Inter-annual variability of precipitation in the Souss Massa region and linkage of the North Atlantic Oscillation

The analysis of the spatial and temporal inter-annual variability of Souss-Massa precipitation is the main objective of this work. The spatial distribution of precipitation in the region during 1980-2010 shows that rainfall follows a gradient from the North to the South and from the West to the East. We study the influence of altitude and distance to the Atlantic Ocean on annual precipitation using the Principal Component Analysis. The regional precipitation increases with high altitude and decrease with low distances to the sea. We distinguish three clusters of stations with the same rainfall behaviour, stations located in the plains, in the mountains and the most distant stations from the Atlantic Ocean. The evolution of the standardized precipitation index during 1980-2010 shows that the wet years represent 16% and the dry years represent 35% of the studied period. No statistically significant trend is detected during 1980-2010 for all the stations according to the results of the Mann-Kendall test. Change-points analyses show no statistically significant change-point according to Buishand test, Pettitt test and the Hubert segmentation. The results of continuous wavelet analysis show multiple significant high energy bands (p=0.05) for the periods of 1 year, (2-4) years, (3-5) years and (5-10) years in most stations, with the persistence of continuous high energy bands of 8 to 9 years around the period 1990-2002. The wavelet coherency analysis indicates a significant antiphase between the NAO and the regional SPI during 1980-2010.