Signal Processing

The measured signals are categorized into three processing levels Level 1, Level 2, and Level 3, and are processed in real time.

Level-1 Processing

Level-2 Processing

The physical quantities below are calculated and stored as Level-2 processed data.

• Z factor (radar reflectivity factor)
• Precipitation intensity (R) determined based on the Z-R relationship
• Differential reflectivity factor (ZDR)
• Linear depolarization ratio (LDR)
• Correlation coefficient between two polarizations (ρHV(0))
• Differential phase shift between two polarizations (φDP) and their specific differential phase (KDP)

This data is used to identify the form of the precipitating particle or to estimate the raindrop size distribution (DSD).

Furthermore, the wind velocity vector (determined using the bistatic Doppler network) and the rain rate estimation (determined using the ZDR, KDP, and k-R relationships, which are not as widely used as the Z-R relationship), is performed and stored as Level-2processed data.

Level-3 Processing

With Level-3 processing, statistical calculations are performed on the precipitation intensity R(Z) data (which consists of Level-2 processed data) to determine 1-hr accumulated precipitation, 1-hr average precipitation, 24-hr accumulated precipitation, 24-hr average precipitation, 48-hr accumulated precipitation, and 48-hr average precipitation.

Data Validation Methods

COBRA data will be validated as follows.

Polarization Observation The polarization observation data collected by the COBRA main radar will be validated using the 400-MHz wind profiler. Ground-based observation using a disdrometer 1-minute precipitation intensity observation using an optical rain gauge Comparison with existing meteorological radars (Japan Meteorological Agency, Ministry of Land, Infrastructure, and Transport)
Bistatic Radar Network Observation Dual observation with the meteorological Doppler radar at the Naha Airport Comparison with the 400-MHz wind profiler