While I was reading a newspaper article about typhoons in Hong Kong, I found some old photos that attracted my attention …
(see https://multimedia.scmp.com/typhoons/, Section Wanda (溫黛, 1962) )
Um… Seems that it was a powerful typhoon long before I was born …
Let’s see if I am able to simulate it using today’s technologies!
Real simulation for historical typhoon
After I generated a customized mesh for Hong Kong (um .. the design of the mesh is a secret that I do not want to disclose), I am ready to simulate whatever typhoons I like.
Let me follow the user guide to order Real Simulation job for TC Wanda (溫黛) ~~
It seems that CPAS cloud platform supports the 60’s simulation, great! (You might see the “Episode start time” is “29/08/1962”, a long long time ago …)
You might wonder why I choose “ERA5” as the “Data source for real-data initial condition”.
Um… It provides a better initial condition because it is global reanalysis data (which is ONLY available after the typhoon has passed, implying that it cannot use ERA5 in real-time forecasting, just as you are not permitted to cheat in school).
Four-Dimensional Data Assimilation
A special technique Four-Dimensional Data Assimilation (FDDA) was used. Hopefully, a more accurate reanalysis field for Wanda (溫黛) can be produced.
It is a technique combining CPAS simulation with historical reanalysis data (ERA5) during the model integration. Therefore, the simulation results would be much closer to the reference guidance (ERA5) since we are continuously feeding in ERA5 to the model during simulation.
Um … Am I cheating in my simulation?!
Yes or no, because we just wanted to simulate Wanda as accurately as possible. Whatever methods work, they work!
I am nudging the simulation towards ERA5 data (upper red box) using "analysis" FDDA (lower red box). Please refer to the above user guide for a detailed explanation of the configurations.
Below is a diagram illustrating the idea of FDDA:
During the model integration (CPAS atmosphere model), reference data (ERA5) is continuously ingested into the model in order to provide a more accurate simulation, as shown in the diagram.
After I pressed the “Order” button to submit a Real Simulation job, the system told me that my Wanda (溫黛) job was running. I was so excited about the simulation results~
After some time ...
My Simulation is done!
I am so happy to visualize TC Wanda (溫黛) using the scripts provided by CPAS cloud platform~
(CPAS provides scripts and a Jupyter Notebook for data visualization, so convenient! )
1. The landuse types used in the simulation is the present day situation, but NOT 60’s Hong Kong.
2. To reduce the frequency of such destructive typhoons attacking Hong Kong, we need to take action on the climate change issue.