A Lower Troposphere Radar: 1.3-GHz Active Phased-Array Type Wind Profiler with RASS

Abstract

We have developed an atmospheric radar (wind profiler) for lower tropospheric observations (Lower Troposphere Radar: LTR), based on the 1357.5-MHz boundary layer radar (BLR), which we previously developed mainly for observations of the atmospheric boundary layer. System gain of this radar is improved due to newly developed large-sized active phased-array antenna, active transmitting modules with higher output power, and pulse compression technique. It has the following functions: an antenna gain of 33 dBi is obtained with a 4 m × 4 m active phased array antenna which has 96 antenna subelements, a peak output power of 2 kW is obtained by 24 active transmitting modules, and maximum S/N is improved 8 times by using a pulse compression technique which uses 8-bit optimized coding developed by Spano and Ghebrebrhan (1996c). The LTR is the first active phased-array 1.3 GHz-band wind profiler radar. It is possible to vary the beam direction by electronically steering the zenith angle within 45°. Atmospheric winds in the lower troposphere, including the atmospheric boundary layer, are obtained with high time and height resolutions in real time. Observations of atmospheric temperature are also possible using the radio acoustic sounding system (RASS) technique with speaker horns. We have confirmed LTR’s potential as a reliable tool for atmospheric observations, using simultaneous observation results with the MU (Middle and Upper atmosphere) radar, a Doppler sodar, and a radiosonde.