Augusto José Pereira Filho

Measurements of drop size distribution in the southwestern Amazon basin

[1] Simultaneous observations of an optical and an impact type disdrometer and their application in radar rainfall estimation are evaluated. The disdrometers and two collocated rain gauges were operated in the southwest Amazon region of Brazil in 1999 as part of a NASA Tropical Rainfall Measuring Mission (TRMM) field campaign and the hydrometeorological component of the Large Scale Biosphere-Atmosphere Experiment (LBA). During the experiment, we observed large drops with diameters greater than 5 mm. These large drops were not adequately detected by the impact disdrometer and resulted in differences in drop size distribution and integral rain parameters derived from the two sensors. Considering coincident observations, we calculated that the impact disdrometer recorded about 11% lower rainfall accumulations than the optical disdrometer. In addition, radar rainfall algorithms, which we derived from the impact and optical disdrometer measurements, showed instrument dependency. Out of four radar rainfall algorithms that we considered, rain rate derived from specific differential phase has the least dependency, while the rain rate derived from reflectivity at horizontal polarization and differential reflectivity combined exhibited the largest. We also observed the characteristics of rainfall and drop size distribution in two distinct wind regimes present during the TRMM - LBA field campaign. Rain was heavier in the easterly regime, with more large drops being present.

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.

Water Demand Forecasting Model for the Metropolitan Area of São Paulo, Brazil

This work is concerned with forecasting water demand in the metropolitan area of São Paulo (MASP) through water consumption, meteorological and socio-environmental variables using an Artificial Neural Network (ANN) system. Possible socio-environmental and meteorological conditions affecting water consumption at Cantareira water treatment station (WTS) in the MASP, Brazil were analyzed for the year 2005. Eight model configurations were developed and used for the Cantareira WTS. The best performance was obtained for 12-h average of the input variables. The ANN model performed best with three times steps in advance. The hourly forecasting was obtained with acceptable error levels. Model results indicate an overall tendency for small errors. The proposed method is useful tool for water demand forecasting and water systems management. The paper is an important contribution since it takes into account weather variables and introduces some diagnostic studies on water consumption in one of the largest urban environments of the planet with its unique peculiarities such as anthropic affects on weather and climate that feeds back into the water consumption. The averaging is a low pass filter indeed and we used it to improve Signal to Noise Ratio (SNR).

Severe Weather Caused by Heat Island and Sea Breeze Effects in the Metropolitan Area of São Paulo, Brazil

The Metropolitan Area of Sao Paulo (MASP) is one of the most populated regions of the planet with one of the largest impervious regions as well. This research work aims to characterize MASP heat island (HI) effect and its interaction with the local sea breeze (SB) inflow in rainfall amounts and deep convection. The combined SB-HI produces direct circulation over the MASP and produces severe weather and socioeconomic impacts. All SB-HI episodes between 2005 and 2008 are identified and analyzed with surface and upper air measurements, weather radar, and satellite data. The current work indicates that intense SB-HI episodes are related to air and dew point temperatures above 30°C and 20°C, respectively, right after the passage of the SB front over MASP. Results indicate that the precipitation related to SB-HI episodes is up to 600 mm or about four times higher than that in rural or less urbanized areas in its surroundings. Measurements indicate that 74% of SB-HI episodes are related to NW winds in earlier afternoon hours. Moving cold fronts in southern Brazil tend to intensify the SB-HI circulation in MASP. A conceptual model of these patterns is presented in this paper.

Metodologia para análise de desempenho de simulações de sistemas convectivos na região metropolitana de São Paulo com o modelo ARPS: sensibilidade a variações com os esquemas de advecção e assimilação de dados

Tempestades seguidas de enchentes e alagamentos em pontos da Regiao Metropolitana de Sao Paulo sao eventos recorrentes nas estacoes chuvosas. O desempenho do modelo ARPS nas simulacoes numericas de alta resolucao espacial, para o evento de 04 de fevereiro de 2004, e avaliado por meio de erros estatisticos e indices de acuracia, com base no confronto entre a distribuicao espacial da precipitacao acumulada simulada e a estimada com o radar meteorologico de Sao Paulo. Os resultados quantificam a influencia dos termos de adveccao das equacoes primitivas nos erros de fase dos sistemas convectivos simulados, para o tipo de configuracao atmosferica dominante no caso estudado. A assimilacao incremental de medidas obtidas em estacoes de superficie durante a execucao do modelo, corrige significativamente a fase das celulas convectivas profundas na regiao de influencia das medidas, a qual e definida durante o processo de analise objetiva. Um novo indice de destreza para modelos de mesoescala e proposto (DPIELKE). As analises preliminares para o desempenho deste indice indicam adequacao de sua formulacao para o tipo de simulacao efetuada.

Análise de desempenho de índices de instabilidade atmosférica na previsão de fenômenos convectivos de mesoescala na região metropolitana de São Paulo entre 28 de janeiro e 04 de fevereiro de 2004

In this work the efficiency of several instability indices as summer convective event predictors of high accumulated surface precipitation observed in the Metropolitan Area of Sao Paulo (MASP) is discussed. During January 28 and February 04, 2004, 5 of 8 events were considered rainy, and associated to thunderstorms at early evening. The K index values were lower than 31 on the 5 observed events, which were affected by the presence of a cold and dry layer on the middle atmosphere level relative to lower levels. The Total Totals index (ITT) failed in detecting 3 of 5 rainy events presenting lower values than the threshold value (ITT=44) expected for heavy showers during all the period. The Lifted index, in the range -4.9 to -4.3, indicated moderate instability for the 5 days. The Showalter index pointed to possibility for severe storms in 4 of the 5 events. The Showalter index and CAPETv values were strongly reduced in the presence of an isothermal layer observed between 910 and 840 hPa in one of the radiosonde measures. The temporal series of CAPETv and Lifted index have shown a good phase agreement, with high linear correlation between them. CINETv ≈ 0 J kg-1, in association to low vertical shear, and Showalter index, Lifted index and CAPETv moderate values, seem to be a common characteristic in days with heavy showers in MASP when large-scale forcing is weak. The need to quantify the probability of detection, frequency of misses, false alarms and frequency of errors in null events for each index is discussed.

Classificação de sistemas meteorológicos e comparação da precipitação estimada pelo radar e medida pela rede telemétrica na bacia hidrográfica do alto Tietê

Estimated precipitation characteristics arising from 145.194 reflectivity fields, from 827 days, during the period from 1998 to 2003, obtained at the Weather Radar of Sao Paulo, were analysed. The events were classified according to the intensity of precipitation in Convectives and Stratiforms. Five types of morphologic systems were identified: Isolated Convection (CI), Maritime Breeze (BM), Squall Lines (LI), Dispersed Bands (BD), and Cold Fronts (FF). Convection events dominate in spring and summer and Stratiforms in the Autumn and Winter. CI and BM have occurred more frequently between October and March, while the cold fronts from April to September. Dispersed Bands occurred throughout the year, and the lines of instability did not occur only on June and July. A comparison between the telemetric measured precipitation and the Radar estimated one has been done, and a positive bias, of the Radar accumulations for 10, 30 and 60 minutes, was shown on the majority of cases. To integrate the precipitation estimations from the Radar to the telemetric network measurements, by means of an objective statistical analysis, the structures of spatial correlation, for rain accumulation during 15, 30, 60 and 120 minutes for the five types of characterized systems, was obtained from the Radar precipitation fields. The average spatial correlation curves of all the precipitation events of each system were fitted to a sixth order polynomial function. The results indicate significant differences in the spatial structures of the correlation among the precipitation systems.

Previsão de chuva a curtíssimo prazo na área de abrangência do radar meteorológico de São Paulo

The evaluation of the rainfall nowcasting within the surveillance area of Sao Paulo weather radar for different types of precipitating systems, mainly those associated to floods and landslides in Metropolitan Area of Sao Paulo, was carried out with a 2D wind advective scheme and rainfall rates estimated by radar. The third-order upstream numerical scheme was used with an uniform wind vector. The rainfall forecast skill for a given time interval was evaluated using the Critical Success Index (CSI), Probability of Detention and False Alarm Rate statistic parameters. Quantitatively, the accuracy of the forecast was evaluated with the mean-square error. The correlation coefficient showed better skill for stratified precipitations than for convective precipitations. The average skills based on critical Success Index for the thresholds of 0.2 mm at 60 minutes of accumulated precipitation are: Cold fronts (77%), Squall lines (67,5%), Dispersed Bands (58%), Isolated Convection (56,4%) and Maritime Breeze (47%). In general, from 90 minutes of advection (convective systems) to 120 minutes (stratiform systems), the forecast skill decreases.

HYDROMETEOR AND LATENT HEAT PROFILES OF TROPICAL CYCLONES CONSON, IVAN AND CATARINA USING PR/TRMM DATA

No presente trabalho foram analisados as caracteristicas microfisicas e termodinâmicas de dois sistemas tropicais, o Furacao Ivan e o Tufao Conson, e um sub-tropical, Catarina, a partir de medicoes feitas com o radar PR a bordo do satelite TRMM. Na analise, os perfis de refletividade foram classificados conforme as tecnicas de Heymsfield et al (2000) e Steiner et al (1995) e em seguida foram calculados os conteudos de agua e gelo, a partir de uma relacao obtida no Estado de Rondonia (Brasil). Com estes perfis calculou-se a taxa de aquecimento diabatico devido a liberacao de calor latente conforme Tao et al (1990). Apos serem comparados os tres furacoes, fez-se uma analise mais detalhada do Catarina, que foi o primeiro furacao oficialmente registrado no Atlântico Sul. Os resultados mostraram que o Ivan e o Conson tiveram um alto teor medio de agua, especialmente nos niveis mais baixos e perto de seus centros. Os resultados indicaram que o furacao Catarina foi mais raso, tinha menor teor de agua liquida e mais concentrada proximo do centro. O teor medio de gelo no Catarina foi cerca de 0,05 g kg-1, enquanto no Conson foi de 0,06 g kg-1 e no Ivan 0,08 g kg-1. O Conson e o Ivan tiveram teor de agua de ate 0,3 g kg-1 acima da isolinha de 0oC, enquanto que o Catarina teve menos de 0,15 g kg-1. A taxa de aquecimento, devido a liberacao de calor latente, no Catarina, mostrou ter magnitudes similares aos outros dois sistemas, com maiores diferencas nas regioes proximas do nucleo.

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.