T. Pekker's research while affiliated with University of Texas at Austin and other places

... The Caspian Sea is the largest lake on Earth with an area of about 371,000 km 2 . Over the past few hundred years, the Caspian Sea level (CSL) has experienced substantial fluctuations up to several meters [1][2][3]. The Caspian Sea is located within an endorheic basin between Europe and Asia, and the CSL change is mainly controlled by water mass exchange between the Caspian Sea and Caspian drainage basin (see Figure 1) via river discharge, precipitation, and evaporation. ...

... Finally, the radiometer drift can also be detected by comparison with the WTC derived from meteorological numerical models. The instrumental WTC is preferred to the modeled correction since it provides a better estimation of the wet troposphere path delay with respect to precision, sensitivity and spatial sampling (Stum, 1994;Urban et al., 2001). However, the modeled corrections remain one of the few independent references to assess the long-term stability of the radiometer corrections. ...

... Kurtenbach et al. (2009) employed short-arc method (Mayer-Gürr et al. 2007) under the principle of Kalman smoothing to conduct the daily snapshot solution, but the stochastic behaviour of the gravity field has to be considered as a priori information. Kang et al. (2008) used traditional dynamic method to generate the so-called 'quick-look' solution with a moving-window strategy (with a window step of one day and window width of 15 d), but those solutions are also stabilized using regularization. An incomplete list of GRACE solutions with various temporal resolutions from different research groups can be found at http://icgem.gfz-potsdam.de/ICGEM/TimeSeries.html. ...

... L'introduction de l'article présente les motivations du travail. Jusqu'à maintenant, de nombreuses études ont étudié le cycle saisonnier des échanges d'eau entre les continents et les océans grâce aux modèles de surface et les données de Topex-Poséidon (par exemple : Cazenave et al. (2000), Chen et al. (2002)). Notre papier se focalise sur l'étude de la modification du cycle saisonnier de ces échanges d'eau. ...

... For example, higher temperatures will increase the energy demand for cooling, reduce the precipitation rate and degrade the water resources (Roshan et al., 2010;Roshan et al., 2011). Regarding the effect of global warming on lakes depth and surface area fluctuation, lots of studies have been run on simulation and prediction of such changes all around the world (Chelton et al.,1982;Fang et al.,1998;Cabanes et al.,2001;Chen et al.,2002;David et al.,2002;Bouzinac et al.,2003;Michael et al.,2009;Mooij et al.,2009;Moernaut et al.,2010). As lakes respond directly to climate changes, quantifying their sensitivity to possible potentials will provide crucial information for the assessment of water resources quality and aquatic ecosystems in future (IPCC, 1996;Hauser et al., 1997;Magnuson et al., 1997;Mulholland et al., 1997;Rouse et al., 1997;Schindler, 1997;Fang et al., 1999, Komatsu et al., 2007. ...

... The missions Gravity Recovery and Climate Experiment (GRACE) (Tapley et al, 2004) and Gravity Recovery and Interior Laboratory (GRAIL) (Zuber et al, 2013) demonstrated the benefits of measuring orbital changes along the line connecting two satellites and, in particular, the relative velocity by means of the inter-satellite radio tracking data Doppler shift (Wolff et al, 1969). GRACE and GRAIL inter-satellite observations were ~2-3 orders of magnitude more accurate than deep space tracking data leading to extremely precise determination of the gravity fields of the Earth (Tapley et al, 2005) and the Moon (Zuber et al, 2013), respectively. An accurate high-resolution mapping of celestial bodies' gravitational anomalies will require extremely precise radio tracking data to reveal the properties of their internal structures. ...