S-Band Radar Rainfall Estimation in Taiwan

Accurate rainfall estimation has been critical and challenging in Taiwan because of its location at the Tropic of Cancer and its complex mountainous terrain environment. This paper is to describe a synthetic algorithm to estimate the rainfall using an S-band radar. The proposed quantitative precipitation estimation (QPE) method merges different rain rate calculations including using specific attenuation (A), specific differential phase (Kdp), and reflectivity (Z). An R(A) scheme is applied for pure liquid precipitation; R(Kdp) is applied in areas with potential hails; R(Z) is applied in the regions within and above the melting layer, where the Z field is corrected from the attenuation and the vertical profile. Minor artifacts between radials in the QPE field, caused by the rainfall estimation from the scans at different heights and the discontinuity due to the canopy or man-made buildings, are mitigated using a referential table.

The performance of the proposed algorithm is validated with gauge measurements. The evaluation results show that the synthetic QPE algorithm is able to take advantage of different estimation methods and deliver a more reliable and accurate rain rate product than using R(Z) only.