From Flood to Famine: The Rainfall Regime in East Africa, Its Interannual Variability, and Large-Scale Teleconnections

该项目研究东非的雨季，包括其年际变化及其与非洲其他地区降雨量变化的联系。 所考虑的地区大致是坦桑尼亚、乌干达和肯尼亚。 该地区的大部分降雨分为两个季节，3月至5月期间的“长雨”和10月至12月期间的“短雨”。 在这两种情况中，短雨占了年际降水变化的大部分，并且与海表温度有更强的联系。 该项目涉及四个一般性专题。 首先，研究将审查该地区普遍干旱的原因，这在赤道地区是不寻常的。 第二，图尔卡纳急流在确定区域降水气候学和降雨的年与年变化方面的作用将被考虑。 图尔卡纳急流是一种低空急流，流经埃塞俄比亚和东非高地之间的狭窄缝隙，尚未得到广泛研究。第三，将确定当地热带辐合带（ITCZ）对降雨季节性和年际变化的影响程度。 非洲大部分地区降雨的季节性和变化通常归因于ITCZ运动，但这种模式在东非是有问题的。 第四，这项研究将对雨季的年际变化进行检查，包括短期和长期降雨，力求了解印度洋（特别是印度洋偶极子模式）、太平洋（厄尔尼诺）和大西洋变化在确定降雨变化方面的相对作用，以及东非和非洲其他地区降雨异常之间偶极子遥相关模式的原因。 这项工作还将考虑该区域近年来气候发生变化的可能性。 这项工作的一个新颖之处是使用了可追溯到1874年的雨量计记录，沿着东非几个地区可追溯到1820年的半定量降水时间序列。这项工作通过关注东非的干旱和洪水行为产生了社会影响，这些干旱和洪水给该地区的人民造成了严重损失。 这项工作可能导致降雨量和海洋表面温度之间的统计关系，这可能有助于预测雨季的变化，包括长期的洪水和干旱。 此外，该项目还资助了两名研究生，从而培养了该领域的下一代研究人员。

This project examines the rainy seasons of East Africa, including their interannual variability and connections to rainfall variability in other parts of Africa. The region considered is roughly Tanzania, Uganda, and Kenya. Most of the rainfall in this region comes in two seasons, the "long rains" occurring between March and May, and the "short rains" during the October to December season. Of the two, the short rains account for most of the interannual rainfall variability and have much stronger connections to sea surface temperature. The project addresses a set of four general topics. First, the research will examine the causes of the general aridity of the region, which is unusual for an equatorial region. Second, the role of the Turkana jet in determining the regional precipitation climatology and the year-to-year variability of the rains will be considered. The Turkana jet is a low-level jet that flows through a narrow gap between the Ethiopian and East African highlands, and has not been extensively studied. Third, the extent to which a local intertropical convergence zone (ITCZ) is responsible for the seasonality and interannual variability of rainfall will be determined. The seasonality and variability of rainfall over much of Africa is commonly attributed to ITCZ movement, but this paradigm is problematic over East Africa. Fourth, the research will provide an examination of interannual variability of the rainy seasons, both for the short and long rains, seeking to understand the relative roles of Indian (particularly the Indian Ocean Dipole Mode), Pacific (El Nino), and Atlantic Ocean variability in determining rainfall variability, and the reasons for dipole teleconnection patterns between rainfall anomalies in East Africa and in other parts of Africa. The work would also consider the possibility that the climate of the region has changed in recent years. A novel aspect of the work is the use of a rain gauge record extending back to 1874, along with semi-quantitative precipitation time series for several regions of East Africa extending back to 1820.The work has societal impact through its focus on the behavior of droughts and floods in East Africa, which take a heavy toll on the people of the region. The work could lead to statistical relationships between rainfall and sea surface temperature which could be useful for forecasting variations in the rainy seasons, including prolonged periods of flood and drought. In addition, the project supports two graduate students, thereby training the next generation of researchers in the field.