Abstract

Soil depth temperature is one of the most effective factors on agricultural products. However, the it has highest missing data in synoptic weather stations. Hence, this research aims to evaluate soil depth temperature changes and determine the accuracy and applicability of ECMWF re-analysis data in estimation of SDT. To do so, soil depth temperature data for different depths (5,10, 20, 30, 50 and 100 cm) of Mehrabad, Geophysic, Shomal-e-Tehran and Doushan Tapeh stations were extracted in hourly time intervals (03, 09, 15 UTC) from Iran’s Meteorology Organization. Then, trend analysis was carried out by Mann-Kendall test. Also, gridded re-analysis SDT data of ERA5 were extracted from ECMWF from 1997 to 2018 statistical period. Re-analysis data were convert from Netcdf format to text using GIS. Then, their accuracy was analyzed by ME, MAE and RMSE tests. The climatic trend of soil depth temperature presents the general increase trend in all studied stations during the 1997-2018. Furthermore, the results showed close correlations between observational and re-analysis data at different depths. Re-analysis data could mainly reproduce the temporal-spatial distributions of soil depth temperature in study area. The correlation coefficient between observational and re-analysis data was 0.97 and 0.95 for first and second studied depths of the soil, respectively. It indicates a significant linear relationship between observational data and ERA5 re-analysis data in hourly time intervals. However, the ERA5 overestimates the SDT data in comparison with observational data