Simulated physical mechanisms associated with climate variability over Lake Victoria basin in East Africa
Simulated physical mechanisms associated with climate variability over Lake Victoria basin in East Africa
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DOI：
10.1175/mwr3266.1
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发表时间：
2006-12-01
影响因子：
3.2
通讯作者：
Xie, Lian
中科院分区：
文献类型：
--
作者：
Anyah, Richard O.;Semazzi, Fredrick H. M.;Xie, Lian
完全耦合的区域气候。 3D湖泊建模系统用于研究与维多利亚湖盆地气候多尺度变化相关的物理机制。为了研究不同过程对湖盆气候的相对影响，通过平滑湖盆周围的地形进行了一系列模型实验。改变湖面特征，并减少或增加通过模型域的四个横向边界平流进入湖区的大规模水汽量。模拟的流域月平均降雨量与卫星（热带降雨测量任务）的估计值相当。午夜和清晨之间的峰值表征了湖泊四个象限降雨量的模拟日变化，与卫星估计一致，尽管模拟峰值出现得稍早一些。在平滑地形的模拟中可以明显看出，湖东山脉产生的上坡/下坡气流和陆湖风环流对影响湖/陆风锋的强度和位置起着重要作用。以及陆湖风环流的水平范围，以及湖盆降水。当湖面被沼泽（水葫芦）取代时，位于湖西区的深夜和清晨最大降雨量急剧减少。我们的模拟还表明，通过盛行的东风贸易输送的大规模水分显着增加了湖盆降水。这与之前一些研究中提出的观点形成鲜明对比，即维多利亚湖仅通过降水-蒸发-再降水循环产生自己的气候（降雨）。
A fully coupled regional climate. 3D lake modeling system is used to investigate the physical mechanisms associated with the multiscale variability of the Lake Victoria basin climate. To examine the relative influence of different processes on the lake basin climate, a suite of model experiments were performed by smoothing topography around the lake basin. altering lake surface characteristics, and reducing or increasing the amount of large-scale moisture advected into the lake region through the four lateral boundaries of the model domain. Simulated monthly mean rainfall over the basin is comparable to the satellite (Tropical Rainfall Measuring Mission) estimates. Peaks between midnight and early morning hours characterize the simulated diurnal variability of rainfall over the four quadrants of the lake, consistent with satellite estimates, although the simulated peaks occur a little earlier. It is evident in the simulations with smoothed topography that the upstope/downslope flow generated by the mountains east of the lake and the land-lake breeze circulations play important roles in influencing the intensity, the location of lake/land breeze fronts. and the horizontal extent of the land-lake breeze circulation, as well as lake basin precipitation. When the lake surface is replaced with marsh (water hyacinth), the late night and early morning rainfall maximum located over the western sector of the lake is dramatically reduced. Our simulations also indicate that large-scale moisture transported via the prevailing easterly trades enhances lake basin precipitation significantly. This is in contrast to the notion advanced in some of the previous studies that Lake Victoria generates its own climate (rainfall) through precipitation-evaporation-reprecipitation recycling only.