2019/2020 drought impacts on South America and atmospheric and oceanic influences

The 2019/2020 drought in South America caused many impacts on several sectors, as agriculture, water resources and environment, which are reported here. Besides, there is a discussion about anomalies in the atmosphere and ocean during the analyzed period. In a regional scale, there was a reduction of humidity flux over the continent, and in a large scale, the occurrence of different processes could have contributed to the dry conditions. There was a persistent pattern of west-east convection anomalies in the tropical Pacific that could be related to the steady conditions observed over South America and southeast South Atlantic from September 2019 to March 2020. The extreme positive phase of the Indian Ocean Dipole during 2019 austral spring was another event that could have influenced temperature and precipitation in South America through a wavetrain from the Indian Ocean to the South American continent. The Sudden Stratospheric Warming that occurred in September 2019 induced the negative phase of the Southern Annular Mode in December, which generated subsidence over the subtropics and affected the precipitation over South America. In addition, from September 2019 to March 2020, the heating observed in the stratosphere propagated to the troposphere over South America. Ocean indices from 1982 to 2020 are analyzed in the context of dry conditions in the continent and it was observed the relations with AMO, PDO, IOD and El Niño 3.4. From September 2019 to March 2020, there were positive SST anomalies in all oceans, mainly in the North Atlantic Ocean, which could have contributed also to subsidence over South America through a meridional circulation, as seen in other cases. At the end of the studied period, the development of La Niña extended the situation of reduced precipitation in Southern Brazil.Fil: Gomes, Mariah Souza. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Fonseca de Albuquerque Cavalcanti, Iracema. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Muller, Gabriela Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingenieria y Ciencias Hidricas. Centro de Estudios de Variabilidad y Cambio Climatico.; Argentin

Precipitacao climatologica no GCM do CPTEC/COLA, resolucao T42 L18

Climatological precipitation from an integration of 11 years using CPTEC/COLA GCM is analysed and compared with observed values. The boundary condition of Sea Surface Temperature (SST) is the climatological SST for the whole period of integration. The 11 years average of climatological precipitation show similar features to the observed field in each season. The SACZ and ZCIT are well represented by the model as well as the minimum precipitation in Central Brazil in the winter season. Some areas, as part of the Amazonia region are not well represented in the summer and autumn. During the integration, the results show similar climatological precipitation for each season, except in the Southeast area, mainly in the summer and springer.Pages:

Episodios El Nino/oscilacao sul durante a decada de 1986 a 1996 e suas influencias sobre o Brasil

Após o intenso episódio El Niño / Oscilação Sul ( ENOS) de 1982/83, o fenômeno ocorreu novamente em 1986/87, porém com menor intensidade, e de 1990 ao início de 1995. Este foi considerado o mais longo evento nos últimos 50 anos, sendo comparável apenas com o episódio de 1911-1915, ( Halpert et al, 1996). Na Fig.1 são mostradas as séries temporais do Índice de Oscilação Sul, anomalia de pressão em Tahiti e Darwin e anomalias de Radiação de Onda Longa, para o período analisado. Durante os episódios ENOS, anomalias são observadas, não só na região de aquecimento do Oceano Pacífico, como em todo o globo. As principais regiões do globo cujas precipitações são relacionadas com o ENOS foram identificadas em Ropelewski and Halpert (1987). O mesmo sinal da anomalia nas regiões nordeste (negativo) e sul do Brasil (positivo) encontrado em Kousky et al (1984) foi verificado por Ropelewski and Halpert (1987), embora na região sul essa relação tenha ocorrido de Novembro a Fevereiro. No estudo de Kousky et al (1984), a precipitação anômala no sul ocorreu no inverno de 1983

Simulations and experiments using CPTEC/COLA AGCM to analyse precipitation anomalies over Southern/Southeastern South America

Several studies on the PROSUL/IAI project performed and in development were shown in my presentation. All these studies show results of the CPTEC/COLA AGCM with emphasis to the Southern/Southeastern Region-SSA (La Plata River Basin). Two of them were presented in the Argentina Meteorological Congress, "Seasonal precipitation anomalies in El Nino 82/83 and La Nina 88/89 simulated by the CPTEC/COLA AGCM" , by IFA Cavalcanti; A Grimm; VBarros, and "Extreme cases of seasonal precipitation anomalies over SSA and the prediction by the CPTEC/COLA AGCM", by IFA Cavalcanti, JA Marengo, CA Nobre, M Nunez.These two studies show anomalies of precipitation over SSA, simulated and predicted by the model and compared to observed data. Anomalies in El Nino and La Nina years are very well simulated by the model, when the observed SSTs are used as boundary conditions. In the prediction cases, the anomalies present the same signal as the observations, in large areas of the SSA, in several seasons of the period 1998-2000.Number of Pages:

Zonal statistics of monthly means: 11 years CPTEC/COLA global model simulation

Global and zonal analyses of meteorological variables are performed in two sets of integrations of 11 years using CPTEC/COLA GCM. Monthly observed SST was applied as boundary condition in one set and climatological SST was used in the other set. The results were compared to reanalyses data. In this study, global zonal winds in both cases showed no trends during the period of the analyses. The interannual variability was smaller in the simulations than in the reanalyses. The vertical profile of the zonal wind was similar in boths experiments and represented well the profile in the reanalyses data. The largest differences between the experiments and the reanalyses ocurred in the middle latitudes of both hemispheres at high levels, and in the north tropical region at middle levels.The zonally averaged precipitation of both experiments were larger than the precipitation from the reanalyses in DJF in both hemispheres, but in JJA the simulations were larger in the Southern Hemisphere and similar to the reanalyses in the Northern Hemisphere. The higher variability observed in the tropical region showed the sensibility of the model to SST variability in this region

A zona de convergencia do Atlantico Sul modelo climatico do Hadley Centre

The South Atlantic Convergence Zone (SACZ) , a cloudiness band oriented NW/SE over South America and South Atlantic which shows an interaction between tropical and middle latitudes systems is analysed in results of the Hadley Centre Model (HADAM2b). Outlongwave radiation (OLR) was analysed in 101 years of the model integration to identify extreme cases of convection associated with the SACZ. The extreme cases which occurred in December, January and February (DJF), during the whole analysed period, were averaged in 3 areas were the ZCAS can be located. The convective band was identified in the 3 areas, and the main characteristics were the presence of positive anomalies to the north and south of the band. The analyses of convective precipitation and specific humidity also show the same characteristics, indicating strong ascent of moist air in the region of the SACZ and subsidence and dry regions to the north and to the south. The area to the south has more intense positive anomalies of OLR and is drier than the area to the north. This feature can be associated with the displacement of zonal fronts which interact with the convection over the continent and which have to the rear, cold and dry air. Positive values of soil moisture in the region of the ZCAS can be a result of the intense precipitation and can also be seen as a feedback to the maintenance of the band.Pages:

Contraste entre duas simulacoes para janeiro de 1998 usando o MCGA do CPTEC/COLA com condicoes de contorno de TSM diferentes

Two experiments using SST anomalies of two different weeks of december 1997 (high positive SST anomalies in the Equatorial Pacific) and january 1998 (low positive SST anomalies in the Equatorial Pacific), were performed with the CPTEC/INPE GCM. The purpose was to identify reasons for the observed positive anomalies of precipitation over Northeast of Brazil (Nordeste) during january 1998, when there was occurrence of an El Nino episode. Normally this occurrence is related to droughts over Nordeste, during the rainy season (MAM). The results showed a small area of above normal precipitation over Nordeste, in the case of the high positive SST anomalies in the Pacific and a large area of above normal precipitation over Nordeste in the case of the low positive SST anomalies in the Pacific. Analysing the SST of the Atlantic Ocean, in both cases there was positive anomalies of SST in the South Atlantic and normal to negative SST anomalies in the North Atlantic, with a dipole configuration favourable to precipitation over Nordeste. In the second case, when the SST anomalies over Pacific were smaller than in the first case, the dipole in the Atlantic Ocean was stronger than in the first case, thus, the two features colaborated to the increased precipitation over Nordeste.Pages: