Water balance components and climate extremes over Brazil under 1.5 °C and 2.0 °C of global warming scenarios.

This work aimed to evaluate changes in water balance components (precipitation, evapotranspiration, and water availability) and precipitation extremes projected under global warming levels (GWLs) of 1.5 °C and 2 °C, in Brazil. An ensemble of eight twenty-first-century projections with the Eta Regional Climate Model and their driving Global Climate Models (CanESM2, HadGEM2-ES, MIROC5, and BESM) were used. Projections of two Representative Concentration Pathway scenarios, RCP4.5 and RCP8.5, considered intermediate and high concentration, respectively, were used. The results indicate that the RCP8.5 scenario under 2 °C GWL is likely to have a higher impact on the water balance components, amplifying trends in drier conditions and increasing the number of consecutive dry days in some regions of Brazil, particularly in the North and Northeast regions. On the other hand, the projections indicate the opposite sign for the South region, with trends toward wetter conditions and significant increases in extreme rainfall. The 0.5 °C difference between the GWLs contributes to intensifying reductions (increases) from 4 to 7% in water availability, mainly in the North-Northeast (South) regions. The projected changes could have serious consequences, such as increases in the number of drought events in hydrographic regions of the Northeast region of Brazil and increases in flood events in the South of the country. The results here presented can contribute to the formulation of adaptive planning strategies aimed at ensuring Brazil's water security towards climate change. Supplementary Information: The online version contains supplementary material available at 10.1007/s10113-023-02042-1.

Ten-year seasonal climate reforecasts over South America using the Eta Regional Climate Model.

Ten-year seasonal climate reforecasts over South America are obtained using the Eta Regional Climate Model at 40 km resolution, driven by the large-scale forcing from the global atmospheric model of the Center for Weather Forecasts and Climate Studies. The objective of this work is to evaluate these regional reforecasts. The dataset is comprised of four-month seasonal forecasts performed on a monthly basis between 2001 and 2010. An ensemble of five members is constructed from five slightly different initial conditions to partially reduce the uncertainty in the seasonal forecasts. The seasonal mean precipitation and 2-meter temperature forecasts are compared with the observations. The comparison shows that, in general, forecasted precipitation is underestimated in the central part of the continent in the austral summer, whereas the forecasted 2 meter temperature is underestimated in most parts of the continent and throughout the year. Skill scores show higher skill in the northern part of the continent and lower skill in the southern part of the continent, but mixed skill signs are seen in the central part of the continent. During the El Niño and La Niña seasons, the forecast skill scores clearly increase. The downscaling of the Eta model seasonal forecasts provides added value over the driver global model forecasts, especially during rainy periods.

Future climate change scenarios in Central America at high spatial resolution.

The objective of this work is to assess the downscaling projections of climate change over Central America at 8-km resolution using the Eta Regional Climate Model, driven by the HadGEM2-ES simulations of RCP4.5 emission scenario. The narrow characteristic of continent supports the use of numerical simulations at very high-horizontal resolution. Prior to assessing climate change, the 30-year baseline period 1961-1990 is evaluated against different sources of observations of precipitation and temperature. The mean seasonal precipitation and temperature distribution show reasonable agreement with observations. Spatial correlation of the Eta, 8-km resolution, simulations against observations show clear advantage over the driver coarse global model simulations. Seasonal cycle of precipitation confirms the added value of the Eta at 8-km over coarser resolution simulations. The Eta simulations show a systematic cold bias in the region. Climate features of the Mid-Summer Drought and the Caribbean Low-Level Jet are well simulated by the Eta model at 8-km resolution. The assessment of the future climate change is based on the 30-year period 2021-2050, under RCP4.5 scenario. Precipitation is generally reduced, in particular during the JJA and SON, the rainy season. Warming is expected over the region, but stronger in the northern portion of the continent. The Mid-Summer Drought may develop in regions that do not occur during the baseline period, and where it occurs the strength may increase in the future scenario. The Caribbean Low-Level Jet shows little change in the future. Extreme temperatures have positive trend within the period 2021-2050, whereas extreme precipitation, measured by R50mm and R90p, shows positive trend in the eastern coast, around Costa Rica, and negative trends in the northern part of the continent. Negative trend in the duration of dry spell, which is an estimate based on evapotranspiration, is projected in most part of the continent. Annual mean water excess has negative trends in most part of the continent, which suggests decreasing water availability in the future scenario.

Sensitivity of the Amazon biome to high resolution climate change projections / Sensibilidade da floresta amazônica a projeções de mudanças climáticas de alta resolução

Despite the reduction in deforestation rate in recent years, the impact of global warming by itself can cause changes in vegetation cover. The objective of this work was to investigate the possible changes on the major Brazilian biome, the Amazon Rainforest, under different climate change scenarios. The dynamic vegetation models may simulate changes in vegetation distribution and the biogeochemical processes due to climate change. Initially, the Inland dynamic vegetation model was forced with initial and boundary conditions provided by CFSR and the Eta regional climate model driven by the historical simulation of HadGEM2-ES. These simulations were validated using the Santarém tower data. In the second part, we assess the impact of a future climate change on the Amazon biome by applying the Inland model forced with regional climate change projections. The projections show that some areas of rainforest in the Amazon region are replaced by deciduous forest type and grassland in RCP4.5 scenario and only by grassland in RCP8.5 scenario at the end of this century. The model indicates a reduction of approximately 9% in the area of tropical forest in RCP4.5 scenario and a further reduction in the RCP8.5 scenario of about 50% in the eastern region of Amazon. Although the increase of CO2 atmospheric concentration may favour the growth of trees, the projections of Eta-HadGEM2-ES show increase of temperature and reduction of rainfall in the Amazon region, which caused the forest degradation in these simulations.

Apesar da redução na taxa de desmatamento nos últimos anos, o impacto do aquecimento global por si só pode causar alterações na cobertura vegetal. O Objetivo deste trabalho foi investigar as possíveis alterações no maior bioma brasileiro, a Floresta Amazônica, levando em consideração diferentes cenários de mudanças climáticas. Os modelos de vegetação dinâmica permitem representar as mudanças na distribuição de vegetação bem como nos processos biogeoquímicos diante de mudanças no clima. Na primeira parte do trabalho, o modelo de vegetação dinâmica Inland foi forçado com condições iniciais e de contorno geradas a partir de dados de reanálise (CFSR) e pela regionalização da simulação histórica de um modelo global do sistema terrestre (HadGEM2-ES) com o modelo Eta. Estas simulações foram validadas utilizando os dados da torre de Santarém-K83. Na segunda parte, avaliou-se o impacto de uma futura mudança climática sobre o bioma floresta através das projeções do modelo Inland forçado com um modelo regional climático. As projeções mostram que algumas áreas de floresta tropical na Amazônia são substituídas por tipo de floresta decídua e pastagem natural no cenário RCP4.5 e apenas por pastagem natural no cenário RCP8.5 no final do século XXI. No Estado do Amazonas, o modelo indica uma redução de cerca de 9% da área de floresta tropical no cenário RCP4.5 e uma redução maior no cenário RCP8.5 de cerca de 50%. Embora o aumento da concentração de CO2 atmosférico possa favorecer o crescimento das árvores, as projeções do modelo Eta-HadGEM2-ES mostram aumento da temperatura e redução da precipitação na região Amazônica, levando a degradação da floresta nestas simulações.

Previsões meteorológicas do Modelo Eta para subsidiar o uso de modelos de previsão agrícola no Centro-Sul do Brasil / Eta model forecasts as input to crop models for the Mid-Southern region of Brazil

Este trabalho tem por objetivo avaliar a precipitação pluvial e as temperaturas máximas e mínimas previstas pelo Modelo Eta para até 120 dias de previsão em 24 localidades distribuídas na região Centro-Sul do Brasil. A avaliação se baseia na comparação de séries históricas de chuva e temperaturas de 1997 a 2002, com as previsões de 30, 60 e 120 dias de antecedência do Modelo Eta para as 24 localidades. Foram utilizados valores de média, mediana e desvio padrão nesta avaliação. Os resultados indicam que estas previsões geralmente subestimam as chuvas e a amplitude térmica nestas localidades. Os menores erros de precipitação pluvial se localizam mais destacadamente em Itumbiara e Rio Verde, enquanto que os maiores, em Porangatu e Manduri. Por outro lado, os menores erros de temperatura máxima se localizam destacadamente em Brasília, Manduri e Piracicaba, enquanto que os maiores ocorrem em Barreiras e Porangatu. Apesar de o modelo apresentar erros sistemáticos nas previsões de temperaturas, estes erros podem ser removidos para que os valores corrigidos possam ser introduzidos nos modelos de culturas.

The objective of this study was to evaluate the 120-day precipitation and maximum and minimum temperature forecasts by Eta Model over 24 locations around the Mid-Southern of Brazil. The evaluation was based on comparing observed time series of precipitation and temperatures from 1997 to 2002 to 30, 60 and 120-day forecasts of Eta Model over these 24 locations. Mean, median and standard deviation were used in the evaluation. The results show that these forecasts generally underestimate rain and temperature range. The smallest precipitation errors occurred in Itumbiara and Rio Verde, whereas the largest errors occurred in Porangatu and Manduri. The smallest maximum temperature errors occurred in Brasília, Manduri and Piracicaba whereas the largest errors in Barreiras and Porangatu. Despite the systematic errors exhibited by the precipitation and temperature forecasts, these errors can be removed and the corrected values input into the crop models.