The elastic crustal response to seasonal water mass changes in the Amazon basin

Transcription

1 Escola Politécnica da Universidade de São Paulo The elastic crustal response to seasonal water mass changes in the Amazon basin Prof. Dr. Denizar Blitzkow (1) Sônia Maria Alves Costa (2) Dra. Ana Cristina Oliveira Cancoro de Matos (1) (1)Laboratory of Topography and Geodesy Department of Transportation Engineering University of São Paulo (2)Brazilian Institute of Geography and Statistics Coordination of Geodesy Geociences Division IVth Scientific Meeting of the ORE-HYBAM, Lima (Peru), 6-96 September 2011

2 Motivation Improvement in the understanding of water cycle in Amazon region and its relation with vertical component variation; Application of two different space geodetic measurement techniques GPS and GRACE in order to analyze the water cycle and its connection with the vertical displacement of the lithosphere; Crust response of the GPS due to water loading; GRACE Equivalent Water Height and the relationship with water storage; In-situ data from ANA (Agência Nacional de Águas) gauge stations are available for the validation of GRACE models/grids; Selection of Gauge stations for this study within a radius of 100 km around GPS stations; Possibility for the estimation of the correlation coefficient between in-situ data and GRACE, anti-correlation of GPS and in-situ data, as well as phase differences between in-situ data and GRACE; Use of Wavelet Power Spectrum (WPS) in order to visualize phase evaluations between ANA and GRACE time series.

3 Data sets Period of study: 2007 to 2010 In-situ water level measurements provided by ANA from 84 gauge stations in Amazon, Tocantins and Paraná Basins. Informations and data available at: 10-day GRACE data geoid solutions computed by (Bruinsma et al., 2010; Lemoine et al., 2007): 145 files ( until ) expressed in Stokes coefficients up to degree 50 (i.e., ~450 km spatial resolution) corrected for atmospheric (ECMWF) and ocean tides (MOG-2D). Informations and data available at: Global Navigation Satellite System (GNSS) data from 24 continuous monitoring stations of Instituto Brasileiro de Geografía e Estatística (IBGE), Low-Latitude Ionospheric Sensor Network (LISN), Serviço Geológico Brasileiro and International GNSS Service (IGS). Informations and data available at: ftp://geoftp.ibge.gov.br (RBMC) (LISN) ftp://igscb.jpl.nasa.gov (IGS)

4 Region of Study with Basins/Sub-basins and Station's distribution

5 GNSS Network A total of 1461 days between years 2007 to 2010 (GPS weeks 1408 to 1616) from 35 stations located in South and Central America, with a densification in Amazon basin, were processed. Software used: Bernese, version 5.0, Bernese Processing Engine (BPE) Processing Strategy (parameters and models) Processing Strategy (parameters and models) Double Difference (DD) solutions using the ionosphere-free linear combination; Phase center corrections of antennas (receptor and satellites) were applied using IGS absolute calibration values, model IGS05; Satellite orbits, EOPs from final combined solution IGS; New ambiguity resolution schedule was implemented applying 4 different strategies in a baseline-by-baseline mode performing the following steps: (1) Melbourne-Wuebbena approach (< 6000 km) (2) Quasi-Ionosphere-Free (QIF) approach (< 2000 km) (3) Phase-based widelane/narrowlane method (< 200 km) (4) Direct L1/L2 method (< 20 km) The ocean loading model used is the FES2004; Solid earth tidal displacement was corrected using the tide model TIDE2000 (IERS 2000). Ocean tides was corrected using OT CSR30 model (IERS 2003 ); Atmospheric parameters: the hydrostatic component of the zenith tropospheric delay was estimated each 2h applying the Niell mapping function.

6 GNSS Network Configuration

7 GNSS Data Analysis Position time series The position time series of stations were obtained from the daily double difference solutions. Each daily solution was aligned to the weekly IGS05 solutions applying minimum constraint strategy. The IGS05 stations used for the reference frame definition were: AREQ, BRFT, CHPI, CRO1, KOUR, LPGS, MANA, RIOP, SCUB and UNSA. Daily position evaluation The time series transformation parameters between daily and IGS05 weekly solutions were estimated in order to check the external fit of daily results. The RMS for the north (N), east (E) and up (U) components to be 1.4, 1.5 and 5.6 mm. Statistics of transformation parameters between daily solutions and IGS05 weekly solutions Mean StdDev TX(mm) TY(mm) TZ(mm) ROT_X(") ROT_Y(") ROT_Z(") SCALE(ppm)

8 Time series of transformation parameters between daily and IGS05 solutions

9 Peak to peak variation of vertical component Seasonal Amplitudes in the GPS stations Anual variation in vertical compoment (mm) GPS Stations The highest values occur between October and November when the ebb period of the river is finishing and rivers have the lowest water level. The lowest values of vertical component occur between April and May when the rain season is finishing and rivers are full of water (flood period).

10 Hydrological in-situ data collection and organization ANA in-situ data were collected from HIDROWED data base - Sistema de Informações Hidrológicas (HIDRO). The following parameters were used for data selection: Stations in a radius of 100 km from GNSS stations; Stations with data available for the period between 2007 to 2010; Stations installed in the main rivers of basins on the water stream ; From the daily data it was computed the Weighed Moving Average for intervals of 10 days and after that the hydrological station's time series were created using the GRACE Reference Dates (RD). OBS: The same procedure was applied for the GPS geometric heights after GNSS data processing.

11 GRACE data collection and organization The Equivalent Water Height (EWH) grids, second release (RL02), deduced from GRACE gravity field models (10-day models), computed by Centre National d Etudes Spatiales/Groupe de Recherches de Géodésie Spatiale (CNES/GRGS). For each 10-day GRACE geoids, the Stokes coefficients are converted into EWH coefficients, and then 1 x1 global grids of water thickness (in mm) are calculated, from degree 2 to 50. For the period between 2007 to 2010, there are 146 grids. The horizontal coordinates of the hydrological stations were interpolated by applying a bi-linear algorithm to the EWH grids and producing the EWH time series. The EWH grids and the hydrological in-situ data time series were used for the analysis of correlation coefficients, phase and amplitude.

12 Methodology For each 10-day geoid, the Stokes coefficients were converted into equivalent water height coefficients (Ramillien et al., 2005), and then 1 x1 global grid of water thickness (in mm) was calculated. From the ground-base station positions, GRACE-based water heights were interpolated by applying a bilinear algorithm to the gridded data. Thus, for the same position, satellite and ground-based data were compared. The reference date (RD) of each grid was taken as the day of the mid-10-day interval. The RD was used to compare GRACE water thickness (EWH) with daily in-situ water level data and GNSS, specifically on the same mean period of 10-day. A linear equation was assumed and fitted by least-square linear inversion: Y(t) = a X(t) + b (model), (Equation 1) where: GRACE X ANA ANA X GPS X(t): GRACE X(t): in situ data (ANA) Y(t): in situ data (ANA) Y(t): GPS a: transfer function slope coefficient b: Y-axis intersection value

13 RESULTS COEFFICIENT OF DETERMINATION (R²)( ) EVALUATION IN-SITU HYDROLOGICAL DATA X GRACE EWH Considerations about the climate (precipitation) and hydrogeology were taken into account when the coefficient of determination R² was analyzed. A good correlation (R² 0,7) is evident in 70% of hydrological stations ( on the water stream ) and the highest values are located between the end of Solimões and beginning of Amazon rivers, as well as in Madeira river and its tributaries, mainly in areas close to Colombia (Tabatinga) and Peru (Guajara-mirim). The low correlation (R² < 0,7) is found in Tocantins and Paraná basins, mainly close to Palmas, Imperatriz and Cuiabá. The same was observed in the north part of Amazon basin, close to São Gabriel da Cachoeira and Boa Vista. It was observed in these areas as well as in regions close to Amazonas mouth a delay between seasonal cycles of hydrological stations and Grace EWH. This is observed in the phase difference results from both observations. IN-SITU HYDROLOGICAL DATA X GPS Considering the GNSS and ANA data strong anti-correlations are found in Manaus, Urukuritiba, Porto Velho, Santarém, Altamira, Guajara-mirim, Marabá and Tefé areas in sedimentary and cenozoic domains; low anti-correlation is found in the neighbour basins (Tocantins and Paraná) and close to Amazonas mouth.

14 Coefficient of Determination between GRACE EWH and Hydrological Stations (ANA) The high coefficient of determination(r²>0.7) is found at the southern edge of the Amazon river and it indicates the strong relation between ANA and GRACE results.

15 (1a) (1b) city/station São Gabriel da Cachoeira basin Amazon river NEGRO state Amazonas latitude longitude Hydro-geological Domain Crystalline Distance GPS/ANA (Km) 3.12 ANA WL Phase (degree) ANA WL Ampli. (mm) GRACE EWH Phase (degree) GPS Phase (degree) Phase dif. (ANA GRACE) days GRACE EWH Ampli. (mm) GPS Ampli. (mm) Phase dif. (ANA GPS) days (1c)

16 coerence cross Wavelet Power Spectrum (WPS) São Gabriel da Cachoeira

17 (2a) (2b) city/station Marabá basin Tocantins river TOCANTINS state Pará latitude longitude Hydro-geological Domain Sedimentary Distance GPS/ANA (Km) 2.64 ANA WL Phase (degree) ANA WL Ampli. (mm) GRACE EWH Phase (degree) GRACE EWH Ampli. (mm) GPS Phase (degree) Phase dif. (ANA GRACE) days GPS Ampli. (mm) Phase dif. (ANA GPS) days (2c)

18 coerence cross Wavelet Power Spectrum (WPS) Marabá

19 (3a) (3b) city/station Porto Velho basin Amazon river MADEIRA state Rondonia latitude longitude Hydro-geological Domain Cenozoic Distance GPS/ANA (Km) 4.87 ANA WL Phase (degree) ANA WL Ampli. (mm) GRACE EWH Phase (degree) GRACE EWH Ampli. (mm) GPS Phase (degree) Phase dif. (ANA GRACE) days GPS Ampli. (mm) Phase dif. (ANA GPS) days (3c)

20 Wavelet Power Spectrum (WPS) Porto Velho coerence cross

21 (4a) (4b) city/station Manaus basin Amazon SOLIMÕES river AMAZONAS state Amazonas latitude longitude Hydro-geological Domain Sedimentary Distance GPS/ANA (Km) ANA WL Phase (degree) ANA WL Ampli. (mm) GRACE EWH Phase (degree) GRACE EWH Ampli. (mm) (4c) GPS Phase (degree) GPS Ampli. (mm) Phase dif. (ANA GRACE) days 3.27 Phase dif. (ANA GPS) days

22 coerence cross Wavelet Power Spectrum (WPS) Manaus

23 Phase(ANA X GRACE) Amplitudes comparison Amplitude(ANA between X GRACE) ANA and GRACE EWH Rivers Amp. ANA Amp. GRACE Amplitude (mm) Uraricoera_Boa_V. Tocantins_Palmas Xingú_Altamira Araguaia Tocantins_Impz Cuiabá Tocantins_Marabá Tapajós_Itaituba Teles Pires/Tapajós Jaru/Jiparana Araguari_Macapá Acre/Abuna_Riob Guama_Belém Guaporé/Branco Teles Pires/Tapajós Javari/Itaguai Madeira_Porto_V. Tapajós_Santarém Amaz./Solimões_Pari Amaz./Solimões_Tefé Amaz./Solimões_Letí Amaz./Solimões_Uruk Mamore_Guajara Amaz./Solimões_Nau Negro_Saga Phase Differences ANA X GRACE EWH Rivers Phase (degrees)

24 Phase differences between Hydrological Stations (ANA) and GRACE EWH from year The year 2009 was selected for the evaluation of phase differences due to highest precipitation recorded. It was observed that in most cases phase differences are negative varying between 0 to -10 in the Amazonas and Solimões rivers.

25 (a) Year 2007 (b) Year 2008 Precipitation (c) (c) Year Year2009 br/ (d) Year 2010

26 Hydro-geological Domains nfoid=756&sid=9

27 Phase in S.G. da Cachoeira ID_ANA YEAR AMPL ANA (mm) PHASE (dg) AMPL_EWH (mm) PHASE (dg) PHASE DIF (days) RIVER Negro Curicuriari Negro Curicuriari 2009 MAX MIN AVER Negro Considering the average phase difference between years 2007, 2008 and 2009, in S.G da Cachoeira an unusual behavior of GRACE EWH can be found. Phase is positive only in this part of Negro River, indicating that Grace EWH cycle is around 20 days in advance with respect to insitu data cycle

28 Time Series of water cycle in S.G. da Cachoeira Negative phase Positive phase River Negro Considering the average phase difference between years 2007, 2008 and 2009, in S.G da Cachoeira an unusual behavior of GRACE EWH can be found. Phase is positive only in this part of Negro River, indicating that Grace EWH cycle is around 20 days in advance with respect to in-situ data cycle.

29 RESULTS EVALUATION OF AMPLITUDE AND PHASE (ANA X GRACE EWH) The Year 2010 could not be included in this evaluation because the observations from the hydrological stations are not yet available. The highest amplitudes of GRACE EWH reach 500 mm in Manaus and Urukuritiba areas. The largest inter-annual amplitudes were observed between years 2008 and 2009 in both data. The highest amplitudes observed by in-situ data have a good agreement when compared with GRACE EWH observations, mainly in the biggest rivers in Amazon basin, like Amazonas, Solimões, Tapajós, Xingú and Madeira. In some cases the Grace EWH amplitudes are not proportional to the observed amplitudes by in-situ data. This is the case of Leticia, in the boundary between Brazil and Colombia. The high amplitude values are observed in 2007 in the north part of Amazon basin and in Amazon and Madeira rivers in % of phase differences are between -10 and -50, meaning that GRACE observations have a delay of ~ 10 to 50 days when compared with in-situ data. The wavelet analysis shows the same results. Positive phase between GRACE and in-situ data was found only in S. Gabriel da Cachoeira (Negro River).

30 Final Considerations This study is important for helping the understanding the hydrological cycle in Amazon basin and its connection with vertical component variation. Grace observations have in general a good response in Amazon Basin due to the great water level variation in this region. In the sedimentary areas of Amazon basin GRACE has a better response mainly in the biggest rivers like Amazonas, Solimões, Tapajós, Xingú and Madeira. For the future, it is planned to look after satellite altimetry in regions with poor hydrological in situ observations.

31 Future Work To evalutate GRACE grids of vertical deflection with GPS results, applying the same corrections in both data (atmospheric and ocean loading). To estimate the crust response based in phase differences of local observations and evaluating hydrogeologic domains. Acknowledgements ANA agency for the hydrometric stations data, CNPq for supporting this research, GRGS (Groupe de Recherche en Géodésie Spatiale) for Geopotential Models.