Fire activity in Indonesia is strongly linked with El Niño events, whose sea surface temperature (SST) patterns can weaken the Walker circulation to induce drought conditions in the region. Here we show via case analyses and idealized climate model simulations that it is the central location of the SST anomalies associated with El Niño, rather than its strength, that is mostly linked with the fire occurrence. During our study period of 1997-2015, Eastern Pacific (EP) El Niño events produced the largest fire events in southern Borneo (i.e., in 1997, 2006, and 2015), while Central Pacific (CP) El Niño events consistently produced minor fire events. The EP El Niño is found to be more capable than the CP El Niño of weakening the Walker circulation that acts to prolong Borneo's drought condition from September to October. The extended dry conditions in October potentially increase the occurrence of fires during EP El Niño years. The 2015 fire event owes its occurrence to the location of the 2015 El Niño but not necessarily its 'Godzilla' strength in affecting the fire episodes over southern Borneo. Projecting the location of El Niño events might be more important than projecting their strength for fire management in southern Borneo.

Tropical deforestation can result in substantial changes in local surface energy and water budgets, and thus in atmospheric stability. These effects may in turn yield changes in precipitation. The Maritime Continent (MC) has undergone severe deforestation during the past few decades but it has received less attention than the deforestation in the Amazon and Congo rain forests. In this study, numerical deforestation experiments are conducted with global (i.e., Community Earth System Model) and regional climate models (i.e., Regional Climate Model version 4.6) to investigate precipitation responses to MC deforestation. The results show that the deforestation in the MC region leads to increases in both surface temperature and local precipitation. Atmospheric moisture budget analysis reveals that the enhanced precipitation is associated more with the dynamic component than with the thermodynamic component of the vertical moisture advection term. Further analyses on the vertical profile of moist static energy indicate that the atmospheric instability over the deforested areas is increased as a result of anomalous moistening at approximately 800-850 hPa and anomalous warming extending from the surface to 750 hPa. This instability favors ascending air motions, which enhance low-level moisture convergence. Moreover, the vertical motion increases associated with the MC deforestation are comparable to those generated by La Niña events. These findings offer not only mechanisms to explain the local climatic responses to MC deforestation but also insights into the possible reasons for disagreements among climate models in simulating the precipitation responses.