Changes in Hadley circulation: the Azores high and winter precipitation over tropical northeast Africa

Iqbal, Muhammad Jawed; Rehman, Saqib Ur; Hameed, Sultan; Qureshi, M. A.

doi:10.1007/s00704-019-02765-4

Cited by 6 publications

(5 citation statements)

References 22 publications

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“…At 47°N, strong AMOC phases, for example, around 1993/1994, 2005/2006, and 2015/2016 (visible in the low‐pass filtered time series, Figures 2a and 2c) are accompanied by a strong NAC (Figure S2 in Supporting Information ), a relationship also found by other studies (Smeed et al., 2014, 2018). These phases coincide with sharp transitions in the local wind stress anomaly (Figure S4 in Supporting Information ), possibly linked to changes in atmospheric pressure patterns resulting in NAO anomalies or meridional shifts of the pressure systems (Buckley & Marshall, 2016; Iqbal et al., 2019). Recalculating the NOAC AMOC with one component held constant at its mean value allows us to investigate their contribution to the total AMOC.…”

Section: Resultsmentioning

confidence: 81%

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

Wett,

Rhein,

Kieke

et al. 2023

Geophysical Research Letters

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Since climate model studies project a decline of the Atlantic Meridional Overturning Circulation (AMOC) in the 21st century, monitoring AMOC changes remains essential. While AMOC variability is expected to be coherent across latitudes on longer than decadal timescales, connectivity on inter‐annual and seasonal timescales is less clear. Model studies and observational estimates disagree on the regions and timescales of meridional connectivity and AMOC observations at multiple latitudes are needed to study its connectivity. We calculate basin‐wide AMOC volume transports (1993–2018) from measurements of the North Atlantic Changes (NOAC) array at 47°N, combining data from moored instruments with hydrography and satellite altimetry. The mean NOAC AMOC is 17.2 Sv exhibiting no long‐term trend. Both the unfiltered and low‐pass filtered NOAC AMOC show a significant correlation with the RAPID‐MOCHA‐WBTS AMOC at 26°N when the NOAC AMOC leads by about one year.

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Section: Resultsmentioning

confidence: 81%

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

Wett,

Rhein,

Kieke

et al. 2023

Geophysical Research Letters

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“…The anomalous positive geopotential height over tropical-subtropical North Atlantic is accompanied by the northeasterly wind at the south tip of it, which results in stronger regional HC over NAM region by enhancing the horizontal momentum flux from the surface into the atmosphere (Cook et al, 2003). Actually, the negative-positive geopotential anomaly over the North Atlantic is not unlike the positive phase of the North Atlantic oscillation, which is always associated with the enhanced HC (Wang et al, 2004;Cook et al, 2003;Iqbal et al, 2019).…”

Section: Mechanisms In Som Runs: the Atmospheric Teleconnection Responsementioning

confidence: 99%

Influence of Tibetan Plateau on the North American summer monsoon precipitation

et al. 2021

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It has been well known that the uplift of the Tibetan Plateau (TP) can significantly enhance the Asian monsoon. Here, by comparing the sensitivity experiments with vs without the TP, we find that TP uplift can also increase the precipitation of North American Summer Monsoon (NASM), with atmosphere teleconnection accounting for 6% and oceanic dynamical process accounting for another 6%. Physically, TP uplift generates a stationary Rossby wave train traveling from Asian continent to the North Atlantic region, resulting in an anomalous high-pressure over tropical-subtropical North Atlantic. The anomalous subtropical high enhances the low level southerly winds, forcing an anomalous upward motion over North American monsoon (NAM) region and then an increased summer precipitation there. In addition, TP uplift enhances the Atlantic meridional overturning circulation, which reduces the meridional temperature gradient and leads to a northward shift of Hadley Cell over eastern Pacific-Atlantic section. The latter shifts the convection center northward to 10N and further increases the NASM precipitation. The enhanced NASM precipitation can also be understood by the northward shift of Intertropical Convergence Zone. Our study implies that the changes of NAM climate can be affected by not only local process but also remote forcing, including the Asian highland.

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“…Notably, The Ferrel and Hadley circulations in the atmosphere are enhanced at times of high NAO index values, and the warm phase of the ENSO is characterized by a weakening in the Pacific Walker circulation, western Pacific Hadley circulation, and Atlantic Hadley circulation and a strengthening in the eastern Pacific Hadley circulation [82]. Moreover, the strengthening in the Hadley circulation in the North Atlantic area during the 1950s is indicated by the Atlantic Hadley's rising pressure [83]. The ENSO Modoki, North Pacific Oscillation (NPO), and NAO all influence the interannual variability in the Western Pacific Hadley cell [84].…”

Section: Abrupt Change In the Iod Indexmentioning

confidence: 99%

Variability in Global Climatic Circulation Indices and Its Relationship

Hasanean,

Almaashi,

Abdulhaleem H. Labban

2023

Atmosphere

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Global climatic circulation indices play a major role in determining regional and global climate conditions. These atmospheric circulation patterns exhibit substantial variability, covering a wide geographical area and affecting weather-related events. The primary goal of this study was to examine and characterize various global climatic variability indices during the 1950 to 2020 period (El Niño Southern Oscillation, ENSO; Southern Oscillation Index, SOI; North Atlantic Oscillation, NAO; Atlantic Meridional Mode, AMM; and Indian Ocean Dipole, IOD). Also, this article try to investigating the link between these global climatic indices. Trend analysis showed that the ENSO index exhibits the highest recurrence frequency of correlation relationships with the other yearly global indices with significance at the 95% and 99% levels, while the NAO index exhibits the lowest recurrence frequency. On a seasonal basis, most indices demonstrate more abrupt changes during the winter season than during the summer. An increase occurred in events of abrupt changes in these indices over the last two decades (2000 to 2020), especially annually and in summer. The SOI exhibits the largest number of abrupt changes throughout the entire study period, spanning from positive to negative significant trends, whereas the IOD did not exhibit abrupt changes annually. Increasing and decreasing trends in the global climatic circulation indices may be related to natural and anthropogenic causes of climate change. Regarding both the correlation coefficient (CC) and partial correlation results, there existed a highly negative association between the ENSO and SOI in the annual, winter and summer time series. On the other hand, there is no relationship between ENSO and NAO. Furthermore, on an annual basis, there existed a highly negative association between the NAO and AMM and a less negative but still statistically significant association between these indices during the winter and summer seasons, respectively. Therefore, through the Azore high, the NAO could promote AMM. Moreover, when the NAO, AMM, and SOI are held constant, a positive and robust correlation is reached between the ENSO and IOD in winter season. Therefore, a developing IOD is intensified and sustained during the onset of an El Niño event in winter season.

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Changes in Hadley circulation: the Azores high and winter precipitation over tropical northeast Africa

Cited by 6 publications

References 22 publications

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

Meridional Connectivity of a 25‐Year Observational AMOC Record at 47°N

Influence of Tibetan Plateau on the North American summer monsoon precipitation

Variability in Global Climatic Circulation Indices and Its Relationship

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