This study presents the first analysis of the energetics associated with a hybrid cyclone's transition in the Southern Hemisphere, Hurricane Catarina (March 2004). Catarina has earned a place in history as the first documented South Atlantic hurricane, but its unusual tropical transition is still poorly understood. Here we show that Catarina's transition was preceded by marked environmental changes in the Lorenz energy cycle, with an abrupt shift from a baroclinic to a predominantly barotropic state. Such changes help to explain the unusual vortex's growth until its transition was completed. Although the vortex's energy flux is not explicitly calculated, a likely mechanism linking the environmental energetics with Catarina is the extraction of eddy kinetic energy from horizontal momentum and heat transfers within the through component of the blocking. The results advance the understanding of this rare event and suggest that the technique has a great potential to study transitioning systems in general.

This study presents the Lorenz energetics of an exceptional baroclinic storm propagating to Nome (Alaska) in October 1992, where it caused severe flooding. The storm track was greatly influenced by the interaction with a blocking high a week before the cyclone was formed. The energetics gives new insights into this dramatic storm, suggesting that the large-scale environment was responsible for its long trajectory and intensification. The blocking high also provided the dynamic steering that facilitated the wave propagation and baroclinic growth. Our results show that the environmental energy transfers can be used as an informative metric for severe storms.

In this paper we study the Lorenz energy cycle of the Walker circulation associated with ENSO. The robust formulation of the energetics allows drawing a clear picture of the global energy and conversion terms associated with the three dimensional domains appropriate to qualify the large scale transfers that influence, and are influenced by, the anomalies during ENSO. A clear picture has emerged in that El Niño and La Niña years have approximately opposite anomalous energy fluxes, regardless of a non-linear response identified in the potential energy fields (zonal and eddy). During El Niños the tropical atmosphere is characterized by an increase of zonal available potential energy, decrease of eddy available potential energy and decrease of kinetic energy fields. This results in weaker upper level jets and a slowingdown of the overall Walker cell. During La Niñas reversed conditions are triggered, with an acceleration of the Walker cell as observed from the positive anomalous kinetic energy. The potential energy in the Walker circulation domain during the cold phase is also reduced. An equally opposite behavior is also experienced by the energy conversion terms according to the ENSO phase. The behavior of anomalous energetics seems to be triggered at about the same time when ENSO starts to manifest for both the positive and negative phases, suggesting a coupled mechanism in which atmospheric and oceanic anomalies interact and feed back onto each other.

So far, only a few studies have evaluated the impact of greenhouse gases emissions on the global and limited area energetics. Furthermore, all of them have concentrated on the increasing of CO2. As new climate projections are now available from a number of climate models under the MPI-ESR-MR experiment, the present study analyses the global and hemispherical energetics under the increase of greenhouse gas forcings that follow Representative Concentration Pathways (RCP26, RCP45, and RCP85). The results have shown a reduction in theLECintensity as the concentration of greenhouse gases increases, with the RCP85 scenario generating the strongest decrease. For both global and hemispherical domains, zonal kinetic energy is the only energy reservoir which increases in a warmer environment, whereas the conversion between eddy kinetic energy and zonal kinetic energy (CK) is the only energy flux also experiencing an increase. A quantitative analysis of the inner processes involved in the conversion terms shows important changes in the horizontal and vertical eddy-transport of momentum and sensible heat. In the case ofCKboth vertical and horizontal eddy-transports of momentum play an important role in the increase of zonal kinetic energy for the global domain.

New aspects of the genesis and partial tropical transition of a rare hybrid subtropical cyclone on the eastern Australian coast are presented. The 'Duck' (March 2001) attracted more recent attention due to its underlying genesis mechanisms being remarkably similar to the first South Atlantic hurricane (March 2004). Here we put this cyclone in climate perspective, showing that it belongs to a class within the 1% lowest frequency percentile in the Southern Hemisphere as a function of its thermal evolution. A large scale analysis reveals a combined influence from an existing tropical cyclone and a persistent mid-latitude block. A Lagrangian tracer showed that the upper level air parcels arriving at the cyclone's center had been modified by the blocking.Lorenz energetics is used to identify connections with both tropical and extratropical processes, and reveal how these create the large scale environment conducive to the development of the vortex. The results reveal that the blocking exerted the most important influence, with a strong peak in barotropic generation of kinetic energy over a large area traversed by the air parcels just before genesis. A secondary peak also coincided with the first time the cyclone developed an upper level warm core, but with insufficient amplitude to allow for a full tropical transition. The applications of this technique are numerous and promising, particularly on the use of global climate models to infer changes in environmental parameters associated with severe storms.

Large-scale aspects of the heat and moisture budgets of the Walker circulation (WC) are analysed for the austral summer during the period from 1970 to 2000. Since several earlier studies discuss theoretical and modelling aspects of the heat and moisture budgets of the WC, our main objective is to make an observational analysis of such budgets, including a composite of five strong El Niño-southern oscillation events covered by the period of study. For this purpose, data from the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis and Global Precipitation Climatology Project are used. Analysis of the moisture budget in the near-equatorial regions of the Southern Hemisphere showed that the three continents (South America, Africa and maritime continents) are characterized by high precipitation and that low precipitation occurs in the intermediate oceans. Regions of high (low) precipitation are associated with the vertically integrated moisture flux convergence (divergence). Analysis of the heat budget for the WC showed, as deduced in some theoretical studies, that the diabatic heating (cooling) is balanced by adiabatic cooling (heating) over regions with a convective (non-convective) regime. The loss of radiation to space over non-convective areas is balanced by adiabatic heating due to the sinking motion. There is heating over the continents, probably associated with the ascending motion in the WC, and cooling over the intermediate oceans, which is related to the loss of radiation in the descending branch of the WC. Analysis of the moisture balance for the entire period and a composite of El Niño periods shows that the WC is associated with precipitation variations in the near-equatorial regions of the continents. The low-level changes in the WC are associated with the moisture flux changes and have the main role in the maintenance of the rainfall anomalies during the El Niño events.

We used climate models to assess the effects of 2 distinct anthropogenic forcings on the water budget in the Amazon basin: (1) increasing global greenhouse gases under the RCP8.5 scenario, and (2) land cover change caused by deforestation. The Eta regional climate model, driven by the Brazilian Earth System Model version 2.5 (BESM 2.5), was used to simulate the climate response under the RCP8.5 scenario and due to deforestation throughout the 21st century. Changes in energy and water budgets led to an increase in temperature that reached 5°C throughout the basin. In the RCP8.5 scenario, moisture convergence, precipitation and evapotranspiration all decreased. In this scenario, the positive feedback mechanism was predominant, as the reductions in evapotranspiration and moisture convergence acted in the same direction to reduce precipitation. In the future deforestation scenarios, reductions in precipitation were even stronger. In this case, the negative feedback mechanism predominated, in which the relative reduction in evapotranspiration was greater than the reduction in precipitation, leading to an increase in moisture convergence over the region. Changes in temperature and the water cycle were intensified in the future deforestation scenarios. These results show that the 2 anthropogenic factors can change the water budget and cause an imbalance in the climate-biome system in the Amazon basin, highlighting the need for public conservation policies to halt the increase in environmental degradation in the Amazon basin and to reduce greenhouse gases emissions due the burning of fossil fuels.

Although much effort has been made to characterize and understand extreme rainfall's causes and effects, little is known about their frequency and intensity. Moreover, knowledge about their contribution to the total rainfall climatology is still minimal, especially over the Amazon where rainfall data are very scarce. In this paper we propose to classify extreme rainfall events by type and analyze their frequency and intensity over South America with a focus on the Amazon basin. Gridded daily data from the MERGE/CPTEC product over a period of 15 years (1998-2013) was used. An adaptation of Rx5d climate index was applied to select different kinds of extreme rainfall for the purpose of quantifying their frequency and intensity as well as their contribution to the accumulated rainfall climatology. According to the results, all kinds of extreme rainfall events can be observed over the studied area. However, the quantity of rainfall produced by each type is different, and consequently their percent contributions to the total accumulated rainfall climatology also differ. For example: in the Amazon region EET-I is responsible for 15% -40% of the total accumulated rainfall. Moreover, in the Brazilian northeast there are regions where EET-I exceeds 40% of the total rainfall. In northeast Brazil EET-II is responsible up to 30% of the total accumulated rainfall. EET-III is responsible for 5% -15% in the Amazon basin, 25% -45% in northeast Brazil and 10% -45% over Roraima State. Area-mean time variation shows that the quantity of rainfall extremes over the