Thermodynamic and Dynamic Responses to Deforestation in the Maritime Continent: A Modeling Study

Abstract

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.

Global climate response to idealized deforestation in CMIP6 models

“…Winckler et al (2019a) showed that the reason for this discrepancy lies in the analyses of observation-based effects of deforestation, which eliminate the non-local effects that propagate signals outside the location of deforestation by advection or changes in atmospheric circulation and constitute mostly a cooling for deforestation. Chen and Dirmeyer (2020) confirmed for temperature extremes that accounting for atmospheric feedbacks could reconcile observations and model simulations.…”

“…Future analyses of the deforest-glob experiments could further focus on the seasonality of vegetation and climate variables (e.g. with regard to large-scale atmospheric circulation changes) to advance the understanding compared to previous studies (Bonan, 2008;Chen and Dirmeyer, 2020;Davin and de Noblet-Ducoudré, 2010;de Noblet-Ducoudré et al, 2012;Pitman et al, 2009). Additionally, the enhanced meridional temperature gradient may alter the large-scale atmospheric circulation that deserves future explorations.…”

“…Previous studies on the temperature effects of large-scale or historical deforestation have shown that the locally induced changes in albedo after boreal deforestation are almost balanced by concurrent changing turbulent heat fluxes. However, the increased boreal albedo can also induce a non-local cooling over land and oceans via advection of cooler and dryer air (Chen and Dirmeyer, 2020;Davin and de Noblet-Ducoudré, 2010;Winckler et al, 2019a). Like in other multimodel studies on the biogeophysical effects of deforestation, it is difficult to separate local and non-local effects without further separation experiments.…”

“…After 30 years, all three models demonstrate a propagation of signals from the centre to the edges of F , and two show a westward propagation across the boreal zone. This emphasizes the importance of non-local biogeophysical effects during and after large-scale deforestation (Chen and Dirmeyer, 2020;Pitman and Lorenz, 2016;Winckler et al, 2019b). FoE is more universally applicable across models as the same amount of deforestation can happen at a different time in each model.…”

Central Taiwan’s hydroclimate in response to land use/cover change

“…While deforestation usually causes less evapotranspiration and higher temperature, leading to reduced precipitation [16][17][18], precipitation in deforested areas could also be more extensive than that in high-density forests [19]. Reference [20] further indicated that deforestation could increase local convection and precipitation by introducing more lateral water vapor transport from the surrounding oceans over the Maritime Continent regions.…”