Fitting parametric tropical cyclone-induced rainfall model for tropical cyclones landfalling onto the Northern Vietnam coast

• Main Authors: Angkanasirikul, Warinthorn, Wei, Jian, Lo, Edmond Yat-Man
• Other Authors: Interdisciplinary Graduate School (IGS)
• Format: Conference or Workshop Item
• Language: English
• Published: 2023
• Subjects: Science::Geology; Rainfall; Tropical Cyclone; Landfall; Axisymmetric
• Online Access: https://hdl.handle.net/10356/165523; https://www.asiaoceania.org/aogs2023/public.asp?page=home.asp
• Institution: Nanyang Technological University

Tropical cyclones (TCs) can cause major flooding individually or collectively due to wind, storm surges and rainfall. This study applies the parametric rainfall climatology and persistence (R-CLIPER) model to analyse the axisymmetric component of 14 TC rainfall events in Northern Vietnam with the observed rainfall dataset from the Global Precipitation Mission from 2001 to 2021. The R-CLIPER model uses two inputs from TC track information: the maximum wind speed and radial distance from the TC centre. Four parameters represent the axisymmetric profile of rainfall rates: T0, Tm, rm, and re. T0 and Tm describe the rainfall intensity at the TC centre, and the maximum intensity which is located at radial distance rm from the centre, respectively. The fall-off from the maximum is exponential with a characteristic distance re. The R-CLIPER model generally assumes linear relationships between the four parameters and a normalised maximum wind speed (U). We adopt the operational coefficients by the National Hurricane Center (NHC) for the Western Pacific region as the initial setting. The observed TC rainfall profiles are further used to fit the parameters using the least-square method. Performance of the R-CLIPER with the initial and fitted settings for predicting the observed 14 rainfall profiles is assessed. T0 and Tm are found to be better represented by logarithm relationships with U, and rm by an exponential relationship, based on their improved R2 values over the R-CLIPER with NHC coefficients for the 14 historical TC events. At 0.1-degree resolution, the equitable threat score demonstrated significant improvement, almost six times at the 100 mm rainfall threshold. Improved root mean square error and bias are also seen for the cumulative rainfall volume and the averaged rainfall intensity. For instance, the bias has reduced by around 50% with the new relationships of the parameters and U in most cases.