Emanuel Giarolla

Amazon Deforestation and Climate Change in a Coupled Model Simulation

Abstract The effects of Amazon deforestation on climate change are investigated using twin numerical experiments of an atmospheric general circulation model (AGCM) with prescribed global sea surface temperature and the same AGCM coupled to an ocean GCM (CGCM) over the global tropics. An ensemble approach is adopted, with 10-member ensemble averages of a control simulation compared with perturbed simulations for three scenarios of Amazon deforestation. The latest 20 yr of simulation from each experiment are analyzed. Local surface warming and rainfall reduction are simulated by both models over the Amazon basin. The coupled model presented a rainfall reduction that is nearly 60% larger compared to its control run than those obtained by the AGCM. The results also indicated that both the fraction of the deforested area and the spatial continuity of the vegetated area might be important for modulating global climate variability and change. Additionally, significant remote atmospheric responses to Amazon defor...

Climate Simulation and Change in the Brazilian Climate Model

AbstractThe response of the global climate system to atmospheric CO2 concentration increase in time is scrutinized employing the Brazilian Earth System Model Ocean–Atmosphere version 2.3 (BESM-OA2.3). Through the achievement of over 2000 yr of coupled model integrations in ensemble mode, it is shown that the model simulates the signal of recent changes of global climate trends, depicting a steady atmospheric and oceanic temperature increase and corresponding marine ice retreat. The model simulations encompass the time period from 1960 to 2105, following the phase 5 of the Coupled Model Intercomparison Project (CMIP5) protocol. Notwithstanding the accurate reproduction of large-scale ocean–atmosphere coupled phenomena, like the ENSO phenomena over the equatorial Pacific and the interhemispheric gradient mode over the tropical Atlantic, the BESM-OA2.3 coupled model shows systematic errors on sea surface temperature and precipitation that resemble those of other global coupled climate models. Yet, the simula...

Is the recent increasing trend of rainfall over northeast Brazil related to sub-Saharan drought?

Abstract In recent years, there has been an increase in rainfall over northeast Brazil (Nordeste), while over the sub-Saharan region there has been a drought. The correlation coefficients between the 11-yr running means of the rainfall series over the two regions are significant (at the 95% confidence level by a two-sided t test), suggesting that both trends are related. The rainfall variations over the two regions are connected to the position of the intertropical convergence zone (ITCZ) over the Atlantic. A more southward (northward) position of the ITCZ is favorable for higher than normal rainfall over Nordeste (sub-Sahara). The correlation coefficient between the position of the ITCZ over the Atlantic and the rainfall over Nordeste (sub-Sahara) is negative (positive) and highly significant, reaching values over 0.9. Thus, this study suggests that a more southward than normal location of the ITCZ in the Atlantic may be the cause for the recent increasing (decreasing) trend of rainfall over Nordeste (su...

The Low-Frequency Variability of the Southern Ocean Circulation

AbstractLong time series of sea surface height (SSH), sea surface temperature, and wind stress curl are used to determine the main modes of low-frequency variability of the Southern Ocean (SO) circulation. The dominant mode is a trend of increasing SSH at an average rate of 3.3 mm yr−1. Similar trends have been reported in previous studies and the analysis indicates that the tendency of sea level increase over the SO has become more spatially homogeneous during the last decade, with changes in the increasing rate in 2000 and 2006. The other modes consist of stationary, basin-type modes, and an eastward-propagating wave. The stationary modes are particularly dominant in the Indian and Atlantic Ocean basins, where their spatial structure appears to be shaped by the basin geometry and the bottom topography. The wavelike patterns travel eastward with a period of approximately 10 years. Two waves were identified in the analysis: a complete cycle between 1997 and 2007 and a second cycle starting in 2000. Such w...