Recent trends and anomalies in mean seasonal and annual temperatures over Sudan

The mean temperature time-series over the period 1941-1996 for 13 stations across Sudan are examined on seasonal and annual bases to explore any possible trends in recent decades. Standardized anomaly indices (SAIs), intraannual coefficients of variability, and autocorrelation coefficients are also developed. The consistency of both seasonal and annual patterns is also studied. South of latitude 16 degrees N, the data show the tendency for annual time-series to follow mostly the wet-season time-series. The zone located northward is also an exception among other parts, as it does not reveal an actual change in its temperature series towards cooling or warming, but rather shows fluctuations between these two phases. In the rest of the country, a linear fit established for annual temperature series indicates significant upward trends, synchronized with those in wet- and hot-season series; the rising trends in the former seasonal series being higher and more significant. Since the 1940s, annual and wet-season temperatures have increased by 0.076-0.20 and 0.082-0.29 degrees C per decade, respectively. The period of greater warmth in Sudan appears to coincide with that of rainfall depletion reported post mid-1960s. A general increase in the coefficient of variability (C-v) of the within-year monthly temperatures has also been noticed. This increase is statistically significant in northern and most central locations. (C) 2000 Academic Press.