The Global Inundation Extent from Multi-Satellites (GIEMS) is a unique dataset that provides the surface water extent and dynamics over the globe and over a long time record (1993-2007), based on a collection of satellite observations. The percentage of inundation is estimated over an equal-area grid (pixels of 0.25°x0.25° at the equator, i.e., roughly 28kmx28km), at a monthly time-scale.
Figure: Annual mean surface water extent, as estimated from satellites, between 1993 and 2007, in km² for each 773km² pixel.
The data set is available upon request to Catherine Prigent (firstname.lastname@example.org).
Methodology - Global wetland extent and dynamics are estimated from a remote-sensing technique employing a suite of complementary satellite observations: it uses both passive and active microwave measurements, along with visible and near-infrared reflectances. Combining observations from different instruments makes it possible to capitalize on their complementary strengths, to extract maximum information about inundation characteristics, and to minimize problems related to one instrument only. The technique is globally applicable without any tuning for particular environments. The satellite data are used to calculate monthly-mean inundated fractions of equal-area grid cells (0.25°x0.25° at the equator), taking into account the contribution of vegetation (Prigent et al., 2001, 2007, 2012; Papa et al., 2010). The resulting GIEMS data set covers 1993 to 2007.
Evaluation - The variability of GIEMS (intra- and inter-annual) has been analyzed, under different environments. These variations have been compared to other hydrological variables such as river height (from gages and altimeters), precipitation, water runoff, or granmetric data Grace, for evaluation of the GIEMS database (Papa et al., 2007, 2008, 2010).
Applications - The GIEMS database has been widely distributed around the world, for multiple applications. The natural wetlands being the world’s largest source of atmospheric methane (a very powerful green-house gas), our data set provides a unique resource for modelling the methane emissions and for reducing uncertainties in the role of natural wetlands in the inter-annual variability of the growth rate of atmospheric methane (e.g., Bousquet et al., 2006; Ringeval et al., 2010; Petrescu et al., 2010; Hodson et al., 2011; Beck et al., 2013 ; Pison et al., 2013 : Wania et al., 2013). GIEMS is also used to evaluate hydrological modelling at continental to global scale (e.g., Decharme et al., 2008, 2011). The GIEMS water extent has also been combined with altimetric water levels to estimate the water volume changes (Frappart et al., 2008, 2010; Papa et al., 2013).
Climate trends - Results for 1993 to 2007 exhibit a large seasonal and inter-annual variability of the inundation extent with an overall decline in global average maximum inundated area of 6% during the fifteen-year period, primarily in tropical and subtropical South America and in South Asia. The largest declines of open water are found where large increases in population have occurred over the last two decades, suggesting a global scale effect of human activities on continental surface freshwater: denser population can impact local hydrology by reducing freshwater extent, by draining marshes and wetlands, and by increasing water withdrawals (Prigent et al., 2012).
High-spatial resolution – GIEMS dataset is being downscaled to provide the same global coverage and time record, but with a spatial resolution of about 100 m (http://www.estellus.fr/index.php?static13/giems-d15). The downscaling methodologies use auxiliary high-resolution information such as Digital Elevation Models (Fluet-Chouinard et al., 2015), satellite SAR measurements (Aires et al., 2013), or visible/ infrared satellite observations (Aires et al., 2014).
GIEMS methodology and evaluation:
- Prigent, C., E. Matthews, F. Aires, and W. B. Rossow, Remote sensing of global wetland dynamics with multiple satellite data sets, Geo. Res. Lett., 28 , 4631-4634, 2001.
- Prigent, C., F. Papa, F. Aires, W. B. Rossow, and E. Matthews, Global inundation dynamics inferred from multiple satellite observations, 1993-2000, J. Geophys. Res., 112, D12107, doi:10.1029/2006JD007847, 2007.
- Papa, F., C. Prigent, and W.B. Rossow, Ob’ River flood inundations from satellite observations: A relationship with winter snow parameters and river runoff. J. Geophys. Res., 112, D18103, doi:10.1029/2007JD008451, 2007.
- Papa, F., C. Prigent, and W. B. Rossow, Monitoring flood and discharge variations in the large Siberian Rivers from a multi-satellite technique, Surv. Geophys., doi:10.1007/s10712-008-9036-0, 2008.
- Papa, F., C. Prigent, C. Jimenez, F. Aires, and W. B. Rossow, Interannual variability of surface water extent at global scale, 1993-2004, J. Geophys. Res., 115, D12111, doi:10.1029/2009JD012674, 2010.
- Prigent, C., F. Papa, F. Aires, C. Jimenez, W. Rossow, and E. Matthews, Changes in land surface water dynamics since the 1990s and relation to population pressure, Geophys. Res. Lett., 39, L08403, doi:10.1029/2012GL051276, 2012.
Analysis of the methane emission:
- Bousquet, P., P. Ciais, J.B. Miller, E.J. Dlugokencky, D. A. Hauglustaine, C. Prigent, G.R. Van der Werf, P. Peylin, E.G. Brunke, C. Carouge, R. L. Langenfelds, J Lathière, F. Papa, M. Ramonet, M. Schmidt, L. P. Steele, S.C. Tyler, and J. White, Contribution of anthropogenic and natural sources to atmospheric methane variability, Nature, 443, 439-443, doi:10.1038/nature05132, 2006.
- Petrescu, A. M. R., R. L.P.H. van Beek, J. Van Huissteden, C. Prigent, T. Sachs, C. A.R. Corradi, F. W. Parmentier, A. J. Dolman, Modeling regional to global CH4 emissions of boreal and arctic wetlands, Global Biogeochemical Cycles, 24, 4, 10.1029/2009GB003610, 2010.
- Ringeval, B., N. de Noblet-Ducoudre, P. Ciais, P. Bousquet, C. Prigent, F. Papa, W. B. Rossow, An attemp to quantify the impact of changes in wetland extent on methane emissions at the seasonal and interannual time scales, Global Biogeochemical Cycles, 24, GB2003, doi:10/1029/2008GB003354, 2010.
- Hodson, E. L., B. Poulter, N. E. Zimmermann, C. Prigent, and J. O. Kaplan, The El Niño–Southern Oscillation and wetland methane interannual variability, Geophys. Res. Lett., 38, L08810, doi:10.1029/2011GL04686, 2011.
- Beck, V. C. Gerbig, T. Koch, M. M. Bela, K. M. Longo, S. R. Freitas, J. O. Kaplan, C. Prigent, P. Bergamaschi, and M. Heimann, WRF−Chem simulations in the Amazon region during wet and dry season transitions: evaluation of methane models and wetland inundation maps, Atmos. Chem. Phys., 13, 7961−7982, 2013.
- Wania, R., Melton, J. R., Hodson, E. L., Poulter, B., Ringeval, B., Spahni, R., Bohn, T., Avis, C. A., Chen, G., Eliseev, A. V., Hopcroft, P. O., Riley, W. J., Subin, Z. M., Tian, H., van Bodegom, P. M., Kleinen, T., Yu, Z. C., Singarayer, J. S., Zürcher, S., Lettenmaier, D. P., Beerling, D. J., Denisov, S. N., Prigent, C., Papa, F., and Kaplan, J. O.: Present state of global wetland extent and wetland methane modelling: methodology of a model inter−comparison project (WETCHIMP), Geosci. Model Dev., 6, 617−641, doi:10.5194/gmd−6−617−2013, 2013.
- Pison, I., B. Ringeval, P. Bousquet, C. Prigent, and F. Papa, Stable atmospheric methane in the 2000s: key−role of emissions from natural wetlands, Atmos. Chem. Phys. Discuss., 13, 9017−9049, 2013.
Evaluation of hydrological models:
- Decharme B., H. Douville, C. Prigent, F. Papa, and F. Aires, A new river flooding scheme for global climate applications: Off-line evaluation over South America, J. Geophys. Res., 113, D11110, doi:10.1029/2007JD009376, 2008.
- Decharme, B., R. Alkama F. Papa, S. Faroux, H. Douville, C. Prigent, Global off-line evaluation of the ISBA-TRIP flood model, Clim. Dyn., DOI 10.1007/s00382-011-1054-9, 2011.
Calculation of water volumes:
- Frappart, F., F. Papa, J. S. Famiglietti, C. Prigent, W. B. Rossow, F. Seyler, Interannual variations of river water storage from a multiple satellite approach: a case study for the Rio Negro River Basin, J. Geophys. Res., 113, D21104, doi:10.1029/2007JD009438, 2008.
- Frappart, F., F. Papa, A. Güntner, S. Werth, G. Ramilien, C. Prigent, W. B. Rossow, M.-P. Bonnet, Interannual variations of the terrestrial water storage in the Lower Ob’ Basin from a multisatellite approach, Hydrology and Earth System Sciences, 14,12, 2010, 2443-2453, 2010.
- Papa, F., F. Frappart, A. Güntner, C. Prigent, F. Aires, A. C. V. Getirana, and R. Maurer, Surface freshwater storage and variability in the Amazon basin from multi−satellite observations, 1993–2007, J. Geophys. Res. Atmos., 118, doi:10.1002/2013JD020500, 2013.
- Aires, F., F. Papa and C. Prigent, A long-term, high-resolution wetland dataset over the Amazon basin, downscaled from a multi-wavelength retrieval using SAR, J. Hydrometeorology, 14, 594-6007, 2013.
- Aires, F., F. Papa, C. Prigent, J.-F. Cretaux and M. Berge-Nguyen, Characterization and downscaling of the inundation extent over the Inner Niger delta using a multi-wavelength retrievals and Modis data, J.. Hydrometeoroloy, 27, 1958-1979, doi: http://dx/doi.org/10.1175/JCLI-D-13-00161.1, 2014.
- Fluet-Chouinard, E., B. Lehner, L-M Rebelo, F. Papa, S.K. Jamiston, Development of a global inundation map at high spatial resolution from topographic downscaling of coarse-scale remote sensing data, Remote Sensing of Environment, in press, 2015.