Advances in China’s Ground-based Remote Sensing Vertical Profiling System

The ground-based profiling observations are essential to improve the understanding of specific weather process. Continuous efforts have been made in China on the ground-based remote sensing vertical profiling system, which consists of five instruments: microwave radiometer, millimeter-wave cloud radar, Global Navigation Satellite System/Meteorology (GNSS/MET), wind profiling radar and aerosol lidar. As part of World Meteorological Organization (WMO) global basic observing network (GBON), this system can provide the detailed profiling information of temperature, water vapor, wind, hydrometeors and aerosols.

A wide range of products have been developed not only from each instrument itself but also the synthetic uses of multi-source observations. Cloud radar plays a key role in the identification of hydrometeors, precipitation and snowfall. Microwave radiometer brightness temperatures are used to retrieve the temperature and humidity profiles under the clear and cloudy atmosphere. Lidar can character the aerosols with their extinction coefficients, backscatter coefficients and depolarization ratio, which are useful to identify the particle size to distinguish different air pollution, such as haze and sandstorms. GNSS/MET can provide relatively reliable estimates of the integration of water vapor and its vertical distribution. Wind profiling radar can provide the wind estimates including the valuable vertical velocity of atmospheric motions. Besides, the multi-element observations are also utilized to generate the weather signal warning products, such as the precipitation potential and several kinds of indices. Some of these products, such as the radiometer temperature profiles, have also been assessed using the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) dataset in Xilinhot, China.

The system is preferred to deploy at the operational in-situ sounding stations, generating the complementary datasets for the sparse temporal samplings of in-situ sounding observations. Owing to its high temporal and vertical spatial resolution, the relatively complete weather processes can be monitored for further analyses and research, such as the low-level jet stream, advection, precipitation, snowfall, etc. For instance, a heavy snowfall process in Beijing on February 20, 2024 and a hail process in Beijing on April 28, 2023 were well captured by this system.

Quality control is another essential part to support the better performances of this system. For example, the co-located sounding profiles are used to evaluate the data quality and equipment stability of microwave radiometer. To support the synthetic applications of the spaceborne and ground-based radiometers, an advanced doubling and adding radiative transfer model based on the discrete ordinate method is developed for integrated satellite-ground forward simulations, to avoid the systematic errors resulting from two different ground-based and spaceborne solvers. It can be used to perform the assessments on brightness temperature observations and analyze the potential connections between the upwelling and downwelling brightness temperature observations from the spaceborne and ground-based radiometers. In the future, the instrument calibration and the synthetic uses of their base products can be priorities, to improve and promote this new profiling system.