Hugo A. Karam

Patterns of Local Circulation in the Itaipu Lake Area: Numerical Simulations of Lake Breeze

Abstract The lake-breeze circulation in the Itaipu region was investigated numerically using a nonhydrostatic version of the Topographic Vorticity Model. The area of study corresponds to a 100 km × 180 km rectangle, located on the Brazil–Paraguay border, with Itaipu Lake in its center. The characteristics of the lake breeze generated by the numerical experiments were consistent with the observations available in the area. The numerical experiments have shown that the land use effect is important in the spatial distribution of the lake-breeze circulation and that the topography contributes to modulating the breeze intensity, with the daytime valley–mountain circulation intensifying the lake breeze. However, the circulation pattern observed during daytime over the region is mainly due to the Itaipu Lake presence. The numerical results indicated that Itaipu Lake is able to generate and sustain a lake breeze, with 3.5 m s−1 of maximum intensity and 1500-m depth, that propagates inland at 5.1 km h−1 under typi...

Estimation of atmospheric turbidity and surface radiative parameters using broadband clear sky solar irradiance models in Rio de Janeiro-Brasil

The main goal of this paper is to estimate a set of optimal seasonal, daily, and hourly values of atmospheric turbidity and surface radiative parameters Ångström’s turbidity coefficient (β), Ångström’s wavelength exponent (α), aerosol single scattering albedo (ωo), forward scatterance (Fc) and average surface albedo (ρg), using the Brute Force multidimensional minimization method to minimize the difference between measured and simulated solar irradiance components, expressed as cost functions. In order to simulate the components of short-wave solar irradiance (direct, diffuse and global) for clear sky conditions, incidents on a horizontal surface in the Metropolitan Area of Rio de Janeiro (MARJ), Brazil (22° 51′ 27″ S, 43° 13′ 58″ W), we use two parameterized broadband solar irradiance models, called CPCR2 and Iqbal C, based on synoptic information. The meteorological variables such as precipitable water (uw) and ozone concentration (uo) required by the broadband solar models were obtained from moderate-resolution imaging spectroradiometer (MODIS) sensor on Terra and Aqua NASA platforms. For the implementation and validation processes, we use global and diffuse solar irradiance data measured by the radiometric platform of LabMiM, located in the north area of the MARJ. The data were measured between the years 2010 and 2012 at 1-min intervals. The performance of solar irradiance models using optimal parameters was evaluated with several quantitative statistical indicators and a subset of measured solar irradiance data. Some daily results for Ångström’s wavelength exponent α were compared with Ångström’s parameter (440–870 nm) values obtained by aerosol robotic network (AERONET) for 11 days, showing an acceptable level of agreement. Results for Ångström’s turbidity coefficient β, associated with the amount of aerosols in the atmosphere, show a seasonal pattern according with increased precipitation during summer months (December–February) in the MARJ.

BALANÇO DE RADIAÇÃO NO PANTANAL SUL MATO-GROSSENSE DURANTE A ESTAÇÃO SECA

Este trabalho apresenta a analise das componentes do balanco de radiacao a superficie sobre o Pantanal Sul Mato-grossense, a partir de medidas experimentais coletadas durante a estacao seca, em setembro de 1999. Neste periodo, as componentes do balanco de radiacao mostraram um ciclo diurno bem definido, associado a densidade de fluxo radiativo de onda curta de 850 Wm-2 ao meio dia. O albedo medio apresentou um comportamento quase especular, com valor minimo de 0,16±0,02 para ângulos zenitais pequenos. Os valores de emissividade da superficie pantaneira, corrigida para temperatura radiativa de um corpo cinza, variaram entre 0,94 e 0,96. A partir das medidas diretas das densidades dos fluxos radiativos de ondas curtas e longas atmosfericas determinou-se os parâmetros otimos empregados nas formulacoes propostas por Monteith e Unsworth (2008), Swinbank (1963) e Brutsaert (1975).

Surface energy budget over the Pantanal wetland during the dry season

In this work, the diurnal cycle of components of the surfaceenergy budget (SEB) are computed to the Brazilian Pantanal wetlandduring the dry season (September 1999). The analyzed data were collectedduring the Interdisciplinary Pantanal Experiment (IPE-2) realized by INPEand UFMS. A very defined diurnal cycle is observed, suggesting that theavailable energy at surface is mainly employed in the evapotranspirationeven during the dry season.

Pollutant transport in a Convective Boundary Layer with LES

This work describes the statistical properties of a Convective Boundary Layer (CBL) and the associated turbulent transport of a passive and inert pollutant, continuously emitted in the atmosphere by an area-source on the surface. The CBL flow and properties are simulating with a Large Eddy Simulation (LES) model. To assure the development of a quasi-steady turbulent regime, both the stability parameter and the Turbulent Kinetic Energy (TKE) criteria were applied to LES with similar results. The vertical structure of the pollutant concentration, potential temperature associated with vertical turbulent fluxes and variances are consistent with the mixed layer similarity predictions. Both the pollutant concentration and the vertical wind skewness fluctuations are associated with the updrafts and downdrafts distributions, emphasizing the importance of the entrainment in the cleaning of the CBL.

Modelagem da Distribuição da Saturação de Água do Solo em Terrenos Complexos Baseada na Teoria de Similaridade: Proposição de Abordagem

This work proposes a Lagrangian modeling of the distribution of water saturation of the soil based on the theory of topographical similarity of complex terrain, highlighting hydrometeorological aspects. The distribution of the precipitated water on the ground is obtained as a consequence of the conservation of mass flow, considered the hydrological similarity along drainage tracks under different topographic slope, catchment and infiltration. The distributor model allows advances in computational optimization of both the saturation deficit and water table. The applicability is exemplified with a surface of a gentle hill and also applied to discuss hydrology of the plain found northward of the Metropolitan Area of Rio de Janeiro. It is shown that a spatial resolution smaller than 90 m should be used to consider the details of the problem. The results highlighted the role of complex topography, including the hydrology of floodplains and anthropogenic modifications of the surface (in the form of urban runoff channels and urbanization) for a more complete understanding of the hydrological distribution of the Metropolitan Area of Rio de Janeiro, RJ, Brazil.

Balanço de Radiação em Superfície na Região Metropolitana do rio de janeiro

The radiation budget at the surface of the Metropolitan Region of Rio de Janeiro was obtained from measurements collected on the radiometric platform located...

RADIATIVE DISTRIBUTION OVER COMPLEX TOPOGRAPHY

In this work, direct, diffuse and global radiation over the complete solar spectrum incident on the earth’s surface was calculated using three parameterizati...

Tropical urban heat island simulation using the Topographic Vorticity Mesoscale (TVM) model

In this work, a numerical simulation of the Urban Heat Island(UHI) of Rio de Janeiro City is set up using the Topographic VorticityMesoscale (TVM) model. At noon, the resulting surface potentialtemperature presents a strong UHI core across the Fluminense Lowlands(Baixada Fluminense), whereas the specific humidity reaches its lowestvalues.

IRRADIÂNCIA SOLAR EM CÂNIONS URBANOS

Neste trabalho apresenta-se a metodologia de derivacao das equacoesda media azimutal da irradiância solar incidente sobre superficies quecompoem os cânions urbanos (telhados, paredes e vias), exemplificada nestetrabalho para a irradiância sobre as vias. As equacoes foram implementadasem um modelo de superficie urbana derivado do modelo Town EnergyBudget (TEB). Os resultados obtidos em um teste de sensibilidade domodelo, em relacao aos fatores (1) variacao do albedo e (2) razao de aspectodos cânions urbanos, indicam a importância relativa destes fatores para aintensidade e evolucao do fluxo de calor sensivel da cidade e da temperaturado ar dentro dos cânions.