The after-runner storm surge along the north coast of Vietnam simulated by the 2D ROMS model

Transcription

1 The after-runner storm surge along the north coast of Vietnam simulated by the 2D ROMS model Nguyen Ba Thuy, Pham Khanh Ngoc, Lars R. Hole 2, Nils Melsom Kristensen 2, Johannes Röhrs 2, Cecilie Wettre 2 Vietnam National Center for Hydro-meteorological Forecasting (NCHMF) 2 Norwegian Meteorological Institute (MET Norway) Cape Town, 3-7 April 27

2 Coastal Dissater related to high water level in Vietnam Storm surge Anormalyze water level (Meteorological tsunami) Spring tide (Hight tide + surge induced by moonson)

3 Possibility Storm Surge in Vietnam June High Vulnerable storm surge (abundant typhoon + shallow water) Less Vulnerable storm surge (rare typhoon + deep water) Dec. Less Vulnerable storm surge (shallow water +rare typhoon) Number of Typhoon

4 Storm surge research and prediction Surge height (m) Numerical Model:.5. Observation Without wave With wave - 2D ROMS + WRF - SuWAT (Surge Wave and Tide) + Best track or WRF.5. 9/29/26 6: 9/3/26 2: //26 8: -.5 Time (h) Time serial of storm surge Coastal inundation due to tide + storm surge + wave setup

5 Spring tide in Hochiminh city Spring tide in Hochiminh City is related to Surge induced by monsoon or not? Maximum tide amplitude Flooding in Ho Chi Minh City in 2//2

6 Surge height (m) Water surface elevation (m) Spring tide in Hochiminh city on 2//23 Hochiminh city * Vung Tau Maximum water surface elevation during the monsoon / /8/23 : /4/23 : OBS-Total water level Model-Surge OBS-Surge /2/23 : Time (s) /26/23 : Time profile of total water surface elevation, predicted and measure surge height It related to flooding in Hochiminh City on 2//23 Wind field at 2//23 Spring tide = high tide+ surge (by moonson)

7 High Oscillation of water level on the middle coast of Vietnam Z (cm) High tide at Tuyhoa in Dec. 26 (No typhoon and calm wind. But the inundunation height up to m, and go in land up to 2m). Meteorological tsunami?. 2//26 : 2/6/26 : 2/2/26 : - Time (h) Time serial of total water level, tide and surge To simulate this phenomenal need high resolution of ocean and atmosphere model. Next study OBS Tide Surge

8 The after runner storm surge on the North coast of Vietnam Area: The north coast of Vietnam Typhoon frequency:.5 typhoons/year Maximum storm surge: 3.4m The after runner storm surge: 6 cases/5 years

9 Storm surge (m) Stoem surge (m) The after runner storm surge.2 Typhoon landfall Normal storm surge 7/29/25 : 7/3/25 : 8/2/25 : -.2 Time (h) Typhoon landfall After runner storm surge 9/6/24 : 9/8/24 : Time (h) Storm surge at Hondau station during typhoon Wukong (25) and Kalmaegy (26)

10 The after runner of storm surge cases H (cm) 45 Time of typhoon landfall Total water level 4 Prediced tide 35 Surge time interval of urge exceed.5m Inundated 5 Kalmeagi (9/24) -5 9/6/24 9:36 9/6/24 4:24 9/6/24 9:2 9/7/24 : Typhoon land fall 9/7/24 4:48 9/7/24 9:36 9/7/24 4:24 Time (h) 9/7/24 9:2 9/8/24 : 9/8/24 4:48 9/8/24 9:36 9/8/24 4:24 No inundation Mirinae (7/26) Observation water level, predicted tide and storm surge at Hondau station

11 Typhoon Kalmaegi (9/24) After runner storm surge case (a) - Damage by wind is not much. - But Storm surge + high tide + high wave generated inundation at Haiphong coast after the typhoon landfall 5 hours. High wave and inundation at Haiphong coast

12 - Empirical Typhoon Model: fdu y D g y Dv x Duv t Dv fdv x D g y Duv x Du t Du by ay w w bx ax w w ) ( ) ( ) ( ) ( 2 2 y Dv x Du t 2 ) / ( ) ( r r P P P r P c (Fujita model) r P fv r v 2 Operational Forecasting Model in 9/24 Two dimensional long wave model + Empirical Typhoon Model

13 Storm surge (m) Result of Operational forecasting (2D long wave model + Fujita model) Typhoon track Maximum storm surge Typhoon Landfall OBS FUJITA 9/6/24 2: 9/7/24 2: 9/8/24 2: -.5 Time (h) - Model and observation storm surge Simulated result showed storm surge not high at Hondau station, and at low tide > No warning. But infact inundation occurred. We miss warning

14 Z (m) Z(m) Storm surge observation data 45 Typhoon land fall 4 OBS 35 Predic. Tide 3 Storm surge /6/24-5 2: 9/7/24 2: 9/8/24 2: Time (h) /6/24 : -5 9/6/24 8: 9/7/24 2: - Typhoon Landfall Time (h) OBS Prec. Tide Storm surge Time profile of total water, tide and storm surge at Hondau and Honngu station

15 Simulated the after runner storm surge by (ROMS 2D + WRF) WRF ROMS Domain for WRF model (7km) and ROMS model (2km)

16 Storm surge (m) Storm surge (m) Results of 2D ROMS + WRF model 2.5 Typhoon Landfall OBS WRF.5 9/6/24 2: 9/7/24 2: 9/8/24 2: -.5 Time (h) - Typhoon landfall OBS WRF ROMS+WRF is well simulated the -.4 storm surge at two station -.6 9/6/24 2: 9/7/24 6: 9/8/24 : -.2 Time (h) Comparison of calculated and simulated storm surge at two station using wind and pressure from WRF

17 Wind and pressure data The WRF model simulated well wind and pressure than the empirical typhoon model Measured and predicted pressure (above) and wind speed (below) and at Hondau station

18 Storm surge (m) Storm surge (m) Effect of front and tail wind field on storm surge.5.5 No wind after typhoon land fall 9/6/24 6: 9/7/24 6: 9/8/24 6: -.5 Time (h) - OBS WRF WRF-No wind after land fall /6/24 : -.2 9/7/24 : 9/8/24 : -.4 Time (h) Storm surge at Hondau station is mostly induced by tail wind. But at Honngu station is due to the inertia force -.6 OBS WRF WRF-No wind after landfall Comparison of calculated and simulated storm surge at two station for two case using WRF model. One using front and tail wind field (above), the other using the front wind field only (below).

19 Effect of front and tail wind field on storm surge Hondau Honngu Maximum storm surge for the case the model using front and tail wind field (left) and front wind field only (right) The result at the Honngu station is not so much different between two cases. It means storm surge at Honngu station is due to water moving from North to the south?.

20 How the surge generated at the Northern part (Hondau station) Wind and water surface elevation At the time typhoon land fall (water level at two station is down) After typhoon land fall 4 hour (water level at Hondau station is going up) The tail wind fields of typhoons are more important than front wind fields. After typhoon land fall 6 hour (water level at Hondau station get maximun)

21 How the surge generate at the Southern part (Honngu station) Wind and water surface elevation After typhoon land fall 4 hour (water level at Hondau station is going up) After typhoon land fall 8 hour Storm surge on the southern part (Honngu station) due to the tail wind and water moving from the north. Water surface elevation and current

22 Effect of wind and pressure on storm surge Storm surge (m).5 OBS Wind and pressure Win only Pressure only.5 9/5/24 2: 9/6/24 2: 9/7/24 2: Time (h) Comparison of calculated and simulated storm surge at two station for 3 cases of wind + pressure, wind only and pressure only (data from WRF model). The contribution of wind is mainly.

23 Effect of tide storm surge Comparison of simulated and observation storm surge. The simulated results for two case, with and without consider tide.

24 Effect of wave on storm surge Comparison of simulated and observation storm surge. The simulated results for two case, with and without consider wave.

25 Future works: - Meteorological tsunami (anormalyze water level) on the middle coast of Vietnam - Wave and ocean current using radar data (assimilation)

26 local/rear/tail winds front winds