Cláudio Moisés Santos e Silva

Seasonality, interannual variability, and linear tendency of wind speeds in the northeast Brazil from 1986 to 2011.

Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Nino and La Nina events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study.Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Niño and La Niña events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study.

CICLO DIÁRIO E SEMIDIÁRIO DE PRECIPITAÇÃO NA COSTA NORTE DO BRASIL

Estudou-se o ciclo diario e o ciclo semidiario da precipitacao na regiao costeira do Norte do Brasil. Usou-se 13 anos de dados ininterruptos de precipitacao estimados atraves do algoritmo 3B42_V6 do projeto TRMM. Os ciclos foram analisados por quadrimestres. Para obter informacoes sobre amplitude, fase e fracao de variância de cada ciclo, utilizou-se a analise harmonica do ciclo composto no periodo de 24 horas para cada quadrimestre. Regioes mais proximas da costa apresentaram ciclos modulados por mecanismos oceânicos e, portanto, tendem a apresentar o maximo de precipitacao no inicio da manha e a noite. Regioes mais afastadas da costa apresentaram maximos as 2100 UTC (17:00 HL) em funcao dos mecanismos de conveccao local. A regiao Nordeste do Para apresentou as maiores amplitudes de precipitacao. Durante o quadrimestre de janeiro a abril observou-se as maiores taxas de precipitacao. Nao ha variacoes sazonais significativas na fase dos ciclos. Os dois harmonicos correspondem a cerca de 80% do total da variância diaria dos dados. No final, algumas sugestoes de trabalhos futuros e aplicabilidade dos dados do 3B42_V6 sao discutidas.

Distribuição espacial da precipitação sobre o Rio Grande do Norte: estimativas via satélites e medidas por pluviômetros

RAINFALL SPATIAL DISTRIBUTION OVER THE RIO GRANDE DO NORTE BRAZILIAN STATE: SATELLITES ESTIMATES AND RAIN GAUGES MEASUREMENTS The aim of this study was to evaluate the monthly rainfall estimates obtained by two data sources (3B43_V6 algorithm and University of Delaware) for the State of Rio Grande do Norte, during the 1998 to 2008 period. Statistical analysis based on the linear correlation coefficient and on the performance index from a 2x2 contingency table was done. Coastland and semiarid precipitation regimes which depend on geographical location and on soil type coverage were considered. It was noted that the 3B43_V6 underestimated the coastland rainfall and overestimated the rainfall over arid zones. The Delaware mean rainfall agreed well with observed rainfall, but shows discrepancies concerning to interpolation method and grid spacing. The results suggests that both 3B43_V6 and Delaware rainfall dataset are able to capture the rainfall mean variability both in time and space; however, they show deficiency in identifing extreme precipitation events. Keywords: 3B43_V6, Delaware, contingency table, TRMM, semiarid.

Impacto de um mecanismo de disparo da convecção na precipitação simulada com o modelo regional BRAMS sobre a bacia amazônica durante a estação chuvosa de 1999

O objetivo deste artigo e mostrar o impacto da implementacao de uma funcao de disparo da conveccao na parametrizacao convectiva de Grell e Devenyi, contida no modelo atmosferico regional BRAMS (Brazilian developments on Regional Atmospheric Model). Para verificar o ciclo de precipitacao foi usado um conjunto de dados do periodo chuvoso de 1999 no âmbito do projetoLarge scale Biosphere-Atmosphere Experiment in Amazonia(LBA). A nova funcao de disparo de conveccao e acoplada aos fluxos de calor sensivel e latente a superficie. Alem disso, possui a vantagem de considerar a media dos primeiros 60 hPa da troposfera para caracterizar a ascencao pseudo adiabatica da parcela. Assim, a parcela em ascencao apresenta reducao daConvective Available Potential Energy (CAPE), o modelo acumula menos CAPE nas primeiras horas do dia e com isso, o maximo de precipitacao e atrasado (embora dependa da regiao analisada). Um aspecto negativo foi que a precipitacao sobre a Cordilheira dos Andes aumentou relativamente a versao original. Conclui-se que o esquema apresenta vantagens e desvantagens e que faz-se necessario avaliar outras parametrizacoes do modelo, principalmente a troca de energia e massa na interface solo-vegetacao-atmosfera a fim de se obter resultados mais realisticos da precipitacao sobe a Amazonia.

Synoptic patterns of atmospheric circulation associated with intense precipitation events over the Brazilian Amazon

The objective of this study is to characterize the atmospheric patterns associated with the occurrence of intense precipitation events (IPE) in different sub-regions of the Brazilian Amazon. Intense rainfall cases over six sub-regions were selected from a precipitation data set for the period from 1983 to 2012. The composition technique was used to characterize the prevailing atmospheric patterns for the occurrence of IPE. In the south of the Amazon, the composition fields showed a favorable configuration for the formation of the South Atlantic Convergence Zone (SACZ). Along the coast, the intense precipitation events must be associated with mesoscale systems, such as squall lines. In the northwest, they are apparently associated with the Intertropical Convergence Zone (ITCZ) and/or local convection. The results reveal the complexity of the synoptic environment associated with the formation and development of weather systems that produce heavy rainfall in the Amazon Basin. Several factors can interfere as conditions in large-scale, local conditions and thermodynamic factors.

Estimating return periods for daily precipitation extreme events over the Brazilian Amazon

This paper aims to model the occurrence of daily precipitation extreme events and to estimate the return period of these events through the extreme value theory (generalized extreme value distribution (GEV) and the generalized Pareto distribution (GPD)). The GEV and GPD were applied in precipitation series of homogeneous regions of the Brazilian Amazon. The GEV and GPD goodness of fit were evaluated by quantile–quantile (Q-Q) plot and by the application of the Kolmogorov–Smirnov (KS) test, which compares the cumulated empirical distributions with the theoretical ones. The Q-Q plot suggests that the probability distributions of the studied series are appropriated, and these results were confirmed by the KS test, which demonstrates that the tested distributions have a good fit in all sub-regions of Amazon, thus adequate to study the daily precipitation extreme event. For all return levels studied, more intense precipitation extremes is expected to occur within the South sub-regions and the coastal area of the Brazilian Amazon. The results possibly will have some practical application in local extreme weather forecast.

Seasonal Analysis of Return Periods for Maximum Daily Precipitation in the Brazilian Amazon

AbstractThe aim of this study is to estimate the return period of maximum daily precipitation for each season of the year in different subregions of the Brazilian Amazon. For this, the extreme value theory was used, through the generalized extreme value (GEV) distribution and the generalized Pareto distribution (GPD). The GEV distribution and GPD were applied in precipitation series from homogeneous regions of the Brazilian Amazon. The GEV and GPD goodness of fit were evaluated by the application of the Kolmogorov–Smirnov (KS) test, which compares the cumulative empirical distributions with theoretical ones. The KS test results indicate that the tested distributions have a good fit, particularly the GEV distribution. Thus, they are adequate to study the seasonal maximum daily precipitation. The results indicate that extremes of more intense rainfall are expected during the rainy or transition seasons of each subregion. Using the GEV distribution (GPD), a daily total of 146.1 (201.6), 143.1 (209.5), and 10...

Ciclo anual de precipitação como função de índices de instabilidade termodinâmica e fluxos de energia estática: análises em Maxaranguape-RN

The relation between thermodynamic instability indexes, precipitable water content, static energy flux, and rainfall annual cycle over Maxaranguape (coastland site, Rio Grande do Norte, Northeast of Brazil) was investigated. The radiosonde dataset covered the period from January 2002 to December 2009 within the South Hemisphere ADditional OZonesondes (SHADOZ) project. The thermodynamics indexes variability do not explain the maximum rainfall in July, however they are in phase with the secondary maximum in April. The annual cycle of the moist and saturated static energy fluxes showed that rainfall cycle is modulated by both thermodynamics and low level moisture convergence mechanisms.

Changes of precipitation extremes indices in São Francisco River Basin, Brazil from 1947 to 2012

The São Francisco River is strategically important due to its hydroelectric potential and for bringing the largest water body of Brazilian Semiarid region, supplying water for irrigation, urban, and industrial activities. Thereby, for the purpose of characterizing changes on the precipitation patterns over São Francisco River basin, 11 extremes precipitation indices as defined by the joint WMO/CCI/ETCCDMI/CLIVAR project were calculated using daily observation from the 59 rain gauges during 1947–2012 period. The extreme climatic indices were calculated with the RClimDex software, which performs an exhaustive data quality control, intending to identify spurious errors and dataset inconsistencies. Weak and significant regional changes were observed in both CDD and SDII indices. Most precipitation extremes indices decreased but without statistical significance. The spatial analysis of indices did not show clearly regional changes due to the complexity of hydrometeorology of the region. In some cases, two rainfall stations exhibited opposite trends with the same significance level although they are separated by a few kilometers. This has occurred more frequently in Lower-Middle São Francisco, probably associated with intense land cover change over the last decades in this region.

Calibration of Ångström-Prescott Equation to Estimate Daily Solar Radiation on Rio Grande do Norte State, Brazil

Abstract Knowledgeofsolarradiationisrequiredformanyapplications.However,thisatmosphericvariableisnotmeasuredwithan adequate space resolution. In this sense, to sites where solar radiation data are not directly measure, estimative usingAngstrom-Prescott equation can be used in order to provide solar radiation data, with input of sunshine duration. Thus,the objective of present study was to calibrate the Angstrom-Prescott equation for different sites in Rio Grande do Nortestate, Brazil. The performance of the calibrated Angstrom-Prescott equation was evaluated by comparing of daily globalsolarradiationobserved insitu .TheMBE(MeanBiasError)waslowerthan1.50MJm -2 day -1 ,thePearson’scorrelationcoefficient about 0.90 and Willmott’s index of agreement higher than 0.90, which are considered satisfactory. Keywords: semiarid region; sunshine duration; Angstrom-Prescott equation. Calibracao da Equacao de Angstrom-Prescott para Estimar a RadiacaoSolar Diaria no Estado do Rio Grande do Norte, Brasil