Reply on CC1

Siming Zheng

doi:10.5194/amt-2021-305-ac3

Abstract

Abstract. The amount of water vapor in the atmosphere is very small, but its content varies greatly in different humidity areas. The change in water vapor will affect the transmission of microwave link signals, and most of the water vapor is concentrated in the lower layer, so the water vapor density can be measured by the change in the near-ground microwave link transmission signal. This study collected 1-year data of the E-band millimeter wave link in Hebei, China, and used a model based on the International Telecommunication Union Radiocommunication Sector (ITU-R) to estimate the water vapor density. An improved method of extracting the water-vapor-induced attenuation value is also introduced. It has a higher time resolution, and the estimation error is lower than the previous method. In addition, this paper conducts the seasonal analysis of water vapor inversion for the first time. The monthly and seasonal evaluation index results show a high correlation between the retrieved water vapor density and the actual water vapor density value measured by the local weather station. The correlation value for the whole year is up to 0.95, the root mean square error is as low as 0.35âgâmâ3, and the average relative error is as low as 5.00â%. Compared with European Center for Medium-Range Weather Forecast (ECMWF) reanalysis, the correlation of the daily water vapor density estimation of the link has increased by 0.17, the root mean square error has been reduced by 3.14âgâmâ3, and the mean relative error has been reduced by 34.00â%. This research shows that millimeter wave backhaul link provides high-precision data for the measurement of water vapor density and has a positive effect on future weather forecast research.

Highlights

The change of water vapor will affect the transmission of microwave link signals, and most of the water vapor is concentrated in the lower layer, so the water vapor density can be measured by the change of the near-ground microwave link transmission signal
The monthly and seasonal evaluation index results show a high correlation between the retrieved water vapor density the actual water vapor density value measured by the local weather station
In 2018, Alpert et al generated an air humidity map based on Israel's commercial microwave link data and compared it with the ERA-Interim humidity map of the European Center for Medium-Range Weather Forecast (ECMWF) for the first time

Summary

Introduction

Water vapor content varies greatly in the atmosphere, and it is the main role of weather changes (Chen and Avissar, 1994). 30 The evaporation and condensation of water vapor can absorb and release latent heat, which directly affects the temperature of the ground and the air (Held and Soden, 2000), so it plays an important role in the vertical stability of the atmosphere and the structure and evolution of the convective storm system (Weckwerth, 2000; Fabry, 2006). The humidity measurement of the near-ground weather station is the most direct way to reflect water vapor (Gu et al, 2004), but it cannot meet the requirements of high spatial resolution because it only provides point observations. 50 Studies have shown that millimeter-waves will be affected by atmospheric factors during propagation, which will cause signal attenuation Based on this feature, Messer et al first proposed a method for monitoring near-surface rainfall and retrieved rainfall rate using a communication link (Messer et al, 2006). In 2009, David et al proposed a new technology to measure 55 atmospheric humidity using data collected by wireless systems (David et al, 2009) This technology can detect water vapor near the ground, and gives estimates of water vapor density values with high temporal and spatial resolution.

Methods

Results

Conclusion