Monitoring Dynamic Distribution of Surface Soil Moisture Using SMAP data in Simineh-Zarrineh Catchment (Semi-arid region), NW of Iran

Soil moisture (SM) acts like an impressive factor in hydrological process, agricultural productivity and monitoring of dangerous outcomes of climate change. The main purpose of this study was to monitoring and pattern recognition of spatial and temporal variation of SMAP soil moisture in five subcatchment of Simineh-Zarrineh catchment in north west of Iran from 2015 to 2017. Precipitation data of thirty-five meteorological stations and 287 soil moisture points derived from the SMAP were used to monitoring SM variations in the time scale. Result indicated that the SM variations are subject to precipitation variations throughout the monthly scale in the catchment. In all seasons of the period SM decreased from north to south of the catchment also on the contrary, east to west does not follow up such a constant pattern. Oscillation SM patterns in this time period were completely coordinated by precipitation pattern. The determination coefficient between monthly SMAP soil moisture and precipitation for each sub-catchment was 0.9, 0.83, 0.7, 0.84 and 0.71 for Bokan, Saqqez, Takab, Saeinqaleh and Miandoab sub-catchment, respectively. Spatial variability of standard deviation for SM values was used to find the amount of deviation from the average value during dry and wet seasons. Result reveal that in seasonal scale northwest (0.067 to 0.069 cm3.cm3) and east parts (0.057 to 0.061 cm3.cm3) of study area have higher values of the SM standard deviations in autumn. Results demonstrated that high value of standard deviation was observed in autumn season because of irregular precipitation events and fluctuation of temperature.