Rainfall and drought: Changes in the synoptic distribution over semi-arid Tunisia

Tunisia is a coastal region of the Mediterranean Sea in North Africa with an area of ​​164,150 km². The physical geography of the region is very heterogeneous with mountains to the north and the Sahara to the south. It is located in the transition zone between the humid Mediterranean climate and the arid Saharan climate. Precipitation is characterized by a large North-South spatial distribution varying between 1400 mm/year in the North to less than 40 mm/year to the South.

Thanks to the consolidation of a quality, long-term, synoptic database over the whole country, the average monthly rainfall was mapped by comparing the beginning and the end of the 20th century to look for a possible change in the spatial distribution of rain across Tunisia. We found a slight change in the spatial distribution of rainfall by comparing average monthly rainfall in the early to late twentieth century. A slight change in the direction of the rainfall gradient is perceptible during transition seasons with a speed of change in spatial structure that is more important at the end of the twentieth century for the fall season. This change may intensify as a result of the impacts of climate change and subsequently have an effect on socio-economic aspects. On the other hand, the phenomenon of meteorological drought continues to migrate towards the North and it appears that the stations with significant tendencies towards the increase of drought are located mainly in the regions of North / North-West of the country.