Modelling of XCO2 Surfaces Based on Flight Tests of TanSat Instruments

摘要： The TanSat carbon satellite is to be launched at the end of 2016. In order to verify the performance of its instruments, a ?ight test of TanSat instruments was conducted in Jilin Province in September, 2015. The ?ight test area covered a total area of about 11,000 km2 and the underlying surface cover included several lakes, forest land, grassland, wetland, farmland, a thermal power plant and numerous cities and villages. We modeled the column-average dry-air mole fraction of atmospheric carbon dioxide (XCO2) surface based on ?ight test data which measured the near- and short-wave infrared (NIR) re?ected solar radiation in the absorption bands at around 760 and 1610 nm. However, it is dif?cult to directly analyze the spatial distribution of XCO2 in the ?ight area using the limited ?ight test data and the approximate surface of XCO2, which was obtained by regression modeling, which is not very accurate either. We therefore used the high accuracy surface modeling (HASM) platform to ?ll the gaps where there is no information on XCO2 in the ?ight test area, which takes the approximate surface of XCO2 as its driving ?eld and the XCO2 observations retrieved from the ?ight test as its optimum control constraints. High accuracy surfaces of XCO2 were constructed with HASM based on the ?ight’s observations. The results showed that the mean XCO2 in the ?ight test area is about 400 ppm and that XCO2 over urban areas is much higher than in other places. Compared with OCO-2’s XCO2, the mean difference is 0.7 ppm and the standard deviation is 0.95 ppm. Therefore, the modelling of the XCO2 surface based on the ?ight test of the TanSat instruments fell within an expected and acceptable range.