RESUMOO principal objetivo deste trabalho é prover novas informações sobre as tendências na precipitação total e eventos extremos de precipitação sobre o Estado do Ceará, fazendo uma análise de diferentes índices de detecção de mudanças climáticas, baseados em dados de precipitação pluvial diária. Utilizaram-se dados de precipitação de 18 postos, no período de 1935 a 2006, representando todas as microrregiões do Estado; o software utilizado no processamento e controle de qualidade dos dados foi o RClimdex 1.9.0. Com base nos resultados encontrados, observou-se que ocorreram mudanças locais na precipitação, assim como um visível aumento nas condições de umidade sobre o Ceará. Palavras Chaves: Mudanças Climáticas, Semi-árido, RClimdex 1.9.0 ABSTRACT: TRENDS OF PRECIPITATION INDICES IN CEARÁ STATEThe principal objective of this work is to provide new information on the trends in the total precipitation and extreme events of precipitation in the State of Ceará, making an analysis of different indices of detection of climatic changes, based on data of daily precipitation. Precipitation data of 18 stations were used, in the period from 1935 to 2006, representing all the microregions of the State; the software used in the processing and quality control of the data was RClimdex 1.9.0. The results show local changes in the precipitation and a visible increase in the humidity conditions in Ceará. Keywords: Climate Change, Semi-arid, RClimdex 1.9.0 INTRODUÇÃOAs mudanças no clima podem acarretar significativos impactos nos setores naturais, social e econômico. Os extremos climáticos associados à temperatura e precipitação podem também afetar consumo de energia, conforto humano e turismo (Subak et al., 2000; Qian e Lin, 2005). O aumento nas perdas econômicas devido a extremos de tempo e, especialmente, o aumento nas perdas de vidas, tem sido regularmente notícias de jornais, despertando o interesse da comunidade científica em estudar tais fenômenos (Kostopoulo e Jones, 2005).Mudanças na precipitação têm implicações no ciclo hidrológico e recursos hídricos. Espera-se que as mudanças climáticas alterem a temperatura média e os valores da precipitação e que aumentem a variabilidade dos eventos de precipitação, que poderão causar inundações e secas mais intensas e freqüentes. Qian e Lin (2005) afirmam que a freqüência e a persistência das secas deverá ser uma das conseqüências do aquecimento global. Walsh e Pittock (1998) sugeriram que as potenciais mudanças nas tempestades tropicais, furacões e eventos extremos de chuva são um resultado das mudanças climáticas. Em geral, muitas atividades econômicas e processos ambientais são altamente dependentes da precipitação. No Nordeste do Brasil (NEB), as atividades agrícolas, quase que em sua totalidade, são baseadas na precipitação e o conhecimento de sua variabilidade é de extrema importância.De forma geral, a atmosfera é constituída por vários gases, sendo que os principais são o Nitrogênio (N 2 ) e o Oxigênio (O 2 ) que, juntos compõem cerca de 99% da proporção em volume. Outros gas...

ABSTRACT:The main objective of this study was to analyse the trends in 20 annual extreme indices of temperature and precipitation for Utah, USA. The analyses were conducted for 28 meteorological stations, during the period from 1930 to 2006, characterized by a long-term and high-quality dataset. The software used to process the data was the RClimdex 1.0. The analyses of extreme temperature indices have identified an increase in air temperature in Utah during the last century. Meanwhile, the analyses of precipitation indices showed a large variation throughout the studied area and time period, and, in general, with few statistically significant trends. Thus, it was not possible to conclude that significant changes in precipitation have occurred in this region over the last century.

SUMMARYField-based soil moisture measurements are cumbersome. Thus, remote sensing techniques are needed because allows field and landscape-scale mapping of soil moisture depth-averaged through the root zone of existing vegetation. The objective of the study was to evaluate the accuracy of an empirical relationship to calculate soil moisture from remote sensing data of irrigated soils of the Apodi Plateau, in the Brazilian semiarid region. The empirical relationship had previously been tested for irrigated soils in Mexico, Egypt, and Pakistan, with promising results. In this study, the relationship was evaluated from experimental data collected from a cotton field. The experiment was carried out in an area of 5 ha with irrigated cotton. The energy balance and evaporative fraction (Λ Λ Λ Λ Λ) were measured by the Bowen ratio method. Soil moisture (θ θ θ θ θ) data were collected using a PR2 -Profile Probe (Delta-T Devices Ltd). The empirical relationship was tested using experimentally collected Λ Λ Λ Λ Λ and θ θ θ θ θ values and was applied using the Λ Λ Λ Λ Λ values obtained from the Surface Energy Balance Algorithm for Land (SEBAL) and three TM -Landsat 5 images. There was a close correlation between measured and estimated θ θ θ θ θ values (p<0.05, R 2 = 0.84) and there were no significant differences according to the Student t-test (p<0.01). The statistical analyses showed that the

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The main objective of this paper is to assess the performance of nine downward longwave radiation equations for clear-sky condition and develop a locally adjusted equation using the observed vapor pressure and air temperature data. The radiation and atmospheric parameters were measured during the months of October 2005 to June 2006 at a micrometeorological tower installed at the experimental site in a banana orchard in the semiarid region of Northeast Brazil. The comparative statistics for the performance of the downward longwave radiation calculation models during daytime and nighttime compared to measured data have shown that the parameterizations with more physical foundations have the best results. The locally adjusted equation and Sugita and Brutsaert model developed in 1993 showed errors less than 1.0% in comparison with measured values. Downward longwave radiation is one of the most expensive and difficult component of the radiation budget to be monitored in micrometeorological studies. Hence, the locally adjusted equation can be used to estimate downward longwave energy, needed as input to some agricultural and hydrological models, in semi-arid regions of the Northeast Brazil, where this component is not monitored.