Land Use Change over the Amazon Forest and Its Impact on the Local Climate

Abstract

One of the most important anthropogenic influences on climate is land use change (LUC).In particular, the Amazon (AMZ) basin is a highly vulnerable area to climate change due to substantial modifications of the hydroclimatology of the region expected as a result of LUC. However, both the magnitude of these changes and the physical process underlying this scenario are still uncertain. This work aims to analyze the simulated Amazon deforestation and its impacts on local mean climate. We used the Common Land Model (CLM) version 4.5 coupled with the Regional Climate Model (RegCM4) over the Coordinated Regional Climate Downscaling Experiment (CORDEX) South America domain. We performed one simulation with the RegCM4 default land cover map (CTRL) and one simulation under a scenario of deforestation (LUC), i.e., replacing broadleaf evergreen trees with C 3 grass over the Amazon basin. Both simulations were driven by ERA Interim reanalysis from 1979 to 2009. The climate change signal due to AMZ deforestation was evaluated by comparing the climatology of CTRL with LUC. Concerning the temperature, the deforested areas are about 2 • C warmer compared to the CTRL experiment, which contributes to decrease the surface pressure. Higher air temperature is associated with a decrease of the latent heat flux and an increase of the sensible heat flux over the deforested areas. AMZ deforestation induces a dipole pattern response in the precipitation over the region: a reduction over the west (about 7.9%) and an increase over the east (about 8.3%). Analyzing the water balance in the atmospheric column over the AMZ basin, the results show that under the deforestation scenario the land surface processes play an important role and drive the precipitation in the western AMZ; on the other hand, on the east side, the large scale circulation drives the precipitation change signal. Dipole patterns over scenarios of deforestation in the Amazon was also found by other authors, but the precipitation decrease on the west side was never fully explained. Using budget equations, this work highlights the physical processes that control the climate in the Amazon basin under a deforestation scenario.

Seasonal tropospheric cooling in Northeast China associated with cropland expansion

“…The significant and negative associations between the vertical profile of GPH and cropland fraction could be explained by a denser air column associated with tropospheric cooling (Snyder 2010), as cold air is more dense than warm air, causing pressure surfaces to be lower. This positive relationship between temperature and GPH is also revealed in a number of studies (Nikolic et al 2019, Tomczyk andBednorz 2019), although some negative relationships may be found at the surface level (Liopart et al 2018). The correlation patterns of cropland fraction with temperature and GPH at different levels are generally insensitive to our focus on significantly increasing cropland regions and to our choice to detrend variables (figures S12-S14), as well as to the magnitude of interannual variability of cropland fraction data (figures S15 and S16).…”

The state of the art and fundamental aspects of regional climate modeling in South America

“…[10][11][12], and RCMs can be run for both past and future climates. They can be applied to sensitivity experiments (e.g., the response of cyclogenesis to South America (SA) topography 13 ), climate process studies (such as the surface-atmosphere interaction 14,15 ), seasonal climate forecast, 16,17 interannual variability, 12,[18][19][20][21] climate extreme events, 22 monsoons, 23 and climate projections, [24][25][26] just to mention a few applications. Therefore, RCMs allow the climate processes to be assessed, the impacts of climate change to be projected, 27 and also help decision makers to come to conclusions.…”

Oscilações decadais da temperatura do ar na América do Sul durante o período de verão austral e suas relações com o Oceano Atlântico Norte

“…A compreensão sobre a magnitude destes impactos em escala global se torna essenciais para o estabelecimento de estratégias de adaptação e mitigação das perdas e danos causados por alterações climáticas (Ren et al, 2013;Llopart et al, 2018). No entanto, a avaliação dos impactos na América do Sul e no Brasil ainda é uma tarefa cientificamente desafiadora por haver uma quantidade limitada de informações sobre mudanças climáticas pretéritas e sobre as estimativas de impactos futuros para o Brasil (Geirinhas et al, 2017;Feron et al, 2019).…”

“…As tendências positivas de aumento da ocorrência destes eventos cobrem áreas maiores do que aquelas áreas que apresentam tendências negativas (Collins et al, 2009;Reguero et al, 2019). Em termos de América do Sul (AS), grande parte dos estudos estão concentrados em entender as variações climáticas que ocorrem especificamente sobre determinadas regiões, como a região Amazônica (Llopart et al, 2018), a Bacia do Prata (Bettolli e Penalba, 2018;Montroull et al, 2018), regiões mais ao Sul do continente (Kayano e Setzer, 2018;Detzer et al, 2019), além das regiões Sudeste (Coelho et al, 2016), Nordeste (Oliveira et al, 2017) e Sul (Cordeiro et al, 2016) de 1948-1976 indicando aumento da (ou das duas) temperatura extrema (mínima ou máxima). No entanto, o cálculo de séries climáticas diárias cobrindo 20 ou 30 anos pode não ser suficiente para indicar alterações em padrões atmosféricos e oceânicos.…”