| 地基微波辐射计工作环境对K波段亮温观测影响 |
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| 引用本文： | 王振会,李青,楚艳丽,朱雅毓.地基微波辐射计工作环境对K波段亮温观测影响[J].应用气象学报,2014,25(6):711-721. |
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| 作者姓名： | 王振会 李青 楚艳丽 朱雅毓 |
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| 作者单位： | 1.南京信息工程大学气象灾害预报预警与评估协同创新中心中国气象局气溶胶-云-降水重点开放实验室, 南京 210044 |
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| 基金项目： | 国家自然科学基金项目(41275043，41005005)，城市气象科学研究基金项目(IUMKY&UMRF201101)，江苏省研究生创新项目（CXLX12 0499） |
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| 摘 要： | 该文研究地基微波辐射计天线性能及其工作环境对K波段20~30 GHz亮温观测数据的影响，根据辐射传输理论和天线性能参数分析建立模型，通过模拟计算给出辐射计20~30 GHz波段亮温观测对天线性能及其工作环境的响应，提出针对工作环境温度变化影响的订正方案，并结合观测资料进行分析验证。结果表明:如果辐射计天线增益和3 dB波束宽度决定的等效主波束效率ηe较低，则即使在能够经常进行辐射计系统液氮定标的情况下也必须考虑天线工作环境 (环境温度与辐射计定标时的情景差异) 对K波段亮温观测的影响。对某一辐射计液氮定标后1年多观测资料的订正验证表明:订正效果明显，尤其是在28.0 GHz和30.0 GHz两通道。
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| 关 键 词： | 地基微波辐射计 K波段亮温观测订正 天线性能 工作环境 |
| 收稿时间： | 4/6/2014 12:00:00 AM |
Environmental Thermal Radiation Interference on Atmospheric Brightness Temperature Measurement with Ground-based K-band Microwave Radiometer |
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| Wang Zhenhui,Li Qing,Chu Yanli and Zhu Yayu.Environmental Thermal Radiation Interference on Atmospheric Brightness Temperature Measurement with Ground-based K-band Microwave Radiometer[J].Quarterly Journal of Applied Meteorology,2014,25(6):711-721. |
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| Authors: | Wang Zhenhui Li Qing Chu Yanli and Zhu Yayu |
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| Institution: | 1.Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, CMA Key Laboratory for Aerosol-Cloud-Precipitation, Nanjing University of Information Science & Technology, Nanjing 2100442.School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing 2100443.Institute of Urban Meteorology, CMA, Beijing 100089 |
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| Abstract: | Effects of operating environment thermal radiation interference on atmospheric brightness temperature measurement with ground-based K-band microwave radiometer especially for channels near 28.0 GHz and 30.0 GHz are studied. A model for simulating antenna temperature which expresses the energy received by the radiometer based on radiative transfer is derived and used to calculate the response of the brightness temperature measurements to parameters such as antenna specifications, radome, surrounding temperature and emissivity. Results show that the equivalent main beam efficiency (ηe) defined by 3 dB points is only 73.17% for a typical antenna, of which the half-beam half width α=3.1° and the gain G=30 dB. The value of ηe would be even smaller if factors like aperture radiation effect, shape-error, and occlusion and so on are taken into account. The brightness temperature would fluctuate by 4.0 K in case that ηe=70%, the surrounding temperature and emissivity would change by ΔTg=10 K and Δε=0.05 around Tg=280 K and ε=0.85 if the radome can be neglected. The fluctuation would increase up to 9.6 K if the size of the opening in the radome is just for the main beam. Therefore, if the equivalent main beam efficiency determined by the antenna gain and 3-dB beam width for the current radiometer system is not large enough, variation of the operating environment must be taken into account during the correction of K-band brightness temperature measurement even though LN calibration of the radiometer system can be performed as manual-required. For this, a brightness temperature correction method for operating environment variation is suggested according to the theoretical relationship and the result from application to observations. Over one year application after LN calibration shows that the fitness and correlation between the observed brightness temperature after correction and the calculated brightness temperature with radiative transfer equation is obviously better than before, especially for channels of 28 GHz and 30 GHz. |
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| Keywords: | ground based microwave radiometer K band brightness temperature correction antenna specifications operating environment interference |
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