In this paper, a preliminary description of the characteristics of wind speed at 10 m in the meteorological station San Julián Aero, Santa Cruz, Argentina was performed. The analysis was conducted in order to assess the wind power generation capacity in the region. A comprehensive quality control process of the wind data series was carried out where it was found periods of malfunction and instrumental changes, so that the series resulted not homogeneous. Daily and annual cycle of each period, as well as their distributions and extreme values associated with the characteristics speed of the wind turbines were described. On the other hand, to explore whether the variability of the wind at10 m is representative of the variability of wind speed at the height of the rotor, wind speed data at 40 m, 50 m and 60 m measured at a nearby tower the surface station were studied. Different MCP (measure-correlate-predict)methods were applied to determine the degree of directional correlation between the data in the tower vs surface data obtaining significant values in all cases, suggesting that it could taken the daily mean wind speed at 10 m as representative to estimate the variability of the wind at the required height to generate wind power. The results show the difficulty of making any study of wind variability and/or extreme values with short series because they are sensitive to the record length, type and quality of the instruments and also to changes in location and height of the measuring instrumental and nearby obstacles.

En el presente trabajo se realizó una descripción preliminar de las características de la velocidad del viento medido a 10 m en la estación meteorológica San Julián Aero, provincia de Santa Cruz, Argentina. El análisis se llevó a cabo con el fin de evaluar los cambios en el potencial eólico en la región. Se llevó a cabo un exhaustivo proceso de control de calidad de la serie de datos donde se encontraron períodos de mal funcionamiento y cambios del instrumental, haciendo que la serie no resulte homogénea. Se describió el ciclo diario y anual de cada período, como así también sus distribuciones y los valores extremos asociados a las velocidades características de los aerogeneradores. Por otro lado, para explorar si la variabilidad del viento medido a 10 m es representativa de la variabilidad del viento a la altura del rotor, se estudiaron los datos de velocidad a 40 m, 50 m y 60 m medidos en una torre cercana a la estación meteorológica de superficie. Se aplicaron distintos métodos de “Medir-Correlacionar-Predecir” (MCP) para conocer el grado de correlación direccional entre los datos de la torre y los de superficie obteniendo valores significativos en todos los casos. Esto indicaría que se podrían asumir las variabilidades de la velocidad media diaria del viento a 10 m como representativas para estimar las variaciones del viento a la altura requerida para generar energía eólica. Los resultados obtenidos manifiestan la dificultad de hacer cualquier estudio de variabilidad del viento y/o estudio de valores extremos con series cortas que son sensibles a la longitud del registro, al tipo y calidad del instrumental y además a los cambios de ubicación y altura del instrumental y a los obstáculos cercanos.

The hourly monthly mean atmospheric pressure variation has a semidiurnal oscillation of few hectoPascals (between approximately 4 and 2 hPa), an effect known as barometric tide. The existence of this oscillation is well known but not well documented, so this work describes the monthly barometric tide for some synoptic stations from Argentina. The semidiurnal variation of pressure is more important during the warm months. The principal maximum and minimum take place between 12 and 14 UTC and 20 and 21 UTC and presents three types of behaviors. The Central and East regions, where the amplitude decreases as the latitude increase and show an important seasonal cycle. The Patagonia region, with smaller amplitude but showing a greater difference between summer and winter than the previous region. And the West region, which has the largest wave amplitude and also the largest difference between summer and winter. The wavelength is 5 hours greater in summer than in winter for the whole synoptic stations studied. The amplitude of these oscillations would modulated not only by the effect of heat from the sun but also for other local effects. Depending of the time of the day, the barometric tide affects in a different way the depth of pressure systems. So this result should be taken into account when defining and characterizing the depth of cyclones / anticyclones for the analyses and weather forecast.

La presión atmosférica horaria media mensual presenta una variación semidiurna regular de unos pocos hectopascales (entre 4 y 2 hPa aproximadamente), efecto conocido como marea barométrica. Si bien la existencia de esta oscilación es ampliamente conocida, en este trabajo se la documenta en forma mensual para algunas estaciones de Argentina. La variación semidiurna es más importante durante los meses cálidos que fríos. Los máximos y mínimos principales tienen lugar entre las 12 y 14 UTC y 20 y 21 UTC, y presenta tres tipos de comportamientos. La región Centro y Este donde la amplitud disminuye con el aumento de la latitud y muestran un ciclo estacional marcado. La región Patagónica con menor amplitud pero con mayor diferencia entre verano e invierno que la región anterior. Y la región Oeste, que presenta la amplitud de onda más importante y además la mayor diferencia entre verano e invierno. La longitud de onda es 5 horas mayor en verano que invierno en las estaciones estudiadas. La amplitud de estas oscilaciones estaría modulada no sólo por el efecto de térmico del sol sino también por otros efectos locales. La marea barométrica afecta de distinta forma a la profundidad de los sistemas báricos según la hora en que ellos tengan lugar, por lo que este resultado debería ser tenido en cuenta en el momento de definir y caracterizar la profundidad de los ciclones/anticiclones para realizar cualquier estudio y/o pronóstico del tiempo.

The performance of NCEP/NCAR I, NCEP/DOE II, JRA-25 and ERA-Interim global databases, implemented as atmospheric forcings of the SWAN model in the Río de la Plata region, was quantitatively tested by calculating the bias, the mean square root error, the determination coefficient and the slope of the line fitted between observed and simulated wave parameters (significant wave height, mean period and direction). Even though statistical estimators showed no evident differences for wave periods and directions some noticeable differences were observed for simulated significant wave heights depending on the forcing used. The lowest bias (0.22 m) was obtained when the SWAN model was forced by ERA-Interim. With regard to the mean square root errors, the lowest values were obtained when NCEP/NCAR I (0.16 m) and NCEP/DOE II (0.19 m) were used as forcing. In addition, the best slope for simulated heights (0.79) was obtained using NCEP/DOE II. Computed determination coefficients for heights, periods and directions were very similar (0.89-0.93) for all the simulations carried out in this study. Energetic and severe wave events were given special consideration. The most energetic wave episode recorded in the Río de la Plata mouth (24 August, 2005) was analyzed and discussed in particular. It was concluded that during energetic atmospheric conditions the best agreement is achieved by implementing NCEP/DOE II as forcing. In the light of these results it is concluded that NCEP/DOE II is the most suitable atmospheric forcing to simulate wave heights with the SWAN model in the Río de la Plata region.

Na região do Rio de la Plata, o desempenho das reanálises globais do NCEP/NCAR I, NCEP/DOE II, JRA-25 e ERAInterim implementadas como forçantes atmosféricas do modelo SWAN foram quantitativamente acessados através do viés, erro quadrático médio, coeficiente de determinação e inclinação da reta. Estes índices foram obtidos dos parâmetros de ondas observados e simulados (alturas significativas de ondas, período principal e direção). Embora as estimativas estatísticas não mostrem diferenças evidentes para períodos e direções, algumas diferenças notáveis foram obtidas para altura de ondas simuladas, dependendo do vento utilizado. O menor viés para altura significativa (0.22 m) foi obtido quando o SWAM foi forçado com a ERAInterim, enquanto o NCEP/NCAR I (0.16 m) e NCEP/DOE II (0.19 m) forneceram menor erro quadrático médio. A melhor inclinação da reta entre simulação e observação de altura significativa (0.79) foi obtida usando NCEP/DOE II. No período de estudo, o maior episódio de onda registrado na boca do Río de la Plata foi analisado e discutido. Neste evento de condições atmosféricas energéticas o melhor ajuste foi alcançado utilizando os ventos do NCEP/DOE II como forçante. Conclui-se que a base de dados NCEP/DOE II é forçante atmosférica mais adequada para simular alturas significativas de ondas com o modelo SWAN na região estudada.