A Novel Method for Characterizing Atmospheric Turbulence Using Global Positioning System (GPS)

来自全球定位系统（GPS）卫星的信号在大气中传播的速度由空气的折射率决定，而空气的折射率又取决于温度、压力和湿度。该奖项支持基于以下原理的研究：在地面同一位置测量的两颗GPS卫星的传播延迟差异取决于沿两条射线路径的综合折射率差异。传播延迟是根据GPS信号的测量相位计算的，由于时钟误差、卫星距离的不确定性和接收机噪声，传播延迟受到不确定性的影响。然而，在几秒到几分钟的周期内，平均相位差的短期波动在很大程度上不受这些不确定性的影响，而主要取决于路径平均折射率的变化。这些波动是由大气结构的变异性引起的，因此可以看作是对不规则性或湍流的一种度量。这项工作的目的是评估通过监测GPS信号对湍流进行连续、准确、全天候遥感的可行性。通过更好地了解湍流的发生和分布，它具有改善天气预报和减轻航空危害的潜力。

Signals from Global Positioning System (GPS) satellites propagate through the atmosphere with a velocity determined by the refractivity of the air, which depends on temperature, pressure, and humidity. This award supports research based on the principle that the difference between the propagation delays from two GPS satellites measured at the same position on the ground depends on the difference in the integrated refractivity along the two ray paths. The propagation delays are calculated from the measured phases of the GPS signals and are subject to uncertainty because of clock errors, uncertainties in satellite range, and receiver noise. However, short-term fluctuations of the phase difference about averages over periods from a few seconds to minutes are largely free of these uncertainties and depend mainly on changes in the path-average refractivity. These fluctuations are caused by the variability of atmospheric structure and hence may be regarded as a measure of the irregularity, or turbulence. The objective of the work is to evaluate the feasibility of continuous, accurate, all-weather remote sensing of turbulence by monitoring GPS signals. It holds the potential of improving weather forecasts and alleviating aviation hazards through better understanding of the occurrence and distribution of turbulence.