Future projections of extreme cold events in southeastern southamerica as reproduced by HadCM3 model

Las simulaciones del modelo HadCM3 fueron de las primeras disponibles para el análisis de proyecciones futuras, reflejándose en la literatura que describe principalmente variables de temperatura y precipitación para Sudamérica. El objetivo de ese trabajo es investigar los cambios en la circulación atmosférica en el sudeste de Sudamérica asociada a eventos extremos fríos, en el escenario de emisiones futuras más crítico denominado A2, para el periodo 2081-2100 respecto a un periodo climatológico de referencia 1961-1990, considerando el modelo HadCM3 y los datos del reanálisis NCEP/NCAR. A partir de la temperatura media diaria en 850 hPa, se identifican los eventos de temperatura negativa para los meses de mayo a septiembre, componiéndose los cinco eventos más extremos para tres áreas que incluyen la Pampa Húmeda (área 1), Uruguay y sur de Brasil (área 2), la parte oriental de Paraguay, norte de Argentina y sur de Brasil (área 3).Los patrones de circulación son analizados tanto para el reanálisis como para las simulaciones en el clima presente y futuro. Los resultados muestran para el clima presente que el modelo simula la incursión de las isotermas de 0°C más al norte respecto del reanálisis, a excepción del área 3 que limita con los trópicos, con anomalías negativas de temperatura más intensas y más extensas en términos latitudinales. A pesar que las configuraciones de los campos de presión sean similaresal reanálisis, se aprecia una mayor penetración del anticiclón continental, a excepción del área 3, con una intensificación de las anomalías en las respectivas áreas. El modelo también tiende a simular una componente de viento del sur más intensa en 850 hPa y captura la profunda vaguada sobre el continente en niveles altos con el jet subtropical bien configurado, típico de estos eventos extremos. En el escenario futuro, el modelo no proyecta eventos extremos de temperatura por debajo de 0°C para el área 3, restringiendo la incursión de la isoterma de 0° C a latitudes más al sur en las otras dos áreas respecto a la simulación en el clima presente, en concordancia con el aumento de temperatura media que el modelo proyecta para Sudamérica.The simulations with the HadCM3 model were among the first available to analyze future projections. This is reflected in the literature, which mainly describes the variables temperature and precipitation for South America. The aim of this paper is to investigate the changes in the atmospheric circulation over southeastern South America associated to extreme cold events in the most critical future emission scenario A2 for the period 2081-2100, with respect to the climatological reference period 1961-1990. To do that the HadCM3 model is used as well as the NCEP/NCAR reanalysis. Were identified the five most extreme events of daily mean negative temperature in 850 hPa from May to September over three areas: Wet Pampa (area 1), Uruguay and southern Brazil (area 2), eastern Paraguay, northern Argentina and southern Brazil (area 3). The obtained circulation patterns are analyzed in both, the reanalysis and the HadCM3 simulations of the present and future climate. In the present climate, with the exception of the area 3 that borders the tropics, the model simulates a more extended northward incursion of the 0oC isotherm than the reanalysis. It also shows more intense negative temperature anomalies, which have more latitudinal extension. Despite the fact that the configurations of the pressure fields are similar to that of the reanalysis, except for the area 3, a further inland penetration of the continental anticyclone is appreciated, with an intensification of the anomalies over the respective areas. The model also tends to simulate a more intense 850 hPa southerly wind component, capturing the high level deep trough over the continent and displaying a properly configured subtropical jet, which is typical of these extreme events. In the future scenario, the model does not project extreme cold events of below 0oC temperatures for area 3. The model also restricts the incursion of the 0oC isotherm to more southerly latitudes in the other two areas with respect to the simulation of the present climate. These facts are consistent with the mean temperature increase projected by the model for South America.Fil: Müller, Gabriela V.. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Rabelo Da Rocha Repinaldo, Cintia. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Andrade, Kelen M.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Cavalcanti, Iracema F. A.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasi

Climate diagnostics of three major drought events in the Amazon and illustrations of their seasonal precipitation predictions

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Avaliação das previsões do modelo Eta na região da Serra do Mar (Estado de São Paulo), Brasil

Comparisons of Eta 5 km mesoscale model forecasts against observations in Cunha, Curucutu, Itanhaém, Paraibuna, Picinguaba, Santa Virgínia e São José dos Campos, located in Serra do Mar (SP) region, is carried out for 2008. The 2 m temperature, station level pressure, winds at 10 m and precipitation are evaluated for the 24 h, 48 h and 72 h forecasts. The results show that the atmospheric pressure was systematically underestimated (overestimated) in Paraibuna and Picinguaba (Cunha and Curucutu), due to differences between the model's altitude and the real station altitude, although its diurnal cycle is well predicted, with two maximum (0 and 12 Z) and two minimum (6 and 18 Z), as observed. For atmospheric pressure, model's performance is better at the 48 h forecast. The temperature's diurnal cycle is very well predicted. The temporal correlation between forecasts and observations are very high, varying from 73 to 91%. In some locations it was observed that temperature was overestimated (near 3ºC in Curucutu and Santa Virgínia and 2ºC in Itanhaém), and that it was a systematic error. The temperature forecasted 24 h in advance is superior than the other forecasts. In general the model shows a tendency of underestimate (overestimate) the frequence of occurrence of calm (strong) winds. The wind direction is the most difficult variable to forecast due probably to the differences between model's topography and the real topography. Although the model shows the characteristic turning of the wind during the day caused by the daily warming. The total monthly precipitation is well predicted, although in Itanhaém, Paraibuna and mainly in Picinguaba the values are overestimated. The frequence of occurrence of rainy events (total daily precipitation < 0,3 mm) is overestimated by the model, although it is the best predicted category, with higher ETS, BIAS and Hit. The analyses shows that one of the model's source of error is related to its topography.Comparações entre as previsões do modelo Eta-5km e observações nas Plataformas de Coleta de Dados meteorológicas em Cunha, Curucutu, Itanhaém, Paraibuna, Picinguaba, Santa Virgínia e São José dos Campos, localizadas na região da Serra do Mar (SP), são realizadas para o ano de 2008. A temperatura a 2 m, pressão atmosférica ao nível da estação, ventos a 10 m e precipitação são avaliados para as previsões de 24, 48 e 72 horas. Os resultados mostraram que a pressão atmosférica ao nível da estação foi subestimada (superestimada) em Paraibuna e Picinguaba (Cunha e Curucutu), devido a diferenças entre a altitude do modelo e a altitude real da estação, porém os ciclos diurnos foram bem previstos, apresentando dois máximos (0 e 12 Z) e dois mínimos (6 e 18 Z), como observados. Para a pressão atmosférica a performance do modelo é superior na previsão de 48-h. O ciclo diurno da temperatura do ar foi muito bem previsto em todas as localidades. Os valores de correlação temporal entre as previsões e observações foram bem elevados, oscilando entre 73 e 91%. Para algumas localidades verificou-se que ocorre superestimativa da temperatura do ar (cerca de 3ºC em Curucutu e Santa Virgínia e 2ºC em Itanhaém), e que tal erro é sistemático. A previsão de temperatura do ar com 24-h de antecedência foi superior às demais. De forma geral o modelo apresentou uma tendência de subestimar (superestimar) a freqüência de ocorrência de ventos calmos cuja velocidade é inferior a 1 m.s-1 (fortes - superior a 7 m.s-1). A direção dos ventos é a variável mais difícil de prever devido provavelmente às diferenças entre a topografia do modelo e a topografia real, contudo nota-se que o modelo produz o giro característico na direção ao longo do dia, provocado pelo aquecimento diurno. Os totais pluviométricos mensais são bem previstos para a maior parte das localidades, contudo em Itanhaém, Paraibuna e principalmente em Picinguaba os totais mensais foram superestimados. Da análise da precipitação diária conclui-se que em geral o modelo superestima a frequência de ocorrência de eventos de chuva (valores diários maiores ou iguais a 0,3 mm). Por outro lado, o modelo apresenta a melhor performance também para prever tais eventos, com maiores valores de ETS, BIAS e índice de acerto (cerca de 90%). As análises mostram que uma das fontes de erro do modelo está relacionada à sua topografia

Evaluation of climate simulations produced with the Brazilian Global Atmospheric Model version 1.2

This paper presents an evaluation of climate simulations produced by the Brazilian Global Atmospheric Model version 1.2 (BAM-1.2) of the Center for Weather Forecast and Climate Studies (CPTEC). The model was run over the 1975-2017 period at two spatial resolutions, corresponding to ~180 and ~100 km, both with 42 vertical levels, following most of the Atmospheric Model Intercomparison Project (AMIP) protocol. In this protocol, observed sea surface temperatures (SSTs) are used as boundary conditions for the atmospheric model. Four ensemble members were run for each of the two resolutions. A series of diagnostics was computed for assessing the model's ability to represent the top of the atmosphere (TOA) radiation, atmospheric temperature, circulation and precipitation climatological features. The representation of precipitation interannual variability, El Niño-Southern Oscillation (ENSO) precipitation teleconnections, the Madden and Julian Oscillation (MJO) and daily precipitation characteristics was also assessed. The model at both resolutions reproduced many observed temperature, atmospheric circulation and precipitation climatological features, despite several identified biases. The model atmosphere was found to be more transparent than the observations, leading to misrepresentation of cloud-radiation interactions. The net cloud radiative forcing, which produces a cooling effect on the global mean climate at the TOA, was well represented by the model. This was found to be due to the compensation between both weaker longwave cloud radiative forcing (LWCRF) and shortwave cloud radiative forcing (SWCRF) in the model compared to the observations. The model capability to represent inter-annual precipitation variability at both resolutions was found to be linked to the adequate representation of ENSO teleconnections. However, the model produced weaker than observed convective activity associated with the MJO. Light daily precipitation over the southeast of South America and other climatologically similar regions was diagnosed to be overestimated, and heavy daily precipitation underestimated by the model. Increasing spatial resolution helped to slightly reduce some of the diagnosed biases. The performed evaluation identified model aspects that need to be improved. These include the representation of polar continental surface and sea ice albedo, stratospheric ozone, low marine clouds, and daily precipitation features, which were found to be larger and last longer than the observed features

Intraseasonal activity and the sacz episodes during austral summer 2003/2004

The 2003/2004 austral summer was very wet in the central portions of Brazil (Southeast and Central-West Regions, and southern Northeast). During this period there were five episodes of South Atlantic Convergence Zone (SACZ). This study explores the atmospheric variability during such SACZ episodes. Daily data from GDAS and daily interpolated OLR were used in the analysis. Results from filtered data and wavelet analysis show that the convection associated with the SACZ was highly modulated by intraseasonal waves that reached South America from Pacific Ocean. Shorter than the Madden Julian intraseasonal oscillation, periods of 14 and 9 days were also obtained during the season. The qualitative relationship between the influence of frontal systems reaching the region and the intraseasonal oscillation on the SACZ activity and maintenance is also explored.Pages: 1009-101

Southern Hemisphere atmospheric blocking diagnostic by ECMWF and NCEP/NCAR data Diagnóstico de bloqueios atmosféricos no Hemisférico Sul com reanálises do ECWMF e NCEP/NCAR

An assessment of blocking episodes over the Southern Hemisphere, selected from the Era-40 and NCEP/NCAR reanalysis are presented in this study. Blocking can be defined by an objective index based on two 500 hPa geopotential height meridional gradients. The seasonal cycle and preferential areas of occurrence are well reproduced by the two data sets. In both reanalysis used in this study, South Pacific and Oceania were the preferred regions for blocking occurrence, followed by the Atlantic Ocean. However the results revealed differences in frequencies of occurrences, which may be related to the choice of assimilation scheme employed to produce the reanalysis data sets. It is important to note that the ERA 40 and NCEP/NCAR reanalysis were produced using consistent models and assimilation schemes throughout the whole reanalyzed period, which are different for each set.Neste artigo é apresentada uma comparação de episódios de bloqueio no Hemisfério Sul, obtidos das reanálises do ERA 40 e NCEP/NCAR. A definição de bloqueio foi obtida a partir de um índice que se baseia em dois gradientes meridionais da altura geopotencial em 500 hPa. O ciclo sazonal e as áreas preferenciais de ocorrência são bem reproduzidos pelos dois conjuntos de dados. Em ambas as reanálises foi possível notar que o Pacífico Sul e Oceania são as regiões preferenciais de ocorrência de bloqueio, seguido pelo Oceano Atlântico. No entanto, os resultados revelaram diferenças nas frequências de ocorrências, que pode estar relacionada com a assimilação adotada para a produção de conjuntos de dados. É importante notar que os dados do ERA-40 e NCEP/NCAR são produzidos através de modelos consistentes e esquemas de assimilação ao longo do período, que são diferentes para cada conjunto

Teleconnection patterns in the Southern Hemisphere represented by ECMWF and NCEP S2S project models and influences on South America precipitation

Precipitation predictions in the sub-seasonal timescale are very important for several sectors such as agriculture and energy in regions of South America that are very much affected by precipitation extremes, both excess and lack of rain. The aim of the present study is to investigate the ability of two S2S project models (ECMWF and NCEP) to detect the Southern Hemisphere teleconnections in model hindcasts and the associated anomalous precipitation over South America. The period of analyses is 1999–2010 for the austral summer season (December–January–February). Both models represented adequately the Southern Annular Mode (SAM) pattern in predictions up to 4 weeks ahead and the Pacific South America (PSA) pattern up to 3 weeks. Atmospheric variables of observed extreme cases of SAM were well predicted by the two models, 2 and 3 weeks in advance. The models predicted well atmospheric variables in observed extreme cases of PSA, 2 weeks in advance and with less intensity in the third week. Precipitation anomaly signals associated with these modes were well predicted 2 weeks in advance, although with different intensities. The good ability of the models hindcast in predicting teleconnection patterns and precipitation anomalies over South America provides more confidence to use predictions at sub-seasonal timescale.Fil: Cavalcanti, Iracema F. A.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Barreto, Naurinete J. C.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Alvarez, Mariano Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Osman, Marisol. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Coelho, Caio A. S.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasi

Assessing the representation of South American monsoon features in Brazil and UK climate model simulations

This paper assesses how well the CPTEC/INPE Brazilian Global Atmospheric Model (BAM-1.2) and the atmospheric component of the UK Met Office Hadley Centre Global Environment Model (HadGEM3-GC3.1) represent the main South American monsoon features. Climatological (1981–2010) ensemble means of Atmospheric Model Intercomparison Project (AMIP)-type climate simulations are evaluated. The assessment evaluated the models’ ability to represent the South America austral summer and winter precipitation contrast and associated circulation, key South American monsoon system elements, the association between south-east Brazil and South America precipitation, and climatological (1997/1998 to 2013/2014) distributions of rainy season onset and demise dates over south-east Brazil (15°S–25°S, 40°W–50°W) and the core monsoon region (10°S–20°S, 45°W–55°W). Despite some identified deficiencies, both models depict the monsoon region and represent the main features, including (1) the north-west–south-east precipitation band and associated ascending motion over central South America; (2) the upper-level Bolivian High and the north-east South America trough during the summer; (3) the lower-level South Atlantic and Pacific subtropical anti-cyclones and (4) the low-level jet east of the Andes. Both models represent upper-level divergence and lower-level convergence over the core monsoon region, and upper-level convergence and lower-level divergence over the Pacific and Atlantic anti-cyclones associated with the regional Walker circulation during the pre-monsoon (spring) and peak monsoon (summer) seasons. Convection over South America is weaker in BAM-1.2 than observed, consistent with continental precipitation deficit. The models reproduce the dipole-like precipitation pattern between south-east Brazil and south-eastern South America during the austral summer but overestimate these patterns spatial extent over the South Atlantic. Both models simulate the main observed climatological features of rainy season onset and demise dates for the two above defined investigated regions. HadGEM3 overestimates onset dates interannual variability. These results can contribute towards understanding climate and land-use change implications for environmental sustainability and for recommending climate adaptation strategies