A UAV-derived thermal infrared remote sensing three-temperature model and estimation of various vegetation evapotranspiration in urban micro-environments

• Estimating the evapotranspiration of different urban vegetation types by the UAV-derived thermal infrared remote sensing 3-T model. • Analyzing quantitatively the diurnal variation characteristics of the evapotranspiration rates of the different urban vegetation types. • Providing the high spatio-temporal resolution urban vegetation evapotranspiration. The large-scale and single-point observations on urban vegetation easily cause the difficulty to quantitatively study the evapotranspiration of vegetation in urban micro-environments. In this content, the three-temperature (3T) model by combining the UAV-derived thermal infrared data was applied to estimate the evapotranspiration of different urban vegetation types at the microscale in Nanjing city, China accurately. The diurnal variation characteristics of the evapotranspiration rates of the different vegetation types such as arbors, shrubs and grasslands in different seasons were quantitatively analysed. The results showed that the estimated vegetation evapotranspiration rate was between 0–1.4 mm/h. The highest evapotranspiration rate among the different vegetation types was that of arbors, followed by shrubs and grasslands. The evapotranspiration rate on the sunny side was significantly higher than that on the shady side. There were obvious seasonal differences in vegetation evapotranspiration, which gradually decreased from spring to winter. The transpiration transfer coefficients of vegetation in summer and winter were significantly higher than those in other seasons, which indicated that the effects of water deficits or environmental stress were the largest at these times. The UAV-derived thermal infrared remote sensing three-temperature (3T) can simplify the complexity of the calculations and ensure the accuracy of the estimation results, which may provide the high spatio-temporal resolution urban vegetation evapotranspiration.