Measuring and Simulating Passive C-band Microwave Relief Effects over Qinghai-Tibet Plateau in Remote Sensing

Spaceborne microwave radiometers have established the superiority of global climate change and hydrographic monitoring in global coverage, day and night, all weather, and strong transmission. For passive microwave remote sensing, topography serves as one of perturbing effects in respect that it represents surface roughness larger than microwave wavelength. The lower frequencies used by C band perform more strongly in comparison with both higher microwave frequencies (>10GHz) under adverse weather, and L band (1to2GHz) at an advantage of relatively elaborate spatial resolution. A numerical simulation of satellite microwave radiometric observations of topographic scenes has been developed. Nerveless, the scarcity of field experiments on relief effects constitutes a major impediment to the further progress in the investigation of rough terrain correction at microwave frequencies. In the interest of simulating brightness temperatures exactly in mountainous area well combined with topographic experiments, Tibetan Plateau in China regarded as our study area, the research carried into execution as the following: (1) Analyzing relief effects for passive C band, and extracting topographic features quantificationally in order to satisfy microwave radiative transfer model in mountainous areas; (2) Referring to the configuration in AMSR-E, by the method of spatial convolution statistic analysis, in accordance with the estimation of the sensitivity for topographic features, selecting efficiency relief factors at C-band ; (3)Building various shapes of artifactitious hills to measure relief effects in the ground experiment based on the observation of Truck-mounted Multi-frequency Microwave Radiometer (TMMR); (4) According to the observation of relief effects validated in the field measurement, reworking the microwave radiative transfer model in rough terrain, and then simulating brightness temperatures in the configuration of AMSR-E. From the result of the comparison between our simulation and AMSR-E data, for dual-polarized microwave signal, vertical polarization is much more optimal to reflect relief effects than horizontal polarization within 3K bias. To correct errors in spaceborne radiometric observation on account of topographic effects, we solved the problem used by vertical polarized microwave radiation characteristics at passive C band. The results have significant implications for soil moisture data assimilation and disaggregation of brightness temperature observations in mountainous areas.