To satisfy the requirement of surface energy budget research on the meso- and micro-scale, a parameterization is developed to calculate high spatial resolution, clear-sky downward longwave radiation （DLR） from HJ-IB...To satisfy the requirement of surface energy budget research on the meso- and micro-scale, a parameterization is developed to calculate high spatial resolution, clear-sky downward longwave radiation （DLR） from HJ-IB thermal data. The DLR algorithm is established based on extensive radiative transfer simulation and statistical analysis. To address the problem that HJ-1B has a single thermal channel and lacks atmospheric information, the brightness temperature of HJ-1B and water vapor content are used in the algorithm. An accuracy evaluation and error analysis for the algorithm is conducted using a simulated radiation da- taset. The result shows that the algorithm performs well in most circumstances, but there is obvious underestimation when wa- ter vapor content is greater than 4 g/cm2. Error analysis indicates the accuracy of estimated DLRs is affected by uncertainties in input parameters, including water vapor content and top-of-atmosphere radiance. It is also affected by the difference between ground and near-surface air temperature. The algorithm is applied to actual HJ-1B data, and validated by ground data from six stations in the Heihe River and Haihe River basins. The estimated DLRs have good consistency with measured data except at Huazhaizi, and root mean square errors at most sites are around 20 W/m2, which is slightly better than the result of MODIS. There is significant overestimation of DLR at Huazhaizi during summer, which is mainly produced by the large ground-air temperature difference. A correction process based on temperature difference is proposed and applied at Huazhaizi. The result shows that the positive bias is largely diminished after correction.展开更多
基金supported by Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q10-2-2)National Natural Science Foundation of China(Grant No.40971204)+1 种基金National High-tech R&D Program of China(Grant No.2012AA12A304)R&D Special Fund for Public Welfare Industry(Meteorology)(Grant No.GYHY200706046-1)
文摘To satisfy the requirement of surface energy budget research on the meso- and micro-scale, a parameterization is developed to calculate high spatial resolution, clear-sky downward longwave radiation （DLR） from HJ-IB thermal data. The DLR algorithm is established based on extensive radiative transfer simulation and statistical analysis. To address the problem that HJ-1B has a single thermal channel and lacks atmospheric information, the brightness temperature of HJ-1B and water vapor content are used in the algorithm. An accuracy evaluation and error analysis for the algorithm is conducted using a simulated radiation da- taset. The result shows that the algorithm performs well in most circumstances, but there is obvious underestimation when wa- ter vapor content is greater than 4 g/cm2. Error analysis indicates the accuracy of estimated DLRs is affected by uncertainties in input parameters, including water vapor content and top-of-atmosphere radiance. It is also affected by the difference between ground and near-surface air temperature. The algorithm is applied to actual HJ-1B data, and validated by ground data from six stations in the Heihe River and Haihe River basins. The estimated DLRs have good consistency with measured data except at Huazhaizi, and root mean square errors at most sites are around 20 W/m2, which is slightly better than the result of MODIS. There is significant overestimation of DLR at Huazhaizi during summer, which is mainly produced by the large ground-air temperature difference. A correction process based on temperature difference is proposed and applied at Huazhaizi. The result shows that the positive bias is largely diminished after correction.
