Luciano Ponzi Pezzi

Global Climatological Features in a Simulation Using the CPTEC–COLA AGCM

Abstract The Center for Weather Forecasting and Climate Studies–Center for Ocean–Land–Atmosphere Studies (CPTEC–COLA) atmospheric general circulation model (AGCM) is integrated with nine initial conditions for 10 yr to obtain the model climate in an ensemble mode. The global climatological characteristics simulated by the model are compared with observational data, and emphasis is given to the Southern Hemisphere and South America. Evaluation of the models performance is presented by showing systematic errors of several variables, and anomaly correlation and reproducibility are applied to precipitation. The model is able to simulate the main features of the global climate, and the results are consistent with analyses of other AGCMs. The seasonal cycle is reproduced well in all analyzed variables, and systematic errors occur at the same regions in different seasons. The Southern Hemisphere convergence zones are simulated reasonably well, although the model overestimates precipitation in the southern porti...

On the influences of the El Niño, La Niña and Atlantic dipole pattern on the Amazonian rainfall during 1960-1998.

The influence of the large-scale climatic variability dominant modes in the Pacific and in the Atlantic on Amazonian rainfall is investigated. The composite technique of the Amazon precipitation anomalies is used in this work. The basis years for these composites arc those in the period 1960-1998 with occurrences of extremes in the Southern Oscillation (El Nino or La Nina) and the north/south warm (or cold) sea surface temperature (SST) anomalies dipole pattern in the tropical Atlantic. Warm (cold) dipole means positive (negative) anomalies in the tropical North Atlantic and negative (positive) anomalies in the tropical South Atlantic. Austral summer and autumn composites for extremes in the Southern Oscillation (El Nino or La Nina) and independently for north/south dipole pattern (warm or cold) of the SST anomalies in the tropical Atlantic present values (magnitude and sign) consistent with those found in previous works on the relationship between Amazon rainfall variations and the SST anomalies in the tropical Pacific and Atlantic. However, austral summer and autumn composites for the years with simultaneous occurrences of El Nino and warm north/south dipole of the SST anomalies in the tropical Atlantic show negative precipitation anomalies extending eastward over the center-eastern Amazon. This result indicates the important role played by the tropical Atlantic in the Amazon anomalous rainfall distribution.

Connectivity of Marine Protected Areas and Its Relation with Total Kinetic Energy

The East Continental Shelf (ECS) of Brazil is a hotspot of endemism and biodiversity of reef biota in the South Atlantic, hosting a number of Marine Protected Areas (MPAs). Connectivity of MPAs through larval dispersal influences recruitment, population dynamics, genetic structure and biogeography in coral reef ecosystems. Connectivity of protected reef ecosystem in the ECS was investigated with a hydrodynamic model (ROMS) forcing an Individual Based Model (IBM—Ichthyop), and used groupers (genus Mycteroperca) as functional group. The hydrodynamic output from ROMS was compared with satellite data and showed good agreement with observed surface fields. Eggs were released, in IBM experiments, from April to September along six years (2002–2007) in five MPAs along the ECS. Intrannual variability in recruitment and self-recruitment of grouper larvae was observed, as well as a negative correlation of these population parameters with total Kinetic Energy (KE) used as a metric of the physical environment. Higher KE leads to increased offshore advection of larvae, reduced total recruitment and connectivity of MPAs. Our results indicate high and uni-directional connectivity between MPAs from north to south influenced by the Brazil Current flowing in the same direction. Results also showed that some MPAs act predominantly as “sink” while others are mainly “source” areas.

Atmospheric boundary layer adjustment to the synoptic cycle at the Brazil‐Malvinas Confluence, South Atlantic Ocean

[1] This study analyzes and discusses atmospheric boundary layer vertical profiles of potential temperature, specific humidity, and wind speed at each of the sides of the Brazil-Malvinas Confluence in the southwestern Atlantic Ocean. Such confluence is characterized by the meeting of water masses with very different characteristics: the southern waters of the Malvinas current can be several degrees colder and appreciably less salty than the northern Brazil current waters. At the same time, a synoptic cycle can be identified at the region, marked by the successive passages of frontal systems and extratropical cyclones. The different phases of the synoptic cycle lead to different thermal advections at the confluence, causing respective different patterns of atmospheric boundary layer adjustment to the surface heterogeneity induced by the confluence. In the present study, this adjustment along the synoptic cycle is analyzed using data from five experiments performed across the confluence from 2003 to 2008. In each of the campaigns a number of soundings were launched from a ship at both sides of the confluence. A climatological analysis with respect to the closest frontal passage is presented, and it suggests that the observations collected at each of the years analyzed are referent to a different day of the synoptic cycle. The average profiles at each side of the confluence are in agreement with previous modeling studies of warm and cold thermal advection patterns over an oceanic front. Furthermore, our study shows that peculiar transitional characteristics are also observed between the conditions of well-established warm and cold advection. At many phases of the synoptic cycle a strongly stratified boundary layer occurs at one or both sides of the confluence. Some of the observed characteristics, such as a large moisture accumulation near the surface, suggest that existing sensible and latent heat fluxes parameterizations fail under very strong stratifications, and the consequences of this deficiency are analyzed.

A sensitivity study using two different convection schemes over south america

The sensitivity of cumulus convection parameterizations is investigated using the CPTEC/COLA Atmospheric General Circulation Model (AGCM) with T62L28 resolution. This model has been used at CPTEC/INPE since 1995 with the Kuo convective scheme for weather and seasonal climate forecasts. In this study, two sets of integrations are performed using climatological Sea Surface Temperature (SST) of the Southern Hemisphere summer season (December, January and February) as bottom boundary conditions. Five integrations with different initial conditions are applied for each ensemble. The study was divided in two groups, one using the adjusted Relaxed Arakawa-Schubert convection scheme considering modifications in the convection physics (ARAS) and the other one using the Kuo convection scheme (KUO). The atmospheric circulation and precipitation model results are compared with NCEP/NCAR reanalysis data and CMAP precipitation data. The results are analyzed mainly over South America and also for the Southern Hemisphere to verify the model response compared to observed data when different convection scheme is applied. The adjusted scheme for RAS suggested in this study, reduced errors in several areas of South America, when comparing with the previous version. Over most of South America areas KUO gives smaller errors than ARAS. Over tropical Pacific Ocean, Southeastern Brazil and south of northeast Brazil, ARAS scheme shows better results.

Air‐sea interaction at the Southern Brazilian Continental Shelf: In situ observations

The influence of the cross-shelf oceanographic front occurring between the Brazil Current (BC) and the Brazilian Coastal Current (BCC) on the local Marine Atmospheric Boundary Layer (MABL) is investigated here. This front is typical of wintertime in the Southern Brazilian Continental Shelf (SBCS) and this is the first time that its effects are investigated over the above MABL. Here we analyze variability, vertical structure, and stability of MABL as well as heat fluxes at air-sea interface, across five oceanographic transects in the SBCS made during a winter 2012 cruise. Local thermal gradients associated with mixing between distinct water masses, play an essential role on MABL modulation and stability. Although weaker when compared with other frontal regions, the cross-shelf thermal gradients reproduce exactly what is expected for open ocean regions: Stronger (weaker) winds, lower (higher) sea level pressure, and a more unstable (stable) MABL are found over the warm (cold) side of the oceanographic front between the BC (warm) and coastal (cold) waters. Our findings strongly support the coexistence of both known MABL modulation mechanisms: the static and hydrostatic MABL stability. This is the first time that these modulation mechanisms are documented for this region. Turbulent fluxes were found to be markedly dependent on the cross-shelf SST gradients resulting in differences of up to 100 W.m−2 especially in the southernmost region where the gradients were more intense.

Variabilidade das anomalias de temperatura da superfície do mar no oceano atlântico sudoeste e sua relação com o fenomeno El Niño-Oscilação Sul

This work presents a study on the variability of satellite-derived sea surface temperature anomaly (SSTA) fields in regions under the influence of different oceanographic and/or biophysical patterns in the South-western Atlantic Ocean (SWA). In order to accomplish that, time series of SSTA from 1985 to 2006 were investigated over nine sub-areas in the SWA, divided into the subtropical, intermediate and sub Antarctic domains. Spectral analysis applied to the SSTA time series reveled cycles in the interannual period between 1.6 and 3.7 years. Cross correlation analysis was used aiming to establish the relation between the cycles present in the SSTA and the El Nino - Southern Oscillation (ENSO) events, represented here by the Multivariate ENSO Index (MEI). The results show a statistically significant, lagged in time, correlation between the ENSO and thermal anomalies in the SWA, however there is no direct association between the warm (cold) El Nino (La Nina) episodes with positive (negative) SSTAs. Among all distinct study areas, the maximum correlation occurs in the Brazil-Malvinas Confluence region (-0,78), with a time lag of 9 months after the La Nina of May 1988 to May 1989.

Satellite observations of the Pacific tropical instability wave characteristics and their interannual variability

Descriptions of tropical instability wave (TIW) characteristics in the tropical Pacific Ocean as a function of the large‐scale climate conditions and interannual variability, such as the El Niño southern oscillation, are made based on satellite data. As others have found, the TIW ocean–atmosphere coupling is caused by atmospheric boundary layer instability and mixing. Our observational investigation extends some of these previous findings and suggests that this mechanism of coupled variability of the wind and sea surface temperature may occur not only during La Niña years, when TIWs are more active, but whenever the TIWs are active. The sea surface temperature and height anomaly covariability phase shift might occur also independent of the TIW season activity. There is evidence that TIW activity increases when under strengthened wind stress conditions either in La Niña years or, by analogy, when oceanic numerical simulations are carried out with stronger wind stress. Observational results show larger TIW wavelengths and shorter periods when the ocean is under the action of strengthened wind stress. On this observational study this occurs when La Niña conditions prevail on the equatorial Pacific.

Regional modeling of the water masses and circulation annual variability at the Southern Brazilian Continental Shelf

The Southern Brazilian Continental Shelf (SBCS) is one of the more productive areas for fisheries in Brazilian waters. The water masses and the dynamical processes of the region present a very seasonal behavior that imprint strong effects in the ecosystem and the weather of the area and its vicinity. This paper makes use of the Regional Ocean Modeling System (ROMS) for studying the water mass distribution and circulation variability in the SBCS during the year of 2012. Model outputs were compared to in situ, historical observations and to satellite data. The model was able to reproduce the main thermohaline characteristics of the waters dominating the SBCS and the adjacent region. The mixing between the Subantarctic Shelf Water and the Subtropical Shelf Water, known as the Subtropical Shelf Front (STSF), presented a clear seasonal change in volume. As a consequence of the mixing and of the seasonal oscillation of the STSF position, the stability of the water column inside the SBCS also changes seasonally. Current velocities and associated transports estimated for the Brazil Current (BC) and for the Brazilian Coastal Current (BCC) agree with previous measurements and estimates, stressing the fact that the opposite flow of the BCC occurring during winter in the study region is about 2 orders of magnitude smaller than that of the BC. Seasonal maps of simulated Mean Kinetic Energy and Eddy Kinetic Energy demonstrate the known behavior of the BC and stressed the importance of the mean coastal flow off Argentina throughout the year.

Efeitos do aumento da tensão de cisalhamento do vento no clima do Hemisfério Sul obtido do modelo acoplado SPEEDO

Studies have suggested intensification and shift of the wind stress maximum towards the south in the Southern Ocean due to wind intensification in extratropical latitudes in the Southern Hemisphere. Considering these evidences, the objective of this study is to investigate the impacts in atmospheric and oceanic circulation due to the increasing wind stress by 50% in the equatorial region and in the extratropical Southern Hemisphere region. Specifically, changes in the Atlantic Dipole and Antarctic Oscillation are analyzed. For this purpose, a coupled climate model of intermediate complexity (SPEEDO) is employed. The results show that the wind stress intensification in the equatorial region causes a decrease in sea surface temperature in the tropical region, due to increased upwelling. This causes changes in Atlantic Dipole and enhanced precipitation over Brazilian northeast. Moreover, the wind stress intensification in the extratropical Southern Hemisphere region induces an increase in sea surface temperature and air temperature in high latitudes of the Southern Hemisphere, and a reduction in the Antarctic sea ice thickness, favoring a weakening of positive Antarctic Oscillation phase.