5.2 Outlook

There is still much to understand about radar calibration, and the myriad of factors that contribute to its stability and reliability. The quality-weighted framework developed in this thesis can be expanded to the spaceborne radar observations as well, by e.g. considering the clutter identification of the Dual-frequency Precipitation Radar of the GPM (Watters et al. 2018). The GPM 2a Ku dataset also includes other variables which could be related to data quality, such as the level of path-integrated attenuation, the quality of brightband detection, and estimation of ground clutter elevation (Iguchi et al. 2010).

Furthermore, the quality-based method for bias estimation and correction can also be extended to the other radars in the Philippine radar network to ensure a consistent and reliable rainfall measurement throughout the country. The Philippine government program Nationwide Operational Assessment of Hazards (Project NOAH), which tackles disaster research and development, makes use of the weather radars together with the Himawari-8 satellite for monitoring and nowcasting rainfall probability in a web-based platform that delivers hazard-related information to the public in near-real-time (Lagmay et al. 2017). The project also conducts flood simulations for early warning using historical and real-time rainfall data based on rain gauges, which at the moment are more reliable in terms of accuracy and availability compared to radar data. With the potential increase in accuracy of radar rainfall estimates through careful bias estimation and calibration, and with the continuous efforts of PAGASA to improve the coverage and availability of the radar data, weather radar observations can be integrated to hydrological simulations for early warnings.

The improvement in the consistency between the Subic and Tagaytay radars after the bias correction of the individual radars signify a step towards better usability of archived data. Despite the remaining fluctuation, we have shown the possibility of increasing the homogeneity of reflectivity records by removing temporally variable calibration biases. Historical calibration of radar data archive could be useful for climatological studies and re-analysis of past events for better understanding of involved processes.

References

Iguchi, Toshio, Shinta Seto, Robert Meneghini, Naofumi Yoshida, Jun Awaka, and Takuji Kubota. 2010. “GPM/DPR Level-2 Algorithm Theoretical Basis Document.” NASA Goddard Space Flight Center, Greenbelt, MD, USA, Tech. Rep.

Lagmay, Alfredo Mahar Francisco, Bernard Alan Racoma, Ken Adrian Aracan, Jenalyn Alconis-Ayco, and Ivan Lester Saddi. 2017. “Disseminating Near-Real-Time Hazards Information and Flood Maps in the Philippines Through Web-GIS.” Journal of Environmental Sciences 59 (September): 13–23. https://doi.org/10.1016/j.jes.2017.03.014.

Watters, Daniel, Alessandro Battaglia, Kamil Mroz, and Frédéric Tridon. 2018. “Validation of the GPM Version-5 Surface Rainfall Products over Great Britain and Ireland.” Journal of Hydrometeorology 19 (10): 1617–36. https://doi.org/10.1175/JHM-D-18-0051.1.