Studying changes of sea level and water storage for coastal regions in West-Africa, using satellite and terrestrial data sets

几个西非国家位于大西洋之外，受到沿海和萨赫勒型降水的影响。对这些国家来说，全球变暖带来了多重严重的经济和社会威胁：海平面上升造成的盐水入侵减少了淡水供应，陆地水循环的变化可能伴随着干旱和洪水发生的频率、持续时间或程度的增加。很明显，这些影响是相互关联的，应该以综合的方式加以观察和监测。关于水文循环、淡水供应和水储存的知识对于水资源管理是必不可少的。水文模拟在确定通量和储存量的时空格局方面发挥着核心作用，但预测的质量取决于边界条件以及模型比较的数据可用性和质量。重力恢复和气候实验（GRACE）任务的数据已经在西非的水循环研究中找到了应用，但是用GRACE研究沿海地区的一个特殊挑战是海洋和陆地信号叠加时产生的泄漏效应。在拟议的活动中，我们建议：1)利用星载（GRACE、SMOS、ASCAT、ERS1/2和雷达测高）、海洋学和陆地（潮汐计、水文）数据和模型，研究沿海地区海平面和储水量的综合分析方法；2)调查和量化气候变化的持续影响，特别强调几个西非国家的沿海地区；3)通过将星载数据同化为陆地水文循环的动态模型，改进区域尺度的水文模拟。鉴于GRACE数据分析和解释将在评估水团变化方面发挥关键作用，很明显，将其空间分辨率提高到超出标准产品所能达到的水平对于我们提出的建议至关重要。因此，我们将使用针对陆地-海洋界面特定挑战的区域分析方法对1b级仪器数据进行再处理。

Several West-African countries are located besides the Atlantic Ocean, being exposed to coastal as well as Sahel-type precipitation regimes. To these countries, global warming poses multiple severe economic and societal threats: saltwater intrusion by sea level rise reduces freshwater availability, and changes in the terrestrial water cycle may be accompanied by increased frequency, duration or magnitude of droughts and floods. It is clear that these effects are linked and should be observed and monitored in an integrative approach. Knowledge concerning the hydrological cycle, freshwater availability and water storages is indispensible for water resource management. Hydrological modeling plays a central role for determining spatio-temporal patterns of fluxes and storages but the quality of the predictions depends on boundary conditions and on data availability and quality for model comparison. Data from the Gravity Recovery and Climate Experiment (GRACE) mission have found applications for studying the water cycle for West Africa, yet a particular challenge for studying coastal regions with GRACE is posed by the leakage effect, occurring where the signals from ocean and land are overlaid.In the proposed activity, we suggest to 1) study methods for the integrated analysis of sea level and water storage for coastal regions, using space-borne (GRACE, SMOS, ASCAT, ERS1/2 and radar-altimetric), oceanographic, and terrestrial (tide-gauge, hydrological) data and models, 2) investigate and quantify ongoing effects of climate change with particular emphasis on the coastal areas of several West-African countries, and 3) improve hydrological modeling at the regional scale by assimilating space-borne data into dynamic models of the terrestrial hydrological cycle.Seen that GRACE data analysis and interpretation will play a key role in assessing water mass change, it is clear that sharpening its spatial resolution beyond what can be reached with standard products is essential for what we propose. Therefore, we will reprocess level-1b instrument data using a regional analysis approach tailored to the specific challenges of the land-ocean interface.