A cyclogenesis index for tropical Atlantic off the African coasts

Sall, Saïdou Moustapha; Sauvageot, Henri; Gaye, Amadou Thierno; Viltard, Alain; Félice, P. de

doi:10.1016/j.atmosres.2005.05.004

Cited by 17 publications

(19 citation statements)

References 59 publications

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“…For Africa, rather little research has been done on MCCs and this work is mainly focused on the Sahel (e.g., Laurent et al 1998;Laing et al 1999;Mathon et al 2002), which can influence hurricane development in the tropical Atlantic (e.g., Sall et al 2005). Apart from the limited attempt of Laing and Fritsch (1993a), we are not aware of any climatological studies of MCCs over southern Africa.…”

Section: Introductionmentioning

confidence: 98%

Mesoscale Convective Complexes over Southern Africa

Blamey

Reason

2012

Journal of Climate

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The maximum spatial correlation technique (MASCOTTE) is an objective and automated method developed to simultaneously determine both the structural properties and evolution (tracking) of cloud shields of convective systems. Originally designed to monitor systems over the Amazon region, this method has now been adapted for subtropical southern Africa. In this paper, a detailed climatology of 70 mesoscale convective complexes (MCCs) that occurred during the austral summer months over southern Africa during the 1998-2006 period are presented. Most MCCs are clustered along the eastern regions of southern Africa, adjacent to the warm waters of the Mozambique Channel and Agulhas Current. A few infrequent systems are found to be developing in Namibia and Botswana. The systems are found to predominantly occur during the months of November-February, with maximum activity occurring in November and December. The transition from a more midlatitude-dominated circulation to a tropical circulation over the region during the late summer leads to an uncharacteristic equatorward migration of the MCC distribution then. The analysis also suggests that there is variability in MCC frequency on monthly and seasonal time scales. Although fewer in number (about nine per season) compared to MCC populations in other regions, the systems do tend to follow the nocturnal life cycle as documented elsewhere.

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Section: Introductionmentioning

confidence: 98%

Mesoscale Convective Complexes over Southern Africa

Blamey

Reason

2012

Journal of Climate

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“…The GPI has been used in applications on various time scales, from intraseasonal to climate change (Camargo et al 2007aVecchi and Soden 2007;Nolan et al 2007;Lyon and Camargo 2009;Yokoi et al 2009;Yokoi and Takayabu 2009;Camargo 2013). Many other alternative indices have been developed, using different predictors or different functional dependences in their indices (DeMaria et al 2001;Royer et al 1998;Sall et al 2006;Bye and Keay 2008;Kotal et al 2009;Murakami and Wang 2010;Bruyère et al 2012;Waters et al 2012;Tang and Emanuel 2012;Holland and Bruyère 2014;Tang and Camargo 2014). While having a similar spatial and temporal distribution in the present climate, the humidity saturation deficit differs from relative humiditybeing the difference between the specific humidity and its saturation value, rather than the ratio, and thus increasing systematically with warming if relative humidity remains constant-in a way that is consequential, and apparently better, for capturing the greenhouse gasforced climate change influence on TCs.…”

Section: Introductionmentioning

confidence: 99%

Testing the Performance of Tropical Cyclone Genesis Indices in Future Climates Using the HiRAM Model

et al. 2014

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Tropical cyclone genesis indices (TCGIs) are functions of the large-scale environment that are designed to be proxies for the probability of tropical cyclone (TC) genesis. While the performance of TCGIs in the current climate can be assessed by direct comparison to TC observations, their ability to represent future TC activity based on projections of the large-scale environment cannot. Here the authors examine the performance of TCGIs in high-resolution atmospheric model simulations forced with sea surface temperatures (SST) of future, warmer climate scenarios. They investigate whether the TCGIs derived for the present climate can, when computed from large-scale fields taken from future climate simulations, capture the simulated global mean decreases in TC frequency. The TCGIs differ in their choice of environmental predictors, and several choices of predictors perform well in the present climate. However, some TCGIs that perform well in the present climate do not accurately reproduce the simulated future decrease in TC frequency. This decrease is captured when the humidity predictor is the column saturation deficit rather than relative humidity. Using saturation deficit with relative SST as the other thermodynamic predictor overpredicts the TC frequency decrease, while using potential intensity in place of relative SST as the other thermodynamic predictor gives a good prediction of the decrease's magnitude. These positive results appear to depend on the spatial and seasonal patterns in the imposed SST changes; none of the indices capture correctly the frequency decrease in simulations with spatially uniform climate forcings, whether a globally uniform increase in SST of 2 K, or a doubling of CO 2 with no change in SST.

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“…Ryan et al, 1992;Watterson et al, 1995;Royer et al, 1998). The Gray parameters were used not only in statistical models for TC genesis prediction but also in index development (Venkatesh and Mathew, 2004;Sall et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Possible relation of the western North Pacific monsoon to the tropical cyclone activity over western North Pacific

Choi

Kim

Zhang

et al. 2015

Intl Journal of Climatology

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This study examined the relationship between the western North Pacific monsoon (WNPM) and the tropical cyclone (TC) activity over western North Pacific during the summer (June to August) in a period from 1977 to 2013. According to the western North Pacific monsoon index (WNPMI), 10 years with high indices (referred to as the positive WNPMI phase) and 10 years with low indices (referred to as the negative WNPMI phase) were chosen. TCs frequently formed in the southeast quadrant of the subtropical western North Pacific in the positive WNPMI phase, and in the northwest quadrant in the negative phase. With respect to the TC track, TCs tended to move northward from the distant sea off the east coast of the Philippines towards Korea and Japan past the East China Sea in the positive WNPMI phase, whereas the characteristic pattern of the negative phase was the TC movement from the Philippines to southern China and the Indochinese peninsula over the South China Sea. As for the TC intensity, the TCs were stronger in the positive WNPMI phase than in the negative WNPMI phase. The anomalous cyclonic circulations in the south of the 30 ∘ N signified strong convection, causing the high TC genesis frequency in the positive WNPMI phase. In addition, the East China Sea, Korea and Japan were shown to be influenced by the anomalous southeasterly, which contributed as the anomalous steering flows and was favourable for the TCs to move into these regions in the positive WNPMI phase. Meanwhile, the positive anomaly of 600 hPa relative humidity and sea surface temperature as well as the negative anomaly of vertical wind shear presented in most regions of the subtropical western North Pacific, creating an environment that facilitated the generation of TCs in the positive WNPMI phase.

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A cyclogenesis index for tropical Atlantic off the African coasts

Cited by 17 publications

References 59 publications

Mesoscale Convective Complexes over Southern Africa

Mesoscale Convective Complexes over Southern Africa

Testing the Performance of Tropical Cyclone Genesis Indices in Future Climates Using the HiRAM Model

Possible relation of the western North Pacific monsoon to the tropical cyclone activity over western North Pacific

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