This paper was to assess the reliability of RADARSAT-2 quad-polarization SAR data in rice mapping and yield estimation. Five scenes of RADARSAT-2 images were acquired in the rice season of 2011 in Jiangsu Province, China. Ground experiments were conducted in accordance with the acquisition dates. For rice mapping, optimal dual-polarization combination was obtained by ratio change detection. The accuracy of rice mapping by HV/HH reaches 79.2% and by VV/HH reaches 84.9%. For rice yield estimation, an improved scheme based on assimilation method has been put forward. ORYZA2000 model was coupled with an empirical rice backscattering model to simulate the dual-polarization ratios. SCE-UA optimization algorithm is employed to determine the optimal set of input parameters during the re-initialization process. As a result, an improved accuracy has been confirmed.
In this study, three scenes of Landsat TM/ETM+ images covering Beijing area were used to examine the relationship
between the UHI and land use and land cover (LULC) changes, as well as between the UHI and vegetation greenness.
The brightness temperatures, LULC, and NDVI were retrieved from the calibrated images. The results showed that the
urban or built-up area in Beijing has increased by 4.07% from 1988 to 2005, with nearly 5.7% of vegetated land lost
during the same period. The barren area was also increased in this period as large number of land was taken over for
urban construction. Seasonal pattern of UHI was obvious with highest UHI intensity observed in summer and lowest in
winter. Moreover, with the rapid urbanization, the extent of UHI expanded with newly hot spots emerged surrounding the
central urban area. In addition, higher NDVI or vegetation coverage leads to higher land surface temperature (LST) in
winter and lower LST in summer. This was due to the different thermal characteristic between vegetated area and
non-vegetated area. Therefore, increasing vegetation coverage can be beneficial to the mitigation of UHI effect in urban
area in hot season while to keep the land warmer in cold season.
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