Amauri Pereira de Oliveira

Correlation models of diffuse solar-radiation applied to the city of São Paulo, Brazil

Measurements of global and diffuse solar-radiation, at the Earths surface, carried out from May 1994 to June 1999 in Sao Paulo City, Brazil, were used to develop correlation models to estimate hourly, daily and monthly values of diffuse solar-radiation on horizontal surfaces. The polynomials derived by linear regression fitting were able to model satisfactorily the daily and monthly values of diffuse radiation. The comparison with models derived for other places demonstrates some differences related mainly to altitude effects.

Annual and Diurnal Wind Patterns in the City of São Paulo

The major topographic, mesoscale, and urban influences on the wind patterns of the City of São Paulo are characterized using one year of surface wind velocity data observed at 11 surface stations within its urban limits. The data was used to study the diurnal and annual variations of wind velocity and horizontal wind divergence within the city. Results showed that the circulation over the investigated area is dominated by three major factors: sea breeze; mountain-valley circulations; and urban effects, such as roughness, building-barrier, and urban heat island. The sea breeze was found to be the dominant feature of the monthly-averaged diurnal variation of São Paulo surface winds during the eight warmest months of the year. The sea breeze front induces a velocity minimum at the time of its passage and a post-frontal afternoon velocity maximum. Mountain-valley thermal effects on the flow can be seen in the temporal divergence/convergence patterns. These thermal effects tend to be more important during colder months, at night, and when the wind velocities are low. Nighttime downslope convergent flows are present over the city during winter and spring and daytime upslope divergent flows are present over the city during summer months.

CHARACTERIZATION OF COHERENT STRUCTURES IN THE ATMOSPHERIC SURFACE LAYER

The ramplike coherent structures, observed in the temporal series of temperature and humidity in the atmospheric surface layer, are analyzed using the intermittency function and the wavelet transforms, with Haar, D4 and Mexican Hat functions as mother wavelets, in order to find the most efficient conditional sampling technique. It was found that the intermittency function and the wavelet transform, using Mexican Hat as mother wavelet, are the only ones that sample structures that fulfill the ramplike coherent structures definition of a slow rise followed by a sudden drop in the temporal series. The conditionally averaged structures detected by both techniques were similar for temperature, humidity, and vertical velocity at heights of 3, 5, and 9.4 m. Significant discrepancies were found among the conditional averaged structures detected by both techniques for zonal and meridional components of the wind at 11.5 m. Considering both techniques, it was observed that the averagedcoherent-structure duration ranged from 23.7 ± 0.5 s to 37.8 ± 3.0 s. Furthermore, the averaged number of events per 20-minute period ranged from 20.0 ± 1.0 to 28.5 ± 1.1, and the averaged intermittency factor from 45.0 ± 0.4% to 59.1 ± 1.3%. It was also observed that the averaged duration of the ramplike coherent structures increases with height, while their intensity, number, and intermittency factor decrease. Despite the good matching obtained for temperature and humidity, the coherent-structure properties did not show the expected variation with wind speed, stability parameter, and friction velocity. The Kolmogorov–Smirnov test indicated that the intermittent function and the wavelet transform did not detect coherent structures belonging to the same population.

Daylight photodynamic therapy for actinic keratoses in São Paulo, Brazil.

To the Editor, There have been several studies about daylight photodynamic therapy (D-PDT) for actinic keratoses (AKs); however, all of them have been performed in Europe. Until now, there have been no studies about D-PDT on other continents. The aim of this study is to present the initial results of a study of the efficacy and safety of D-PDT for AKs in São Paulo, Brazil, and to validate this method in that city.

Radiation balance at the surface in the city of São Paulo, Brazil: diurnal and seasonal variations

The main goal of this work is to describe the diurnal and seasonal variations of the radiation balance components at the surface in the city of São Paulo based on observations carried out during 2004. Monthly average hourly values indicate that the amplitudes of the diurnal cycles of net radiation (Q*), downwelling and upwelling shortwave radiation (SWDW, SWUP), and longwave radiations (LWDW, LWUP) in February were, respectively, 37%, 14%, 19%, 11%, and 5% larger than they were in August. The monthly average daily values indicate a variation of 60% for Q*, with a minimum in June and a maximum in December; 45% for SWDW, with a minimum in May and a maximum in September; 50% for SWUP, with a minimum in June and a maximum in September; 13% for LWDW, with a minimum in July and a maximum in January; and 9% for LWUP, with a minimum in July and a maximum in February. It was verified that the atmospheric broadband transmissivity varied from 0.36 to 0.57; the effective albedo of the surface varied from 0.08 to 0.10; and the atmospheric effective emissivity varied from 0.79 to 0.92. The surface effective emissivity remained approximately constant and equal to 0.96. The albedo and surface effective emissivity for São Paulo agreed with those reported for urban areas in Europe and North America cities. This indicates that material and geometric effects on albedo and surface emissivity in São Paulo are similar to ones observed in typical middle latitudes cities. On the other hand, it was found that São Paulo city induces an urban heat island with daytime maximum intensity varying from 2.6°C in July (16:00 LT) to 5.5°C in September (15:00 LT). The analysis of the radiometric properties carried out here indicate that this daytime maximum is a primary response to the seasonal variation of daily values of net solar radiation at the surface.

The Amazon river breeze and the local boundary layer: II. Linear analysis and modelling

Observed boundary-layer circulations close to the confluence of the Negro and Solimões rivers near Manaus in the Brazilian equatorial Amazon forest were presented in Part I. These are shown through linear analysis and second-order turbulence modelling to be aspects of a river breeze superimposed on the basic flow. Linear analysis is presented to estimate the spatial structure and intensity of a breeze induced by a river with width and thermal contrast similar to that observed in the central Amazon. It is found that observed thermal contrasts are sufficient to produce a river breeze that can be perceived more than 20 km inland daily. A one-dimensional second-order closure model is used to show that observed nocturnal low-level wind maxima and diurnal surface wind rotation are aspects of a river breeze interacting with the seasonally-varying mean flow. At night, partial decoupling of the surface from the lower atmosphere allows the land breeze to be expressed as a low-level wind maximum. During the day, convective mixing communicates upper level winds to the surface during rapid morning boundary-layer growth. Rotation of the surface wind follows as the river breeze circulation is then superimposed.

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...

A New Shadow-Ring Device for Measuring Diffuse Solar Radiation at the Surface

A new shadow-ring device for measuring diffuse solar radiation at the surface is presented. In this device the seasonal variation of shadow is followed by moving the detector horizontally. This unique characteristic facilitates its application for long and continuous periods of time. The blocking effect caused by the ring and other related geometric properties are formulated considering the diffuse solar radiation isotropic. The correction factor, shadow size, and ring-detector distance are derived as a function of radius and width of the ring, sun position, and local latitude. The largest blocking occurs during summer, when the ring-detector distance and the shadow width are the smallest, and it is compensated by a smaller blocking effect in the winter period. The performance of the new device is verified comparing daily values of diffuse solar radiation measured simultaneously with a similar device from Kipp & Zonen, Inc. The results show a very good agreement (within 2.5%) between both devices. The new device was also able to reproduce the radiometric properties of the local atmosphere based on 3-yrlong measurements of direct solar radiation using a pyrheliometer. The new device can be applied to estimate daily values of diffuse solar radiation at the surface in the range of 30 8N‐308S with results comparable to other similar apparatuses.

An Analytical Method to Evaluate Mixing Length Scales for the Planetary Boundary Layer

Abstract An analytical method to evaluate the Lagrangian length scales for a turbulent planetary boundary layer (PBL) under stable and convective conditions is described in this paper. The method is based on the Taylors diffusion theory. Agreement with the mixing lengths found in the literature indicates that the hypothesis of using Lagrangian length scale as a surrogate for mixing length scale in the turbulent PBL is valid.

An Application of Neural Network Technique to Correct the Dome Temperature Effects on Pyrgeometer Measurements

Univ Sao Paulo, IAG, Dept Ciencias Atmosfericas, Grp Micrometeorol, BR-05508900 Sao Paulo, Brazil