Dust‐rainfall feedback in West African Sahel

Abstract

Drought persistence in West African Sahel has often been explained as an effect of positive vegetation-atmosphere feedback associated with surface albedo or the partitioning of solar radiation into sensible and latent heat fluxes. An often overlooked aspect of land-atmosphere coupling results from vegetation controls on dust emissions and the ability of mineral aerosols to suppress precipitation. Here we first consider the case of local (endogenous) dynamics within the Sahel, whereby enhanced dust emissions resulting from a decrease in vegetation partly suppress precipitation, thereby further reducing vegetation cover. We then account for teleconnections between Sahel precipitation and exogenous (i.e., Saharan) dust emissions due to an increase in Saharan wind speed in years of above average Sahel precipitation. We find that in both cases vegetation-climate dynamics may have two stable states, one with low precipitation and high concentration of atmospheric dust and the other with high precipitation and lower levels of atmospheric dust.

Rainfall regimes of the Green Sahara

“…The prominent role of dust in forcing the Green Sahara agrees with 20th century analyses of Sahel rainfall, suggesting that dust feedbacks are as important as sea surface temperature and vegetation changes in driving observed historical trends ( 50 ). Furthermore, the features seen in our data, including the rapid termination of the Green Sahara and the prolonged 8 ka pause, are consistent with the idea that the Sahara has multiple stable states, mediated by vegetation or dust feedbacks ( 8 , 51 ). …”

Climate change, ecosystems and abrupt change: science priorities

“…Insect pest outbreaks [140] and feedbacks to fire regimes [141] may give rise to more ACES in boreal forests. In the Sahel, a vegetation-albedorainfall positive feedback mechanism was originally proposed to explain alternative stable states of vegetation [142,143], but recent observations support an alternative vegetation-rainfallrecycling positive feedback mechanism [144], potentially augmented by increased dust emission under dry conditions [145]. There are strong feedbacks between vegetation cover, soil moisture and rainfall at fine and intermediate scales [146][147][148], and vegetation-soil water feedbacks maintain vegetation patterns in parts of the Sahel at fine scales [149,150].…”

The Role of Vegetation in Reducing Anthropogenic CO2 in Bogor City

“…Faktor iklim yang dapat mempengaruhi jumlah konsentrasi gas CO2 di atmosfer antara lain curah hujan, kecepatan angin, dan intensitas sinar matahari. Curah hujan berperan secara langsung mengurangi konsentrasi gas CO2 melalui pencucian polutan di udara (Yu et al, 2015). Sedangkan pada kondisi kecepatan angin yang rendah, konsentrasi gas CO2 di atmosfer permukaan akan bernilai tinggi, hal tersebut karena CO2 terdispersi secara lambat (Herlina et al, 2017).…”