e.g., Timmermann et al. 2018 ; Xie et al. 2018 ) and meridional modes ( Chiang and Vimont 2004 ; Chang et al. 2006 ; Zhang et al. 2013 , 2014 , 2015 ), and
1. Introduction The intertropical convergence zone (ITCZ) is the globe-encircling band of converging trade winds and maximum rainfall in the tropics (e.g., Schneider et al. 2014 ). The ITCZ controls the hydrological cycle in the tropics, is intrinsic to tropical climate variability such as El Niño–Southern Oscillation (ENSO) (e.g., Timmermann et al. 2018 ; Xie et al. 2018 ) and meridional modes ( Chiang and Vimont 2004 ; Chang et al. 2006 ; Zhang et al. 2013 , 2014 , 2015 ), and
1. Introduction Tropical rainfall is often associated with a discontinuous zonal precipitation band commonly known as the intertropical convergence zone (ITCZ). The ITCZ migrates between the Northern and Southern Hemispheres with the seasonal cycle, with a zonal-mean, time-mean position of approximately 6°N ( Schneider et al. 2014 ). The ITCZ is collocated with the ascending branch of the Hadley circulation, where strong moist convection leads to high rainfall. The upper branches of the Hadley
1. Introduction Tropical rainfall is often associated with a discontinuous zonal precipitation band commonly known as the intertropical convergence zone (ITCZ). The ITCZ migrates between the Northern and Southern Hemispheres with the seasonal cycle, with a zonal-mean, time-mean position of approximately 6°N ( Schneider et al. 2014 ). The ITCZ is collocated with the ascending branch of the Hadley circulation, where strong moist convection leads to high rainfall. The upper branches of the Hadley
summer), are related via the meridional displacement of the intertropical convergence zone (ITCZ) in boreal spring ( Servain et al. 1999 ; Murtugudde et al. 2001 ). These early studies indicate that the anomalous meridional movement of ITCZ during spring is an important precursor to the AZM. Chiang et al. (2002) attribute the variability of the ITCZ position in the Atlantic to two factors, namely, the cross-equatorial SST gradient (or AMM) and the remote forcing from the equatorial Pacific through
summer), are related via the meridional displacement of the intertropical convergence zone (ITCZ) in boreal spring ( Servain et al. 1999 ; Murtugudde et al. 2001 ). These early studies indicate that the anomalous meridional movement of ITCZ during spring is an important precursor to the AZM. Chiang et al. (2002) attribute the variability of the ITCZ position in the Atlantic to two factors, namely, the cross-equatorial SST gradient (or AMM) and the remote forcing from the equatorial Pacific through
to identify changes in semipermanent atmospheric systems such as the intertropical convergence zone (ITCZ), subtropical high-pressure centers, and jet streams, as well as their energetics. The detection of long-term trends in these regional systems is limited by the availability of reliable observations of atmospheric and oceanic parameters on global and regional scales. In general, reliable observations for the tropical region are available from ground- and space-based platforms for just the
to identify changes in semipermanent atmospheric systems such as the intertropical convergence zone (ITCZ), subtropical high-pressure centers, and jet streams, as well as their energetics. The detection of long-term trends in these regional systems is limited by the availability of reliable observations of atmospheric and oceanic parameters on global and regional scales. In general, reliable observations for the tropical region are available from ground- and space-based platforms for just the
1. Introduction The intertropical convergence zone (ITCZ) refers to the narrow and approximately east–west-oriented belt of concentrated vigorous cumulonimbus convection in the Tropics and represents the ascending branch of the meridional Hadley circulation. Observations show that the ITCZ typically resides between the latitudes 4° to 12° away from the equator over warm oceanic regions (e.g., Waliser and Somerville 1994 ). However, the precise latitudinal location varies greatly with season
1. Introduction The intertropical convergence zone (ITCZ) refers to the narrow and approximately east–west-oriented belt of concentrated vigorous cumulonimbus convection in the Tropics and represents the ascending branch of the meridional Hadley circulation. Observations show that the ITCZ typically resides between the latitudes 4° to 12° away from the equator over warm oceanic regions (e.g., Waliser and Somerville 1994 ). However, the precise latitudinal location varies greatly with season
