Weighted mean tropospheric temperature and transmittance determination at millimeter‐wave frequencies for ground‐based applications
Weighted mean tropospheric temperature and transmittance determination at millimeter‐wave frequencies for ground‐based applications
复制标题
地面应用毫米波频率下的加权平均对流层温度和透射率测定
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
N. Kämpfer
中科院分区：
文献类型：
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作者：
T. Ingold;R. Peter;N. Kämpfer
辐射测定对流层透过率的一个简单模型是基于等温对流层。在该模式中，关键参数是加权平均对流层温度TM，它表征了对流层的辐射和温度特性。本文介绍了利用地面温度、地面相对湿度和辐射计数据对该参数进行建模的统计方法。为了确定TM模型的统计系数和透过率反演算法中使用的参数，在瑞士中心平面上的一个站点和一个阿尔卑斯山站点的毫米波传播模型中使用了无线电探空仪数据。考虑了在不同毫米波频率下的不同观测几何形状。利用地面温度确定TM，其均方根误差为4-5K(低海拔)和3-4K(高海拔)。通过结合相对湿度或辐射计数据，根据频率和地点的不同，相对于这些值最高可提高25%。我们的最佳模型对低海拔站点的天顶透过率估计在38 GHz处的均方根误差为0.5%，在94、110和142 GHz处的均方根误差为1%，在115 GHz处为1.5%，在204 GHz处为2%，在279 GHz处为3.5%，而对于高海拔站点，所有的均方根误差都在1%以下。纳入20和31 GHz的辐射信息并没有带来任何额外的改进，142 GHz的实际测量证实了这一点。
A simple model for the radiometric determination of tropospheric transmittance is based on an isothermal troposphere. In this model the key parameter is the weighted mean tropospheric temperature Tm, which characterizes the radiation and temperature properties of the troposphere. Statistical approaches in modeling this parameter are presented here by using ground temperature, ground relative humidity, and radiometer data. In order to determine the statistical coefficients for Tm modeling and the parameters used in the transmittance retrieval algorithm, radiosonde data were used in a millimeter‐wave propagation model for a site in the Swiss central plane and an Alpine site. Various observing geometries at different millimeter‐wave frequencies were considered. A determination of Tm from ground temperature was achieved with a rms error between 4–5 K for the low‐altitude site and 3–4 K for the high‐altitude site. By incorporating relative humidity or radiometer data, an improvement of up to 25% relative to these values results, depending on frequency and site. The zenith transmittance estimations for the low‐altitude site with our best model have a rms error of 0.5% at 38 GHz, 1% at 94, 110, and 142 GHz, 1.5% at 115 GHz, 2% at 204 GHz, and 3.5% at 279 GHz, whereas for the high‐altitude site all rms errors are below 1%. The inclusion of radiometric information at 20 and 31 GHz did not provide any additional improvement, which was confirmed by actual measurements at 142 GHz.