Ms. Le Thi Thanh Nga, Deputy Director of the Institute of Meteorology, Hydrology and Climate Change (Ministry of Natural Resources and Environment) answered VnExpress about the impact of El Nino on the three regions.
- In early June, the international meteorological agency announced that El Nino had begun to appear, but why did Vietnam experience hot days from April to May with many records set?
- First, we must understand El Nino. El Nino and La Lina are two opposite phases of the ENSO phenomenon, indicating the abnormal warming and cooling of sea surface temperatures in the eastern and central equatorial Pacific Ocean, with a cycle of about 8-12 months, sometimes 3-4 years. ENSO is one of the most important climate phenomena on Earth due to its ability to change large-scale atmospheric circulation, thereby affecting global temperature and rainfall. However, the impact will vary in scale and time in different regions.
Historical data shows that in El Nino years, Vietnam usually has temperatures higher than average for many years, with a lack of rainfall, causing heat, drought and saltwater intrusion. The most typical are the two severe droughts and saltwater intrusions that occurred during the strong El Nino period, the 2015-2016 and 2019-2020 dry seasons. El Nino will have very different impacts between climate zones and according to each period of activity, such as before, forming, starting, developing and weakening.
Ms. Le Thi Thanh Nga answers VnExpress about El Nino. Photo: Gia Chinh
Last April and May were the period before El Nino formed, a rapid phase change from cold to warm, with strong disturbances in ocean surface temperatures, leading to forced changes in the atmosphere. This sign shows that the ocean surface temperature in April and May this year was higher than the average of many years.
However, the unusual heat in April and May was not the result of El Nino but of global warming, which led to many changes in atmospheric circulation; the early and strong activity of the western low pressure combined with the foehn effect (due to Vietnam's terrain conditions). The average global temperature has been increasing every year since 2015, regardless of whether it is an El Nino or La Nina phase.
- El Nino appeared right at the peak of summer in the North and Central regions, but why has the weather been cool in the North for the past 20 days?
- As mentioned above, the impact of El Nino on temperature is very different between active periods and is often most evident during the developing and weakening stages. In the first 20 days of June, some areas in the North had sunny days and thunderstorms in the evenings and nights, so we felt cooler and more comfortable. The meteorological agency also did not record any temperature records.
However, in reality, from the temperature monitoring data in the first 20 days of June, the North and Central regions are generally 0.5-1 degrees Celsius higher than the average value of many years in the same period, and in some places 1.5-2 degrees Celsius. The average daily temperature in the South Central and Southern regions is also about 0.5 degrees Celsius higher than the average value of many years.
- How will El Nino affect the three regions of Vietnam?
- It is forecasted that in most regions of the country, the average temperature will tend to be higher than normal; heat waves may be more frequent and more severe; many records may appear. When El Nino appears, heat waves increase in the summer (shown in the maximum temperature or the number of hot days), reducing the chance of severe cold spells lasting in the winter.
Rainfall will be deficient in most areas of the country with a common level of 25-50%, even in Buon Ma Thuot's history, there was a recorded 69% shortage. From there, there is a high risk of local or widespread drought in some regions such as the North Central, South Central, Central Highlands and the South.
Storm and tropical depression activities in the East Sea and their impact on Vietnam may not be much, but they are concentrated in the middle of the season and are more unusual in both intensity and trajectory.
El Nino years can also cause unusual heavy rains and cold spells in some areas, such as the 2015-2016 El Nino that caused record heavy rains in Quang Ninh from July 25 to August 4. Or in the winter of 2015-2016, severe cold spells occurred in the North, with the lowest temperature in Sa Pa dropping to -4.2, Mau Son to -4.4, Pha Din to -4.3 degrees Celsius. Snow and ice appeared in places that had never seen snow before, such as Ba Vi (Hanoi) and Ky Son (Nghe An). Therefore, unusual or irregular conditions are also risks due to the impact of El Nino.
The Da River is dry, June 2023. Photo: Ngoc Thanh
- When and in which region is the most negative impact of El Nino predicted to occur in Vietnam?
- El Nino combined with the global warming trend due to climate change makes Asia likely to suffer from strong heat waves, with record breaking temperatures in South Asia, southern China to Southeast Asia. However, compared to other regions such as India, Australia, the average temperature increase in Vietnam is lower, mainly in June-July and the northern region of Vietnam.
In Vietnam, the most negative impact of El Nino is during the development, recession and disintegration period, especially hot weather, reduced rainfall in some areas, leading to water shortages, droughts, and saltwater intrusion that can occur with high frequency. For example, droughts in spring and summer in the North Central and South Central regions and droughts in winter and spring in the South and Central Highlands.
- In Vietnam, how long will El Nino last?
- According to current forecasts from major centers around the world, El Nino could last until early spring 2024 with a probability of about 80%. Analysis by the National Oceanic and Atmospheric Administration (USA) shows that sea surface temperatures in the Nino 3.4 region could peak from October 2023 to February 2024, when El Nino is at its strongest.
The impact of El Nino on Vietnam will increase in the last months of 2023 and early 2024. The dry season in the Central Highlands and the South is likely to be more severe, with drought and saltwater intrusion likely to occur on a large scale during this period.
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