Estimation of Temporal Variation of Refractive Index Using C-band Doppler Radar Equipped with Magnetron Transmitter

Abstract

An estimation method for temporal variation of refractive index (RI) using phase data observed by a C-band Doppler radar equipped with a magnetron transmitter is presented. Temporal variation of RI was estimated from phase increments that were caused by temporal atmospheric variations. Because the wavelength of the C-band radar is as short as 5.7 cm, phase wrapping frequently occurs. Thus, number of phase wrapping was counted by monitoring the phase increments at the interval of 30 seconds. Effect of frequency drift of the magnetron transmitter was removed by using phase increments of a reference target and atmospheric delay between the radar site and the reference target. The method was applied to a case study of daytime sea-breeze front in the Kanto plain. The estimated variation of RI, which has the information of water vapor, showed an agreement with the position of the cloud band that was generated in the surface convergence zone.