Research on the Method of the Network-Based Weather Radar Attenuation Correction

Abstract

The precipitation process detected by X-band weather radar is susceptible to strong attenuation caused by the scattering of rain area and the absorption of electromagnetic energy, which has become the main factor affecting its detection accuracy and leading to inaccurate quantitative estimation of precipitation. However, due to its advantages of small size, low power consumption and high spatial and temporal resolution, etc, there are application requirements in the meteorological observation service. Therefore, it is particularly important to study the X-band radar attenuation correction method. This paper focuses on the attenuation of electromagnetic waves along the path during X-band weather radar detection. Different attenuation correction methods are used for comparative analysis. Three correction methods are involved: (1) $\mathrm{Z}_{\mathrm{H}}-\mathrm{K}_{\mathrm{D}\mathrm{P}}$ method comprehensive correction algorithm uses echo parameter reflectivity factor $\mathrm{Z}_{\mathrm{H}}$ and differential propagation phase shift constant $\mathrm{K}_{\mathrm{D}\mathrm{P}}$ to attenuate and correct reflectivity $\mathrm{Z}_{\mathrm{H}}$. (2) The adaptive constraint algorithm is proposed on the basis of the revised extended precipitation profile (ZPHI) algorithm: by cyclically adjusting the system parameters, the optimal coefficient in the linear relationship $\mathrm{A}_{\mathrm{H}}\sim \mathrm{K}_{\mathrm{D}\mathrm{P}}$ is obtained. (3) The network radar attenuation correction algorithm uses multiple radar detection data to attenuate and correct the radar data in the common observation area. The X-band radar attenuates strongly along the path, and the echo intensity after detecting strong convective rain areas is often low or even completely absent. The network radar uses multiple radars to observe together to make up for the observation defect of a single radar. With the end of the rain area as the constraint condition, the attenuation of all distance banks in a radial direction is calculated according to the integral equation, and the result is brought into the iterative operation of the evaluation function to calculate the optimal value. In this paper, the observation data of three X-band weather radars in our school's airport campus, Longquan campus and Ziyang Meteorological Bureau are used for comparative analysis of different attenuation correction methods,and compared with the provincial bureau's C-band operational weather radar. The results of data processing show that the difference between the results of the three correction algorithms at the close range is small, while the correction results at the long range are obviously different. Among them, the correction value of $\mathrm{Z}_{\mathrm{H}}-\mathrm{K}_{\mathrm{D}\mathrm{P}}$ method is relatively small in the near detection, while it is excessively revised in the far detection, resulting in corresponding errors due to its large dependence on empirical parameters. However, the adaptive constraint algorithm takes raindrop spectrum, particle shape and other factors into consideration, and the overall correction effect is good, but there are certain errors in the correction of long-distance strong echoes. However, the results of the network radar correcting the common observation area are basically the same as those of the C-band weather radar.