Remotely forced variability in the tropical Atlantic Ocean

Huang, Bohua

doi:10.1007/s00382-004-0443-8

Cited by 94 publications

(100 citation statements)

References 43 publications

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“…Tropical/extratropical structure over Atlantic in Figure 7A is quite similar to the pattern reported by observational studies (Trzaska et al, 2007;Polo et al, 2008;Nnamchi and Li, 2011). Global pattern in Figure 7D resembles the tele-connection patterns from the Southern Pacific basin via extra-tropical Rossby wave train (Penland and Matrosova, 1998;Barreiro et al, 2004;Huang, 2004) with an associated SST dipolar pattern at both sides of 25S.…”

Section: Origin Of the Ea Modesupporting

confidence: 83%

Growth and decay of the equatorial Atlantic SST mode by means of closed heat budget in a coupled general circulation model

et al. 2015

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Citation:Polo I, Lazar A, Rodriguez-Fonseca B and Mignot J (2015) Tropical Atlantic variability is strongly biased in coupled General Circulation Models (GCM). Most of the models present a mean Sea Surface Temperature (SST) bias pattern that resembles the leading mode of inter-annual SST variability. Thus, understanding the causes of the main mode of variability of the system is crucial. A GCM control simulation with the IPSL-CM4 model as part of the CMIP3 experiment has been analyzed. Mixed layer heat budget decomposition has revealed the processes involved in the origin and development of the leading inter-annual variability mode which is defined over the Equatorial Atlantic (hereafter EA mode). In comparison with the observations, it is found a reversal in the anomalous SST evolution of the EA mode: from west equator to southeast in the simulation, while in the observations is the opposite. Nevertheless, despite the biases over the eastern equator and the African coast in boreal summer, the seasonality of the inter-annual variability is well-reproduced in the model. The triggering of the EA mode is found to be related to vertical entrainment at the equator as well as to upwelling along South African coast. The damping is related to the air-sea heat fluxes and oceanic horizontal terms. As in the observation, this EA mode exerts an impact on the West African and Brazilian rainfall variability. Therefore, the correct simulation of EA amplitude and time evolution is the key for a correct rainfall prediction over tropical Atlantic. In addition to that, identification of processes which are responsible for the tropical Atlantic biases in GCMs is an important element in order to improve the current global prediction systems.

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Section: Origin Of the Ea Modesupporting

confidence: 83%

Growth and decay of the equatorial Atlantic SST mode by means of closed heat budget in a coupled general circulation model

et al. 2015

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“…For an ensemble forecast, the patterns of the internal variability can be estimated from the departures of individual members from their ensemble mean. To further eliminate the influences of the internal noise in the ensemble forecast, it is useful to apply MSN EOF, which isolates the most predictable patterns by maximizing the ratio of the variances of the ensemble mean and within-ensemble deviations (Allen and Smith 1997;Venzke et al 1999;Huang 2004). By definition, the pattern described by the MSN EOF mode is predictable if the forced response is consistent and matches observations significantly.…”

Section: Model Data and Analysis Methodsmentioning

confidence: 99%

Predictable patterns and predictive skills of monsoon precipitation in Northern Hemisphere summer in NCEP CFSv2 reforecasts

Zuo

Yang

et al. 2013

Clim Dyn

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“…Kushnir, 1994;Mehta, 1998;Enfield and MestasNuñez, 1999), reflecting lower SSTs in the North Atlantic in the 1980s and 1990s and a warm phase in the 1950s and 1960s. Another is the Antarctic Oscillation (Huang, 2003;Huang and Shukla, 2005), which appears to affect the South Atlantic. Chelliah and Bell (2004) have also defined a tropical multidecadal mode based on 200 mb velocity potential and surface temperature in the region 30°N-30°S.…”

Section: Interannual Persistence Of Rainfall Anomaliesmentioning

confidence: 99%

A physical basis for the interannual variability of rainfall in the Sahel

Nicholson¹,

Webster²

2007

Quart J Royal Meteoro Soc

108

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A major factor in rainfall variability over Sahelian West Africa is the latitudinal location of the tropical rainbelt. When it is displaced abnormally far northward, the Sahel experiences a wet year. An anomalous southward displacement results in drought. In this paper we examine the question of what controls the location during the boreal summer, hypothesizing that inertial instability plays a role. An analysis of surface pressure and temperature fields, wind fields, divergence and vertical motion show that the criteria for inertial instability are satisfied in wet Augusts but not in dry ones. The key determinant appears to be the surface pressure gradient between the continent and the equatorial Atlantic. When this is large, inertial instability results in the development of a low-level westerly jet. The presence of this jet enhances the horizontal and vertical shear, and displaces the African Easterly Jet northwestward. Associated with this situation is strong vertical motion over the Sahel and subsidence over the Guinea Coast, producing dry conditions over the latter. The result is a rainfall dipole, one of two major modes of variability over West Africa. Important factors include sea surface temperatures (SSTs) in the equatorial Atlantic and pressure in the South Atlantic. The first of these factors suggests a link with the Atlantic Niño mode of tropical Atlantic variability; while the second suggests a possible link with the Pacific and the extratropical South Atlantic. Overall, our study relates the well-known SST influence on Sahel rainfall to atmospheric dynamics over the continent.

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Remotely forced variability in the tropical Atlantic Ocean

Cited by 94 publications

References 43 publications

Growth and decay of the equatorial Atlantic SST mode by means of closed heat budget in a coupled general circulation model

Growth and decay of the equatorial Atlantic SST mode by means of closed heat budget in a coupled general circulation model

Predictable patterns and predictive skills of monsoon precipitation in Northern Hemisphere summer in NCEP CFSv2 reforecasts

A physical basis for the interannual variability of rainfall in the Sahel

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