Preliminary study on the characteristics of sand-surface reflective spectra in the hinterland of the Taklimakan deserter in winter

To sum up, the conclusions about the characteristics of the sand-surface reflectivities of visible light channel and near infrared channel in the Tazhong region in the hinterland of the Taklimakan Desert in winter are as following:(1) On fine days, the sand-surface average reflectivities of visible light channel and near infrared channel in the Tazhong region are 25.8% and 28.6% respectively. It is roughly estimated that the atmosphere can reduce the reflectivities of these two channels for 5.2% and 7.5% respectively comparing with the RS data of NOAA satellite in the corresponding period.2 On fine days, the reflectivities of visible light channel and near infrared channel have the following characteristics: 1 At all the positions of a dune, the reflectivity of near infrared channel is higher than that of visible light channel, and 4.3% higher in maximum on the sand-falling slope and the left wing of dune; 2 Among the different positions of a dune, the reflectivity change of visible light channel is low but that of near infrared channel is high, and the latter is about 5 times of the former: 3The reflectivities of both visible light channel and near infrared channel on the south-facing slopes are slightly higher than that on the north-facing slopes.(3) The reflectivities of visible light channel and near infrared channel are the highest on cloudy days comparing with that on fine days and thin-cloudy days; from the fine days to the thin-cloudy days and cloudy days, the green values, reflectivity difference between the near infrared channel and visible light channel of dunes, and the maximum reflectivity difference of near infrared channel between the different dune positions are successively reduced; but the maximum reflectivity difference of visible light channel between the different dune positions are gradually increased.(4) On fine days, the dune reflectivities of visible light channel and near infrared channel are reduced with the increase of sun's altitude, but the negative correlation between the reflectivity of visible light channel and the sun's altitude is higher than that between the reflectivity of near infrared channel and the sun's altitude.(5) Frost on sand surface can increase the reflectivities of visible light channel and near infrared channel, and increase for 2.6% and 3.5% respectively compared with that without frost.