No abstract

No abstract

Cyclogenesis over the southern region of South America is studied in relation to the evolution of dynamic and thermodynamic fields over the continent, using storm tracking and derived composite analysis over a 25 yr period. Results show that, irrespective of the season, there is always a moist-entropy reservoir northwest of the cyclone formation region. One day before cyclone formation, moist entropy over North Argentina is anomalously high and increasing, due to an intensification of the northerly flow along the eastern flank of the Andes, peaking at the time of cyclogenesis. The new cyclone is fed by warm and moist air coming from the continent but, as it intensifies and moves eastwards, imposes an anomalously southerly flow reducing the moist-entropy anomaly over South America. The presence of the Andes Cordillera plays a major role controlling the location of the main cyclone formation area in the region by (i) channelling the warm moist northerly flow in the lower troposphere and (ii) inducing cyclonic circulation in the lee side, when upper troughs travelling eastwards move over the mountain range at the middle latitudes.

A B S T R A C T Cyclogenesis over the southern region of South America is studied in relation to the evolution of dynamic and thermodynamic fields over the continent, using storm tracking and derived composite analysis over a 25 yr period. Results show that, irrespective of the season, there is always a moist-entropy reservoir northwest of the cyclone formation region. One day before cyclone formation, moist entropy over North Argentina is anomalously high and increasing, due to an intensification of the northerly flow along the eastern flank of the Andes, peaking at the time of cyclogenesis. The new cyclone is fed by warm and moist air coming from the continent but, as it intensifies and moves eastwards, imposes an anomalously southerly flow reducing the moist-entropy anomaly over South America. The presence of the Andes Cordillera plays a major role controlling the location of the main cyclone formation area in the region by (i) channelling the warm moist northerly flow in the lower troposphere and (ii) inducing cyclonic circulation in the lee side, when upper troughs travelling eastwards move over the mountain range at the middle latitudes.

Abstract. An Artificial Neural Networks (ANNs) approach was used to reproduce the precipitation anomalies for the rainy seasons over the south and north parts of the Northeast of Brazil (NEB) during 1982–2009 period. The seasonal hindcasts of precipitation anomalies from Climate Forecast System v2 (CFSv2) model and the observed dominant modes of anomalous Sea Surface Temperature over the South and North Atlantic Ocean were used as explanatory variables separately. The reduction of dispersion between the explanatory and dependent variables after the fit of the networks suggest the ANN as an important complementary technique for the climate studies over the NEB. However, a large dataset are required to the models capture the non-linear process in more details. The practical implication of the results is that ANNs constructed here could be applied in further analyses, for example, to explore the ANN's ability in improving the seasonal climate forecasts considering that the numerical and statistical methods must be complementary tools.

ABSTRACT:On the basis of ERA40 and NCEP/NCAR Reanalysis (NNR) and simulations from CCCma, CCSM, CSIRO, HadCM3, MIROC-MEDRES and GFDL, which support the Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (AR4), we demonstrated that the amplitude of the annual and the semi-annual harmonics delivered by the ERA40 and NNR is dominated by distinct seasonal variability. The maximum first harmonic amplitude of near surface temperature 2-metre air temperature (t2m) according the NNR is located over the Plateau of East Antarctica, whereas analyses for ERA40 show maximum amplitude over the west Antarctic ice sheet. The spatial pattern of the first harmonic of t2m in NNR more closely corresponds to station observations, suggesting that the seasonal cycle of t2m over Antarctica may be biased in ERA-40. A comparison between the global climate models (GCMs) and NNR demonstrates that the models satisfactorily simulate the amplitude of the first and second harmonics; however, the modelling results differ among themselves in terms of the amplitude values. Larger seasonal variability is identified for CCCma, HadCM3 and MIROC-MEDRES with values as high as 20°C over the Antarctic plateau. We have further identified that the CSIRO GCM does not reproduce the seasonal amplitude of t2m as compared to other models, which is primarily due to its overestimation of the cloud cover and weak seasonal changes of precipitation. Calculations of the harmonic analysis based upon greenhouse warming (GW) conditions reveal that there is no substantial seasonal difference between the amplitude of the first harmonic as projected by GW and present day (PD) simulations over the Antarctic continent. Over the polar ocean, however, the amplitude of the first harmonic is reduced in all climate models under future conditions. In order to narrow down the uncertainties on future climate projections, analyses of the cloud forcing which include the short-and long-wave radiation and the surface mass balance (SMB) may provide substantial information on the cause of the discrepancies as simulated by climate models over the Antarctic region.

Resumo O monitoramento de longo prazo dos eventos de Influência do Buraco de Ozônio Antártico sobre o Sul do Brasil foi realizado no período de 35 anos entre 1979 e 2013 e calculada a climatologia e anomalias dos campos estratosféricos quando de sua ocorrência. Para isso, foram analisados os dados da coluna total de ozônio (CTO) obtidos através de Espectrofotômetros Brewer, instalados no Observatório Espacial do Sul - OES/CRS/INPE - MCTIC (29,4 °S; 53,8 °O; 488,7 m) e pelos instrumentos de satélite Total Ozone Mapping Spectrometer (TOMS) e Ozone Monitoring Instrument (OMI), além de parâmetros da reanálise II do NCEP/DOE (National Centers for Environmental Prediction/ Departament of Energy) e trajetórias retroativas do modelo HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory). A metodologia empregada mostrou-se eficaz na identificação de 62 eventos com uma redução média de -9,35 ± 2,93% no conteúdo de ozônio. Além disso, foi realizada a identificação do padrão de circulação estratosférica através de campos médios e anomalias da vorticidade potencial, vento e temperatura para os dias de ocorrência do fenômeno, sendo observado um padrão de deslocamento de onda, embebida dentro de uma ampla região de circulação ciclônica, com ventos predominantemente de sul é advectado em direção ao Sul do Brasil.

Forest fires destroy productive land throughout the world. In Brazil, mainly the Northeast of Brazil (NEB) is strongly affected by forest fires and bush fires. Similarly, there is no adequate study of long-term data from ground and satellite-based estimation of fire foci in NEB. The objectives of this study are: (i) to evaluate the spatiotemporal estimation of fires in NEB biomes via environmental satellites during the long term over 1998–2018, and (ii) to characterize the environmental degradation in the NEB biomes via orbital products during 1998–2018, obtained from the Burn Database (BDQueimadas) for 1794 municipalities. The spatiotemporal variation is estimated statistically (descriptive, exploratory and multivariate statistics) from the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and Standardized Precipitation Index (SPI) through the Climate Hazards Group InfraRed Precipitation Station (CHIRPS). Moreover, we identify 10 homogeneous groups of fire foci (G1–G10) with a total variance of 76.5%. The G1 group is the most extended group, along with the G2 group, the exception being the G3 group. Similarly, the G4–G10 groups have a high percentage of hotspots, with more values in the municipality of Grajaú, which belongs to the agricultural consortium. The gradient of fire foci from the coast to the interior of the NEB is directly associated with land use/land cover (LULC) changes, where the sparse vegetation category and areas without vegetation are mainly involved. The Caatinga and Cerrado biomes lose vegetation, unlike the Amazon and Atlantic Forest biomes. The fires detected in the Cerrado and Atlantic Forest biomes are the result of agricultural consortia. Additionally, the two periods 2003–2006 and 2013–2018 show periods of severe and prolonged drought due to the action of El Niño.