Interannual and long‐term climate variability over the Zaire River Basin during the last 30 years

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Abstract
Climatological data records of temperature, rainfall, and number of rainy days provided by the Zaire Meteorological Agency (METTELSAT) at seven Zairian stations for the 1960–1992 period are analyzed for the first time since the 1970s. Our investigations focus on climate variability as related with environmental changes over the Zaire River Basin, which is climatologically and biogenetically one of the most important regions in the world. On the basis of the 30‐year monthly mean climatologies, it is shown that the solar annual cycle dominates the seasonal changes of both the temperature and rainfall over this region. On the interannual time‐scales, the variability of these climatic variables is characterized by (1) a 2‐to 5‐year oscillation strongly correlated to the southern oscillation index, thus to the ENSO phenomenon, and (2) a nearly 10‐year oscillation (called here the quasi‐decadal oscillation, QDO) with a very remarkable correlationship with the solar activity (sunspots number). On the long‐term timescale, a remarkable decreasing trend in rainfall and number of rainy days, as well as increasing temperatures over the 30‐year period, has been detected as the most dominant climatological features all over the basin. The magnitudes of temperature increase are by far larger than those reported in previous works for both the global mean and hemispherical mean warmings. We postulate that this trend of regional warming and desiccation from within the heart of the African rainforests is due to the increase in surface albedo, itself triggered by uncontrolled land‐use policies and forests development over this area (logging, slash and burn, bushfire, fuelwood, farming, ranching, urbanization, etc.).