Simulation And Application Of Diurnal Variation Of Soil Depth Layer Temperature In Shandian River Basin

As one of the key control variables in the process of water and energy exchange between land and air,land surface temperature(LST)has a wide range of application value in meteorology,climate,hydrology,ecology and other disciplines,and has also become a research hotspot at home and abroad.At present,many remote sensing satellites can carry out remote sensing observation of surface temperature,but their transit frequency is relatively small and fixed,so they can not obtain complete characteristics of soil temperature daily change.At the same time,cloud,wind speed,atmospheric temperature,vegetation cover and other factors will affect the accuracy of LST inversion,and then affect the space-time continuity of LST products.Therefore,based on the improvement of soil water daily cycle model and soil temperature with depth change model,and based on the research of soil heat inversion method,further soil water inversion is carried out to improve the space-time continuity of LST products.This paper mainly does the following work:1.Establish the soil temperature daily cycle model.In this paper,based on the measured data of soil temperature and humidity network stations in the lightning River Basin,the model of soil temperature daily cycle change based on limited observation data is calibrated,and a DTC model with only four parameters is established by model fitting.The model can be applied to all kinds of LST remote sensing observations with discontinuous time.2.Establishing a model of soil temperature changing with depth.Using the soil temperature data of 3cm,5cm,10 cm and 20 cm obtained from August 2018 to July2019 in the lightning River Basin,the continuous change rule of soil temperature with time in different depth layers was observed.After the establishment of the model,an index function can be used to represent the change of soil temperature,and the changeof soil temperature in a continuous day can be simulated according to the measured data of existing stations.3.Improved apparent thermal inertia method for soil water inversion.The diurnal temperature difference of soil temperature in each layer for one month in September was obtained by using the data of lightning River Basin,and the linear correlation between soil temperature and apparent thermal inertia was obtained by combining with the albedo data of MODIS.The experimental results show that the apparent thermal inertia model has good accuracy,and the best correlation R with soil temperature can reach 0.8.Soil water can be obtained by inversion of the apparent thermal inertia model.4.Soil moisture inversion.The simplified ATI model of apparent thermal inertia is directly used to retrieve soil moisture.According to different land types,different vegetation types and different soil textures,the most matching daily soil temperature change model and soil depth change model are used to estimate soil temperature data,and then the most accurate ATI data and ideal results of apparent thermal inertia are obtained Soil moisture products.