Enio Pereira de Souza

CAPE and Convective Events in the Southwest during the North American Monsoon

Abstract The relationship between atmospheric stability, measured as CAPE, and deep precipitating convection has been widely studied but is not definitive. In the maritime tropics, CAPE and precipitation are usually inversely correlated. In continental convection (i.e., midlatitude and tropical), no consistent relationship has been found. In this study of the semiarid Southwest, a moderate positive correlation exists, approaching 0.6. Correlations based on radiosonde data are found to be sensitive to the parcel level of origin. The strongest correlations are found by modifying the preconvective morning sounding with the maximum reported surface temperature, assuming well-mixed adiabatic layers to the level of free convection with pseudoadiabatic ascent. These results show that the upper bounds on parcel instability correlate best with precipitation. Furthermore, the CAPE–precipitation relationship is argued to depend on the convective regime being considered. The North American monsoon convective regime r...

Fostering collaboration to better manage water resources

Good water management is literally vital for the arid and semi‐arid regions of the planet. Yet good water management requires multidisciplinary expertise, since one must consider climatic, hydrological, economical and social aspects to make balanced decisions on water usage. We here present SegHidro, a Grid portal designed to foster scientific, technical and operational collaboration to improve water resources management. The portal targets researchers and decision makers, enabling them to execute and couple their computational models in a workflow. The portal provides a framework which allows seamless integration of the models, meaning that each phase of the flow may be executed by a different expert and that the resulting data are shared among other portal users. Due to the nature of these applications and the need to execute many prospective scenarios, their execution requires high computing power. However, we go beyond providing high‐performance computational Grid capabilities. We also enable people to complement each others expertise in understanding the trade‐offs in the water allocation decisions. The SegHidro portal is about sharing: human expertise, data and computing power. Copyright

Moist convection in Amazonia: implications for numerical modelling

A review of the literature on convection in Amazonia, with a focus on it parameterization in numerical models, is presented here. Studies based on observational data obtained during field campaigns are examined. The basic characteristics of deep convection in the Amazon, its temporal and geographical variability are discussed focusing of the difficulties convective parameterizations have in capturing this variability, particularly the diurnal cycle. The role of thermodynamic variables such as CAPE and CIN are argued to be critical in understanding the deficiencies in properly representing the diurnal cycle of convection. Other elements of the model physics relevant to convective parameterization, particularly those related to surface energy fluxes and development of the boundary layer are also considered. The interaction of shallow convection with radiation is presented. Superparameterization, as a tool for explicitly representing convection is reviewed as it is a possible future direction for the simulation of convective effects in numerical models. To conclude, various suggestions are made for future studies in order to better our understanding of convective processes and their parameterizations.

Evaluation of the Wind Power in the State of Paraíba Using the Mesoscale Atmospheric Model Brazilian Developments on the Regional Atmospheric Modelling System

This work aims to describe the wind power density in five sites in the State of Paraiba, as well as to access the ability of the mesoscale atmospheric model Brazilian developments on the regional atmospheric modeling system (BRAMS) in describing the intensity of wind in Sao Goncalo Monteiro, Patos, Campina Grande, and Joao Pessoa. Observational data are wind speed and direction at 10 m high, provided by the National Institute of Meteorology (INMET). We used the numerical model BRAMS in simulations for two different months. We ran the model for rainy months: March and April. It was concluded that the BRAMS model is able to satisfactorily reproduce the monthly cycle of the wind regime considered, as well as the main direction. However the model tends to underestimate the wind speed.

INFLUÊNCIA DOS JATOS EM MÉDIOS E BAIXOS NÍVEIS NOS PROCESSOS DE NUVEM: ESTUDO NUMÉRICO DE UMA LINHA DE INSTABILIDADE AMAZÔNICA

Squall lines (SL) are multicellular storms and it is well known that factors such as vertical wind shear can act to organize their convection. However there is few evidences of how medium and low level jets can alter the cloud processes, and as a consequence to affect the intensity, duration and propagation of such systems. This work attempts to clarify those jets role by discussing a simulated case of an Amazon SL based on an atmospheric wind profile over Belem - Brazil at 12:00 UTC of May 30, 2008. To accomplish the proposed goal a set of eight numeric experiments, with different wind profiles was performed using the BRAMS model. The results showed that the occurrence of a deep and intense jet may increase ventilation in clouds, resulting in more evaporation and drying, i.e. more mass entrainment. If the entrainment is higher, it can influence downdrafts, cold pools, convergence ahead of the system, and updrafts, so that more energy can be available to the system. Thus, under these conditions SL are more likely to propagate at higher speed with longer life time.

Estudo numérico da interação entre convecção rasa e radiação com ênfase no ciclo diurno do balanço de energia à superfície na Amazônia

The effect of shallow convection on the diurnal cycle of the surface energy budget is investigated. Focus is on the role of the cloud shading on the establishment of the surface convective forcing. A scheme for calculating the shallow cumulus cover was implemented in the BRAMS atmospheric model. Two sets of experiments were performed: in the first experiment, the model had no interaction between shallow convection and radiation, and in the second type of experiment shallow convection interacts with radiation. Results show that the consideration of the interaction between shallow cumulus and radiation leads to more realistic simulations. This is more pronounced around the local noon and early afternoon, when the shallow cumulus activity reaches a maximum. The surface fluxes and the cumulus cover were very sensitive to the variations in the radiative forcing. Even though, from a qualitative viewpoint, there is an improvement on the quality of the simulated fluxes, it became evident a model flaw in representing these fluxes during the first hours of the diurnal cycle.

Influence of boundary conditions on the Southern Hemisphere atmospheric circulation during the last glacial maximum

Based upon coupled climate simulations driven by present day and glacial boundary conditions, we demonstrate that although the ice sheet topography modifications during the glacial period are primarily placed in the Northern Hemisphere (NH), a climate simulation that employs the ICE-5G glacial topography delivers significantly enhanced climate anomalies in the Southern Hemisphere (SH) as well. These conditions, in association with climate anomalies produced by the modification of the atmospheric CO 2 concentration characteristic of the Last Glacial Maximum (LGM) interval, are shown to be the primary forcing of the SH climate during this epoch. Climate anomalies up to -6°C over the Antarctic region and -4°C over South America are predicted to occur in respect to present day conditions. Accompanying the SH cooling in the LGM simulation there exists a remarkable reduction in the specific humidity, which in turn enforces the overall Southern Hemisphere cooling due to the weaker greenhouse capacity of the dry atmosphere.

Assessing the Grell‐Freitas Convection Parameterization in the NASA GEOS Modeling System

Abstract We implemented and began to evaluate an alternative convection parameterization for the NASA Goddard Earth Observing System (GEOS) general circulation model (GCM). The proposed parameterization follows the mass flux approach with several closures, for equilibrium and nonequilibrium convection, and includes scale and aerosol aware functionalities. Recently, we extended the scheme to a trimodal spectral size distribution of allowed convective plumes to simulate the transition among shallow, congestus, and deep convection regimes. In addition, the inclusion of a new closure for nonequilibrium convection resulted in a substantial gain of realism in the model representation of the diurnal cycle of convection over the land. We demonstrated the scale‐dependence functionality with a cascade of global‐scale simulations from a nominal horizontal resolution of 50 km down to 6 km. The ability to realistically simulate the diurnal cycle of precipitation over various regions of the earth was verified against several remote sensing‐derived intradiurnal precipitation estimates. We extended the model performance evaluation for weather‐scale applications by bringing together some available operational short‐range weather forecast models and global atmospheric reanalyses. Our results demonstrate that the GEOS GCM with the alternative convective parameterization has good properties and competitive skill in comparison with state‐of‐the‐art observations and numerical simulations.

An analysis of rainfall based on entropy theory

The principle of maximum entropy can provide consistent basis for analyzing rainfall and for geophysical processes in general. The daily rainfall data was assessed using the Shannon entropy for a 10-years period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and isoentropy maps were then constructed for delineating annual and seasonal characteristics of rainfall. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy for two sample stations. The marginal entropy values of rainfall were higher for locations and periods with highest amount of rainfall. The results also showed that the marginal entropy decreased exponentially with increasing coefficient of variation. The Shannon theory produced spatial patterns which led to a better understanding of rainfall characteristics throughout the northeastern region of Brazil. Trend analysis indicated that most time series did not have any significant trends.

Influência da Temperatura da Superfície do Mar na Ocorrência de Linhas de Instabilidade na Costa Norte e Nordeste do Brasil

Abstract This work aimed to verify the possible relationships of sampling points of the sea surface temperature spatially distrib-uted in the tropical Atlantic and the development of squall lines in North northeast coast of Brazil using techniques ofgeneralizedlinearmodeling.Forthis,weusedgeneralizedlinearmodelsfromthelinearregressionPoissonandnegativebinomial, for analysis of the relationship established by modeling was applied ANOVA variance test with significancelevel of 0.05 probability to determine which independent variables were more significant in modeling. Also the wastegenerated by the adjustment of the models in order to identify the distribution that best fitted the data were analyzed. AllstaticanalysiswasperformedinR.softwareAmongthe132pairsofobservations,themagnitudeofthecorrelationcoef-ficient of Pearson (r) ranged from 0.06 (p < 0.04) between (LI and TSM5) and 0.88 (p < 0.0001) (TSM2 and TSM5), de-spite relations TSM and episodes of LI present no linear relationship or perfect positive linear relationship between theRevista Brasileira de Meteorologia,