Assessment and Selection of Regional Automatic Weather Stations in China Based on the RRR Principle of the WMO

The density of the national surface weather stations is not enough to monitor the small and medium scale severe weather events, as well as to meet the high-resolution numerical forecast system for data assimilation and verification. On the other hand, more than 58,000 automatic weather stations （AWSs） were built by different local meteorological offices without unified standard. In order to strengthen the capability of the national network to serve the monitoring, prediction of the high-impact weather events, the assessment and selection of regional AWSs is carried out by China Meteorological Administration (CMA) .

The process is divided to three stages. The first stage is the quality assessment of AWS. The instruments, environment, calibration and maintenance of AWSs were evaluated station by station, and the data deviation against the EC reanalysis field was assessed at this stage. The second stage is evaluation for the needs of weather system analysis and severe weather events monitoring to AWSs. 7 kinds of weather systems and 4 kinds of severe weather events were considered at this stage. The third stage is evaluating the needs of numerical forecast model to AWSs. The methods of Observation System Experiments (OSEs), Observation System Simulation Experiments (OSSEs), and Forecasting Sensitivity to Observation (FSO) were used at this stage. At last, based on the results of three stages, the total of 8174 AWSs were selected from more than 58,000 regional AWSs to supply the national weather station network. The spatial resolution of the national surface observation network is improved from 30 -200km (average 71km) to 1590km (average 33km).

The performance of the new network is inspected by weather analysis and numerical weather prediction (NWP). The results show that the majority characteristics of weather events with 20-50km scale can be captured by the new network. The data from the new network assimilated to the NWP system shows the positive impact to the prediction.

This work practices the Rolling Requirements Review (RRR) principle advocated by World Meteorological Organization (WMO) for optimizing the layout of observation network.