The Role of Vegetation in the Dynamics of West African Monsoons

Zheng, Xinqian; Eltahir, Elfatih A. B.

doi:10.1175/1520-0442-11.8.2078

Cited by 170 publications

(99 citation statements)

References 63 publications

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“…Eltahir and Gong 1996;Zheng and Eltahir 1998) have highlighted the role of complex surface-atmosphere interactions to explain the maintenance of the convective activity and the strong monsoon flux south of the convective band (i.e. around 5°N) nearly 90 days after the SHL onset whereas the WAHL weakens and the meridional gradient of the geopotential diminishes.…”

Section: The Onset Of the Saharan Heat Low And Its Link With The Westmentioning

confidence: 99%

Seasonal evolution of the West African heat low: a climatological perspective

Lavaysse¹,

Flamant²,

et al. 2009

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The West African heat low (WAHL), a region of high surface temperatures and low surface pressures, is a key element of the West African monsoon system. In this study, we propose a method to detect the WAHL in order to monitor its climatological seasonal displacement over West Africa during the period 1979-2001, using the European Centre for Medium-range Weather Forecast (ECMWF) ERA-40 reanalyses. The low-level atmospheric thickness (LLAT), a variable defined as the difference of geopotential heights at 700 and 925 hPa, is used to detect the dilatation of these levels generated by an increase of the temperature. We define grid points with 10% highest values of the LLAT as the WAHL. We show that our method reliably positions the WAHL over areas of high surface temperatures and low surface pressures, and that it is effective at detecting heat lows. In the course of the year,

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Section: The Onset Of the Saharan Heat Low And Its Link With The Westmentioning

confidence: 99%

Seasonal evolution of the West African heat low: a climatological perspective

Lavaysse¹,

Flamant²,

et al. 2009

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“…Nevertheless in most cases, these experiments showed a decrease in precipitation and an increase in temperature over the region as a result of deforestation. Another set of experiments have investigated the issue of the effects of subtropical African deforestation and land degradation on the West Africa monsoon, using both global and regional climate models (RCMs) (Charney, 1975;Zheng and Eltahir, 1998;Clark et al ., 2001;Abiodun et al ., 2007;Zeng and Neelin, 1999;Dirmeyer and Shukla, 1994;Henderson-Sellers and Gornitz, 1984;Werth and Avissar, 2005). They showed that the land surface conditions can affect the development of the West Africa Monsoon through the modification of moist static energy gradients.…”

Section: Introductionmentioning

confidence: 99%

Impact of Congo Basin deforestation on the African monsoon

Nogherotto

Coppola

Giorgi

et al. 2013

Atmospheric Science Letters

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The interactions between land cover change in Central Africa and the Africa monsoon is investigated using a regional climate model simulation (2000-2007) under a Congo Basin deforestation scenario. Decreased evaporation over the deforested area locally produces a heat low and reduced precipitation. In JJA, this low strengthens the West Africa monsoon causing increased precipitation over the Sahel and decreased precipitation over the Guinea coast. In DJF, it strengthens the south-equatorial African monsoon causing an increase of precipitation over south-equatorial Africa. Therefore our simulations indicate that the biosphere-state in Central Africa may play an important role locally but also remotely via interactions with regional monsoon dynamics.

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“…Simulations of changed vapor f lows due to land-cover change in East Asia have affected the behavior of the East Asian Monsoon, including a weakening of the summer monsoon low-pressure system and an increase in irregular northerly f low (12,19). Modeled vegetation changes for agricultural expansion in West Africa have shown potentially dramatic impacts on rainfall in the African monsoon circulation, especially through deforestation along the southern coast, because this deforestation decreases the vapor f low into the region (20).…”

mentioning

confidence: 99%

Human modification of global water vapor flows from the land surface

Gordon

Steffen

Jönsson

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

341

262

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It is well documented that human modification of the hydrological cycle has profoundly affected the flow of liquid water across the Earth's land surface. Alteration of water vapor flows through land-use changes has received comparatively less attention, despite compelling evidence that such alteration can influence the functioning of the Earth System. We show that deforestation is as large a driving force as irrigation in terms of changes in the hydrological cycle. Deforestation has decreased global vapor flows from land by 4% (3,000 km 3 ͞yr), a decrease that is quantitatively as large as the increased vapor flow caused by irrigation (2,600 km 3 ͞yr). Although the net change in global vapor flows is close to zero, the spatial distributions of deforestation and irrigation are different, leading to major regional transformations of vapor-flow patterns. We analyze these changes in the light of future landuse-change projections that suggest widespread deforestation in sub-Saharan Africa and intensification of agricultural production in the Asian monsoon region. Furthermore, significant modification of vapor flows in the lands around the Indian Ocean basin will increase the risk for changes in the behavior of the Asian monsoon system. This analysis suggests that the need to increase food production in one region may affect the capability to increase food production in another. At the scale of the Earth as a whole, our results emphasize the need for climate models to take land-use change, in both land cover and irrigation, into account.deforestation ͉ irrigation ͉ land-use changes ͉ climate change ͉ evapotranspiration

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The Role of Vegetation in the Dynamics of West African Monsoons

Cited by 170 publications

References 63 publications

Seasonal evolution of the West African heat low: a climatological perspective

Seasonal evolution of the West African heat low: a climatological perspective

Impact of Congo Basin deforestation on the African monsoon

Human modification of global water vapor flows from the land surface

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