Changes in climate extremes in Vietnam
Authors: Van Thang Nguyen, Van Khiem Mai, Van Thang Vu, Dang Mau Nguyen, Ngoc Bich Phuong Nguyen, Duy Diep Le, Truong Minh Ha, Nhat Linh Luu
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This study represents the observed and projected changes in climate extremes in the context of climate change. A linear regression method was used to identify trends and variations of climate extremes in the past, while projected changes in climate extremes were detected based on dynamical downscaling and compared with the baseline period (1986-2005). The results show that daily maximum and minimum surface air temperatures (Txx, Tnn) increased considerably with the highest value of about 0.9oC/decade during the period of 1961-2014. The number of hot days increased across most observed stations, especially in Central Vietnam. Trends of extreme precipitation varied among the regions: decreasing across most stations in the Northwest, Northeast and Red River Delta; and increasing at other stations. In Vietnam, over the period 1959-2015, there were no obvious changes in the frequency of tropical cyclones causing landfall events, including typhoons and tropical depressions. However, the rate of occurrence of the very strongest typhoons are currently on the increase. In recent years, typhoon seasons tend to end later than in the past, and typhoons occur more frequently in Southern regions. Predicted results of climate extremes in the future for the periods 2046-2065 and 2080-2099, compared with the baseline period of 1986-2005 under the medium and high scenario (RCP 4.5 and RCP 8.5) show that temperature extremes will likely increase considerably in the future. The number of hot days will likely increase in both frequency and intensity, while the number of extreme cold days will likely decrease at most stations in the North. A maximum 1-day rainfall will also likely increase across all regions in Vietnam. Results from models show that the number of strong typhoons will likely increase in the mid- and late-century.