Surface emissivity primary influences the accuracy of land surface temperature retrieval using remote sensing methods. This parameter is important in thermal infrared remote sensing. This paper aims to investigate the effects of soil water content and roughness on the thermal infrared emissivity of bare soil through an experimental method. This work can provide useful information for developing a soil emissivity retrieval method via remote sensing. The spectral emissivity of two soils（loam and sandy loam） with different soil water contents was measured by a Nicolet IS10 Fourier-transform infrared spectrometer with an integrating sphere. Data were used to analyze the effects of soil water content on soil spectral emissivity. The average emissivity of both soil types with different particle sizes of 8—14 μm was determined using an active-passive diffuse emissivity measuring device. This device can determine the effects of soil water content on the average soil emissivity for 8—14 μm particles. Soil emissivity increases with increasing soil water content because of the high emissivity of water.The average emissivity of loam soil with water contents of 0%

13.7%

26.1%

and 43.4%are 0.81

0.92

0.93

and 0.95

respectively

for wavelengths from 3 μm to 11 μm

as well as 0.73

0.89

0.93

and 0.96

respectively

for wavelengths from 3.3 μm to 5.3 μm. Moreover

the average emissivity of sandy loam soil with water contents of 0%

8.8%

25.3%

and 28.6% are 0.82

0.92

0.94

and 0.95

respectively

for the wavelengths from 3 μm to 11 μm

as well as0.75

0.89

0.95

and 0.96

respectively

for wavelengths from 3.3 μm to 5.3 μm. For the effects of soil roughness on emissivity

the results show that the average emissivities from 8—14 μm are 0.916

0.934

and 0.937 for particles with sizes less than 0.6

0.6—1

and 1—2 mm

respectively

for the dry sandy loam soil

as well as 0.936

0.951

and 0.959

respectively

for the dry loam soil. Soil emissivity increases with increasing soil moisture. Wavelengths from 3.3 μm to 3.5 μm are the most affected by soil moisture. In this wavelength range

the band-average difference in soil emissivity between dry and wet soils is higher than 0.2. The wavelengths with minimal effect include 11 μm to 15 μm

when the band-average difference in soil emissivity between dry and wet soils is lower than 0.015. For the thermal infrared atmospheric window waveband（8—14 μm）

wavelengths from 8 μm to 9.5 μm are the most influenced by soil moisture. In this range

the band-average difference for soil emissivity is 0.05. Soil emissivity slightly increases with increasing particle size for dry and wet soils. Furthermore

soil emissivity increases by more than 0.05 for bands 10

11

and 12 of ASTER data with increasing soil water content.