The Role of El Niño in Modulating the Maritime Continent's Deforestation Effects

Abstract:

The Maritime Continent (MC) is suffering from frequent drought and forest fire events in the past several decades, and most of the fire events are due to the anthropogenic deforestation. Deforested MC would change the local hydro-climatological cycle, and the changed mean precipitation might alter the magnitude and frequency of the fire events.

Furthermore, the extreme drought and fire events over MC were more severe when El Niño occurred. Therefore, this study explores how deforestation may affect the local hydrological cycle under the influence of El Niño. We used the coupled atmosphere-land model to simulate the effect of deforested MC in a different mean state—climatological sea surface temperature and El Niño conditions. Comparing the deforestation’s impact under the two mean states, we found that the increased precipitation due to deforested MC is higher in El Niño case than in the neutral-year case. The subsidence due to El Niño didn’t inhibit the enhanced convection from the local deforestation forcing. Instead, the subsidence reduces the cloud cover in MC, increasing the incoming solar radiation and further warming the surface temperature. In other words, El Niño creates a more suitable local environment that would induce more lateral moisture convergence and enhance stronger convection after deforestation. Therefore, this research implies the self-constraint mechanism that the anomalously negative precipitation under the El Niño may be mitigated under the local deforestation forcing.