Exploration of Surface Temperature and Cloudiness for Soil Moisture Remote Sensing
Zhuo, Lu; Han, Dawei
University of Bristol, UNITED KINGDOM

Soil moisture is a key variable in the water and energy exchange between the land surface and atmosphere. Remote sensing of soil moisture can be achieved using visible light, infrared and microwave. Most studies have been focused on the microwave band and there is a lack of research on the thermal properties of moist soil which could be used for satellite thermal infrared sensors. In this study, two catchments with different climate and geographic conditions in England and Australia are analysed to explore the relationships between soil moisture and surface temperature based on thermal inertia and energy balance theories. The data are grouped into different sets based on seasons, cloudiness, and rainy/no rainy days. The result showed a strong correlation between surface temperature and soil moisture in both catchments. The correlation results in both catchments give Spearman rank correlation on at 0.856 and -0.766 respectively with in-situ soil moisture sensors (the negative value is with the soil moisture content and the positive value is with the capacitance frequency). In the Australian catchment, it was also found that the correlation had a near threefold increase when the surface temperature was normalised by daily maximum solar radiation. The identified optimal sample time point for the surface temperature may be used in selecting suitable satellites that pass a specific studied area. By applying the proposed method, soil moisture can be determined without surface micro-meteorological and atmospheric measurements. This information can then be fused with microwave soil moisture data and Numerical Weather Modelling to provide soil moisture estimation with better spatial and temporal resolutions.