Dilution effect in tissues associated with higher water and carbon contents per unit weight of plants. Drought is the cause of desertification of the Sahel landscape. The ITCZ produces a rain belt that moves south to north in July. Annual rainfall is higher in savanna regions of the Sahel than in arid grasslands to the north. Precipitation of calcium and magnesium salts iii.
Sodium ions are the dominant cation in the soil solution iv.
An El Nino event appears around Christmas time. The temperature of surface waters in the eastern Pacific Ocean shows an anomalous high value. An El Nino event starts as an upwelling of cold water off the Peruvian coast. An El Nino event apparently leads to changes in weather patterns in the northern hemisphere. Timing of Sahel droughts and El Nino events are broadly correlated.