A case study of the daytime intense radar backscatter and strong ionospheric scintillation related to the low-latitude E-region irregularities

The special daytime echoes, which present the V-shaped echo pattern between 90-180 km ranges in the Range-Time-Intensity (RTI) plot, were occasionally recorded by the Hainan COherent scatter Phased Array Radar (HCOPAR) located at the low-latitude of China. Four cases with distinct echo traces are presented to display the common characteristics of the V-shaped echoes. They usually occur between 10:00- 15:00 LT in the daytime with the enhanced top frequency and blanketing frequency of Es-layer (f_t Es and f _b Es ). Their left/right wings present negative/positive Doppler velocity. A case on 16 August 2015 was investigated by the joint observation of the HCOPAR, the Hainan Digisonde, and a scintillation receiver. The echo spectra show that the V-shaped echoes were backscattered from the type-2 irregularities. The formation of the V-shaped echo pattern wa s due to the leakage of the antenna sidelobe for the very intense scatter from Es-layer. The irregularities were found travelling westward with the velocity of 41.12±2.08 m/s. While the occurrence of the intense irregularities , there were periodic peaks appearing on the f_t Es and f_bEs curves and the maximum f_tEs- f_bEs reached 10.31 MHz . At the same time, the strong ionospheric scintillation event was recorded by the scintillation receiver . The wind shear is considered to produce the sharp density gradient in the Es plasma and then induce the gradient drift instability. The large-scale gravity waves have the possibility to induce the E-region wind shear.