Estimation of humidity profiles by combining co-located VHF and UHF wind-profiling radar observation

摘要

The turbulence echo intensity observed by a wind-profiling radar is closely related to the vertical gradient of refractive index squared (M-2), which largely depends on the vertical humidity gradient in a moist atmosphere. We have developed a radar remote-sensing technique for determining humidity profiles by using the turbulence echo characteristics. The sign of M is determined so that the precipitable water vapor determined by the radar agrees with that derived from the GPS measurements. In this study we have combined the results collected with two co-located radars; the MU (Middle and Upper atmosphere) and Lower Troposphere Radar (LTR) operating at 46.5 MHz and 1.3 GHz frequencies, respectively, and humidity profiles determined at 0.3-7.5 km. The echo power profiles (signal-to-noise ratio, SNR) with the two radars are connected smoothly in a height range between 1.5 and 1.95 km, by considering reduction of the receiver sensitivity for the MU radar due to leakage of the transmission signal. The retrieved humidity profiles show detailed time-height variations, which agree well with the simultaneous Raman lidar and radiosonde measurements.