Mechanisms associated with September to November (SON) rainfall over Uganda during the recent decades

Geographica Pannonica

Kisesa Makula Exavery¹  Ngoma Hamida¹  Ayugi Brian¹  Wen Wang¹  Karim Rizwan¹ 

[1] Ministry of Education (KLME), Nanjing University of Information Science and Technology, Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CICFEMD), Joint International Research Laboratory of Climate and Environment Change (ILCEC), Key Laboratory of Meteorological Disaster, Nanjing, China;

关键词: rainfall;    extreme;    circulation;    uganda;    east africa;   

DOI  :  10.5937/gp25-29932

来源: DOAJ

【 摘 要 】

This study revisits teleconnections associated with the anomalous events of September to November (SON) rainfall over Uganda during 1981-2019, owing to the recent intensification of extreme events. Empirical Orthogonal Function (EOF), Composite and Correlation analysis are employed to examine the variability of SON rainfall over the study domain and associated circulations anomalies. The first EOF mode (dominant mode) displays a positive monopole pattern and explains 67.2% of the variance. The results revealed that SON rainfall is largely influenced by a Walker circulation mode over the Indian Ocean, whereby, wet events are associated with an ascending limb of the Walker circulation on the western part of the Indian Ocean characterized by convergence at low levels and divergence at upper level. The study showed that SON rainfall is positively (negatively) correlated with Indian Ocean (Atlantic Ocean) sea surface temperatures (SST). Furthermore, Indian Ocean Dipole (IOD) events have impact on SON rainfall with strong positive correlation, whereas Southern Oscillation Index (SOI) revealed negative correlation. The results also reveal that there is a lag in ENSO and IOD episodes during wet/dry events over the region. ENSO and IOD also tend to extend the rainfall season of SON and thus study of extreme events may not be well captured by studies focusing on SON. Future studies might consider the season of October to December or December to February. These phenomena need to be closely monitored and considered when making seasonal forecasts.

【 授权许可】

Unknown