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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Downscaling estoc?stico para extremos clim?ticos via interpola??o espacial

Carvalho, Daniel Matos de 31 May 2010 (has links)
Made available in DSpace on 2014-12-17T15:26:38Z (GMT). No. of bitstreams: 1 DanielMC_DISSERT.pdf: 1549569 bytes, checksum: 5ad46f43cc6bf2e74f6fc1e20e5e2dc5 (MD5) Previous issue date: 2010-05-31 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Present day weather forecast models usually cannot provide realistic descriptions of local and particulary extreme weather conditions. However, for lead times of about a small number of days, they provide reliable forecast of the atmospheric circulation that encompasses the subscale processes leading to extremes. Hence, forecasts of extreme events can only be achieved through a combination of dynamical and statistical analysis methods, where a stable and significant statistical model based on prior physical reasoning establishes posterior statistical-dynamical model between the local extremes and the large scale circulation. Here we present the development and application of such a statistical model calibration on the besis of extreme value theory, in order to derive probabilistic forecast for extreme local temperature. The dowscaling applies to NCEP/NCAR re-analysis, in order to derive estimates of daily temperature at Brazilian northeastern region weather stations / Os dados de rean?lise de temperatura do ar e precipita??o do NCEP National Centers for Environmental Predictions ser?o refinados para a produ??o dos n?veis de retorno para eventos extremos nas 8 capitais do Nordeste Brasileiro - NB: S?o Luis, Teresina, Fortaleza, Natal, Jo?o Pessoa, Recife, Macei?, Aracaju e Salvador. A grade do Ncep possui resolu??o espacial de 2.5? x 2.5? disponibilizando s?ries hist?ricas de 1948 a atualidade. Com esta resolu??o a grade envolve o NB utilizando 72 localiza??es (s?ries). A primeira etapa consiste em ajustar os modelos da Distribui??o Generalizada de Valores Extremos (GEV) e da Distribui??o Generalizada de Pareto (GPD) para cada ponto da grade. Utilizando o m?todo Geoestat?stico denominado Krigagem, os par?metros da GEV e GPD ser?o interpolados espacialmente. Considerando a interpola??o espacial dos par?metros, os n?veis de retorno para extremos de temperatura do ar e precipita??o poder?o ser obtidos aonde o NCEP n?o fornece informa??o relevante. Visando validar os resultados desta proposta, ser?o ajustados os modelos GEV e GPD as s?ries observacionais di?rias de temperatura e precipita??o de cada capital nordestina, e assim comparar com os resultados obtidos a partir da interpola??o espacial. Por fim o m?todo de Regress?o Quant?lica ser? utilizado como m?todo mais tradicional com a finalidade de compara??o de m?todos.

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