The invention discloses a 
sky hemisphere 
thermal infrared atmospheric downward 
radiation ground measurement method. through approximate expression of 
thermal infrared directional atmospheric downwardradiation, a 
linear relationship model between directional atmospheric downward 
radiation and an observation angle cosine value is constructed; and further in combination of an angular integral relationship between the directional atmospheric downward 
radiation and 
sky hemisphere atmospheric downward radiation, a simplified model for using a slope and an intercept in the 
linear relationship modelto calculate the 
sky hemisphere atmospheric downward radiation is developed. As long as an 
infrared radiometer on the ground is used to perform three times of measurement on different observation angles of the sky, the slope and the intercept can be fit according to the constructed 
linear relationship model, and thus, the sky hemisphere 
thermal infrared atmospheric downward radiation is calculated. The complicated calculation of the hemisphere integral is saved, release of a sounding 
balloon in the field to acquire 
atmospheric profile data is not needed either, the 
infrared radiometer is onlyused on the ground to perform three times of measurement in different directions of the sky, the sky hemisphere thermal 
infrared atmospheric downward radiation data can thus be quickly obtained, materials and financial resources are saved, and a great significance is achieved in ground 
verification of a thermal infrared surface temperature 
remote sensing inversion product.