María Cristina Pacino

Water Storage Changes from GRACE Data in the La Plata Basin

Aquatic environments perform important functions in nature such as the control of climate, floods and nutrients, and they provide goods and services for humanity. To monitor these environments at large spatial scales, the satellite gravity mission GRACE provides time-variable gravity field models that reflect the Earth’s gravity field variations due to mass transport processes like continental water storage variations.

The Progress of the Geoid Model for South America Under GRACE and EGM2008

The efforts to compute the geoid model for South America, limited by 15° N and 57° S in latitude and 30° W and 95° W in longitude, are presented. The terrestrial gravity data for the continent have been updated with the most recent measurements in Argentina, Brazil, Chile, Ecuador and Paraguay. An attention was also addressed to DTM, on the basis of SRTM (Shuttle Radar Topography Mission). The complete Bouguer gravity anomaly; the direct, secondary and primary indirect topographic effects; and direct and primary indirect atmospheric effects have been derived through the Canadian package SHGEO (Stokes-Helmert Geoid software). The short wavelength component was estimated via FFT with Featherstone, Evans and Olliver (1998) modified kernel. The geopotential model EGM2008 represents an important contribution to the long and medium wavelength component knowledge of the gravitational field and it has been used as a reference field restricted to degree and order 150. The model has been validated over 1,411 GPS observations on Bench Marks of the spirit leveling network, where the geoidal height was derived from the association of the geodetic and the orthometric heights. The height anomaly derived from EGM2008 (degree and order 2,159 with additional coefficients to degree 2,190 and order 2,159), EIGEN_05c (degree and order 360) and MAPGEO2004 (official geoid model in Brazil since 2004) have also been compared with the GPS points.

A Preliminary Geoid Model for Argentina

Instituto de Fisica de Rosario (IFIR), Facultad de Ciencias Astronomicas y Geofisicas de La Plata (FCAGLP) in a cooperation with Escola Politecnica of the University of Sao Paulo are involved in an effort for the determination of the geoid in Argentina. For this purpose, softwares have been set up at FCAGLP in order to perform the main tasks for geoid computations: processing of gravity data to derive mean gravity anomalies, dealing with geopotential models, performing the numerical integration of the modified Stokes’s formula. The recent NASA/NIMA geopotential model, EGM96, is used as a reference field in the remove-restore technique. A preliminary model has been computed for Argentina with a resolution of 20’ × 20’. A total of 55 GPS points established on the geometric leveling network have been used for a comparison with the undulations derived from gravimetric information. The activities related to the geoid in Argentina are carried out under the umbrella of the Sub-Commission for the Geoid in South America (SCGSA).

Data Processing for a Geoid Model in Argentina

Instituto de Fisica Rosario (IFIR), Facultad de Ciencias Astronomicas y Geofisicas de La Plata (FCAGLP), in a cooperation with the Politechnic School of the University of Sao Paulo (EPUSP), have been involved in the last few years in an effort for the determination of the Argentinian geoid. For this purpose as many gravity data as possible have been compiled and tests were undertaken in order to solve the problems concerning the quality of the data. The main gravity data set was basically compiled at IFIR. This data base consists of about 15.000 gravity stations, mainly from IGM (Instituto Geografico Militar) and from National Universities. They were referred to different references, so that in a first step transformations were performed in order to have the gravity values homogeneously related to IGSN 71. The gravity anomalies have been computed and referred to WGS 84. Taking advantage of the South American Gravity Project (GETECH — University of Leeds), links have been established between IFIR, IGM, the Sub-Commission for the Geoid in South America (SCGSA) and GETECH. In this way new efforts have been carried out in the last few years to improve the gravity data coverage and the DTM. For this purpose topographic maps have been digitised, in particular in the Andes, and a 3’x3’ grid generated for Argentina. All these efforts are described in the paper.

ANALYSIS OF WATER MASS VARIATION IN WETLANDS REGIONS USING DATA FROM GRACE SATELLITE MISSION: THE PANTANAL CASE

ABSTRACT. The natural heritage of biodiversity of the Paraguay river basin is subject to potential impacts due to climate change. To monitor these environments at large spatial scales, the satellite gravity mission GRACE (Gravity Recovery and Climate Experiment) provides time-variable Earth’s gravity field models that reflect the variations due to mass transport processes, like continental... Keywords : water storage, satellite gravity mission, river gauge, rainfall. RESUMO . O patrimonio natural de biodiversidade da bacia do rio Paraguai esta sujeito a potenciais impactos das mudancas climaticas. Para monitorar esse ambiente em escala espacial, a missao satelital GRACE (Gravity Recovery and Climate Experiment) fornece modelos do campo de gravidade da Terra variaveis no tempo devido ao processo de transporte de massa, como as variacoes de armazenamento de agua... Palavras-chave : armazenamento de agua, missao satelital, cotas do nivel d’agua, precipitacao.

ANÁLISIS DE LA MAREA TERRESTRE GRAVIMÉTRICA EN LA ESTACIÓN SAN JUAN (ARGENTINA)

Las mediciones de gravedad en la estacion San Juan con un gravimetro automatico Scintrex CG-5 fueron analizadas con el proposito de obtener los parametros de amplitud y diferencia de fase de mareas terrestres. Las observaciones abarcan un numero total de 35 dias. Para esta locacion, este es el primer analisis de marea basado en mediciones de gravedad. El desarrollo de Tamura fue usado para el potencial de marea normal. Los parametros de marea fueron estimados y analizados con el foco sobre las ondas de marea diurna y semidiurna. Se obtuvo un error cuadratico medio en la unidad de peso de 13,548 nm/s-2 como resultado de un procedimiento de ajuste tomando en cuenta los cambios de presion barometrica. Los factores de amplitud computados para los principales constituyentes de onda fueron comparados con los parametros correspondientes segun la respuesta de marea solida para un modelo de Tierra inelastica no hidrostatica de Dehant, Defraigne y Wahr (DDW). Los factores gravimetricos locales calculados difieren hasta  2,7 % del modelo DDW.