Using GADI index to determine the drought and the dry areas in Kerman province

Aridity as a spatial concept and drought as a temporal concept have always been studied in different aspects as two distinct categories. However, both concepts indicate anomalies from normal condition. Several indices have been introduced to examine each of these concepts using one or more hydrological cycle’s components. Meanwhile, soil moisture and changes in its spatial and temporal variations can be considered as one of the most important factors in detecting the drought and determining the areas of drought. Due to difficulties including cost and time consuming measurements, soil moisture has not been used so far. In this study, the intensity and the persistence of drought in Kerman province were evaluated using soil moisture from the output of NASA Global Land Data Assimilation System (GLDAS). For this purpose, the new GLDAS based Aridity and Drought Index (GADI) was used, which realized the drought and aridity in each region simultaneously. The soil moisture time series in four soil layers were derived from NOAH land surface model for the years 1953 until 2017. GADI were employed to map aridity and drought conditions. The results showed that the severity of drought increased in lower soil layers. The low percentage of soil moisture in the lower layers indicates that lower layers had not been fed from rainfall as a result of sever evaporation losses. This also shows the existence of long-term droughts in these layers.