利用地面气象观测资料确定对流层加权平均温度

Determination of Weighted Mean Tropospheric Temperature Using Ground Meteorological Measurement

地基GPS气象学的核心思想是通过垂直方向上GPS信号的湿分量延时确定出可降水分 ,而这两个物理量之间的转换必须使用对流层加权平均温度。本文首先讨论了上述转换估计中加权平均温度的几种逼近方式及其容许误差 ,然后利用香港地区的地面和高空气象资料 ,采用逐步回归分析方法 ,建立了适合香港地区的对流层加权平均温度计算公式 ,通过数据分析表明 ,这个公式有效地消除了在香港地区使用Bevis经验公式引起的系统误差 ,较好地满足了地基GPS气象应用中实时性和高精度的要求。本研究也充分表明 ,在地基GPS气象研究中 ,应该利用本地区的气象资料来确定适合本地区的估计对流层加权平均温度的经验公式。

The weighted mean tropospheric temperature is a critical parameter in the conversion of wet zenith delay to precipitable water vapor in GPS meteorology.Four existing methods,namely,approximate close form,constant method,Bevis method and numerical integration,were developed to perform this conversion.However,the approximate close form is very difficult to realize due to their three assumptions; the constant method induces a large error in the conversion.The Bevis method has a systematic error in the calculation of weighted mean temperature and the numerical integration cannot provide the weighted mean temperature in real_time from the radiosonde data because of the restriction of maintenance costs.The conversion parameter from wet zenith delay to precipitable water vapor is a function of weighted mean tropospheric temperature.We find that the admissible error of weighted mean temperature should be smaller than 3.4K if the conversion accuracy is better than 1mm.The weighted mean temperature is strongly correlated to the surface meteorological measurement based on the correlation analysis of 13 months surface and upper_air meteorological data in Hong Kong.An empirical formula,which is a function of surface temperature,is established using sequential regression analysis method based on these surface and upper_air meteorological measurements.Another two months data are used to demonstrate the validation of this new empirical formula.This real_time formula satisfies the requirement of both real_time and accuracy in GPS meteorology,and it is able to eliminate the systematic error caused by the Bevis method in the Hong Kong region.These results also exhibit that the empirical formula for weighted mean tropospheric temperature should be determined using regional meteorological measurements in the GPS meteorology application.