Multiple trend tests on air temperature and precipitation anomalies in Vietnam

Abstract

An informed decision on building climate resilience and adaptation requires a deep understanding of long-term changes in temperature and precipitation, especially for most vulnerable countries to climate extremes like Vietnam. Hence, this study aimed to comprehend spatiotemporal trend possibilities of temperature and precipitation in Vietnam by employing multiple non-parametric statistical trend tests. This study also suggested a modified procedure, represented as a Hovmöller-like diagram, for enhancing the characterization of long-term spatiotemporal trends by applying multiple monotonic trend tests to all latitude coordinates through all possible 30-year periods. The superiority of multiple trend tests over a single one is that this methodology can assess the sensitivity of trend test results to the beginning years, ending years, and record lengths, thus emphasizing the necessity of performing monotonic trend tests repeatedly. The results show consistent warming trends in all climate sub-regions over the last 4–5 decades, with the estimated trend slopes varying from approximately 0.010–0.042 °C/year. Precipitation anomalies in most climate sub-regions, especially in the southern part, experienced significant increasing trends at the rate of around 0.29–2.76%/year during the last 3–5 decades. These findings are expected to contribute more insights into the spatiotemporal trend patterns of temperature and precipitation in Vietnam.

Ethnic Minority Farmers’ Perceptions of Climate Change and Its Effects on Crop Production in Northwest Vietnam: A Case Study of H’mong Farmers in Pa Lau Commune, Tram Tau District, Yen Bai Province

“…The average annual rainfall tended to increase at a rate of 111 mm/decade and was statistically significant (P <0.05). This result was also similar to the assessment of annual rainfall changes in recent decades in the northern climates of Vietnam, including Yen Bai (Le et al, 2020;Phuong et al, 2022). Rainfall tended to increase towards the end of the year, possibly due to an increase in tropical depressions and typhoons at this time (MONRE, 2022) Unlike rainfall's trend, the minimum, maximum, and average annual temperatures by year, and by spring and summer crops all statistically tended to increase (except for the average maximum temperature for the summer cropping season P >0.1) (Figure 3).…”

“…The increased rates for the annual mean values were 0.31 o C, 0.23 o C, and 0.29 o C per decade for the minimum, maximum, and average temperatures, respectively. Similar results were found by MONRE (2022) and Phuong et al (2022) when assessing the average annual temperature change rates for the Northwest in the past three to four decades. The highest temperature increase rate was found in spring crops with a maximum temperature increase of 0.51 o C per decade and an average temperature increase of 0.4 o C per decade.…”