Applicability evaluation of AMSR-E remote sensing soil moisture products in Qinghai-Tibet plateau

Abstract: Soil moisture products generated from satellite remote sensing have wide applications, but their accuracy has drawn great attention in the relevant research studies. In this paper, to evaluate the accuracy of soil moisture estimated by passive microwave remote sensing, three kinds of Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) soil moisture products have been inter-compared and analyzed. First, the ground measured soil moisture data was used for evaluating the precision of three kinds of soil moisture products and analyzing the effects of different vegetation coverage and precipitation on passive microwave soil moisture estimates. For this purpose, four soil moisture observation networks, which were displayed in the Qinghai-Tibet Plateau, were taken into account to ensure that this experiment considered most land cover types. In each network, at least six field measurement points were used to calculate the mean value of the corresponding pixels to reduce the deviation caused by scale effect. The results showed that the estimated soil moisture in a flat and bare soil area was more accurate with its correlation coefficient above 0.7 and RMSE below 0.16, while in the high vegetation density area, the correlation coefficient was less than 0.7 and RMSE could reach to 0.2. In general, NASA's soil moisture product performs well in all land cover types with stable relativity. VUA's soil moisture product has less RMSE in high soil moisture areas. Otherwise, JAXA's soil moisture product's relativity rises in low soil moisture areas. Especially in the area where the soil moisture was less than 0.12m3/m3, JAXA's soil moisture product had the highest correlation coefficient of three kinds of soil moisture products. It showed potential for drought monitoring. When precipitation occurs, the accurate of the three kinds of soil moisture products all decreased to different degrees. However, NASA's product sustained preferable stability with a 0.69 correlation coefficient. Based on this, the soil moisture maps of the Qinghai-Tibet Plateau were generated to analyze the space-temporal distributed characteristics of the three kinds of soil moisture products. It proved that NASA's and VUA's soil moisture products were in solid agreement with the actual situation. In addition, the monthly variations of NASA's and VUA's soil moisture were basically the same with the monitoring results of the China Meteorological Administration. But the magnitudes of these two kinds of soil moisture products had a great difference with the actual situation, while JAXA's soil moisture product was not in accordance with the reality in spatial distribution in the northwest and southeast of Qinghai-Tibet Plateau.