Equatorial Atlantic Ocean dynamics in a coupled ocean–atmosphere model simulation

The ocean temperatures and zonal currents at the equatorial Atlantic simulated by an improved version of the Brazilian earth system model (BESM), with changes in the cloud cover scheme and optical properties of the atmospheric component, are analyzed and compared to those obtained from a previous version of BESM and also from other seven selected CMIP5 models. It is shown that this updated version of BESM, despite some persistent biases, more accurately represents the surface temperature variation at the Equator and the equatorial thermocline east–west slope. These improvements are associated to a more realistic seasonal cycle achieved for the Atlantic equatorial undercurrent, as well as sea surface temperatures and zonal wind stress. The better simulation of the equatorial undercurrent is, in its turn, credited to a more realistic representation of the surface wind position and strength at the tropical Atlantic by the coupled model. With many of the systematic errors noticed in the previous version of the model alleviated, this version of BESM can be considered as a useful tool for modelers involved in Atlantic variability studies

Convective cloud cover in tropical region of South America and around ocean using fulldisk GOES images

This study presents the convective clouds cover characteristics in Intertropical Convergence Zone (ITCZ) over the longitudes 150W - 0E and same relationship with the continental convection using GOES images during 2003-2004. A simple threshold method was adopted in the diary minimun infrared brightness temperature dataset to derive the convective clouds frequency of occurence in 20 km spatial resolution. The oceans convective couds distribution was related with the continetal activity. The range of latitudinal convection occurence over Atlantic is graeter than Pacific, diferences in Atlantic and continent convection fase influence in North litoral and same other regions.Pages: 1237-124

Estimativa de radiacao solar por satelite: desempenho do modelo operacional GL 1.2

O modelo GL1 do CPTEC avalia irradiância solar média diária para a região da América do Sul, a partir de imagens do canal visível do satélite GOES, com resolução de 0,04°´0,04° e representando uma média em 0,12o´0,12o aproximadamente. A versão GL1.2 (atualmente operacional) apresenta desempenho dentro de padrões aceitos internacionalmente: desvio médio mensal da ordem ou inferior a \ub110 W.m-2 e desvio padrão dos dados mensais inferior a 20 W.m-2, em condições de carga de aerossol fraca. São apresentadas suas características e limitações, e analisados alguns aspectos do seu desempenho

Modelo CPTEC GL para estimativa de radiacao solar por satelite: versoes GL1.0 e GL1.1.

It is described the model GL1.0 run at CPTEC for assessing solar radiation at ground level, which is based on GOES-8 VIS channel imagery. Some limitations of the model were improved by a GL1.1 version which introduces a more complete assessment of atmospheric gases absorption and an essential change of cloudiness estimates. Errors of the improved model for daily values of mean irradiance have mean value 3 W.m -2 and a standard deviation of 29 W.m -2 .Pages: 3768-377

Classificacao de cenas em imagens GOES multiespectrais mediante um metodo de agrupamento dinamico

Foi desenvolvido um método de classificação de alvos em imagens GOES 8, baseado no uso de quatro variáveis: reflectância (canal 1) e temperatura de brilho (canal 4), e suas respectivas texturas (variâncias locais). O princípio do método reside em classificar cada elemento de imagem segundo a menor distância euclidiana a um conjunto de centróides de referência num espaço multidimensional. O método é iterativo, de forma que os centróides são definidos por sucessivos processos de classificação até atingir um critério de estabilidade. A aplicação a imagens do setor Sul-Sudeste do Brasil permitiu estabelecer coordenadas típicas dos centróides para diferentes tipos de coberturas. Estes podem ser utilizados para classificação de novas imagens, agora por um processo não supervisionado. Neste trabalho apresentamos a utilização da classificação de um conjunto de imagens mensais para definir reflectâncias típicas relativas a transição de uma cobertura cumuliforme para estratiforme.Pages: 3915-392

Classificacao automatica de alvos: uma analise da informacao contida em imagens GOES-8 multiespectrais

GOES-8 five channel images were analysed for a region extended over South American region (from 17S to 26S and 69W to 35W) for January 1997. Day and night time situations were chosen. Each pixel was considered as 8- or 10-dimensional (defined by reflectance factor in channel 1 and brightness temperature in channels 2 to 5, as well as by local texture in five channels). Thirty-five centroids were defined through clustering by a "dynamic clusters" method using euclidean distance. Hyerarchical clustering of these centroids showed that between five and thirteen types of scenes could be reasonably separated. On the other hand, factor analysis made evident that only three principal components account for the most part of information, while varimax rotation showed that channels 1 and 4 are enough to provide the basic information for cloud identification

Modelo de estimativa de radiação solar por satélite no CPTEC: versão GL1.2

It was found that top-of-atmosphere solar flux as well as transmittance in ultraviolet interval 0.3-0.4 µm are not negligible, leading to systematic underestimation of ground values assessed by the CPTEC’s GL1.1 model (which assesses solar radiation based on GOES 8 imagery). It is shown that a simple correction including this flux satisfactorily corrects that error.Pages: 3270-327

Daily Cycles of Type and Amount of Cloud Cover Over Amazon Region Deduced From GOES-8 Imagery

The type and amount of cloud cover over Amazon region (75W to 45W, 19S to 5N) was analyzed in different spatial scales for the period September 2002, that is, during the Dry-to-Wet AMC/LBA Campaign. Multispectral GOES-8 imagery was classified following a clustering method developed at DSA/CPTEC, which is iterative (of the "dynamical centroids"-type), considering each pixel as an 11-dimensional vector (with components defined by brightness temperature in channels 2 to 5, and related variables as texture and difference between channels). VIS channel was not included, in order to avoid sharp discontinuities during one daily cycle. About 7 million pixels were clustered for five days, distributed in eight different times, defining 232 11-dimensional centroids. Factor analysis suggests de existence of no more than 4-6 principal modes (factors) and about 40 different groups of scenes. Resulting groups exhibit coherence with nephanalysis (visual inspection). Once defined the clustering method and typical centroids, classification of all images (eight by day) during one month allows to describe daily cover evolution for main types of cloudy (Cu, St, Ci, deep convective type) and clear-sky pixels, as well as transitions between them. Preliminary results (averaged over the region) suggest that clear-sky area varied between a minimum of 30% (at 06 GMT) and a maximum of about 45% (nearly constant between 12 and 24 GMT). Deep convection showed maximal area at 21-24 GMT, being minimal at 15 GMT. Cu cover showed influence of diurnal solar cycle, attaining up to 20% of the region at about 18 GMT

Shortwave radiative flux monitoring over South American area using GOES VIS imagery

Mean daily solar irradiance is assessed at CPTEC/INPE (Brazil) based on GOES VIS channel imagery, covering a region which includes South America and neighboring oceanic areas with space resolution of about 12 km. It is a simplified physical model, considering two broad bands for solar spectrum (visible+ultraviolet, and infrared). Version GL1.2 considers an atmosphere with low aerosol optical depth. Monthly means of solar irradiance show performance compatible with the proposal of bias lower than 10 W.m-2 and standard deviation lower than 25 W.m-2 in regions without influence of burning mass forests/cultures or urban industrial pollution.Pages:

Classificação automatica de nebulosidade e relações com campos de precipitação prognosticados por um modelo de circulação global

Cluster analysis was performed for Goes 8 images, defining 8 cloud cover types over lhe South American tropical belt, May 1996 at 1500 GMT. The resulting class distributions were compared withprecipitation pattern forecasts from CPTEC/COLA GCM. Considering lhe spatial resolution and lhe data input for model, precipitation areas forecast satisfactorily fits to actually observed convective complexes and stratiform systems locations. This is not always lhe case for complexes in a smaller time and space scale, not forecast by lhe modelo.Pages: 1457-146