The global continental water budget using GRACE spaceborne gravimetry and high-resolution consistent geodetic-hydrometeorological data analysis

GRACE重力测量提供了大陆上水存储变化的直接测量。因此，这项新技术首次能够在大范围内关闭大陆水平衡。我们建议使用GRACE重量法从大型流域的降水量和流量的地面测量中直接确定大尺度的实际蒸散量。该项目还将提供以前无法获得的从储存、变化和排放中直接确定大流域大气水分通量的方法。因此，它能够对大气模型数据进行新的评估。然而，常规GRACE产品的各向异性误差结构限制了它们的使用，即使对于可用的最大盆地也是如此。水文准信号出现在没有信号的地区，例如沙漠。为此，我们开发了一种新的GRACE误差建模方法，该方法利用已知的质量变化及其不确定性，这些变化来自选定地区的水文约束，例如，输入可以忽略的地区(沙漠)或蒸发蒸腾可以忽略的地区(冰雪、高海拔地区)。这一策略允许超越传统的去混叠过程对重力信号进行校正，从而在空间、时间和质量方面提高分辨率。这种密切的跨学科合作将确保GRACE成为可靠的水文传感器。我们对大尺度实际蒸散量和大气水汽通量特征的研究使我们能够利用GRACE数据预测未测流域的流量并评估相应的不确定度。因此，测量和未测量流域数据的全球复盖面将改进对全球大陆和各自大气水收支的确定，只需最少的模型假设。

GRACE gravity measurements provide a direct measure of water storage changes over continents. Thus, this novel technique enables¿for the first time¿to close the continental water balance on large scales. We propose to use GRACE gravimetry to directly determine large scale actual evapotranspiration from ground-based measurements of precipitation and discharge on large basins. The project will also provide a previously not available direct determination of atmospheric moisture fluxes on large basins from storage changes and discharge. As such, it enables a novel evaluation of atmospheric model data. However, the anisotropic error structure of conventional GRACE products is limiting their utility even for the largest basins available. Hydrological quasi-signals appear in areas, e.g. deserts, where no signal exists. To this end, we develop a new approach to GRACE error modelling, that makes use of known mass changes and their uncertainties, derived from hydrological constraints for selected areas, e.g. with negligible inputs (deserts) or with negligible evapotranspiration (snow/ice -, high altitude regions). This strategy allows for a correction of the gravity signal beyond the conventional de-aliasing procedures and thus an improvement of resolution in terms of space, time and mass. The close interdisciplinary collaboration will ensure the establishment of GRACE as a reliable hydrological sensor. Our investigations of the characteristics of both the large scale actual evapotranspiration and the atmospheric moisture flux enable us to predict discharge from ungauged basins and to evaluate the corresponding uncertainty by use of GRACE data. The global coverage of data from gauged and ungauged basins will hence lead to an improved determination of the global continental and the respective atmospheric water budget with a minimum of model assumptions.