Radio-frequency interference （RFI） affects greatly the quality of the data and retrieval products from space-borne microwave radiometry. Analysis of the Advanced Microwave Scanning Radiometer on the Earth Observing System （AMSR-E） Aqua satellite observations reveals very strong and widespread RFI contam- inations on the C- and X-band data. Fortunately, the strong and moderate RFI signals can be easily identified using an index on observed brightness temperature spectrum. It is the weak RFI that is diffi- cult to be separated from the nature surface emission. In this study, a new algorithm is proposed for RFI detection and correction. The simulated brightness temperature is used as a background signal （B） and a departure of the observation from the background （O–B） is utilized for detection of RFI. It is found that the O–B departure can result from either a natural event （e.g., precipitation or flooding） or an RFI signal. A separation between the nature event and RFI is further realized based on the scattering index （SI）. A positive SI index and low brightness temperatures at high frequencies indicate precipitation. In the RFI correction, a relationship between AMSR-E measurements at 10.65 GHz and those at 18.7 or 6.925 GHz is first developed using the AMSR-E training data sets under RFI-free conditions. Contamination of AMSR-E measurements at 10.65 GHz is then predicted from the RFI-free measurements at 18.7 or 6.925 GHz using this relationship. It is shown that AMSR-E measurements with the RFI-correction algorithm have better agreement with simulations in a variety of surface conditions.
[Objective] The research aimed to study the structure and propagation characteristics of climatological mean kinetic energy of disturbance of intraseasonal oscillation in Asian summer monsoon zone. [Method] When South China Sea monsoon started to break out, the kinetic energy of intraseasonal oscillation disturbance in the monsoon zone was analyzed, especially the researches about the variation of South China Sea monsoon, the development of Indian monsoon and the advancement of East Asian monsoon. [Result] The developed process of Asian summer monsoon had the close relationship with the kinetic energy activity of 30-60 d low-frequency oscillation disturbance. The kinetic energy of disturbance explained the eruption, occurrence, development and termination of monsoon from the energy angle. It was found that the kinetic energy of disturbance in Arabian Sea zone, Bay of Bengal and South China Sea area was the strongest, especially in Arabian Sea zone. It illustrated that Arabian Sea zone (Somali jet) was the biggest energy source of Asian monsoon. The starting mark of monsoon eruption in the whole Asia was the abrupt eruption of South China Sea monsoon. The eruption of South China Sea monsoon in the middle dekad of May was the westward transmission result of kinetic energy of disturbance on the east sea surface of Philippines. The kinetic energy of disturbance in East Asian monsoon zone had the seasonal northward advancement in summer. The high kinetic energy center of disturbance in Indian monsoon zone changed from one to two. They were respectively in Arabian Sea and Bay of Bengal. [Conclusion] The research provided the theory basis for analyzing the atmospheric intraseasonal oscillation.
大气气溶胶的光学特性可对大气能量、大气环境和气候变化等产生巨大影响。为使遥感定量化更精确,反演气溶胶光学特性就变得很有必要。本文利用CE318-DP的观测数据,结合连续阶散射(successive order of scattering,SOS)算法,反演了870nm的散射相函数,并与AERONET网站对应的相函数比对,验证了反演的正确性并分析了误差来源。在此基础上,反演了6通道的单次散射反照率和偏振相函数。结果表明:在反演精度上,对数正态谱反演得到的散射相函数精度要优于由Junge谱反演得到的相函数精度;一般使用的大陆型和城市型等基本气溶胶模型已难以准确描述气溶胶特性,实际反演得到的散射相函数和偏振相函数比起用模型得到的更有应用价值;偏振相函数作为气溶胶的偏振特性参数,对气溶胶粒子的吸收性质十分敏感;偏振相函数与Angstrom指数同步变化,能够用偏振相函数表征气溶胶粒子的大小。本研究能提供更多的偏振信息,从而对不同通道的偏振相函数进行对比分析,有效提高对气溶胶光学特性的反演能力。
