Discussion on the variations of MST/ST radar echo power with an atmospheric layer resolved by frequency domain interferometry technique

The relationship between an atmospheric layer and its VHF backscatter resolved by the frequency domain interferometry (FDI) technique is investigated in this article. A theoretical expression connecting the radar echo power with the thickness and position of an atmospheric layer and the range weighting function of a matched filter is derived. It shows that the farther the layer locates from the central height of the radar volume, the weaker the echo power will be. This feature is attributed to the range weighting effect of the radar system. FDI observations also show that the echo power from the atmospheric layer located close to the central height of the radar volume is usually greater than that from the layer located at the edge of the volume, which is in good agreement with the theoretical prediction. Moreover, the correlation between the echo power and layer position is negative (positive) if the layer locates in the upper (lower) part of the radar volume. This behavior is consistent with the theoretical prediction and can also be interpreted by the range weighting effect. It is also suggested that the power-position relation is capable of indicating the system bias causing the systematic error of FDI-estimated layer position. In addition, numerical simulation is performed in this article to examine the difference between the range weighting functions resulting from rectangular and nonrectangular radar pulses for a given receiver impulse response.