Spatial distribution and evaluation of aridity indices in Northern Algeria
Oussama Derdous, Salah Eddine Tachi, Hamza Bouguerra
Abstract
The objective of the study presented herein is to provide an accurate climate classification on the basis of aridity in northern Algeria. The aridity indices used in this study were the De Martonne index (IDM), the Emberger index (IEmberger), and the United Nations Environment Program index (IUNEP), generally admitted in the Mediterranean region. The data required for their calculation were taken from 37 meteorological stations, and processed in a Geographical Information System (GIS) environment to generate climate classification maps according to each index. Generally, the three indices revealed the prevalence of semi-arid conditions in the study area. Similar climate classifications were identified with the IUNEP and the IDM, while the IEmberger has identified larger arid extent. The obtained maps were then validated against the long-term soil moisture data extracted from a gridded global data set. The validation results indicated that the three indices gave very satisfactory results since they showed strong correlation coefficients with the soil moisture data. However, the IEmberger slightly outperformed the IUNEP and the IDM with coefficients of determination (R2) of 0.80, 0.78, and 0.77, respectively. The seasonal investigation of aridity allowed to identify regions and seasons in which irrigation is needed for the main crops cultivated in the study area.