Clear-Air Turbulence (CAT) Identification with X-Band Dual Polarimetric Radar Based on Bayesian Approach

Jianli Ma,Siteng Li,Mingxuan Chen,Li Luo

doi:10.3390/atmos12121691

Abstract

The echo of weather radar is seriously disturbed by clear-air turbulence echo (CAT) which needs identifying and eliminating to improve the data quality of weather radar. Using the data observed with the five X-band dual polarimetric radars in Changping, Fangshan, Miyun, Shunyi, and Tongzhou, Beijing in 2018, the probability density distribution (PDD) of the horizontal texture of four radar moments reflectively factor (ZH), differential reflectivity (ZDR), correlation coefficient (ρHV), differential propagation phase shift (ΦDP), and then the CAT is identified and removed using Bayesian method. The results show that the radar data can be effectively improved after the CAT has been eliminated, which include: (1) the removal rate of CAT is more than 98.2% in the analyzed cases. (2) In the area with high-frequency distribution of CAT, the CAT can be effectively suppressed; in the area with low-frequency distribution, some weather echo in the edge with SNR < 15 dB may be mistakenly identified as CAT, but the proportion of meteorological echoes to the total echoes is more than 85%, which indicate that the error rate is very low and does not affect the radar operation.

Highlights

X-band dual-polarization radar is applied to monitor small scale basins weather in mountainous regions and urban areas [1,2], and it can be a cost-effective system for filling up gaps in existing national radar networks [3]
clear-air turbulence echo (CAT) is just one type of echoes observed by X-POL, the others are including, (1) ground clutter (GC), (2) anomalous propagation (AP), (3) biological echo, (4) meteorological echoes (ME)
The Bayes classifier (BC) is assessed against an existing method for CAT identification

Summary

Introduction

X-band dual-polarization radar (hereinafter X-POL) is applied to monitor small scale basins weather in mountainous regions and urban areas [1,2], and it can be a cost-effective system for filling up gaps in existing national radar networks [3]. Clear air turbulence echoes (hereafter CATs) can be observed by X-band radar [4,5,6]. The CATs of five X-POLs are source of contaminations for radar precipitation estimations, it is need to remove CATs and only retain the precipitation echoes.

Results

Conclusion