Yoshihiro Yamasaki

Validação da assimilação de dados na inferência da refletividade de um radar com o sistema MM5

On certain occasions the Rio Grande do Sul State is affected by atypical weather systems events which are in the category of mesoscale phenomena. The inability of global forecast models to appropriately simulate several localized effects, which occurs over the most different regions, associated to the fast increase of computational resource, is facilitating and increasingly inducing the use of mesoscale models to improve the understanding of anomalous and severe events and also as a necessary and indispensable operational tool. In order to evaluate the skill of mesoscale model to provide precipitation forecasts, with space and time scales compatible with those of a Doppler meteorological radar, a mesoscale modeling system, the MM5, is implemented to explore the occurrence of the relatively severe precipitation event; occurred near the city of Cangucu / RS, on January 11, 2008. The event was arbitrarily selected; to evaluate the model skill in inferring the reflectivity of the meteorological radar, installed in Cangucu / RS, running the MM5 model with and without conventional data assimilations, as well as to get an approach of the thermo-hydrodynamics and synoptic conditions analysis.

PERFORMANCE ANALYSIS OF THE WRF MODEL WITH HIGH SPATIAL RESOLUTION ON CUMULATIVE RAINFALL FORECASTING

Events of extremely intense rainfall which occurs duringrelatively short time span have been occurring with somefrequency in Brazil. One of Brazilian state which has beenstrongly affected by these events is the Rio Grande do Sul. In2013 the Metropolitan Region of Porto Alegre, in particular,has been devastated several times by events of this sort. Inespecial, the November 11th event in the city of Porto Alegre,registered an average rainfall, in 24 hours, which exceeded themonthly average value. This event caused several economicand social losses, with flood over several locals over the city,giving rise to disruption of the trensurbs bus lines, due to thelarge volume of the accumulated precipitation. The analysis ofthis event is performed with the mesoescale model WRFprocessing, configured with high spatial resolution, as well asobservational data of the INMET collected in the automaticweather stations network. The model results show a consistentand compatible values of precipitation compared with theobserved values, for the 24 and 48 hours periods, evaluatedwith respect to the collected data in some points of observation.

WRF-4DVAR EVALUATION OF AN EXTREME EVENT OVER RIO GRANDE DO SUL

The WRF mesoscale system 4DVAR data assimilation technique have been used with the purpose of evaluating the impact of the meteorological data assimilation on the numeric time prognosis over the Rio Grande do Sul state. It has been done utilizing the surface and altitude data. The consistency analysis has been done evaluating the numerical prognosis exploring the differences between the analysis with and without data assimilation. The produced prognosis results have been compared spatially using the TRMM satellite data as well as the Cangucu radar reflectivity data. The accumulated rainfall has been validated and compared spatially with the TRMM data for the time period of 12 hours comprehended between October 29th and 30th of 2014. It was possible to realize that as well as the WRF, the WRFVAR overestimated the rainfall values. The radar reflectivity field without data assimilation for October 30th at 06:00UTC detected most accurately the reflectivity centers over the state. On the other hand this field with data assimilation did not present good skill. The temperature field analyses reveal that the 4DVAR assimilation system contributes, one way or another, presenting a little improvement for some points compared to the real data.

ANALYSIS OF THE VERTICALLY INTEGRATED MOISTURE FLUX CONVERGENCE OVER BRAZIL PREDICTED BY WRF MODEL

In the South America the regions of occurrence of the Low-Level-Jet at East Andes (LLJEA) and South Atlantic Convergence Zone (SACZ) where there are the largest import continental moisture. These two systems act over southern and southeast especially in the warm seasons of the year. Throughout 2011, the forecasts made by non-hydrostatic mesoscale Weather Research and Forecasting (WRF) model (SKAMAROCK et al., 2008) with 18 km grid spatial resolution and 35 vertical levels were used to analyze the Vertically Integrated Moisture Flux Convergence (VIMFC) fields and explore its relevance in the short-term forecasting activities. Several events of intense precipitation occurred during the 2011 year over Brazil were associated with LLJEA and SACZ, and two of them are presented. The results show meaning especially in their prediction with forecast horizon of 3 hours before the occurrence of storms. The study showed that the VIMFC prognosis indicated that there is a good agreement in terms of the location of cloudclusters that have been developed, compared with the corresponding representations in sequences compared with the of satellite images in the three hours after.

O Estado da Arte dos Métodos de Assimilação de Dados

The procedure to combine mathematical models with inaccurate and noisy data, improving weather forecasting by statistical methods, is an important and challenging line of research in meteorology, known as data assimilation. Current techniques of data assimilation are based on Gaussian Least Squares Method. This paper presents the main advances in data assimilation, since the empirical methods, created in the 1950s, to the current methods, as well as their derivatives and hybrid versions. It is note that the emergence of hybrid methods ensemble/variational and improved in the satellite and radar data assimilation techniques are major advances in the field in recent years. It is concluded that the variational methods and the Kalman filtering are the state of the art of data assimilation techniques.

Assimilação de Dados Via Método 3D-Var em Dinâmica Caótica do Modelo de Lorenz

This paper explores some aspects of data assimilation by 3D-Var method implemented in the Lorenz model. This system was chosen because, although simple, has similar structure to the atmosphere under certain parameters. Conceptual models allow difficult judgments to be made in primitive equation models with their various nonlinear interactions at various scales. It is shown the need to apply data assimilation techniques in highly sensitive models to initial conditions. It was also shown that 3D-Var method is very dependent on the number of cycles during the process of minimizing of the cost function. In the experiment performed on this work was found that at least 1,000 interactions are necessary to solve this minimization problem. However the technique fail to 40% noise added to initial conditions, comparing to control. Additional experiments show the difficulty of performing high quality data assimilation in chaotic dynamics for underdetermined systems, such as the Earths atmosphere.

WIND POWER ASSESSMENT OVER BRAZIL IN 2011

The increasing demand and electric energy consumption, by both economic and social society, in addition to the worldwide politics for the implementation of generation systems employing renewable sources, has been determinant factors of the expansion of wind farms in different countries. Given that, scarcely the wind measurement data needed are available to consolidate the basic and fundamental requirements, particularly over Brazil, it is proposed, developed and a methodology is applied, for the assessment of wind energy potential over the country for a year. The required data for the mapping and assessment of wind energy potential, during the year 2011 were produced, for every hour, throughout the mesoscale model WRF (Weather Research and Forecasting) forecasting. The general conclusion of the performed analysis has been the characterization of some region of the country, located nearby the shoreline of the Northeast and South of the county, as remarkable locals favorable for the installation of wind farms. However, it has been also pointed out that there are several other areas, scattered over the country, which can be suitable places with great energy potentiality.

EVALUATION OF TIME RANGE FORECASTING OF SURFACE WIND OF WRF

The WRF mesoscale model has been configured andprocessed with a domain covering the Rio Grande do Sulstate, using the GFS/NCEP forecasting (of 00Z, 06Z, 12Zand 18Z) during the October 18th to 21st, 2013 time periodas initial and lateral boundary conditions. The 16 modelintegrations have been processed, generating hourlyforecasting up to 120 hours. The surface wind forecastinghave been evaluated throughout comparison with thedata as collected by the INMET remote station installedat Passo Fundo city – RS. The main focus has beenestablished on October 21st, due the occurrence of quiteintense winds over the whole northern sector of RioGrande do Sul state, particularly over Passo Fundo city.The gathered results reveal that, in a general sense, theWRF presented very good skill for strong wind, as wellas - even up to ninety six hours ahead.