Spatio‐temporal variability of the annual and monthly extreme temperature indices in Nepal

Abstract

AbstractInvestigating the changes in the extreme temperature indices is crucial for the assessment of climate change and to recommend practical adaptation strategies particularly in countries like Nepal, which is highly prone to the impacts of extreme climatic events. This study analyses the mean temperatures and the changes of extreme temperature indices at 25 stations located in different physiographic regions in Nepal at monthly and annual time scales for 1986–2015. Ten extreme temperature indices recommended by ETCCDI are selected and examined. Quality control is first conducted for original daily maximum and minimum temperature data. In Nepal, it is warming in general with maximum temperature (0.04°C year−1) increasing faster than minimum temperature (0.02°C year−1) on countrywide average which is contrary to the changes in the Tibetan Plateau and its surroundings and the global average. The changes in extreme temperatures are spatiotemporally heterogeneous and unique. Annually, cold extremes increase but the percentage of days below 10th percentile becomes less frequent. Terai and Siwalik plain regions show negative annual trends in cold indices (TNn and TXn), but mixed changes in other extreme indices. There are strong correlations between the trends of maximum temperature‐related variables and elevation. This analysis also adds the evidence of pronounced warming in higher elevation only for day‐time extreme temperatures but not for temperature minima in Nepal which differs from the other studies around the world. This study also reveals that December and January tend to have colder days in the Terai. However, summer months are getting hotter in each region across the country. Kathmandu, the most urbanized city in Nepal shows a significant increase in minimum temperature (Tmin) and minimum Tmin (TNn) indicating the influence of urbanization in temperature change ‐ an urban heat island effect.