The response to deforestation and desertification in a model of West African monsoons

Zheng, Xinqian; Eltahir, Elfatih A. B.

doi:10.1029/96gl03925

Cited by 117 publications

(54 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several studies have indicated a possible link between droughts in the Sahel and change in albedo (Courel et al 1984;Xue et al 1990;Xue 1997;Zheng and Eltahir 1997;Zeng et al 1999). The main hypothesis is that a reduction in vegetation caused by drought, overgrazing, and deforestation for cropping triggers an increase in albedo, which in turn tends to weaken convective activity and to reinforce subsidence in the Sahel reducing precipitation.…”

Section: Introductionmentioning

confidence: 99%

Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

2015

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

2015

View full text Add to dashboard Cite

“…Many of the earlier studies tended to be more idealized or the imposed land-cover changes were generally idealized to provide qualitative estimates of the precipitation response (e.g. Zheng and Eltahir 1997;Xue 1997). More recently however the need for quantitatively assessing the impact of land-use change to better understand the relative role of SST and land cover/land use change on the African climate has been recognized.…”

Section: Introductionmentioning

confidence: 99%

Assessment of uncertainties in the response of the African monsoon precipitation to land use change simulated by a regional model

et al. 2014

View full text Add to dashboard Cite

Land use and land cover (LULC) over Africa have changed substantially over the last 60 years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties of model simulated response in the African monsoon system and Sahel precipitation due to LULC change using a set of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Although the magnitude of the response covers a broad range of values, most of the simulations show a decline in Sahel precipitation due to the expansion of pasture and croplands at the expense of trees and shrubs and an increase in surface air temperature. The relationship between the model responses to LULC change and the climatologists of the control simulations is also examined. Simulations that are climatologically too dry or too wet compared to observations and reanalyses have weak response to land use change because they are in moisture or energy limited regimes respectively. The ones that lie in between have stronger response to the LULC changes, showing a more significant role in land-atmosphere interactions. Much of the change in precipitation is related to changes in circulation, particularly to the response of the intensity and latitudinal position of the African Easterly Jet, which varies with the changes in meridional surface temperature gradients. The study highlights the need for measurements of the surface fluxes across the meridional cross-section of the Sahel to evaluate models and thereby allowing human impacts such as land use change on the monsoon to be projected more realistically.

show abstract

“…Examples of these include the largescale coupling between the ocean-land-atmosphere and the WAM (e.g. Peyrillé et al, 2007); the north-south sea surface temperature (SST) gradient (Ward, 1998;Chou et al, 2001); the surface vegetation contrast between the Guinea coast and the Sahara which ensures the development of a strong meridional planetary boundary-layer gradient and the induction of the WAM circulation (Zheng and Eltahir, 1997); the interaction between the convection in the WAM with the large-scale planetary and equatorially trapped waves (Wheeler and Kiladis, 1999;Matthews, 2004), and on smaller scales (10s -1000s km), the positive feedback between soil moisture and convection via the surface fluxes (Clark and Taylor, 2004;Taylor, 2008).…”

Section: Introductionmentioning

confidence: 99%

The impact of moist processes on the African easterly jet–African easterly wave system

Cornforth

Hoskins

Thorncroft

2009

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

ABSTRACT:The African Easterly Jet-Easterly Wave (AEJ-AEW) system was explored in an idealised model. Prescribed zonally symmetric surface temperature and moisture profiles determine the AEJ which becomes established through meridional contrasts in dry and moist convection.As in previous studies, a realistic AEJ developed with only dry convection. Including moist processes, increased its development rate, but reduced its speed and meridional extent. AEWs grew through barotropic-baroclinic conversions. Negative meridional potential vorticity (PV) gradients arose in the zonally symmetric state through the intrusion of the low-PV Saharan boundary layer. Since moist processes strengthened this significantly through diabatically generated PV in the Intertropical Convergence Zone, moist AEWs were three times stronger. Larger barotropic conversions and faster AEJ development increased the moist wave growth-rate. Jet-level and northerly low-level amplitudes grew, but in the moist case the low-level amplitudes weakened as the AEW interacted with convection, consistent with their absence from observations during the peak monsoon. Striking dependencies between the AEJ, AEW and rainfall existed. Two time-scales governed their evolution, depending on the transfer coefficients: (1) the AEJ's replenishment rate influenced by heat fluxes, and (2) the wave growth-rate, by damping, and the slower jet development rate.Moist AEWs were characterized by intermittent growth/decay, with growth preceded by increased mean rainfall and later, weakening AEJs. These dependencies established an internal 8-10-day variability, consistent with intra-seasonal observations of 9-day rainy sequences. This internal variability offers an alternative explanation to the previously proposed external forcing and a new view of the moist AEW life cycle.

show abstract

The response to deforestation and desertification in a model of West African monsoons

Cited by 117 publications

References 28 publications

Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

Impact of burned areas on the northern African seasonal climate from the perspective of regional modeling

Assessment of uncertainties in the response of the African monsoon precipitation to land use change simulated by a regional model

The impact of moist processes on the African easterly jet–African easterly wave system

Contact Info

Product

Resources

About