The Water Balance of the East African Lakes And its Application to the Study of Past Climates

Nicholson9973150东非的大型湖泊是气候变化的敏感指标。 这些湖泊的波动记录了在实际降雨测量可用之前热带大片大陆地区的降雨变化。 在之前的工作中，P.I.对1800年以来10个湖泊的波动进行了详细的重建。 为了更好地解释这些波动，维多利亚湖的水平衡进行了准确的评估，并制定了一个水文模型，其逐年波动。 该模型被用来量化产生这些波动的降雨条件。 在这里，我们建议将我们的工作扩展到其他东非湖泊，本研究的最终目标是为选定的非洲湖泊提供更好的水平衡估计，开发湖泊年际波动模型，反演模型以解释湖泊的过去事件，并确定湖泊对其他环境参数的敏感性。 最令人关注的是对湖面降雨量和云量的评估。 关于这些条件的直接信息很难获得，因此只能从海岸线观测站进行评估。 由于受到海岸的影响，这种方法不能提供足够的湖本身的图像。 在我们的研究中，高分辨率的卫星数据将被用来确定直接在湖泊上空的云量和降雨量。 这对较大的湖泊尤其重要，因为中尺度环流系统改变了降雨和云量的模式，该项目的成果将是对非洲湖泊水量平衡的可靠估计、年度间波动的简单模型、对整个十九世纪降雨情况的定量评估，以及一种通用工具，可用于以后根据高分辨率沉积记录解释古气候。

Nicholson9973150The large lakes of East Africa are sensitive indicators of climatic change. Fluctuations of these lakes register rainfall variability in a large continental region of the tropics prior to the availability of actual rainfall measurements. In prior work, the P.I. produced detailed reconstructions of the fluctuations of 10 lakes since 1800. To better interpret these fluctuations, an accurate assessment of the water balance of Lake Victoria was made and a hydrologic model of its year-to-year fluctuations was developed. The model was applied to quantifying the rainfall conditions that produced these fluctuations. Here, we propose to extend our work to other East African lakes.The ultimate goals of this study are to produce improved esrtimates of water balance for selected African lakes, to develop models of the lakes' interannual fluctuations, to invert the models to interpret the lakes' past rainfalls, and to determine the lakes' sensitivity to other environmental parameters. The most concern is assessment of rainfall and cloudiness over the lake. Direct information on these terms is so difficult to obtain that they have been assessed from shoreline stations. Because of the influence of the shore, this approach does not provide an adequate picture over the lake itself. In our study, high-resolution satellite data will be used to determine cloudiness and rainfall directly over the lakes. This is particularly important for the larger lakes where mesoscale circulation systems alter the patterns of rainfall and cloudiness.The results of the project will be reliable estimates of water balances for African lakes, simple models of internannual fluctuations, a quantitative assessment of rainfall conditions throughout the nineteenth century, and a generic tool that can be later applied to interpreting paleoclimate from the high-resolution sedimentary record.