☁️ conclusion ☁️
Intensity
We hypothesized that the increased sea level temperature during the El Niño period would increase the intensity of typhoons, and examined the size, central air pressure, wind speed, and lifespan of typhoons. In size, large typhoons developed more in the normal periods during the third and fourth cases. It was difficult to conclude that El Niño always increases the intensity of typhoons because it did not show any significant difference in the rest of the cases, although there was a tendency to conform to the hypothesis in cases 1, 2, and 5 at the wind speed and in cases 1, 2 at central air pressure and lifespan.
In the third and fourth cases, All four factors showed an inconsistent distribution with the hypothesis. And we expect that to be the result associated with the El Niño index. El Niño index was especially low in cases 3 and 4, and the impact of El Niño was smaller than the rest of the cases, so it would not have had a relatively significant impact on the intensity of the typhoons in the third and fourth cases.
Occurrence Location
We hypothesized that during the El Niño period, the temperature in the center of the Pacific Ocean would increase overall, so the typhoon's location would shift eastward than the normal period.
To check this, we analyzed the longitude and latitude of each typhoon from the first to the fifth cases. As a result, the longitude of all El Niño periods was larger than the normal periods.
In particular, the difference was even greater in the first and fifth cases when the El Niño index was higher than any other period. Latitude showed no significant difference between El Niño periods and the normal periods. Therefore, it was confirmed that typhoons occurred more east
during the El Niño period than the normal period.
< case 1 - Normal >
< case 2 - Normal >
< case 3 - Normal >
< case 4 - Normal >
< case 5 - Normal >
< case 1 - El Niño >
< case 2 - El Niño >
< case 3 - El Niño >
< case 4 - El Niño >
< case 5 - El Niño >
They are videos that show the typhoon's location change and the monthly average SST anomaly for each case at once. They can show the sea surface temperature and the location of the typhoons more visually. Cases 1 and 5, which had a high El Niño index, showed a more obvious difference in location.
Limitation
This exploration is the most basic approach to the correlation between El Niño and typhoons.
Therefore, it has the following limitations:
1. There is a limitation that other factors that may affect the occurrence of typhoons have not been considered. We considered only the effects of sea-level temperature among the factors that caused the typhoon. However, typhoons can also be affected by other factors such as sea level pressure and atmospheric temperature. Furthermore, the intensity of typhoons can be changed by other mechanisms between the atmosphere and ocean as they grow.
2. When analyzing the occurrence location of typhoons, there is a limitation that it is not analyzed based on the exact occurrence location. We analyzed data provided by the Korea Meteorological Administration (KMA) assuming that the location where the typhoon was first observed is where it occurred. However, this is not the exact ‘occurrence location’ of typhoons,
as it is the first ‘observed’ location.
3. The samples are not large enough to analyze the correlation between El Niño and typhoons.
We set cases 1 to 5 to analyze the typhoons that have occurred in the last 20 years. However, both El Niño and typhoons are a global natural phenomenon, so there is a limitation to analyze the correlation with just 20 years. And there is another limitation that we didn’t cover all typhoons because our sets of periods don't cover overall 20 years.
4. There should be a further study about the extent of El Niño's effects on typhoons
by the El Niño index. In case 1 to 5, the relatively large El Niño index is case 1, 2, 5.
Nevertheless, only case 1 and 5 showed significant differences in the occurrence location.
Case 2 showed no significant difference despite the similarity index with case 5.
We guessed that it is because of the difference of pre-El Niño marine conditions in case 2 and case 5,
but more precise studies of El Niño indexes and typhoons are needed.