INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.3578 Linkages between global sea surface temperatures and decadal rainfall variability over Eastern Africa region Philip Omondi, a * Laban A. Ogallo, a Richard Anyah, b J. M. Muthama c and J. Ininda c a IGAD Climate Prediction and Applications Centre (ICPAC), Nairobi, Kenya b Department of Natural Resources and the Environment, University of Connecticut, USA c Department of Meteorology University of Nairobi, Nairobi, Kenya ABSTRACT: Linkages between dominant spatio-temporal decadal rainfall variability modes and the global sea surface temperature (SST) modes are investigated over East Africa region for the period 1950–2008. Singular value decomposition (SVD) and canonical correlation analysis (CCA) techniques are employed to examine potential linkages and predictability of decadal rainfall variability over the region. When the ten-year periodicity is filtered out from the observed monthly rainfall data, distinct decadal rainfall regimes are exhibited in the time series of mean seasonal rainfall anomalies. Spectral density analysis of rainfall time series showed dominance of a ten-year periodicity, significant at 95% confidence level. The Principal Component Analysis (PCA) results yielded nine and seven homogeneous decadal rainfall zones for long rains; March–May (MAM), and the short rains: October–December (OND) seasons, respectively. The third season of June–August (JJA) which is mainly experienced in western and coastal sub-regions had eight homogenous zones delineated. Results show that the leading three SVD-coupled modes explain greater than 75% of the squared covariance between the two fields. The first SVD mode for Indian, Atlantic and Pacific Oceans contributed to 50, 43 and 38% of the total square covariance for MAM season, respectively. The same mode accounted for 65, 48 and 40% for OND rainfall season, respectively. For the JJA season, mode one contributed to about 61, 39 and 42% of the variance. The study showed that forcing of decadal rainfall over the region is associated with El Ni˜ no mode that is prominent over the Pacific Ocean, while Indian Ocean dipole is the leading mode over the Indian Ocean basin. An inter-hemispheric dipole mode that is common during ENSO was a prominent feature in the Atlantic Ocean forcing regional decadal rainfall. The high variability of these modes highlighted the significant roles of all the global oceans in forcing decadal rainfall variability over the region. In addition, results from multiple linear regression model showed substantial variation of the model prediction skill of the decadal rainfall variability modes within various homogenous zones and for different seasons. Copyright  2012 Royal Meteorological Society KEY WORDS decadal rainfall variability; Eastern Africa; decadal modes of variability; global oceans SSTs Received 31 May 2011; Revised 11 July 2012; Accepted 14 July 2012 1. Introduction Societal needs for climate information on decadal time- scales is continuing to grow in terms of its potential value and relevance as a driver in sector decision making. How- ever, such information is currently lacking. Predictions and observationally based analyses for decadal climate variability and change are needed. A large timescale gap, especially the one that goes from one year to about 20 years, exists in climate predictions. Long-term scale climate predictions over East Africa region has not been done with enough precision to adequately carry out assessment of impacts of climate anomalies at the sub- regional level (Anyah and Qiu, 2012). For interventions and planning purposes, climate information is required on average of 5–10 years. Only recently has this received ∗ Correspondence to: P. Omondi, IGAD Climate Prediction and Applications Centre, ICPAC, Nairobi, Kenya. E-mail: philip.omondi@gmail.com attention of the scientific community despite the rele- vance of this timescale to many societal and developmen- tal applications (Anyah and Qiu, 2012). These scientific and technical shortcomings in turn act as a major hur- dle that limits the ability to design and justify investment decisions for the development and design of appropriate adaptation strategies. Knowledge on decadal climate variability is popu- larly emerging as a new direction in climate science (Knutson and Tuleya, 2004; CLIVAR, 2007; Meehl and Hibbard, 2007; Seager et al., 2007; Meehl et al., 2009), especially in light of increased demand for cli- mate and climate change information. Numerous assess- ments of climate information user needs have identified this timescale as being important to infrastructure plan- ners, water resource managers, and many others. Decadal prediction lies between seasonal/interannual forecasting and longer term climate change projections, and further focuses on time-evolving regional climate conditions over the next 10–30 years. Perhaps the most striking find- ing is the linkage of decadal drought frequency in the Copyright  2012 Royal Meteorological Society