On the Relation between the Boreal Spring Position of the Atlantic Intertropical Convergence Zone and Atlantic Zonal Mode

Pottapinjara, Vijay; Girishkumar, M. S.; Murtugudde, Raghu; Ashok, Karumuri; Ravichandran, M.

doi:10.1175/jcli-d-18-0614.1

Cited by 10 publications

(7 citation statements)

References 58 publications

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“…In general, easterly winds transport atmospheric humidity along the central Atlantic, and the moisture transport patterns are similar to those of the VIMF. During the most TC active season, the boreal summer, the ITCZ is normally northward positioned over 108N (Carvalho and Oyama 2013;Pottapinjara et al 2019), and we denote, along the text, the source to the north of the ITCZ as NATL and the source to the south as SATL.…”

Section: Resultsmentioning

confidence: 99%

Where does the moisture for North Atlantic tropical cyclones come from?

Pérez‐Alarcón

Sorí

Fernández‐Alvarez

et al. 2022

Journal of Hydrometeorology

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In this study, we identified the origin of the moisture associated with the tropical cyclones (TCs) precipitation in the North Atlantic Ocean basin during their three well-differentiated life stages between 1980 and 2018. The HURDAT2 database was used to detect the location of 598 TCs during their genesis, maximum intensification peak, and dissipation phases. The global outputs of the Lagrangian FLEXPART model were then used to determine the moisture sources. Using a K-means cluster analysis technique, seven different regions were identified as the most common locations for the genesis and maximum intensity of the TC phases, while six regions were found for the dissipation points. Our results showed that the origin of moisture precipitating was not entirely local over the areas of TC occurrence. The North Atlantic Ocean to the north of the Inter Tropical Convergence Zone at 10°N (NATL) -especially from tropical latitudes, the Caribbean Sea and the Gulf of Mexico- provides most of the moisture for TCs (∼87%). The Atlantic Ocean basin southward the ITCZ (SATL) played a non-negligible role (∼11%), with its contribution being most pronounced during the TC genesis phase, while the eastern tropical Pacific Ocean made the smallest contribution (∼2%). The moisture supported by TCs varied depending on their category, being higher for hurricanes than for major hurricanes or tropical storms. Additionally, the approach permitted to estimate the mean residence time of the water vapour uptake that produce the precipitation during TC activity, which ranged between 2.6 and 2.9 days.

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Section: Resultsmentioning

confidence: 99%

Where does the moisture for North Atlantic tropical cyclones come from?

Pérez‐Alarcón

Sorí

Fernández‐Alvarez

et al. 2022

Journal of Hydrometeorology

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“…Despite these multi-decadal fluctuations, there is limited evidence for any sustained change in the AMM (Chang et al, 2011;Martín-Rey et al, 2018) and AZM (Martín-Rey et al, 2018;Nnamchi et al, 2020) during the instrumental period. The AZM and AMM interact on interannual timescales (Servain et al, 1999;Foltz and McPhaden, 2010;Pottapinjara et al, 2019) leading in 2009 to extremes of both modes in which the negative phase of the AMM (Foltz et al, 2012;Burmeister et al, 2016) preceded an equatorial cold tongue cold event that was unprecedented in the prior 30 years (Foltz and McPhaden, 2010;Burmeister et al, 2016).…”

Section: Atlantic Meridional (Amm) and Zonal Modes (Azm)mentioning

confidence: 99%

Changing State of the Climate System

2023

Climate Change 2021 – The Physical Science Basis

120

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Chapter 2 assesses observed large-scale changes in climate system drivers, key climate indicators and principal modes of variability. Chapter 3 considers model performance and detection/attribution, and Chapter 4 covers projections for a subset of these same indicators and modes of variability. Collectively, these chapters provide the basis for later chapters, which focus upon processes and regional changes. Within Chapter 2, changes are assessed from in situ and remotely sensed data and products and from indirect evidence of longer-term changes based upon a diverse range of climate proxies. The timeevolving availability of observations and proxy information dictate the periods that can be assessed. Wherever possible, recent changes are assessed for their significance in a longer-term context, including target proxy periods, both in terms of mean state and rates of change.The increase in GMST since the mid-19th century was preceded by a slow decrease that began in the mid-Holocene (around 6500 years ago) (medium confidence). {2.3.1.1, Cross-Chapter Box 2.1} Changes in GMST and global surface air temperature (GSAT) over time differ by at most 10% in either direction (high confidence), and the long-term changes in GMST and GSAT are presently assessed to be identical. There is expanded uncertainty in GSAT estimates, with the assessed change from 1850-1900 to 1995-2014 being 0.85 [0.67 to 0.98] °C. {Cross-Chapter Box 2.3} The troposphere has warmed since at least the 1950s, and it is virtually certain that the stratosphere has cooled. In the Tropics, the upper troposphere has warmed faster than the near-surface since at least 2001, the period over which new observational techniques permit more robust quantification (medium confidence). It is virtually certain that the tropopause height has risen globally over 1980-2018, but there is low confidence in the magnitude. {2.3.1.2} Changes in several components of the global hydrological cycle provide evidence for overall strengthening since at least 1980 (high confidence). However, there is low confidence in comparing recent changes with past variations due to limitations in paleoclimate records at continental and global scales. Global land precipitation has likely increased since 1950, with a faster increase since the 1980s (medium confidence). Nearsurface specific humidity has increased over both land (very likely) and the oceans (likely) since at least the 1970s. Relative humidity has very likely decreased over land areas since 2000. Global total column water vapour content has very likely increased during the satellite era. Observational uncertainty leads to low confidence in global trends in precipitation minus evaporation and river runoff. {2.3.1.3} Several aspects of the large-scale atmospheric circulation have likely changed since the mid-20th century, but limited proxy evidence yields low confidence in how these changes compare to longer-term climate. The Hadley circulation has likely widened since at least the 1980s, and extratropical storm tracks have likely shi...

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“…The trends in wind stress in Figure 1a correspond to a strengthening of the climatogical wind stress south of the equator and over the western equatorial Atlantic where wind changes are considered key to the tongue changes (Castaño-Tierno et al, 2018;Keenlyside & Latif, 2007;Nnamchi et al, 2015;Pottapinjara et al, 2019;Richter et al, 2013;Zebiak, 1993). The wind stress changes point to an acceleration of the southeasterly trade winds (as discussed by Servain et al, 2014), although there are some uncertainties in the Atl3 region among the different reanalysis data sets (Figures 1a and 3).…”

Section: The Warming Holementioning

confidence: 88%

A satellite era warming hole in the equatorial Atlantic Ocean

Nnamchi

Latif

Keenlyside

et al. 2020

Preprint

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<p>Although the globally averaged surface temperature of the Earth has considerably warmed since the beginning of global satellite measurements in 1979, a warming hole, with hardly any surface warming that is most pronounced in boreal summer, has been observed in the equatorial Atlantic region during this period. The warming hole occurs in an extended area of the equatorial Atlantic that includes the cold tongue, the region of locally cooler ocean surface waters that develops just south of the equator in boreal summer, partly reflecting the upwelling of deep cold waters by the action of the southeasterly trade winds. This lack of surface warming of the cold tongue denotes an 11% amplification of the mean annual cycle of the sea surface temperature during the satellite era. The warming hole is driven by an intensification of the equatorial upwelling of cold waters into the ocean surface layers and damped by the surface heat flux. In observations, the tendency for surface cooling appears to reflect intrinsic variability of the climate system and is not unusual during the instrumental period. The warming hole is associated with wind-induced ocean circulation changes to the south and north of the northward of the equator. Coupled model ensembles forced by the observed varying concentrations of atmospheric greenhouse gases and natural aerosols as well as unforced runs were analyzed. The ensembles suggest a strong role for atmospheric aerosols in the warming hole. However, although aerosols can cause a cooling of the cold tongue, intrinsic climate variability as represented in the unforced experiment can potentially cause larger cooling than has been observed during the satellite era. This study highlights the difficulty in reconciling observations and the climate models for the attribution of the warming hole.</p>

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On the Relation between the Boreal Spring Position of the Atlantic Intertropical Convergence Zone and Atlantic Zonal Mode

Cited by 10 publications

References 58 publications

Where does the moisture for North Atlantic tropical cyclones come from?

Where does the moisture for North Atlantic tropical cyclones come from?

Changing State of the Climate System

A satellite era warming hole in the equatorial Atlantic Ocean

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