An evaluation of rain attenuation correction for the Multi Parameter Phased Array Weather Radar

The Dual Polarization Phased Array Weather Radar (Multi Parameter Phased Array Radar, MP-PAWR) is developed and installed at the Saitama University, Saitama prefecture, Japan (N35.8615°, E139.6090°) in December 2017. The radar was developed aiming to observe three-dimensional structure of the rain cell with high time and scale-resolution. The MP-PAWR can observe 114 angles from 0.0 to 90.0 deg every 30 seconds. The XRAIN is X-band Multi-Parameter Radar Network in Japan and its observation data is utilized for disaster prevention. The XRAIN observes 12 elevation angles from 1 to 20 deg every 5 minutes. The high time resolution dual-polarized volume scanning observation data can be helpful for growth and decay forecasting of convective rain cells.

In this study, the accuracy of the horizontal polarization radar reflectivity, ZH was evaluated in comparison with the XRAIN radar which is installed 3.96km displaced from the MP-PAWR. In the comparison, azimuth angles of 4.79-60.01deg at an elevation angle of 9.69 deg observations used in order to avoid clutter. 90 hours of observation data during 24th June to 30th September 2018 were acquired for this research. As a result, biases between two radars was 0.21dBZ and its standard deviation was 4.8dBZ.

In hard rain case, such as typhoon, the MP-PAWR attenuates by rain. In July 28, 2018 a typhoon passes the west side of Kanto plain area. In the case, the MP-PAWR 6.8dBZ under estimates than the XRAIN. After self-consistent rain attenuation correction algorithm [1] is applied to the MP-PAWR, mean bias became -0.7dBZ.

Acknowledgements

The authors wish to thank the party of Toshiba Corporation for valuable comment about the hardware of the phased array weather radar. XRAIN data sets used for this study are provided by Ministry of Land, Infrastructure, Transport and Tourism, Japan. The DIAS dataset is archived and provided under the framework of the Data Integration and Analysis System (DIAS) funded by Ministry of Education, Culture, Sports, Science and Technology (MEXT).

References

[1] S. Park, M. Maki, K. Iwanami, V. N. Bringi, and V. Chandrasekar, "Correction of radar reflectivity and differential reflectivity for rain attenuation at X band. Part I: Theoretical and empirical basis", J. Atmos. Oceanic Technol., 22, 1633-1655, 2005.