An Analysis of the Within-season Rainfall Characteristics and Simulation of the Daily Rainfall in Two Savanna Zones in Ghana
An Analysis of the Within-season Rainfall Characteristics and Simulation of the Daily Rainfall in Two Savanna Zones in Ghana
复制标题
加纳两个稀树草原带季节内降雨特征分析及日降雨量模拟
DOI：
10.1016/s0168-1923(96)02414-8
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发表时间：
1997
影响因子：
6.2
通讯作者：
G. Dowuona
中科院分区：
文献类型：
--
作者：
S. Adiku;P. Dayananda;C. Rose;G. Dowuona
本文调查了在选定的网站（阿克拉和塔马利）在加纳的两个热带稀树草原区的季节内降雨量的变化。平均持续时间的干旱和潮湿的法术估计每个网站的长期降雨概率参数。在阿克拉，干旱期的平均持续时间从3月（7天）到6月（2天）减少，7月又增加（5天）。在塔马利，雨季的平均干旱时间约为3天。在这两个地点观察到的降雨模式似乎表明，塔马利将为作物生产提供更有利的条件。然而，一个完整的答案，这样一个重要的问题，需要考虑在每个网站的水平衡，包括土壤的蓄水能力。还为这两个地点建立了一个降雨模拟模型，并对这两个地点的降雨模式和降雨量进行了合理的模拟。模拟的雨季每个月的雨天数，无论是短期和长期同意与观察在阿克拉（R2= 0.98）和塔马利（R2= 0.95），提供了适当的短期或长期模型参数。模拟的月降雨总量也是如此（阿克拉R2= 0.97;塔马利R2= 0.97）。然而，从长期降雨量记录中得出的模型参数显然不能用来模拟通常观察到的短期降雨量波动，特别是在阿克拉。为了克服这一缺陷，我们寻求降雨参数和其他全球因素之间可能存在的关系，影响或修改当地的降雨模式的网站。特别是，研究重点是降雨参数和南方涛动指数（SOI）之间的关系。溶胶和一些模型参数之间的相关系数高达0.78。因此，似乎可以使用来自一系列SOI值的信息来修改模型参数的数值，然后再将其用于模拟运行。最后讨论了利用这种方法改进降雨模拟的前景。
This paper has investigated the within-season rainfall variability at selected sites (Accra and Tamale) in two savanna zones of Ghana. The average duration of the dry and wet spells was estimated for each site from the long-term rainfall probability parameters. At Accra, the average duration of dry spells decreases from March (7 days) to June (2 days) and rises again in July (5 days). At Tamale, the average length of a dry spell during the rainy season is about 3 days. The observed patterns of rainfall at the two sites seem to suggest that Tamale would offer more favourable conditions for rainfed crop production. However, a complete answer to such an important question needs to consider the water balance at each site including the water storage ability of the soils. A rainfall simulation model was also developed for the two sites, and simulated the rainfall patterns and amounts reasonably well at both sites. Simulated number of rainy days in each month of the rainy season for both the short and long term agreed well with observations at Accra (R2= 0.98) and Tamale (R2= 0.95), provided the appropriate short- or long-term model parameters were used. This was also the situation for the simulated monthly rainfall totals (Accra R2= 0.97; Tamale R2= 0.97). It was, however, obvious that the model parameters derived from the long-term rainfall records could not be used to simulate the short-term rainfall fluctuations which were commonly observed, especially at Accra. In a quest to overcome this deficiency, we sought possible relations between the rainfall parameters and other global factors that affect or modify the local rainfall patterns at the sites. In particular, the study focused on the relationship between the rainfall parameters and the Southern Oscillation Index (SOI). A correlation coefficient as high as 0.78 was established between the Sol and some of the model parameters. Thus, it appears possible to use information from a series of the SOI values to modify the numerical values of the model parameters before their use in the simulation runs. Prospects of using such an approach to improve the simulation of rainfall are discussed.