Comparison of the climate indices based on the relationship between yield loss of rain-fed winter wheat and changes of climate indices using GEE model.

Climate change is one of the most important meteorological phenomena that has had a lot of impacts on different sections with different spatial scales. In recent decades, climate changes affected by various factors especially human activities have had various impacts in different sections such as melting glaciers, various flood occurrence, occurrence of different droughts and etc. UNEP aridity Index (UNEP) and Modified De-Martonne index (MDM) are two more used indices to evaluate climate conditions in various regions of the world. In this paper; 1) the temporal trend of changes in climate conditions based on UNEP and MDM indices using climatological data (from 1967 to 2017) of 16 meteorological stations using parametric and non-parametric statistical tests were evaluated 2) the accuracy of UNEP and MDM indices were compared to assess climate conditions, based on the correlation between mentioned indices and percent of annual yield loss (AYL) in rain-fed winter wheat using simple and multiple Generalizes Estimation Equation (GEE) methods (for help managers to select more suitable and more accurate index to assess climate condition). Results showed, based on UNEP and MDM indices, climate indices in 93.75% and 87.5% of stations had a decreasing trend, but decreasing trend only in 56.25% and 50% of stations were significant at 5% level (respectively). The evaluation of the accuracy of UNEP and MDM indices showed that, in all stations, |B| coefficients between calculated AYL and UNEP and MDM indices and R2 coefficients between simulated AYL using AquaCrop model and predicted AYL using simple and multiple GEE methods in UNEP aridity index were more than MDM index. So, it is recommended to use UNEP aridity index to assess the climate conditions in different regions.