Resumo Neste trabalho objetivou-se verificar as possíveis relações de pontos amostrais da tempera... more Resumo Neste trabalho objetivou-se verificar as possíveis relações de pontos amostrais da temperatura da superfície do mar distribuídos espacialmente no Atlântico Tropical e o desenvolvimento de linhas de instabilidade atuantes na costa Norte e Nordeste do Brasil utilizando-se de técnicas de modelagem linear generalizada. Para isso, foram usados modelos lineares generalizados a partir da regressão linear de Poisson e da Binomial Negativa. Na análise das relações instituídas pela modelagem foi aplicada o teste de variância ANOVA com nível de significância de 0,05 de probabilidade para determinar que variáveis independentes foram mais significativas. Também foram analisados os resíduos gerados pelo ajuste dos modelos no intuito de identificar a distribuição que melhor se ajustasse aos dados. Toda análise estática foi realizada no software R. Entre os 132 pares de observações, a magnitude do coeficiente de correlação linear de Pearson (r) oscilou entre 0,06 (p < 0,04) entre (LI e TS...
The present study presents an analysis of the annual mean tropical heat balance and its associati... more The present study presents an analysis of the annual mean tropical heat balance and its association with the Walker circulation (WC) using NCEP/NCAR Reanalysis data. This study shows the relative importance of diabatic data to produce vertical motion in the tropics and for the WC region. It is shown that ascending motion in the WC's upward branch is determined by the joint effect of latent heating and radiative cooling processes while infrared radiation loss is associated to sink motions on the WC's descending branch. In ascending branches of the WC vertical velocity from reanalysis is overestimated when latent heat is taken into account to drive motions. Radiative cooling is indentified as the main physical process yielding sinking motion in the WC's downward branches. In upward branches of the WC, resulting diabatic processes (latent heat release) are balanced by adiabatic expansion (due rising motions). In descending branches of the WC, there is a near balance between...
The GEOS-1 data from multiyear reanalysis are using. An altered Walker Circulation is initiated b... more The GEOS-1 data from multiyear reanalysis are using. An altered Walker Circulation is initiated by the rising motion created over the warm ocean surface on the eastern Pacific. This occurred during the major El Niño event of 1982-1983. To compensate the rising motion, a sinking motion is generated over western Pacific completing the formation of the altered Walker Circulation. Thus, the initiation of the altered Walker Circulation is by the sea surface gradient as originally envisioned by Bjerknes.
The primitive equation barotropic unstable linear normal modes are computed using an eigenvalue a... more The primitive equation barotropic unstable linear normal modes are computed using an eigenvalue approach for daily latitudinal profiles of zonal flow in the upper-tropospheric layer of 100–350 hPa before and after formation of cyclonic vortices during January 1993 and November 2001 off the coast of northeast Brazil. The wave kinetic energy equation for u- and υ-motion is presented. Equations are derived to isolate the contribution of divergence and other dynamical processes in the movement and growth of unstable modes. Numerical accuracy and physical nature of unstable modes are tested. In a short span of 2–3 days, prior to formation of vortices, a progressive and a sharp intensification of the basic flow shear zone and its barotropic instability are seen with time. The horizontal structure, momentum transport, and zonal and meridional scales of the most unstable normalized wave are obtained and compared with the vortex extracted from the 200-hPa observed winds using a bandpass smoo...
Journal of Geophysical Research: Atmospheres, 2009
In an attempt to validate the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR)... more In an attempt to validate the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) over Brazil, TRMM PR estimates are compared with rain gauge station data from Agência Nacional de Energia Elétrica (ANEEL). The analysis is conducted on a seasonal basis and considers five geographic regions with different precipitation regimes. The results showed that TRMM PR seasonal rainfall is well correlated with ANEEL rainfall (correlation coefficients are significant at the 99% confidence level) over most of Brazil. The random and systematic errors of TRMM PR are sensitive to seasonal and regional differences. During December to February and March to May, TRMM PR rainfall is reliable over Brazil. In June to August (September to November) TRMM PR estimates are only reliable in the Amazonian and southern (Amazonian and southeastern) regions. In the other regions the relative RMS errors are larger than 50%, indicating that the random errors are high.
Journal of Geophysical Research: Atmospheres, 2004
Chou and Suarez's solar and infrared radiation models are incorporated in a statistical‐dynam... more Chou and Suarez's solar and infrared radiation models are incorporated in a statistical‐dynamical model with biosphere and atmosphere interaction in order to study the climatic effects due to biomass burning in Amazonian forest. In the control experiment the mean annual zonally averaged climate is well simulated by the model when compared with observed data. Biomass burning plays an important role on the earth's radiative balance and climate through the release of large amounts of greenhouse gases and aerosols in the atmosphere and the alteration of the land surface characteristics. For investigating the relative importance of these changes five experiments are performed: (1) degradation of the surface, (2) change in the smoke aerosols concentration, (3) change in the CO2 concentration, (4) change in CH4 concentration, and (5) all the changes together. The results show that biomass burning in Amazonian forest causes a reduction in the absorbed solar radiation and net radiati...
In recent years, there has been an increase in rainfall over northeast Brazil (Nordeste), while o... more 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 ove...
Journal of Applied Meteorology and Climatology, 2008
The relationships between coastal upwelling and local winds at Cabo Frio (Brazil) are studied usi... more The relationships between coastal upwelling and local winds at Cabo Frio (Brazil) are studied using SST and time series of surface wind for a 10-yr period (1971–80). The results show that the seasonal variations of SST and local winds are closely related. Sea-breeze circulation is intensified by the enhancement of the land–sea temperature gradient due to cold water upwelling near the coast; coastal upwelling, in turn, is associated with strong northeasterlies. This result confirms the conclusions of earlier modeling studies. Interannual variability is also apparent in the results. During the period from 1971 to 1980, the highest SST values occur during the years 1972–73 (strong El Niño event) and the lowest occur in 1977 (moderate El Niño event). This suggests some possible effects of atmospheric teleconnections on South Atlantic SSTs. However, a record longer than 10 yr is needed to confirm the connection with El Niño and La Niña events. Time–frequency analyses of the SST and zonal...
Journal of Applied Meteorology and Climatology, 2008
Large precipitation deficits observed during the 2001 austral summer over the southeast region of... more Large precipitation deficits observed during the 2001 austral summer over the southeast region of Brazil contributed to the worsening of the energy crisis that was occurring in the country, with unprecedented social and economic consequences. Reliable information on the beginning of the rainy season was essential for the Brazilian government to manage the energy crisis. The purpose of this study is to determine the rainy season in this region and to point out the risk of using outgoing longwave radiation (OLR) data to estimate the beginning of it. The results show that when OLR data are used the beginning and the end dates of the rainy season are wrongly anticipated and delayed, respectively. The present study aims to provide useful information for the management of the impact of adverse climate conditions such as the one in 2001 by basing the analysis on rainfall data instead of on OLR.
Resumo Neste trabalho objetivou-se verificar as possíveis relações de pontos amostrais da tempera... more Resumo Neste trabalho objetivou-se verificar as possíveis relações de pontos amostrais da temperatura da superfície do mar distribuídos espacialmente no Atlântico Tropical e o desenvolvimento de linhas de instabilidade atuantes na costa Norte e Nordeste do Brasil utilizando-se de técnicas de modelagem linear generalizada. Para isso, foram usados modelos lineares generalizados a partir da regressão linear de Poisson e da Binomial Negativa. Na análise das relações instituídas pela modelagem foi aplicada o teste de variância ANOVA com nível de significância de 0,05 de probabilidade para determinar que variáveis independentes foram mais significativas. Também foram analisados os resíduos gerados pelo ajuste dos modelos no intuito de identificar a distribuição que melhor se ajustasse aos dados. Toda análise estática foi realizada no software R. Entre os 132 pares de observações, a magnitude do coeficiente de correlação linear de Pearson (r) oscilou entre 0,06 (p < 0,04) entre (LI e TS...
The present study presents an analysis of the annual mean tropical heat balance and its associati... more The present study presents an analysis of the annual mean tropical heat balance and its association with the Walker circulation (WC) using NCEP/NCAR Reanalysis data. This study shows the relative importance of diabatic data to produce vertical motion in the tropics and for the WC region. It is shown that ascending motion in the WC's upward branch is determined by the joint effect of latent heating and radiative cooling processes while infrared radiation loss is associated to sink motions on the WC's descending branch. In ascending branches of the WC vertical velocity from reanalysis is overestimated when latent heat is taken into account to drive motions. Radiative cooling is indentified as the main physical process yielding sinking motion in the WC's downward branches. In upward branches of the WC, resulting diabatic processes (latent heat release) are balanced by adiabatic expansion (due rising motions). In descending branches of the WC, there is a near balance between...
The GEOS-1 data from multiyear reanalysis are using. An altered Walker Circulation is initiated b... more The GEOS-1 data from multiyear reanalysis are using. An altered Walker Circulation is initiated by the rising motion created over the warm ocean surface on the eastern Pacific. This occurred during the major El Niño event of 1982-1983. To compensate the rising motion, a sinking motion is generated over western Pacific completing the formation of the altered Walker Circulation. Thus, the initiation of the altered Walker Circulation is by the sea surface gradient as originally envisioned by Bjerknes.
The primitive equation barotropic unstable linear normal modes are computed using an eigenvalue a... more The primitive equation barotropic unstable linear normal modes are computed using an eigenvalue approach for daily latitudinal profiles of zonal flow in the upper-tropospheric layer of 100–350 hPa before and after formation of cyclonic vortices during January 1993 and November 2001 off the coast of northeast Brazil. The wave kinetic energy equation for u- and υ-motion is presented. Equations are derived to isolate the contribution of divergence and other dynamical processes in the movement and growth of unstable modes. Numerical accuracy and physical nature of unstable modes are tested. In a short span of 2–3 days, prior to formation of vortices, a progressive and a sharp intensification of the basic flow shear zone and its barotropic instability are seen with time. The horizontal structure, momentum transport, and zonal and meridional scales of the most unstable normalized wave are obtained and compared with the vortex extracted from the 200-hPa observed winds using a bandpass smoo...
Journal of Geophysical Research: Atmospheres, 2009
In an attempt to validate the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR)... more In an attempt to validate the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) over Brazil, TRMM PR estimates are compared with rain gauge station data from Agência Nacional de Energia Elétrica (ANEEL). The analysis is conducted on a seasonal basis and considers five geographic regions with different precipitation regimes. The results showed that TRMM PR seasonal rainfall is well correlated with ANEEL rainfall (correlation coefficients are significant at the 99% confidence level) over most of Brazil. The random and systematic errors of TRMM PR are sensitive to seasonal and regional differences. During December to February and March to May, TRMM PR rainfall is reliable over Brazil. In June to August (September to November) TRMM PR estimates are only reliable in the Amazonian and southern (Amazonian and southeastern) regions. In the other regions the relative RMS errors are larger than 50%, indicating that the random errors are high.
Journal of Geophysical Research: Atmospheres, 2004
Chou and Suarez's solar and infrared radiation models are incorporated in a statistical‐dynam... more Chou and Suarez's solar and infrared radiation models are incorporated in a statistical‐dynamical model with biosphere and atmosphere interaction in order to study the climatic effects due to biomass burning in Amazonian forest. In the control experiment the mean annual zonally averaged climate is well simulated by the model when compared with observed data. Biomass burning plays an important role on the earth's radiative balance and climate through the release of large amounts of greenhouse gases and aerosols in the atmosphere and the alteration of the land surface characteristics. For investigating the relative importance of these changes five experiments are performed: (1) degradation of the surface, (2) change in the smoke aerosols concentration, (3) change in the CO2 concentration, (4) change in CH4 concentration, and (5) all the changes together. The results show that biomass burning in Amazonian forest causes a reduction in the absorbed solar radiation and net radiati...
In recent years, there has been an increase in rainfall over northeast Brazil (Nordeste), while o... more 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 ove...
Journal of Applied Meteorology and Climatology, 2008
The relationships between coastal upwelling and local winds at Cabo Frio (Brazil) are studied usi... more The relationships between coastal upwelling and local winds at Cabo Frio (Brazil) are studied using SST and time series of surface wind for a 10-yr period (1971–80). The results show that the seasonal variations of SST and local winds are closely related. Sea-breeze circulation is intensified by the enhancement of the land–sea temperature gradient due to cold water upwelling near the coast; coastal upwelling, in turn, is associated with strong northeasterlies. This result confirms the conclusions of earlier modeling studies. Interannual variability is also apparent in the results. During the period from 1971 to 1980, the highest SST values occur during the years 1972–73 (strong El Niño event) and the lowest occur in 1977 (moderate El Niño event). This suggests some possible effects of atmospheric teleconnections on South Atlantic SSTs. However, a record longer than 10 yr is needed to confirm the connection with El Niño and La Niña events. Time–frequency analyses of the SST and zonal...
Journal of Applied Meteorology and Climatology, 2008
Large precipitation deficits observed during the 2001 austral summer over the southeast region of... more Large precipitation deficits observed during the 2001 austral summer over the southeast region of Brazil contributed to the worsening of the energy crisis that was occurring in the country, with unprecedented social and economic consequences. Reliable information on the beginning of the rainy season was essential for the Brazilian government to manage the energy crisis. The purpose of this study is to determine the rainy season in this region and to point out the risk of using outgoing longwave radiation (OLR) data to estimate the beginning of it. The results show that when OLR data are used the beginning and the end dates of the rainy season are wrongly anticipated and delayed, respectively. The present study aims to provide useful information for the management of the impact of adverse climate conditions such as the one in 2001 by basing the analysis on rainfall data instead of on OLR.
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